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1. Performance of the HAWC Observatory and TeV Gamma-Ray Measurements of the Crab Nebula with Improved Extensive Air Shower Reconstruction Algorithms

Author

A. Albert, R. Alfaro, C. Alvarez, A. Andrés, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, A. Bernal, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, F. Carreón, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, D. Depaoli, N. Di Lalla, R. Díaz Hernández, B. L. Dingus, M. A. DuVernois, K. Engel, T. Ergin, C. Espinoza, K. L. Fan, K. Fang, N. Fraija, S. Fraija, J. A. García-González, F. Garfias, H. Goksu, M. M. González, J. A. Goodman, S. Groetsch, J. P. Harding, S. Hernández-Cadena, I. Herzog, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, S. Kaufmann, A. Lara, J. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Montes, E. Moreno, M. Mostafá, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, M. Osorio-Archila, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, E. Ruiz-Velasco, H. Salazar, D. Salazar-Gallegos, A. Sandoval, M. Schneider, G. Schwefer, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, E. Varela, X. Wang, I. J. Watson, K. Whitaker, E. Willox, H. Wu, S. Yu, S. Yun-Cárcamo, H. Zhou, and HAWC Collaboration

Subjects
High energy astrophysics, Gamma-rays, Gamma-ray detectors, Astrophysics, QB460-466
Abstract

The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, located on the side of the Sierra Negra volcano in Mexico, has been fully operational since 2015. The HAWC collaboration has recently significantly improved their extensive air shower reconstruction algorithms, which has notably advanced the observatory performance. The energy resolution for primary gamma rays with energies below 1 TeV was improved by including a noise-suppression algorithm. Corrections have also been made to systematic errors in direction fitting related to the detector and shower plane inclinations, ${ \mathcal O }(0\buildrel{\circ}\over{.} 1)$ biases in highly inclined showers, and enhancements to the core reconstruction. The angular resolution for gamma rays approaching the HAWC array from large zenith angles (>37°) has improved by a factor of 4 at the highest energies (>70 TeV) as compared to previous reconstructions. The inclusion of a lateral distribution function fit to the extensive air shower footprint on the array to separate gamma-ray primaries from cosmic-ray ones based on the resulting χ ^2 values improved the background rejection performance at all inclinations. At large zenith angles, the improvement in significance is a factor of 4 compared to previous HAWC publications. These enhancements have been verified by observing the Crab Nebula, which is an overhead source for the HAWC Observatory. We show that the sensitivity to Crab-like point sources ( E ^−2.63 ) with locations overhead to 30° zenith is comparable to or less than 10% of the Crab Nebula’s flux between 2 and 50 TeV. Thanks to these improvements, HAWC can now detect more sources, including the Galactic center.

Published
2024
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2. Exploring the Coronal Magnetic Field with Galactic Cosmic Rays: The Sun Shadow Observed by HAWC

Author

R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, K. P. Arunbabu, D. Avila Rojas, R. Babu, E. Belmont-Moreno, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, P. Colín-Farias, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, D. Depaoli, R. Diaz Hernandez, J. C. Díaz-Vélez, M. Durocher, M. A. DuVernois, K. Engel, C. Espinoza, K. L. Fan, N. Fraija, J. A. García-González, F. Garfias, A. Gonzalez Muñoz, M. M. González, J. A. Goodman, J. P. Harding, D. Huang, F. Hueyotl-Zahuantitla, A. Iriarte, S. Kaufmann, A. Lara, J. Lee, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, T. Niembro, R. Noriega-Papaqui, N. Omodei, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, E. Ruiz-Velasco, J. Ryan, H. Salazar, D. Salazar-Gallegos, A. Sandoval, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Turner, F. Ureña-Mena, E. Varela, L. Villaseñor, X. Wang, I. J. Watson, E. Willox, S. Yun-Cárcamo, and H. Zhou

Subjects
Active solar corona, Solar magnetic fields, Solar physics, Astrophysics, QB460-466
Abstract

Galactic cosmic rays (GCRs) are charged particles that reach the heliosphere almost isotropically in a wide energy range. In the inner heliosphere, the GCR flux is modulated by solar activity so that only energetic GCRs reach the lower layers of the solar atmosphere. In this work, we propose that high-energy GCRs can be used to explore the solar magnetic fields at low coronal altitudes. We used GCR data collected by the High-Altitude Water Cherenkov observatory to construct maps of GCR flux coming from the Sun’s sky direction and studied the observed GCR deficit, known as Sun shadow (SS), over a 6 yr period (2016–2021) with a time cadence of 27.3 days. We confirm that the SS is correlated with sunspot number, but we focus on the relationship between the photospheric solar magnetic field measured at different heliolatitudes and the relative GCR deficit at different energies. We found a linear relationship between the relative deficit of GCRs represented by the depth of the SS and the solar magnetic field. This relationship is evident in the observed energy range of 2.5–226 TeV, but is strongest in the range of 12.4 33.4 TeV, which implies that this is the best energy range to study the evolution of magnetic fields in the low solar atmosphere.

Published
2024
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3. Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow

Author

S. Lesage, P. Veres, M. S. Briggs, A. Goldstein, D. Kocevski, E. Burns, C. A. Wilson-Hodge, P. N. Bhat, D. Huppenkothen, C. L. Fryer, R. Hamburg, J. Racusin, E. Bissaldi, W. H. Cleveland, S. Dalessi, C. Fletcher, M. M. Giles, B. A. Hristov, C. M. Hui, B. Mailyan, C. Malacaria, S. Poolakkil, O. J. Roberts, A. von Kienlin, J. Wood, M. Ajello, M. Arimoto, L. Baldini, J. Ballet, M. G. Baring, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, R. D. Blandford, R. Bonino, P. Bruel, S. Buson, R. A. Cameron, R. Caputo, P. A. Caraveo, E. Cavazzuti, G. Chiaro, N. Cibrario, S. Ciprini, P. Cristarella Orestano, M. Crnogorcevic, A. Cuoco, S. Cutini, F. D’Ammando, S. De Gaetano, N. Di Lalla, L. Di Venere, A. Domínguez, S. J. Fegan, E. C. Ferrara, H. Fleischhack, Y. Fukazawa, S. Funk, P. Fusco, G. Galanti, V. Gammaldi, F. Gargano, C. Gasbarra, D. Gasparrini, S. Germani, F. Giacchino, N. Giglietto, R. Gill, M. Giroletti, J. Granot, D. Green, I. A. Grenier, S. Guiriec, M. Gustafsson, E. Hays, J. W. Hewitt, D. Horan, X. Hou, M. Kuss, L. Latronico, A. Laviron, M. Lemoine-Goumard, J. Li, I. Liodakis, F. Longo, F. Loparco, L. Lorusso, M. N. Lovellette, P. Lubrano, S. Maldera, A. Manfreda, G. Martí-Devesa, M. N. Mazziotta, J. E. McEnery, I. Mereu, M. Meyer, P. F. Michelson, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, E. Nuss, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, G. Panzarini, M. Persic, M. Pesce-Rollins, R. Pillera, F. Piron, H. Poon, T. A. Porter, G. Principe, S. Rainò, R. Rando, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, F. Ryde, M. Sánchez-Conde, P. M. Saz Parkinson, L. Scotton, D. Serini, C. Sgrò, V. Sharma, E. J. Siskind, G. Spandre, P. Spinelli, H. Tajima, D. F. Torres, J. Valverde, T. Venters, Z. Wadiasingh, K. Wood, and G. Zaharijas

Subjects
Gamma-ray bursts, Astrophysics, QB460-466
Abstract

We report the discovery of GRB 221009A, the highest flux gamma-ray burst (GRB) ever observed by the Fermi Gamma-ray Burst Monitor (Fermi-GBM). This GRB has continuous prompt emission lasting more than 600 s, which smoothly transitions to afterglow emission visible in the Fermi-GBM energy range (8 keV–40 MeV), and total energetics higher than any other burst in the Fermi-GBM sample. By using a variety of new and existing analysis techniques we probe the spectral and temporal evolution of GRB 221009A. We find no emission prior to the Fermi-GBM trigger time ( t _0 ; 2022 October 9 at 13:16:59.99 UTC), indicating that this is the time of prompt emission onset. The triggering pulse exhibits distinct spectral and temporal properties suggestive of the thermal, photospheric emission of shock breakout, with significant emission up to ∼15 MeV. We characterize the onset of external shock at t _0 + 600 s and find evidence of a plateau region in the early-afterglow phase, which transitions to a slope consistent with Swift-XRT afterglow measurements. We place the total energetics of GRB 221009A in context with the rest of the Fermi-GBM sample and find that this GRB has the highest total isotropic-equivalent energy ( E _γ _,iso = 1.0 × 10 ^55 erg) and second highest isotropic-equivalent luminosity ( L _γ _,iso = 9.9 × 10 ^53 erg s ^–1 ) based on its redshift of z = 0.151. These extreme energetics are what allowed us to observe the continuously emitting central engine of Fermi-GBM from the beginning of the prompt emission phase through the onset of early afterglow.

Published
2023
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4. The Third Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars

Author

D. A. Smith, S. Abdollahi, M. Ajello, M. Bailes, L. Baldini, J. Ballet, M. G. Baring, C. Bassa, J. Becerra Gonzalez, R. Bellazzini, A. Berretta, B. Bhattacharyya, E. Bissaldi, R. Bonino, E. Bottacini, J. Bregeon, P. Bruel, M. Burgay, T. H. Burnett, R. A. Cameron, F. Camilo, R. Caputo, P. A. Caraveo, E. Cavazzuti, G. Chiaro, S. Ciprini, C. J. Clark, I. Cognard, A. Corongiu, P. Cristarella Orestano, M. Crnogorcevic, A. Cuoco, S. Cutini, F. D’Ammando, A. de Angelis, M. E. DeCesar, S. De Gaetano, R. de Menezes, J. Deneva, F. de Palma, N. Di Lalla, F. Dirirsa, L. Di Venere, A. Domínguez, D. Dumora, S. J. Fegan, E. C. Ferrara, A. Fiori, H. Fleischhack, C. Flynn, A. Franckowiak, P. C. C. Freire, Y. Fukazawa, P. Fusco, G. Galanti, V. Gammaldi, F. Gargano, D. Gasparrini, F. Giacchino, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. A. Grenier, L. Guillemot, S. Guiriec, M. Gustafsson, A. K. Harding, E. Hays, J. W. Hewitt, D. Horan, X. Hou, F. Jankowski, R. P. Johnson, T. J. Johnson, S. Johnston, J. Kataoka, M. J. Keith, M. Kerr, M. Kramer, M. Kuss, L. Latronico, S.-H. Lee, D. Li, J. Li, B. Limyansky, F. Longo, F. Loparco, L. Lorusso, M. N. Lovellette, M. Lower, P. Lubrano, A. G. Lyne, Y. Maan, S. Maldera, R. N. Manchester, A. Manfreda, M. Marelli, G. Martí-Devesa, M. N. Mazziotta, J. E. McEnery, I. Mereu, P. F. Michelson, M. Mickaliger, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, M. E. Monzani, A. Morselli, M. Negro, R. Nemmen, L. Nieder, E. Nuss, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, M. Palatiello, D. Paneque, G. Panzarini, A. Parthasarathy, M. Persic, M. Pesce-Rollins, R. Pillera, H. Poon, T. A. Porter, A. Possenti, G. Principe, S. Rainò, R. Rando, S. M. Ransom, P. S. Ray, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, N. Renault-Tinacci, R. W. Romani, M. Sánchez-Conde, P. M. Saz Parkinson, L. Scotton, D. Serini, C. Sgrò, R. Shannon, V. Sharma, Z. Shen, E. J. Siskind, G. Spandre, P. Spinelli, B. W. Stappers, T. E. Stephens, D. J. Suson, S. Tabassum, H. Tajima, D. Tak, G. Theureau, D. J. Thompson, O. Tibolla, D. F. Torres, J. Valverde, C. Venter, Z. Wadiasingh, N. Wang, P. Wang, P. Weltevrede, K. Wood, J. Yan, G. Zaharijas, C. Zhang, and W. Zhu

Subjects
Binary pulsars, Millisecond pulsars, Pulsar timing method, Rotation powered pulsars, Pulsars, Gamma-rays, Astrophysics, QB460-466
Abstract

We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs) discovered in deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with LAT sources also likely harbor gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and candidates, 10% of all known pulsars, compared to ≤11 known before Fermi. Half of the gamma-ray pulsars are young. Of these, the half that are undetected in radio have a broader Galactic latitude distribution than the young radio-loud pulsars. The others are MSPs, with six undetected in radio. Overall, ≥236 are bright enough above 50 MeV to fit the pulse profile, the energy spectrum, or both. For the common two-peaked profiles, the gamma-ray peak closest to the magnetic pole crossing generally has a softer spectrum. The spectral energy distributions tend to narrow as the spindown power $\dot{E}$ decreases to its observed minimum near 10 ^33 erg s ^−1 , approaching the shape for synchrotron radiation from monoenergetic electrons. We calculate gamma-ray luminosities when distances are available. Our all-sky gamma-ray sensitivity map is useful for population syntheses. The electronic catalog version provides gamma-ray pulsar ephemerides, properties, and fit results to guide and be compared with modeling results.

Published
2023
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5. HAWC Study of the Very-high-energy γ-Ray Spectrum of HAWC J1844−034

Author

A. Albert, C. Alvarez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, M. Breuhaus, T. Capistrán, A. Carramiñana, S. Casanova, J. Cotzomi, S. Coutiño de León, E. De la Fuente, D. Depaoli, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, M. Durocher, K. Engel, C. Espinoza, K. L. Fan, K. Fang, N. Fraija, J. A. García-González, M. M. González, J. A. Goodman, S. Groetsch, J. P. Harding, I. Herzog, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, T. B. Humensky, P. Hüntemeyer, V. Joshi, S. Kaufmann, J. Lee, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, M. Mostafá, L. Nellen, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, E. Ruiz-Velasco, H. Salazar, D. Salazar-Gallegos, A. Sandoval, M. Schneider, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, E. Varela, L. Villaseñor, X. Wang, I. J. Watson, E. Willox, H. Zhou, and HAWC collaboration

Subjects
γ-ray sources, Pulsars, Supernova remnants, Astrophysics, QB460-466
Abstract

Recently, the region surrounding eHWC J1842−035 has been studied extensively by γ-ray observatories due to its extended emission reaching up to a few hundred TeV and potential as a hadronic accelerator. In this work, we use 1910 days of cumulative data from the High Altitude Water Cherenkov (HAWC) observatory to carry out a dedicated systematic source search of the eHWC J1842−035 region. During the search, we found three sources in the region, namely, HAWC J1844−034, HAWC J1843−032, and HAWC J1846−025. We have identified HAWC J1844−034 as the extended source that emits photons with energies up to 175 TeV. We compute the spectrum for HAWC J1844−034, and by comparing with the observational results from other experiments, we have identified HESS J1843−033, LHAASO J1843−0338, and TASG J1844−038 as very-high-energy γ-ray sources with a matching origin. Also, we present and use the multiwavelength data to fit the hadronic and leptonic particle spectra. We have identified four pulsar candidates in the nearby region in which PSR J1844−0346 is found to be the most likely candidate due to its proximity to HAWC J1844−034 and the computed energy budget. We have also found SNR G28.6−0.1 as a potential counterpart source of HAWC J1844−034 for which both leptonic and hadronic scenarios are feasible.

Published
2023
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6. Low-energy Electron-track Imaging for a Liquid Argon Time-projection-chamber Telescope Concept Using Probabilistic Deep Learning

Author

M. Buuck, A. Mishra, E. Charles, N. Di Lalla, O. A. Hitchcock, M. E. Monzani, N. Omodei, and T. Shutt

Subjects
Gamma-ray telescopes, Gamma-ray transient sources, Convolutional neural networks, Gamma-ray detectors, Astronomy image processing, Astrophysics, QB460-466
Abstract

The GammaTPC is an MeV-scale single-phase liquid argon time-projection-chamber gamma-ray telescope concept with a novel dual-scale pixel-based charge-readout system. It promises to enable a significant improvement in sensitivity to MeV-scale gamma rays over previous telescopes. The novel pixel-based charge readout allows for imaging of the tracks of electrons scattered by Compton interactions of incident gamma rays. The two primary contributors to the accuracy of a Compton telescope in reconstructing an incident gamma-ray’s original direction are its energy and position resolution. In this work, we focus on using deep learning to optimize the reconstruction of the initial position and direction of electrons scattered in Compton interactions, including using probabilistic models to estimate predictive uncertainty. We show that the deep-learning models are able to predict locations of Compton scatters of MeV-scale gamma rays from simulated 500 μ m pixel-based data to better than 1 mm rms error and are sensitive to the initial direction of the scattered electron. We compare and contrast different deep-learning uncertainty estimation algorithms for reconstruction applications. Additionally, we show that event-by-event estimates of the uncertainty of the locations of the Compton scatters can be used to select those events that were reconstructed most accurately, leading to improvement in locating the origin of gamma-ray sources on the sky.

Published
2023
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7. Search for Gamma-Ray and Neutrino Coincidences Using HAWC and ANTARES Data

Author

H. A. Ayala Solares, S. Coutu, D. Cowen, D. B. Fox, T. Grégoire, F. McBride, M. Mostafá, K. Murase, S. Wissel, AMON Team, A. Albert, S. Alves, M. André, M. Ardid, S. Ardid, J.-J. Aubert, J. Aublin, B. Baret, S. Basa, B. Belhorma, M. Bendahman, F. Benfenati, V. Bertin, S. Biagi, M. Bissinger, J. Boumaaza, M. Bouta, M. C. Bouwhuis, H. Brânzaş, R. Bruijn, J. Brunner, J. Busto, B. Caiffi, D. Calvo, A. Capone, L. Caramete, J. Carr, V. Carretero, S. Celli, M. Chabab, T. N. Chau, R. Cherkaoui El Moursli, T. Chiarusi, M. Circella, J. A. B. Coelho, A. Coleiro, R. Coniglione, P. Coyle, A. Creusot, A. F. Díaz, G. de Wasseige, B. De Martino, C. Distefano, I. Di Palma, A. Domi, C. Donzaud, D. Dornic, D. Drouhin, T. Eberl, T. van Eeden, D. van Eijk, N. El Khayati, A. Enzenhöfer, P. Fermani, G. Ferrara, F. Filippini, L. Fusco, J. García, P. Gay, H. Glotin, R. Gozzini, R. Gracia Ruiz, K. Graf, C. Guidi, S. Hallmann, H. van Haren, A. J. Heijboer, Y. Hello, J. J. Hernández-Rey, J. Hößl, J. Hofestädt, F. Huang, G. Illuminati, C. W. James, B. Jisse-Jung, M. de Jong, P. de Jong, M. Kadler, O. Kalekin, U. Katz, A. Kouchner, I. Kreykenbohm, V. Kulikovskiy, R. Lahmann, M. Lamoureux, R. Le Breton, D. Lefèvre, E. Leonora, G. Levi, S. Le Stum, D. Lopez-Coto, S. Loucatos, L. Maderer, J. Manczak, M. Marcelin, A. Margiotta, A. Marinelli, J. A. Martínez-Mora, K. Melis, P. Migliozzi, A. Moussa, R. Muller, L. Nauta, S. Navas, E. Nezri, B. Ó Fearraigh, A. Păun, G. E. Păvălaş, C. Pellegrino, M. Perrin-Terrin, V. Pestel, P. Piattelli, C. Pieterse, C. Poirè, V. Popa, T. Pradier, N. Randazzo, D. Real, S. Reck, G. Riccobene, A. Romanov, A. Sánchez-Losa, D. F. E. Samtleben, M. Sanguineti, P. Sapienza, J. Schnabel, J. Schumann, F. Schüssler, J. Seneca, M. Spurio, Th. Stolarczyk, M. Taiuti, Y. Tayalati, S. J. Tingay, B. Vallage, V. Van Elewyck, F. Versari, S. Viola, D. Vivolo, J. Wilms, S. Zavatarelli, A. Zegarelli, J. D. Zornoza, J. Zúñiga, ANTARES Collaboration, C. Alvarez, J. C. Arteaga-Velázquez, R. Babu, E. Belmont-Moreno, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, O. Chaparro-Amaro, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, R. Diaz Hernandez, M. A. DuVernois, M. Durocher, J. C. Díaz-Vélez, K. Engel, C. Espinoza, K. L. Fan, M. Fernández Alonso, N. Fraija, J. A. García-González, F. Garfias, M. M. González, J. A. Goodman, J. P. Harding, S. Hernandez, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, V. Joshi, S. Kaufmann, A. Lara, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, I. Martinez-Castellanos, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, A. Nayerhoda, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, N. Omodei, A. Peisker, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, E. Ruiz-Velasco, H. Salazar, F. Salesa Greus, A. Sandoval, M. Schneider, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, E. Varela, X. Wang, K. Whitaker, E. Willox, A. Zepeda, H. Zhou, and HAWC Collaboration

Subjects
High energy astrophysics, Astrophysics, QB460-466
Abstract

In the quest for high-energy neutrino sources, the Astrophysical Multimessenger Observatory Network has implemented a new search by combining data from the High Altitude Water Cherenkov (HAWC) Observatory and the Astronomy with a Neutrino Telescope and Abyss environmental RESearch (ANTARES) neutrino telescope. Using the same analysis strategy as in a previous detector combination of HAWC and IceCube data, we perform a search for coincidences in HAWC and ANTARES events that are below the threshold for sending public alerts in each individual detector. Data were collected between 2015 July and 2020 February with a live time of 4.39 yr. Over this time period, three coincident events with an estimated false-alarm rate of

Published
2023
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8. Searching for TeV Dark Matter in Irregular Dwarf Galaxies with HAWC Observatory

Author

R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, O. Chaparro-Amaro, U. Cotti, J. Cotzomi, E. De la Fuente, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, M. Durocher, J. C. Díaz-Vélez, C. Espinoza, K. L. Fan, N. Fraija, J. A. García-González, F. Garfias, M. M. González, J. P. Harding, S. Hernández-Cadena, D. Huang, F. Hueyotl-Zahuantitla, A. Iriarte, V. Joshi, S. Kaufmann, D. Kieda, J. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, N. Omodei, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, H. Salazar, D. Salazar-Gallegos, A. Sandoval, J. Serna-Franco, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, L. Villaseñor, X. Wang, E. Willox, H. Zhou, C. de León, The HAWC Collaboration, V. Gammaldi, E. Karukes, and P. Salucci

Subjects
Dark matter, Cold dark matter, Galaxies, Dwarf irregular galaxies, Particle astrophysics, Gamma-rays, Astrophysics, QB460-466
Abstract

We present the results of dark matter (DM) searches in a sample of 31 dwarf irregular (dIrr) galaxies within the field of view of the HAWC Observatory. dIrr galaxies are DM-dominated objects in which astrophysical gamma-ray emission is estimated to be negligible with respect to the secondary gamma-ray flux expected by annihilation or decay of weakly interacting massive particles (WIMPs). While we do not see any statistically significant DM signal in dIrr galaxies, we present the exclusion limits (95% C.L.) for annihilation cross section and decay lifetime for WIMP candidates with masses between 1 and 100 TeV. Exclusion limits from dIrr galaxies are relevant and complementary to benchmark dwarf Spheroidal (dSph) galaxies. In fact, dIrr galaxies are targets kinematically different from benchmark dSph, preserving the footprints of different evolution histories. We compare the limits from dIrr galaxies to those from ultrafaint and classical dSph galaxies previously observed with HAWC. We find that the constraints are comparable to the limits from classical dSph galaxies and ∼2 orders of magnitude weaker than the ultrafaint dSph limits.

Published
2023
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9. Detailed Analysis of the TeV γ-Ray Sources 3HWC J1928+178, 3HWC J1930+188, and the New Source HAWC J1932+192

Author

A. Albert, R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, C. Brisbois, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, O. Chaparro-Amaro, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, R. Diaz Hernandez, J. C. Díaz-Vélez, B. L. Dingus, M. A. DuVernois, M. Durocher, K. Engel, C. Espinoza, K. L. Fan, M. Fernández Alonso, N. Fraija, J. A. García-González, F. Garfias, H. Goksu, M. M. González, J. A. Goodman, J. P. Harding, S. Hernandez, J. Hinton, B. Hona, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, S. Kaufmann, D. Kieda, W. H. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, R. López-Coto, K. Malone, V. Marandon, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, A. Peisker, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, E. Ruiz-Velasco, H. Salazar, D. Salazar-Gallegos, F. Salesa Greus, A. Sandoval, M. Schneider, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, L. Villaseñor, X. Wang, F. Werner, E. Willox, H. Zhou, and HAWC collaboration

Subjects
High energy astrophysics, Gamma-ray astronomy, Pulsars, Pulsar wind nebulae, Non-thermal radiation sources, Astrophysics, QB460-466
Abstract

The latest High Altitude Water Cherenkov (HAWC) point-like source catalog up to 56 TeV reported the detection of two sources in the region of the Galactic plane at galactic longitude 52° < ℓ < 55°, 3HWC J1930+188 and 3HWC J1928+178. The first one is associated with a known TeV source, the supernova remnant SNR G054.1+00.3. It was discovered by one of the currently operating Imaging Atmospheric Cherenkov Telescope (IACT), the Very Energetic Radiation Imaging Telescope Array System (VERITAS), detected by the High Energy Stereoscopic System (H.E.S.S), and identified as a composite SNR. However, the source 3HWC J1928+178, discovered by HAWC and coincident with the pulsar PSR J1928+1746, was not detected by any IACT despite their long exposure on the region, until a recent new analysis of H.E.S.S. data was able to confirm it. Moreover, no X-ray counterpart has been detected from this pulsar. We present a multicomponent fit of this region using the latest HAWC data. This reveals an additional new source, HAWC J1932+192, which is potentially associated with the pulsar PSR J1932+1916, whose γ -ray emission could come from the acceleration of particles in its pulsar wind nebula. In the case of 3HWC J1928+178, several possible explanations are explored, in an attempt to unveil the origins of the very-high-energy γ -ray emission.

Published
2023
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10. The Fermi-LAT Lightcurve Repository

Author

S. Abdollahi, M. Ajello, L. Baldini, J. Ballet, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, A. Berretta, E. Bissaldi, R. Bonino, A. Brill, P. Bruel, E. Burns, S. Buson, R. A. Cameron, R. Caputo, P. A. Caraveo, N. Cibrario, S. Ciprini, P. Cristarella Orestano, M. Crnogorcevic, S. Cutini, F. D’Ammando, S. De Gaetano, S. W. Digel, N. Di Lalla, L. Di Venere, A. Domínguez, V. Fallah Ramazani, S. J. Fegan, E. C. Ferrara, A. Fiori, H. Fleischhack, A. Franckowiak, Y. Fukazawa, P. Fusco, V. Gammaldi, F. Gargano, S. Garrappa, C. Gasbarra, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. A. Grenier, S. Guiriec, M. Gustafsson, E. Hays, D. Horan, X. Hou, G. Jóhannesson, M. Kerr, D. Kocevski, M. Kuss, L. Latronico, J. Li, I. Liodakis, F. Longo, F. Loparco, L. Lorusso, B. Lott, M. N. Lovellette, P. Lubrano, S. Maldera, A. Manfreda, G. Martí-Devesa, M. N. Mazziotta, I. Mereu, M. Meyer, P. F. Michelson, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, G. Panzarini, J. S. Perkins, M. Persic, M. Pesce-Rollins, R. Pillera, T. A. Porter, G. Principe, J. L. Racusin, S. Rainò, R. Rando, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, M. Sánchez-Conde, P. M. Saz Parkinson, Jeff Scargle, L. Scotton, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, H. Tajima, D. J. Thompson, D. F. Torres, J. Valverde, T. Venters, Z. Wadiasingh, S. Wagner, and K. Wood

Subjects
Gamma-ray astronomy, Active galactic nuclei, Light curves, Astrophysics, QB460-466
Abstract

The Fermi Large Area Telescope (LAT) lightcurve repository (LCR) is a publicly available, continually updated library of gamma-ray lightcurves of variable Fermi-LAT sources generated over multiple timescales. The Fermi-LAT LCR aims to provide publication-quality lightcurves binned on timescales of 3, 7, and 30 days for 1525 sources deemed variable in the source catalog of the first 10 yr of Fermi-LAT observations. The repository consists of lightcurves generated through full likelihood analyses that model the sources and the surrounding region, providing fluxes and photon indices for each time bin. The LCR is intended as a resource for the time-domain and multimessenger communities by allowing users to search LAT data quickly to identify correlated variability and flaring emission episodes from gamma-ray sources. We describe the sample selection and analysis employed by the LCR and provide an overview of the associated data access portal.

Published
2023
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11. The first X-ray polarimetric observation of the black hole binary LMC X-1

Author

J Podgorný, L Marra, F Muleri, N Rodriguez Cavero, A Ratheesh, M Dovčiak, R Mikušincová, M Brigitte, J F Steiner, A Veledina, S Bianchi, H Krawczynski, J Svoboda, P Kaaret, G Matt, J A García, P-O Petrucci, A Lutovinov, A Semena, A Di Marco, M Negro, M C Weisskopf, A Ingram, J Poutanen, B Beheshtipour, S Chun, K Hu, T Mizuno, Z Sixuan, F Tombesi, S Zane, I Agudo, L A Antonelli, M Bachetti, L Baldini, W H Baumgartner, R Bellazzini, S D Bongiorno, R Bonino, A Brez, N Bucciantini, F Capitanio, S Castellano, E Cavazzuti, C Chen, S Ciprini, E Costa, A De Rosa, E Del Monte, L Di Gesu, N Di Lalla, I Donnarumma, V Doroshenko, S R Ehlert, T Enoto, Y Evangelista, S Fabiani, R Ferrazzoli, S Gunji, K Hayashida, J Heyl, W Iwakiri, S G Jorstad, V Karas, F Kislat, T Kitaguchi, J J Kolodziejczak, F La Monaca, L Latronico, I Liodakis, S Maldera, A Manfreda, F Marin, A Marinucci, A P Marscher, H L Marshall, F Massaro, I Mitsuishi, C-Y Ng, S L O’Dell, N Omodei, C Oppedisano, A Papitto, G G Pavlov, A L Peirson, M Perri, M Pesce-Rollins, M Pilia, A Possenti, S Puccetti, B D Ramsey, J Rankin, O J Roberts, R W Romani, C Sgrò, P Slane, P Soffitta, G Spandre, D A Swartz, T Tamagawa, F Tavecchio, R Taverna, Y Tawara, A F Tennant, N E Thomas, A Trois, S S Tsygankov, R Turolla, J Vink, K Wu, and F Xie

Published
2023
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12. A gamma-ray determination of the Universe’s star formation history

Author

S. Abdollahi, M. Ackermann, M. Ajello, W. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, J. Becerra González, R. Bellazzini, E. Bissaldi, R. Blandford, E. Bloom, R. Bonino, E. Bottacini, S. Buson, J. Bregeon, P. Bruel, R. Buehler, R. Cameron, R. Caputo, P. A. Caraveo, E. Cavazzuti, E. Charles, S. Chen, T. Cheung, G. Chiaro, S. Ciprini, J. Cohen-Tanugi, L. Cominsky, J. Conrad, D. Costantin, S. Cutini, F. D’Ammando, F. de Palma, A. Desai, S. Digel, N. Di Lalla, M. Di Mauro, L. Di Venere, A. Domínguez, C. Favuzzi, S. Fegan, J. Finke, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, G. Gallardo Romero, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. Grenier, L. Guillemot, S. Guiriec, D. H. Hartmann, E. Hays, K. Helgason, D. Horan, G. Jóhannesson, D. Kocevski, M. Kuss, S. Larsson, L. Latronico, J. Li, F. Longo, F. Loparco, B. Lott, M. Lovellette, P. Lubrano, G. Madejski, J. Magill, S. Maldera, A. Manfreda, L. Marcotulli, M. Mazziotta, J. McEnery, M. Meyer, P. Michelson, T. Mizuno, M. E. Monzani, A. Morselli, I. Moskalenko, M. Negro, E. Nuss, R. Ojha, N. Omodei, M. Orienti, E. Orlando, J. Ormes, M. Palatiello, V. Paliya, D. Paneque, J. Perkins, M. Persic, M. Pesce-Rollins, V. Petrosian, F. Piron, T. Porter, J. R. Primack, G. Principe, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, P. Saz Parkinson, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, H. Tajima, M. Takahashi, J. Thayer, L. Tibaldo, D. F. Torres, E. Torresi, G. Tosti, A. Tramacere, E. Troja, J. V. Valverde, G. Vianello, M. Vogel, K. Wood, and G. Zaharijas

Published
2018
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13. The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

Author

M. Ajello, R. Angioni, M. Axelsson, J. Ballet, G. Barbiellini, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, E. Bissaldi, E. D. Bloom, R. Bonino, E. Bottacini, P. Bruel, S. Buson, F. Cafardo, R. A. Cameron, E. Cavazzuti, S. Chen, C. C. Cheung, S. Ciprini, D. Costantin, S. Cutini, F. D’Ammando, P. de la Torre Luque, R. de Menezes, F. de Palma, A. Desai, N. Di Lalla, L. Di Venere, A. Domínguez, F. Fana Dirirsa, E. C. Ferrara, J. Finke, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, S. Garrappa, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. A. Grenier, S. Guiriec, S. Harita, E. Haywood, D. Horan, R. Itoh, G. Jóhannesson, M. Kovac’evic’, F. Krauss, M. Kreter, M. Kuss, S. Larsson, C. Leto, J. Li, I. Liodakis, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, S. Maldera, A. Manfreda, G. Martí-Devesa, F. Massaro, M. N. Mazziotta, I. Mereu, M. Meyer, G. Migliori, N. Barrios, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, R. Nemmen, E. Nuss, L. S. Ojha, R. Ojha, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, V. S. Paliya, Z. Pei, H. Peña-Herazo, M. Persic, M. Pesce-Rollins, L. Petrov, F. Piron, H. Poon, G. Principe, S. Rainò, R. Rando, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, F. K. Schinzel, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, Y. Tachibana, D. J. Thompson, D. F. Torres, E. Torresi, E. Troja, J. Valverde, P. van Zyl, and M. Yassine

Subjects
Astrophysics, Astronomy
Abstract

The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains $2863$ objects located at high Galactic latitudes (| b| > 10^9). It includes 85% more sources than the previous 3LAC catalog based on 4 yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.

Published
2020
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14. Fermi Large Area Telescope Fourth Source Catalog

Author

S. Abdollahi, F. Acero, M. Ackermann, M. Ajello, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, E. D. Bloom, R. Bonino, E. Bottacini, T. J. Brandt, J. Bregeon, P. Bruel, R. Buehler, T. H. Burnett, S. Buson, R. A. Cameron, R. Caputo, P. A. Caraveo, J. M. Casandjian, D. Castro, E. Cavazzuti, E. Charles, S. Chaty, S. Chen, C. C. Cheung, G. Chiaro, S. Ciprini, J. Cohen-Tanugi, L. R. Cominsky, J. Coronado-Blázquez, D. Costantin, A. Cuoco, S. Cutini, F. D'Ammando, M. DeKlotz, P. de la Torre Luque, F. de Palma, A. Desai, S. W. Digel, N. Di Lalla, M. Di Mauro, L. Di Venere, A. Dominguez, D. Dumora, F. Fana Dirirsa, S. J. Fegan, E. C. Ferrara, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, T. Glanzman, D. Green, I. A. Grenier, S. Griffin, M.-H. Grondin, J. E. Grove, S. Guiriec, A. K. Harding, K. Hayashi, E. Hays, J. W. Hewitt, D. Horan, G. Jóhannesson, T. J. Johnson, T. Kamae, M. Kerr, D. Kocevski, M. Kovac’evic’, M. Kuss, D. Landriu, S. Larsson, L. Latronico, M. Lemoine-Goumard, J. Li, I. Liodakis, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, S. Maldera, D. Malyshev, A. Manfreda, E. J. Marchesini, L. Marcotulli, G. Martí-Devesa, P. Martin, F. Massaro, M. N. Mazziotta, J. E. McEnery, I. Mereu, M. Meyer, P. F. Michelson, N. Mirabal, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, E. Nuss, R. Ojha, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, M. Palatiello, V. S. Paliya, D. Paneque, Z. Pei, H. Peña-Herazo, J. S. Perkins, M. Persic, M. Pesce-Rollins, V. Petrosian, L. Petrov, F. Piron, H. Poon, T. A. Porter, G. Principe, S. Raino', R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, Q. Remy, T. Reposeur, R. W. Romani, P. M. Saz Parkinson, F. K. Schinzel, D. Serini, C. Sgro', E. J. Siskind, D. A. Smith, G. Spandre, P. Spinelli, A. W. Strong, D. J. Suson, H. Tajima, M. N. Takahashi, D. Tak, J. B. Thayer, D. J. Thompson, L. Tibaldo, D. F. Torres, E. Torresi, J. Valverde, B. Van Klaveren, P. van Zyl, K. Wood, M. Yassine, and G. Zaharijas

Subjects
Astrophysics
Abstract

We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.

Published
2020
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15. Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow

Author

M. Ajello, M. Arimoto, M. Axelsson, L. Baldini, G. Barbiellini, D. Bastieri, R. Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, R. Bonino, E. Bottacini, J. Bregeon, P. Bruel, R. Buehler, E. Burns, S. Buson, R. A. Cameron, R. Caputo, P. A. Caraveo, E. Cavazzuti, S. Chen, G. Chiaro, S. Ciprini, J. Cohen-Tanugi, D. Costantin, S. Cutini, F.D’Ammando, M. DeKlotz, P. de la Torre Luque, F. de Palma, A. Desai, N. Di Lalla, L. Di Venere, F. Fana Dirirsa, S. J. Fegan, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, R. Gill, F. Giordano, M. Giroletti, J. Granot, D. Green, I. A. Grenier, M.-H. Grondin, S. Guiriec, E. Hays, D. Horan, G. Jóhannesson, D. Kocevski, M. Kovac’evic’, M. Kuss, S. Larsson, L. Latronico, M. Lemoine-Goumard, J.Li, I. Liodakis, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, S. Maldera, D. Malyshev, A. Manfreda, G. Martí-Devesa, M. N. Mazziotta, J. E. McEnery, I. Mereu, M. Meyer, P. F. Michelson, W. Mitthumsiri, T. Mizuno, M. E. Monzani, E. Moretti, A. Morselli, I. V. Moskalenko, M. Negro, E. Nuss, N. Omodei, M. Orienti, E. Orlando, M. Palatiello, V. S. Paliya, D. Paneque, Z. Pei, M. Persic, M. Pesce-Rollins, V. Petrosian, F. Piron, H. Poon, T. A. Porter, G. Principe, J. L. Racusin, S. Rainò, R. Rando, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, F. Ryde, P. M. Saz Parkinson, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, H. Tajima, K. Takagi, M. N. Takahashi, D. Tak, J. B. Thayer, D. J. Thompson, D. F. Torres, E. Troja, J. Valverde, B. Van Klaveren, K. Wood, M. Yassine, G. Zaharijas, B. Mailyan, P. N. Bhat, M. S. Briggs, W. Cleveland, M. Giles, A. Goldstein, M. Hui, Christian Malacaria, R. Preece, O. J. Roberts, P. Veres, C. Wilson-Hodge, A. von Kienlin, S. B. Cenko, P. O’Brien, A. P. Beardmore, A. Lien, J. P. Osborne, A. Tohuvavohu, V. D’Elia, A.D’Aì, M. Perri, J. Gropp, N. Klingler, M. Capalbi, G. Tagliaferri, M. Stamatikos, and M. De Pasquale

Subjects
Astronomy
Abstract

We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process.

Published
2020
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16. Observation of inverse Compton emission from a long γ-ray burst

Author

P. Veres, P. N. Bhat, M. S. Briggs, W. H. Cleveland, R. Hamburg, C. M. Hui, B. Mailyan, R. D. Preece, O. J. Roberts, A. von Kienlin, C. A. Wilson-Hodge, D. Kocevski, M. Arimoto, D. Tak, K. Asano, M. Axelsson, G. Barbiellini, E. Bissaldi, F.Fana Dirirsa, R. Gill, J. Granot, J. McEnery, N. Omodei, S. Razzaque, F. Piron, J. L. Racusin, D. J. Thompson, S. Campana, M. G. Bernardini, N. P. M. Kuin, M. H. Siegel, S. B. Cenko, P. O’Brien, M. Capalbi, A. Daì, M. De Pasquale, J. Gropp, N. Klingler, J. P. Osborne, M. Perri, R. L. C. Starling, G. Tagliaferri, A. Tohuvavohu, A. Ursi, M.Tavani, M. Cardillo, C. Casentini, G. Piano, Y. Evangelista, F. Verrecchia, C. Pittori, F. Lucarelli, A. Bulgarelli, N. Parmiggiani, G. E. Anderson, J. P. Anderson, G. Bernardi, J. Bolmer, M. D. Caballero-García, I. M. Carrasco, A. Castellón, N. Castro Segura, A. J. Castro-Tirado, S. V. Cherukuri, A. M. Cockeram, P. D’Avanzo, A. Di Dato, R. Diretse, R. P. Fender, E. Fernández-García, J. P. U. Fynbo, A. S.Fruchter, J. Greiner, M. Gromadzki, K. E. Heintz, I. Heywood, A. J. van der Horst, Y.-D. Hu, C. Inserra, L. Izzo, V. Jaiswal, P. Jakobsson, J. Japelj, E. Kankare, D. A.Kann, C. Kouveliotou, S. Klose, A. J. Levan, X. Y. Li, S. Lotti, K. Maguire, D. B. Malesani, I. Manulis, M. Marongiu, S. Martin, A. Melandri, M. J.Michałowski, J. C. A. Miller-Jones, K. Misra, A. Moin, K. P. Mooley, S. Nasri, M. Nicholl, A. Noschese, G. Novara, S. B. Pandey, E. Peretti, C. J. Pérez del Pulgar, M. A. Pérez-Torres, D. A. Perley, L. Piro, F. Ragosta, L. Resmi, R. Ricci, A. Rossi, R. Sánchez-Ramírez, J. Selsing, S. Schulze, S. J. Smartt, I. A. Smith, V. V. Sokolov, J. Stevens, N. R. Tanvir, C. C. Thöne, A. Tiengo, E. Tremou, E. Troja, A. de Ugarte Postigo, A. F. Valeev, S. D. Vergani, M. Wieringa, P. A. Woudt, D. Xu, O. Yaron, D. R. Young, V. A. Acciari, S. Ansoldi, L. A. Antonelli, A. Arbet Engels, D. Baack, A. Babić, B. Banerjee, U. Barres de Almeida, J. A. Barrio, J. Becerra González, W. Bednarek, L. Bellizzi, E. Bernardini, A. Berti, J. Besenrieder, W. Bhattacharyya, C. Bigongiari, A. Biland, O. Blanch, G. Bonnoli, Ž. Bošnjak, G. Busetto, R. Carosi, G. Ceribella, Y. Chai, A. Chilingaryan, S. Cikota, S. M. Colak, U. Colin, E. Colombo, J. L. Contreras, J. Cortina, S. Covino, V. D’Elia, P. Da Vela, F. Dazzi, A. De Angelis, B. De Lotto, M. Delfino, J. Delgado, D. Depaoli, F. Di Pierro, L. Di Venere, E. Do Souto Espiñeira, D. Dominis Prester, A. Donini, D. Dorner, M. Doro, D. Elsaesser, V. Fallah Ramazani, A. Fattorini, G. Ferrara, D. Fidalgo, L. Foffano, M. V. Fonseca, L. Font, C. Fruck, S. Fukami, R. J. García López, M. Garczarczyk, S.Gasparyan, M. Gaug, N. Giglietto, F. Giordano, N. Godinović, D. Green, D. Guberman, D. Hadasch, A. Hahn, J. Herrera, J. Hoang, D. Hrupec, M. Hütten, T. Inada, S. Inoue, K. Ishio, Y. Iwamura, L. Jouvin, D. Kerszberg, H. Kubo, J. Kushida, A. Lamastra, D. Lelas, F. Leone, E. Lindfors, S. Lombardi, F. Longo, M. López, R. López-Coto, A. López-Oramas, S. Loporchio, B. Machado de Oliveira Fraga, C. Maggio, P. Majumdar, M. Makariev, M. Mallamaci, G. Maneva, M. Manganaro, K. Mannheim, L. Maraschi, M. Mariotti, M. Martínez, D. Mazin, S. Mićanović, D. Miceli, M. Minev, J. M. Miranda, R. Mirzoyan, E. Molina, A. Moralejo, D. Morcuende, V. Moreno, E. Moretti, P. Munar-Adrover, V. Neustroev, C. Nigro, K. Nilsson, D. Ninci, K. Nishijima, K. Noda, L. Nogués, S. Nozaki, S. Paiano, M. Palatiello, D. Paneque, R. Paoletti, J. M. Paredes, P. Peñil, M. Peresano, M. Persic, P. G. Prada Moroni, E. Prandini, I. Puljak, W. Rhode, M. Ribó, J. Rico, C. Righi, A. Rugliancich, L. Saha, N. Sahakyan, T. Saito, S. Sakurai, K. Satalecka, K. Schmidt, T. Schweizer, J. Sitarek, I. Šnidarić, D. Sobczynska, A. Somero, A. Stamerra, D. Strom, M. Strzys, Y. Suda, T. Surić, M. Takahashi, F. Tavecchio, P. Temnikov, T. Terzić, M. Teshima, N. Torres-Albà, L. Tosti, V. Vagelli, J. van Scherpenberg, G. Vanzo, M. Vazquez Acosta, C. F. Vigorito, V. Vitale, I. Vovk, M. Will, D. Zarić, and L. Nava

Subjects
Space Sciences (General)
Abstract

Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C. Here we report multifrequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10^(−6) to 10^(12) electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.

Published
2019
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17. Gamma Rays from Fast Black-hole Winds

Author

M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, E. D. Bloom, R. Bonino, P. Bruel, S. Buson, R. A. Cameron, D. Caprioli, R. Caputo, E. Cavazzuti, G. Chartas, S. Chen, C. C. Cheung, G. Chiaro, D. Costantin, S. Cutini, F. D’Ammando, P. de la Torre Luque, F. de Palma, A. Desai, R. Diesing, N. Di Lalla, F. Dirirsa, L. Di Venere, A. Domínguez, S. J. Fegan, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. A. Grenier, S. Guiriec, D. Hartmann, D. Horan, G. Jóhannesson, C. Karwin, M. Kerr, M. Kovačević, M. Kuss, S. Larsson, L. Latronico, M. Lemoine-Goumard, J. Li, I. Liodakis, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, S. Maldera, A. Manfreda, S. Marchesi, L. Marcotulli, G. Martí-Devesa, M. N. Mazziotta, I. Mereu, P. F. Michelson, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, N. Omodei, M. Orienti, E. Orlando, V. Paliya, D. Paneque, Z. Pei, M. Persic, M. Pesce-Rollins, T. A. Porter, G. Principe, J. L. Racusin, S. Rainò, R. Rando, B. Rani, M. Razzano, A. Reimer, O. Reimer, P. M. Saz Parkinson, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, D. Tak, D. F. Torres, E. Troja, K. Wood, G. Zaharijas, and J. Zrake

Published
2021
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18. The High-Altitude Water Cherenkov (HAWC) Observatory in México: The Primary Detector

Author

A.U. Abeysekara, A. Albert, R. Alfaro, C. Alvarez, J.D. Álvarez, M. Araya, J.C. Arteaga-Velázquez, K.P. Arunbabu, D. Avila Rojas, H.A. Ayala Solares, R. Babu, A.S. Barber, A. Becerril, E. Belmont-Moreno, S.Y. BenZvi, O. Blanco, J. Braun, C. Brisbois, K.S. Caballero-Mora, J.I. Cabrera Martínez, T. Capistrán, A. Carramiñana, S. Casanova, M. Castillo, O. Chaparro-Amaro, U. Cotti, J. Cotzomi, S. Coutiño de León, E. de la Fuente, C. de León, T. De Young, R. Diaz Hernandez, B.L. Dingus, M.A. DuVernois, M. Durocher, J.C. Díaz-Vélez, R.W. Ellsworth, K. Engel, C. Espinoza, K.L. Fan, K. Fang, B. Fick, H. Fleischhack, J.L. Flores, N. Fraija, J.A. García-González, G. Garcia-Torales, F. Garfias, G. Giacinti, H. Goksu, M.M. González, A. González-Muñoz, J.A. Goodman, J.P. Harding, E. Hernandez, S. Hernandez, J. Hinton, B. Hona, D. Huang, F. Hueyotl-Zahuantitla, C.M. Hui, T.B. Humensky, P. Hüntemeyer, A. Iriarte, A. Imran, A. Jardin-Blicq, V. Joshi, S. Kaufmann, D. Kieda, G.J. Kunde, A. Lara, R. Lauer, W.H. Lee, D. Lennarz, H. León Vargas, J.T. Linnemann, A.L. Longinotti, G. Luis-Raya, J. Lundeen, K. Malone, V. Marandon, A. Marinelli, O. Martinez, I. Martínez-Castellanos, J. Martínez-Castro, H. Martínez-Huerta, J.A. Matthews, P. Miranda-Romagnoli, T. Montaruli, J.A. Morales-Soto, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, M.U. Nisa, R. Noriega-Papaqui, T. Oceguera-Becerra, L. Olivera-Nieto, N. Omodei, A. Peisker, Y. Pérez Araujo, E.G. Pérez-Pérez, E. Ponce, J. Pretz, C.D. Rho, D. Rosa-González, E. Ruiz-Velasco, H. Salazar, D. Salazar-Gallegos, F. Salesa Greus, A. Sandoval, M. Schneider, H. Schoorlemmer, J. Serna-Franco, G. Sinnis, A.J. Smith, Y. Son, K. Sparks Woodle, R.W. Springer, I. Taboada, A. Tepe, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, T.N. Ukwatta, E. Varela, M. Vargas-Magaña, L. Villaseñor, X. Wang, I.J. Watson, F. Werner, S. Westerhoff, E. Willox, I. Wisher, J. Wood, G.B. Yodh, D. Zaborov, A. Zepeda, and H. Zhou

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Nuclear and High Energy Physics, FOS: Physical sciences, High Energy Physics, Molecular Developmental Biology, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in M\'exico at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware., Comment: Accepted for publications in Nuclear Inst. and Methods in Physics Research, A (2023) 168253 ( https://www.sciencedirect.com/science/article/abs/pii/S0168900223002437 ); 39 pages, 14 Figures

Published
2023
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19. The Fermi-LAT Light Curve Repository

Author

S. Abdollahi, M. Ajello, L. Baldini, J. Ballet, D. Bastieri, J. Becerra Gonzalez, R. Bellazzini, A. Berretta, E. Bissaldi, R. Bonino, A. Brill, P. Bruel, E. Burns, S. Buson, R. A. Cameron, R. Caputo, P. A. Caraveo, N. Cibrario, S. Ciprini, P. Cristarella Orestano, M. Crnogorcevic, S. Cutini, F. D’Ammando, S. De Gaetano, S. W. Digel, N. Di Lalla, L. Di Venere, A. Domínguez, V. Fallah Ramazani, S. J. Fegan, E. C. Ferrara, A. Fiori, H. Fleischhack, A. Franckowiak, Y. Fukazawa, P. Fusco, V. Gammaldi, F. Gargano, S. Garrappa, C. Gasbarra, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. A. Grenier, S. Guiriec, M. Gustafsson, E. Hays, D. Horan, X. Hou, G. Jóhannesson, M. Kerr, D. Kocevski, M. Kuss, L. Latronico, J. Li, I. Liodakis, F. Longo, F. Loparco, L. Lorusso, B. Lott, M. N. Lovellette, P. Lubrano, S. Maldera, A. Manfreda, G. Martí-Devesa, M. N. Mazziotta, I. Mereu, M. Meyer, P. F. Michelson, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, G. Panzarini, J. S. Perkins, M. Persic, M. Pesce-Rollins, R. Pillera, T. A. Porter, G. Principe, J. L. Racusin, S. Rainò, R. Rando, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, M. Sánchez-Conde, P. M. Saz Parkinson, Jeff Scargle, L. Scotton, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, H. Tajima, D. J. Thompson, D. F. Torres, J. Valverde, T. Venters, Z. Wadiasingh, S. Wagner, K. Wood, and UAM. Departamento de Física Teórica

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Active galactic nuclei, Light Curves (918), Gamma-ray astronomy, Space and Planetary Science, Física, FOS: Physical sciences, Gamma-ray astronomy, Active galactic nuclei, Light curves, Astrophysics - High Energy Astrophysical Phenomena, Gamma-Ray Astronomy (628), Astronomy and Astrophysics, Active Galactic Nuclei (16), Light curves, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiere, The Fermi Large Area Telescope (LAT) lightcurve repository (LCR) is a publicly available, continually updated library of gamma-ray lightcurves of variable Fermi-LAT sources generated over multiple timescales. The Fermi-LAT LCR aims to provide publication-quality lightcurves binned on timescales of 3, 7, and 30 days for 1525 sources deemed variable in the source catalog of the first 10 yr of Fermi-LAT observations. The repository consists of lightcurves generated through full likelihood analyses that model the sources and the surrounding region, providing fluxes and photon indices for each time bin. The LCR is intended as a resource for the time-domain and multimessenger communities by allowing users to search LAT data quickly to identify correlated variability and flaring emission episodes from gamma-ray sources. We describe the sample selection and analysis employed by the LCR and provide an overview of the associated data access portal, M.N. and J.V. acknowledge that the material is based upon work supported by NASA under award number 80GSFC21M0002. D.K. and M.N. acknowledge support to this work from NASA Fermi GI Program under grant number 80NSSC23K0242. A.B. is supported by the NASA Postdoctoral Program at NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities. INFN and ASI personnel performed in part under ASI-INFN Agreements No. 2021-43-HH.0. Work at NRL is supported by NASA. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. This work performed in part under DOE Contract DE-AC02-76SF00515

Published
2023
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20. Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

Author

R Farinelli, S Fabiani, J Poutanen, F Ursini, C Ferrigno, S Bianchi, M Cocchi, F Capitanio, A De Rosa, A Gnarini, F Kislat, G Matt, R Mikusincova, F Muleri, I Agudo, L A Antonelli, M Bachetti, L Baldini, W H Baumgartner, R Bellazzini, S D Bongiorno, R Bonino, A Brez, N Bucciantini, S Castellano, E Cavazzuti, S Ciprini, E Costa, E Del Monte, L Di Gesu, N Di Lalla, A Di Marco, I Donnarumma, V Doroshenko, M Dovčiak, S R Ehlert, T Enoto, Y Evangelista, R Ferrazzoli, J A Garcia, S Gunji, K Hayashida, J Heyl, W Iwakiri, S G Jorstad, V Karas, T Kitaguchi, J J Kolodziejczak, H Krawczynski, F La Monaca, L Latronico, I Liodakis, S Maldera, A Manfreda, F Marin, A P Marscher, H L Marshall, I Mitsuishi, T Mizuno, C-Y Ng, S L O’Dell, N Omodei, C Oppedisano, A Papitto, G G Pavlov, A L Peirson, M Perri, M Pesce-Rollins, P O Petrucci, M Pilia, A Possenti, S Puccetti, B D Ramsey, J Rankin, A Ratheesh, R W Romani, C Sgrò, P Slane, P Soffitta, G Spandre, T Tamagawa, F Tavecchio, R Taverna, Y Tawara, A F Tennant, N E Thomas, F Tombesi, A Trois, S S Tsygankov, R Turolla, J Vink, M C Weisskopf, K Wu, F Xie, S Zane, Farinelli, R, Fabiani, S, Poutanen, J, Ursini, F, Ferrigno, C, Bianchi, S, Cocchi, M, Capitanio, F, De Rosa, A, Gnarini, A, Kislat, F, Matt, G, Mikusincova, R, Muleri, F, Agudo, I, Antonelli, L A, Bachetti, M, Baldini, L, Baumgartner, W H, Bellazzini, R, Bongiorno, S D, Bonino, R, Brez, A, Bucciantini, N, Castellano, S, Cavazzuti, E, Ciprini, S, Costa, E, Del Monte, E, Di Gesu, L, Di Lalla, N, Di Marco, A, Donnarumma, I, Doroshenko, V, Dovčiak, M, Ehlert, S R, Enoto, T, Evangelista, Y, Ferrazzoli, R, Garcia, J A, Gunji, S, Hayashida, K, Heyl, J, Iwakiri, W, Jorstad, S G, Karas, V, Kitaguchi, T, Kolodziejczak, J J, Krawczynski, H, Monaca, F La, Latronico, L, Liodakis, I, Maldera, S, Manfreda, A, Marin, F, Marscher, A P, Marshall, H L, Mitsuishi, I, Mizuno, T, Ng, C-Y, O’Dell, S L, Omodei, N, Oppedisano, C, Papitto, A, Pavlov, G G, Peirson, A L, Perri, M, Pesce-Rollins, M, Petrucci, P O, Pilia, M, Possenti, A, Puccetti, S, Ramsey, B D, Rankin, J, Ratheesh, A, Romani, R W, Sgrò, C, Slane, P, Soffitta, P, Spandre, G, Tamagawa, T, Tavecchio, F, Taverna, R, Tawara, Y, Tennant, A F, Thomas, N E, Tombesi, F, Trois, A, Tsygankov, S S, Turolla, R, Vink, J, Weisskopf, M C, Wu, K, Xie, F, and Zane, S

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, Settore FIS/05, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with $kT_{\rm in} \approx$ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature $kT_{\rm e} = 3$ keV and optical depth $\tau \approx 4$, assuming a slab geometry. We measure the polarization degree in the 2-8 keV band $P=1.8 \pm 0.3$ per cent and polarization angle $\phi = 140^{\circ} \pm 4^{\circ}$, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree $P =4.0 \pm 0.7$ per cent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line., Comment: 10 pages, 7 figures, accepted for publication in MNRAS

Published
2023

21. HAWC Study of the Ultra-high-energy Spectrum of MGRO J1908+06

Author

A. Albert, R. Alfaro, C. Alvarez, J. D. Álvarez, J. R. Angeles Camacho, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, C. Brisbois, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, M. Durocher, J. C. Díaz-Vélez, K. Engel, C. Espinoza, K. L. Fan, K. Fang, M. Fernández Alonso, N. Fraija, D. Garcia, J. A. García-González, F. Garfias, G. Giacinti, H. Goksu, M. M. González, J. A. Goodman, J. P. Harding, J. Hinton, B. Hona, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, S. Kaufmann, D. Kieda, W. H. Lee, J. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, V. Marandon, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, A. Peisker, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, H. Salazar, F. Salesa Greus, A. Sandoval, M. Schneider, H. Schoorlemmer, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, L. Villaseñor, X. Wang, I. J. Watson, E. Willox, A. Zepeda, H. Zhou, M. Breuhaus, H. Li, and H. Zhang

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, ddc:530, High Energy Physics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report TeV gamma-ray observations of the ultra-high-energy source MGRO J1908+06 using data from the High Altitude Water Cherenkov (HAWC) Observatory. This source is one of the highest-energy known gamma-ray sources, with emission extending past 200 TeV. Modeling suggests that the bulk of the TeV gamma-ray emission is leptonic in nature, driven by the energetic radio-faint pulsar PSR J1907+0602. Depending on what assumptions are included in the model, a hadronic component may also be allowed. Using the results of the modeling, we discuss implications for detection prospects by multi-messenger campaigns., Comment: accepted by ApJ, in press

Published
2022

22. MAGIC and Fermi-LAT gamma-ray results on unassociated HAWC sources

Author

M. L. Ahnen, S. Ansoldi, L. A. Antonelli, C. Arcaro, D. Baack, A. Babic, B. Banerjee, P. Bangale, U. Barres de Almeida, J. A. Barrio, J. Becerra Gonzalez, W. Bednarek, E. Bernardini, R. Ch. Berse, A. Berti, W. Bhattacharyya, A. Biland, O. Blanch, G. Bonnoli, R. Carosi, A. Carosi, G. Ceribella, A. Chatterjee, S. M. Colak, P. Colin, E. Colombo, J. L. Contreras, J. Cortina, S. Covino, P. Cumani, P. Da Vela, F. Dazzi, A. De Angelis, B. De Lotto, M. Delfino, J. Delgado, F. Di Pierro, A. Domınguez, D. Dominis Prester, D. Dorner, M. Doro, S. Einecke, D. Elsaesser, V. Fallah Ramazani, A. Fernandez-Barral, D. Fidalgo, M. V. Fonseca, L. Font, C. Fruck, D. Galindo, R. J. Garcıa Lopez, M. Garczarczyk, M. Gaug, P. Giammaria, N. Godinovic, D. Gora, D. Guberman, D. Hadasch, A. Hahn, T. Hassan, M. Hayashida, J. Herrera, J. Hose, D. Hrupec, K. Ishio, Y. Konno, H. Kubo, J. Kushida, D. Kuvezdic, D. Lelas, E. Lindfors, S. Lombardi, F. Longo, M. Lopez, C. Maggio, P. Majumdar, M. Makariev, G. Maneva, M. Manganaro, K. Mannheim, L. Maraschi, M. Mariotti, M. Martınez, S. Masuda, D. Mazin, K. Mielke, M. Minev, J. M. Miranda, R. Mirzoyan, A. Moralejo, V. Moreno, E. Moretti, T. Nagayoshi, V. Neustroev, A. Niedzwiecki, M. Nievas Rosillo, C. Nigro, K. Nilsson, D. Ninci, K. Nishijima, K. Noda, L. Nogues, S. Paiano, J. Palacio, D. Paneque, R. Paoletti, J. M. Paredes, G. Pedaletti, M. Peresano, M. Persic, P. G. Prada Moroni, E. Prandini, I. Puljak, J. R. Garcia, I. Reichardt, W. Rhodes, M. Ribo, J. Rico, C. Righi, A. Rugliancich, T. Saito, K. Satalecka, T. Schweizer, J. Sitarek, I. Snidaric, D. Sobczynska, A. Stamerra, M. Strzys, T. Suric, M. Takahashi, L. Takalo, F. Tavecchio, P. Temnikov, T. Terzic, M. Teshima, N. Torres-Alba, A. Treves, S. Tsujimoto, G. Vanzo, M. Vazquez Acosta, I. Vovk, J. E. Ward, M. Will, D. Zaric, A. Albert, R. Alfaro, C. Alvarez, R. Arceo, J. C. Arteaga-Velazquez, D. Avila Rojas, H. A. Ayala Solares, A. Becerril, E. Belmont-Moreno, S. Y. BenZvi, A. Bernal, J. Braun, K. S. Caballero-Mora, T. Capistran, A. Carraminana, S. Casanova, M. Castillo, U. Cotti, J. Cotzomi, S. Coutino de Leon, C. De Leon, E. De la Fuente, R. Diaz Hernandez, S. Dichiara, B. L. Dingus, M. A. DuVernois, J. C. Dıaz-Velez, R. W. Ellsworth, K. Engel, O. Enriquez-Rivera, D. W. Fiorino, H. Fleischhack, N. Fraija, J. A. Garcıa-Gonzalez, F. Garfias, A. Gonzalez-Munoz, M. M. Gonzalez, J. A. Goodman, Z. Hampel-Arias, J. P. Harding, S. Hernandez, F. Hueyotl-Zahuantitla, C. M. Hui, P. Huntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, S. Kaufmann, A. Lara, R. J. Lauer, W. H. Lee, D. Lennarz, H. Leon Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, R. Luna-Garcıa, R. Lopez-Coto, K. Malone, S. S. Marinelli, O. Martinez, I. Martinez-Castellanos, J. Martınez-Castro, H. Martınez-Huerta, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, A. Nayerhoda, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, R. Pelayo, J. Pretz, E. G. Perez-Perez, Z. Ren, C. D. Rho, C. Riviere, D. Rosa-Gonzalez, M. Rosenberg, E. Ruiz-Velasco, F. Salesa Greus, A. Sandoval, M. Schneider, M. Seglar Arroyo, G. Sinnis, A. J. Smith, R. W. Springer, P. Surajbali, I. Taboada, O. Tibolla, K. Tollefson, I. Torres, T. N. Ukwatta, G. Vianello, L. Villasenor, F. Werner, S. Westerhoff, J. Wood, T. Yapici, G. Yodh, A. Zepeda, H. Zhou, J. D. Alvarez, M. Ajello, L. Baldini, G. Barbiellini, B. Berenji, E. Bissaldi, R. D. Blandford, R. Bonino, E. Bottacini, T. J. Brandt, J. Bregeon, P. Bruel, R. A. Cameron, R. Caputo, P. A. Caraveo, D. Castro, E. Cavazzuti, G. Chiaro, S. Ciprini, D. Costantin, F. D'Ammando, F. de Palma, A. Desai, N. Di Lalla, M. Di Mauro, L. Di Venere, C. Favuzzi, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, D. Green, I. A. Grenier, S. Guiriec, A. K. Harding, E. Hays, J. W. Hewitt, D. Horan, G. Johannesson, M. Kuss, S. Larsson, I. Liodakis, F. Loparco, P. Lubrano, J. D. Magill, S. Maldera, A. Manfreda, M. N. Mazziotta, I. Mereu, P. F. Michelson, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, E. Nuss, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, M. Palatiello, V. S. Paliya, M. Pesce-Rollins, V. Petrosian, F. Piron, T. A. Porter, G. Principe, S. Raino, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, C. Sgro, E. J. Siskind, G. Spandre, P. Spinelli, H. Tajima, J. B. Thayer, David J Thompson, D. F. Torres, E. Torresi, E. Troja, J. Valverde, K. Wood, and M. Yassine

Subjects
Astronomy, Astrophysics
Abstract

The HAWC Collaboration released the 2HWC catalogue of TeV sources, in which 19 show no association with any known high-energy (HE; E ≳ 10 GeV) or very-high-energy (VHE; E ≳ 300 GeV) sources. This catalogue motivated follow-up studies by both the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) and Fermi-LAT (Large Area Telescope) observatories with the aim of investigating gamma-ray emission over a broad energy band. In this paper, we report the results from the first joint work between High Altitude Water Cherenkov (HAWC), MAGIC, and Fermi-LAT on three unassociated HAWC sources: 2HWC J2006+341, 2HWC J1907+084*, and 2HWC J1852+013*. Although no significant detection was found in the HE and VHE regimes, this investigation shows that a minimum 1° extension (at 95 per cent confidence level) and harder spectrum in the GeV than the one extrapolated from HAWC results are required in the case of 2HWC J1852+013*, whilst a simply minimum extension of 0.16° (at 95 per cent confidence level) can already explain the scenario proposed by HAWC for the remaining sources. Moreover, the hypothesis that these sources are pulsar wind nebulae is also investigated in detail.

Published
2019
Full Text
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23. Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer

Author

F Ursini, A Marinucci, G Matt, S Bianchi, F Marin, H L Marshall, R Middei, J Poutanen, D Rogantini, A De Rosa, L Di Gesu, J A García, A Ingram, D E Kim, H Krawczynski, S Puccetti, P Soffitta, J Svoboda, F Tombesi, M C Weisskopf, T Barnouin, M Perri, J Podgorny, A Ratheesh, A Zaino, I Agudo, L A Antonelli, M Bachetti, L Baldini, W H Baumgartner, R Bellazzini, S D Bongiorno, R Bonino, A Brez, N Bucciantini, F Capitanio, S Castellano, E Cavazzuti, S Ciprini, E Costa, E Del Monte, N Di Lalla, A Di Marco, I Donnarumma, V Doroshenko, M Dovciak, S R Ehlert, T Enoto, Y Evangelista, S Fabiani, R Ferrazzoli, S Gunji, J Heyl, W Iwakiri, S G Jorstad, V Karas, T Kitaguchi, J J Kolodziejczak, F La Monaca, L Latronico, I Liodakis, S Maldera, A Manfreda, A P Marscher, I Mitsuishi, T Mizuno, F Muleri, C Y Ng, S L O’Dell, N Omodei, C Oppedisano, A Papitto, G G Pavlov, A L Peirson, M Pesce-Rollins, P-O Petrucci, M Pilia, A Possenti, B D Ramsey, J Rankin, R W Romani, C Sgrò, P Slane, G Spandre, T Tamagawa, F Tavecchio, R Taverna, Y Tawara, A F Tennant, N E Thomas, A Trois, S S Tsygankov, R Turolla, J Vink, K Wu, F Xie, S Zane, Ursini, F, Marinucci, A, Matt, G, Bianchi, S, Marin, F, L Marshall, H, Middei, R, Poutanen, J, De Rosa, A, Di Gesu, L, A Garc??a, J, Ingram, A, E Kim, D, Krawczynski, H, Puccetti, S, Soffitta, P, Svoboda, J, Tombesi, F, C Weisskopf, M, Barnouin, T, Perri, M, Podgorny, J, Ratheesh, A, Zaino, A, Agudo, I, A Antonelli, L, Bachetti, M, Baldini, L, H Baumgartner, W, Bellazzini, R, D Bongiorno, S, Bonino, R, Brez, A, Bucciantini, N, Capitanio, F, Castellano, S, Cavazzuti, E, Ciprini, S, Costa, E, Del Monte, E, Di Lalla, N, Di Marco, A, Donnarumma, I, Doroshenko, V, Dovciak, M, R Ehlert, S, Enoto, T, Evangelista, Y, Fabiani, S, Ferrazzoli, R, Gunji, S, Heyl, J, Iwakiri, W, G Jorstad, S, Karas, V, Kitaguchi, T, J Kolodziejczak, J, La Monaca, F, Latronico, L, Liodakis, I, Maldera, S, Manfreda, A, P Marscher, A, Mitsuishi, I, Mizuno, T, Muleri, F, Y Ng, C, L O???Dell, S, Omodei, N, Oppedisano, C, Papitto, A, G Pavlov, G, L Peirson, A, Pesce-Rollins, M, Petrucci, P-O, Pilia, M, Possenti, A, D Ramsey, B, Rankin, J, W Romani, R, Sgr??, C, Slane, P, Spandre, G, Tamagawa, T, Tavecchio, F, Taverna, R, Tawara, Y, F Tennant, A, E Thomas, N, Trois, A, S Tsygankov, S, Turolla, R, Vink, J, Wu, K, Xie, F, Zane, S, Ministerio de Ciencia e Innovación (España), Centre National D'Etudes Spatiales (France), and Agenzia Spaziale Italiana

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Scattering, Galaxies: individual: Circinus, X-rays: galaxies, Galaxies: Seyfert, Settore FIS/05, Space and Planetary Science, Polarization, FOS: Physical sciences, Astronomy and Astrophysics, Galaxies: active, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Full list of authors: Ursini, F.; Marinucci, A.; Matt, G.; Bianchi, S.; Marin, F.; Marshall, H. L.; Middei, R.; Poutanen, J.; Rogantini, D.; De Rosa, A.; Di Gesu, L.; Garcia, J. A.; Ingram, A.; Kim, D. E.; Krawczynski, H.; Puccetti, S.; Soffitta, P.; Svoboda, J.; Tombesi, F.; Weisskopf, M. C.; Barnouin, T.; Perri, M.; Podgorny, J.; Ratheesh, A.; Zaino, A.; Agudo, I; Antonelli, L. A.; Bachetti, M.; Baldini, L.; Baumgartner, W. H.; Bellazzini, R.; Bongiorno, S. D.; Bonino, R.; Brez, A.; Bucciantini, N.; Capitanio, F.; Castellano, S.; Cavazzuti, E.; Ciprini, S.; Costa, E.; Del Monte, E.; Di Lalla, N.; Di Marco, A.; Donnarumma, I; Doroshenko, V; Dovciak, M.; Ehlert, S. R.; Enoto, T.; Evangelista, Y.; Fabiani, S.; Ferrazzoli, R.; Gunji, S.; Heyl, J.; Iwakiri, W.; Jorstad, S. G.; Karas, V; Kitaguchi, T.; Kolodziejczak, J. J.; La Monaca, F.; Latronico, L.; Liodakis, I; Maldera, S.; Manfreda, A.; Marscher, A. P.; Mitsuishi, I; Mizuno, T.; Muleri, F.; Ng, C. Y.; O'Dell, S. L.; Omodei, N.; Oppedisano, C.; Papitto, A.; Pavlov, G. G.; Peirson, A. L.; Pesce-Rollins, M.; Petrucci, P-O; Pilia, M.; Possenti, A.; Ramsey, B. D.; Rankin, J.; Romani, R. W.; Sgro, C.; Slane, P.; Spandre, G.; Tamagawa, T.; Tavecchio, F.; Taverna, R.; Tawara, Y.; Tennant, A. F.; Thomas, N. E.; Trois, A.; Tsygankov, S. S.; Turolla, R.; Vink, J.; Wu, K.; Xie, F.; Zane, S., We report on the Imaging X-ray Polarimetry Explorer (IXPE) observation of the closest and X-ray brightest Compton-thick active galactic nucleus (AGN), the Circinus galaxy. We find the source to be significantly polarized in the 2–6 keV band. From previous studies, the X-ray spectrum is known to be dominated by reflection components, both neutral (torus) and ionized (ionization cones). Our analysis indicates that the polarization degree is 28 ± 7 per cent (at 68 per cent confidence level) for the neutral reflector, with a polarization angle of 18° ± 5°, roughly perpendicular to the radio jet. The polarization of the ionized reflection is unconstrained. A comparison with Monte Carlo simulations of the polarization expected from the torus shows that the neutral reflector is consistent with being an equatorial torus with a half-opening angle of 45°–55°. This is the first X-ray polarization detection in a Seyfert galaxy, demonstrating the power of X-ray polarimetry in probing the geometry of the circumnuclear regions of AGNs, and confirming the basic predictions of standard Unification Models. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society., The Imaging X ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). JPou and SST were supported by the Academy of Finland grants 349373 and 349906. AIng acknowledges support from the Royal Society. MDov, JSvo, and VKar acknowledge the support from the GACR project 21-06825X. POP acknowledges financial support from the French High Energy Program (PNHE/CNRS) and from the French spatial agency (CNES)., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

Published
2022

24. Study of the Very High Energy Emission of M87 through its Broadband Spectral Energy Distribution

Author

R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, E. Belmont-Moreno, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, R. Diaz Hernandez, M. A. DuVernois, M. Durocher, J. C. Díaz-Vélez, C. Espinoza, K. L. Fan, M. Fernández Alonso, N. Fraija, J. A. García-González, F. Garfias, M. M. González, J. A. Goodman, J. P. Harding, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, V. Joshi, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, R. Noriega-Papaqui, N. Omodei, A. Peisker, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, H. Salazar, D. Salazar-Gallegos, F. Salesa Greus, A. Sandoval, J. Serna-Franco, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, F. Ureña-Mena, L. Villaseñor, X. Wang, E. Willox, and A. Zepeda

Subjects
Space and Planetary Science, Astronomy and Astrophysics, ddc:530
Abstract

The radio galaxy M87 is the central dominant galaxy of the Virgo Cluster. Very high-energy (VHE, ≳0.1 TeV) emission from M87 has been detected by imaging air Cherenkov telescopes. Recently, marginal evidence for VHE long-term emission has also been observed by the High Altitude Water Cherenkov Observatory, a gamma-ray and cosmic-ray detector array located in Puebla, Mexico. The mechanism that produces VHE emission in M87 remains unclear. This emission originates in its prominent jet, which has been spatially resolved from radio to X-rays. In this paper, we construct a spectral energy distribution from radio to gamma rays that is representative of the nonflaring activity of the source, and in order to explain the observed emission, we fit it with a lepto-hadronic emission model. We found that this model is able to explain nonflaring VHE emission of M87 as well as an orphan flare reported in 2005.

Published
2022

25. Gamma/Hadron Separation with the HAWC Observatory

Author

R. Alfaro, C. Alvarez, J.D. Álvarez, J.R. Angeles Camacho, J.C. Arteaga-Velázquez, D. Avila Rojas, H.A. Ayala Solares, R. Babu, E. Belmont-Moreno, C. Brisbois, K.S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, O. Chaparro-Amaro, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, C. de León, R. Diaz Hernandez, B.L. Dingus, M.A. DuVernois, M. Durocher, J.C. Díaz-Vélez, R.W. Ellsworth, K. Engel, C. Espinoza, K.L. Fan, M. Fernández Alonso, N. Fraija, D. Garcia, J.A. García-González, F. Garfias, M.M. González, J.A. Goodman, J.P. Harding, S. Hernandez, B. Hona, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, S. Kaufmann, G.J. Kunde, A. Lara, W.H. Lee, J. Lee, H. León Vargas, J.T. Linnemann, G. Luis-Raya, J. Lundeen, K. Malone, V. Marandon, O. Martinez, J. Martínez-Castro, J.A. Matthews, P. Miranda-Romagnoli, J.A. Morales-Soto, A. Nayerhoda, L. Nellen, M.U. Nisa, R. Noriega-Papaqui, L. Olivera-Nieto, N. Omodei, A. Peisker, Y. Pérez Araujo, E.G. Pérez-Pérez, C.D. Rho, D. Rosa-González, E. Ruiz-Velasco, H. Salazar, F. Salesa Greus, A. Sandoval, P.M. Saz Parkinson, J. Serna-Franco, A.J. Smith, R.W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, L. Villaseñor, X. Wang, I.J. Watson, F. Werner, E. Willox, J. Wood, A. Zepeda, and H. Zhou

Subjects
HAWC - Abteilung Hinton, High Energy Astrophysical Phenomena (astro-ph.HE), Nuclear and High Energy Physics, Physics - Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Instrumentation
Abstract

The High Altitude Water Cherenkov (HAWC) gamma-ray observatory observes atmospheric showers produced by incident gamma rays and cosmic rays with energy from 300 GeV to more than 100 TeV. A crucial phase in analyzing gamma-ray sources using ground-based gamma-ray detectors like HAWC is to identify the showers produced by gamma rays or hadrons. The HAWC observatory records roughly 25,000 events per second, with hadrons representing the vast majority ($>99.9\%$) of these events. The standard gamma/hadron separation technique in HAWC uses a simple rectangular cut involving only two parameters. This work describes the implementation of more sophisticated gamma/hadron separation techniques, via machine learning methods (boosted decision trees and neural networks), and summarizes the resulting improvements in gamma/hadron separation obtained in HAWC., 35 pages, 9 figures, published in Nuclear Instruments and Methods in Physics Research Section A

Published
2022

26. Investigating the Nature of Late-Time High-Energy GRB Emission Through Joint

Author

M, Ajello, L, Baldini, G, Barbiellini, D, Bastieri, R, Bellazzini, E, Bissaldi, R D, Blandford, R, Bonino, E, Bottacini, J, Bregeon, P, Bruel, R, Buehler, R A, Cameron, R, Caputo, P A, Caraveo, G, Chiaro, S, Ciprini, J, Cohen-Tanugi, D, Costantin, F, D'Ammando, F, DE Palma, N, DI Lalla, M, DI Mauro, L, DI Venere, A, Domínguez, C, Favuzzi, A, Franckowiak, Y, Fukazawa, S, Funk, P, Fusco, F, Gargano, D, Gasparrini, N, Giglietto, F, Giordano, M, Giroletti, D, Green, I A, Grenier, S, Guiriec, C, Holt, D, Horan, G, Jóhannesson, D, Kocevski, M, Kuss, G, LA Mura, S, Larsson, J, Li, F, Longo, F, Loparco, P, Lubrano, J D, Magill, S, Maldera, A, Manfreda, M N, Mazziotta, P F, Michelson, T, Mizuno, M E, Monzani, A, Morselli, M, Negro, E, Nuss, N, Omodei, M, Orienti, E, Orlando, V S, Paliya, J S, Perkins, M, Persic, M, Pesce-Rollins, F, Piron, G, Principe, J L, Racusin, S, Rainò, R, Rando, M, Razzano, S, Razzaque, A, Reimer, O, Reimer, C, Sgrò, E J, Siskind, G, Spandre, P, Spinelli, D, Tak, J B, Thayer, D F, Torres, G, Tosti, J, Valverde, M, Vogel, and K, Wood

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Article
Abstract

We use joint observations by the Neil Gehrels Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveal that LAT non-detections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the non-detected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1–100 GeV energy range considered for this analysis.

Published
2022

27. Probing the extragalactic mid-infrared background with HAWC

Author

A. Albert, R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, E. Belmont-Moreno, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, O. Chaparro-Amaro, U. Cotti, J. Cotzomi, S. Coutiño de León, E. De la Fuente, R. Diaz Hernandez, M. A. DuVernois, M. Durocher, J. C. Díaz-Vélez, K. Engel, C. Espinoza, K. L. Fan, M. Fernández Alonso, N. Fraija, J. A. García-González, F. Garfias, M. M. González, J. A. Goodman, J. P. Harding, S. Hernandez, D. Huang, F. Hueyotl-Zahuantitla, P. Hntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, D. Kieda, W. H. Lee, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, N. Omodei, A. Peisker, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, H. Salazar, D. Salazar-Gallegos, F. Salesa Greus, A. Sandoval, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, L. Villaseñor, X. Wang, T. Weisgarber, E. Willox, H. Zhou, and C. de León

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, ddc:520, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract

The extragalactic background light (EBL) contains all the radiation emitted by nuclear and accretion processes in stars and compact objects since the epoch of recombination. Measuring the EBL density directly is challenging, especially in the near- to far-infrared waveband, mainly due to the zodiacal light foreground. Instead, gamma-ray astronomy offers the possibility to indirectly set limits on the EBL by studying the effects of gamma-ray absorption in the very high energy (VHE:$>$100 GeV) spectra of distant blazars. The High Altitude Water Cherenkov gamma ray observatory (HAWC) is one of the few instruments sensitive to gamma rays with energies above 10 TeV. This offers the opportunity to probe the EBL in the near/mid IR region: $\lambda$ = 1 $\mu$m - 100 $\mu$m. In this study, we fit physically motivated emission models to Fermi Large Area Telescope (LAT) GeV data to extrapolate the intrinsic TeV spectra of blazars. We then simulate a large number of absorbed spectra for different randomly generated EBL model shapes and calculate Bayesian credible bands in the EBL intensity space by comparing and testing the agreement between the absorbed spectra and HAWC extragalactic observations of two blazars. The resulting bands are in agreement with current EBL lower and upper limits, showing a downward trend towards higher wavelength values $\lambda>10\, \mu$m also observed in previous measurements., Comment: Submitted to ApJ

Published
2022
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28. Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

Author

S. Abdollahi, M. Ackermann, M. Ajello, A. Albert, W. B. Atwood, L. Baldini, G. Barbiellini, R. Bellazzini, E. Bissaldi, E. D. Bloom, R. Bonino, E. Bottacini, T. J. Brandt, P. Bruel, S. Buson, M. Caragiulo, E. Cavazzuti, A. Chekhtman, S. Ciprini, F. Costanza, A. Cuoco, S. Cutini, F. D’Ammando, F. de Palma, R. Desiante, S. W. Digel, N. Di Lalla, M. Di Mauro, L. Di Venere, B. Donaggio, P. S. Drell, C. Favuzzi, W. B. Focke, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, S. Guiriec, A. K. Harding, T. Jogler, G. Jóhannesson, T. Kamae, M. Kuss, S. Larsson, L. Latronico, J. Li, F. Longo, F. Loparco, P. Lubrano, J. D. Magill, D. Malyshev, A. Manfreda, M. N. Mazziotta, M. Meehan, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, M. E. Monzani, A. Morselli, M. Negro, E. Nuss, T. Ohsugi, N. Omodei, D. Paneque, J. S. Perkins, M. Pesce-Rollins, F. Piron, G. Pivato, G. Principe, S. Rainò, R. Rando, M. Razzano, A. Reimer, O. Reimer, C. Sgrò, D. Simone, E. J. Siskind, F. Spada, G. Spandre, P. Spinelli, A. W. Strong, H. Tajima, J. B. Thayer, D. F. Torres, E. Troja, J. Vandenbroucke, G. Zaharijas, and S. Zimmer

Published
2017
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29. Resolving the Extragalacticγ-Ray Background above 50 GeV with the Fermi Large Area Telescope

Author

M. Ackermann, M. Ajello, A. Albert, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, E. Bissaldi, R. D. Blandford, E. D. Bloom, R. Bonino, J. Bregeon, R. J. Britto, P. Bruel, R. Buehler, G. A. Caliandro, R. A. Cameron, M. Caragiulo, P. A. Caraveo, E. Cavazzuti, C. Cecchi, E. Charles, A. Chekhtman, J. Chiang, G. Chiaro, S. Ciprini, J. Cohen-Tanugi, L. R. Cominsky, F. Costanza, S. Cutini, F. D’Ammando, A. de Angelis, F. de Palma, R. Desiante, S. W. Digel, M. Di Mauro, L. Di Venere, A. Domínguez, P. S. Drell, C. Favuzzi, S. J. Fegan, E. C. Ferrara, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, G. Godfrey, D. Green, I. A. Grenier, S. Guiriec, E. Hays, D. Horan, G. Iafrate, T. Jogler, G. Jóhannesson, M. Kuss, G. La Mura, S. Larsson, L. Latronico, J. Li, L. Li, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, J. Magill, S. Maldera, A. Manfreda, M. Mayer, M. N. Mazziotta, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, M. Negro, E. Nuss, T. Ohsugi, C. Okada, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, J. S. Perkins, M. Pesce-Rollins, V. Petrosian, F. Piron, G. Pivato, T. A. Porter, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, R. W. Romani, M. Sánchez-Conde, J. Schmid, A. Schulz, C. Sgrò, D. Simone, E. J. Siskind, F. Spada, G. Spandre, P. Spinelli, D. J. Suson, H. Takahashi, J. B. Thayer, L. Tibaldo, D. F. Torres, E. Troja, G. Vianello, M. Yassine, and S. Zimmer

Published
2016
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30. Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope

Author

M. Ackermann, M. Ajello, A. Albert, W. B. Atwood, L. Baldini, G. Barbiellini, D. Bastieri, R. Bellazzini, E. Bissaldi, R. D. Blandford, R. Bonino, E. Bottacini, J. Bregeon, P. Bruel, R. Buehler, G. A. Caliandro, R. A. Cameron, M. Caragiulo, P. A. Caraveo, E. Cavazzuti, C. Cecchi, A. Chekhtman, J. Chiang, G. Chiaro, S. Ciprini, R. Claus, J. Cohen-Tanugi, F. Costanza, A. Cuoco, S. Cutini, F. D’Ammando, A. de Angelis, F. de Palma, R. Desiante, S. W. Digel, L. Di Venere, P. S. Drell, C. Favuzzi, S. J. Fegan, W. B. Focke, A. Franckowiak, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, J. E. Grove, S. Guiriec, A. K. Harding, J. W. Hewitt, D. Horan, X. Hou, G. Iafrate, G. Jóhannesson, T. Kamae, M. Kuss, S. Larsson, L. Latronico, J. Li, L. Li, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, J. Magill, S. Maldera, A. Manfreda, M. Mayer, M. N. Mazziotta, P. F. Michelson, W. Mitthumsiri, T. Mizuno, M. E. Monzani, A. Morselli, S. Murgia, E. Nuss, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, J. S. Perkins, M. Pesce-Rollins, V. Petrosian, F. Piron, G. Pivato, S. Rainò, R. Rando, M. Razzano, A. Reimer, O. Reimer, T. Reposeur, C. Sgrò, E. J. Siskind, F. Spada, G. Spandre, P. Spinelli, H. Takahashi, J. B. Thayer, D. J. Thompson, L. Tibaldo, D. F. Torres, G. Tosti, E. Troja, G. Vianello, B. L. Winer, K. S. Wood, M. Yassine, F. Cerutti, A. Ferrari, and P. R. Sala

Published
2016
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32. Bright Gamma-Ray Flares Observed in GRB 131108A

Author

M. Ajello, M. Arimoto, K. Asano, M. Axelsson, L. Baldini, G. Barbiellini, D. Bastieri, R. Bellazzini, A. Berretta, E. Bissaldi, R. D. Blandford, R. Bonino, E. Bottacini, J. Bregeon, P. Bruel, R. Buehler, S. Buson, R. A. Cameron, R. Caputo, P. A. Caraveo, E. Cavazzuti, S. Chen, G. Chiaro, S. Ciprini, D. Costantin, S. Cutini, F. D’Ammando, P. de la Torre Luque, F. de Palma, N. Di Lalla, L. Di Venere, F. Fana Dirirsa, S. J. Fegan, A. Franckowiak, Y. Fukazawa, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, F. Giordano, M. Giroletti, D. Green, I. A. Grenier, M.-H. Grondin, S. Guiriec, E. Hays, D. Horan, G. Jóhannesson, D. Kocevski, M. Kovac’evic’, M. Kuss, S. Larsson, L. Latronico, J. Li, I. Liodakis, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, S. Maldera, A. Manfreda, G. Martí-Devesa, M. N. Mazziotta, J. E. McEnery, I. Mereu, P. F. Michelson, T. Mizuno, M. E. Monzani, E. Moretti, A. Morselli, I. V. Moskalenko, M. Negro, E. Nuss, M. Ohno, N. Omodei, M. Orienti, E. Orlando, M. Palatiello, V. S. Paliya, D. Paneque, Z. Pei, M. Persic, M. Pesce-Rollins, V. Petrosian, F. Piron, H. Poon, T. A. Porter, G. Principe, J. L. Racusin, S. Rainò, R. Rando, B. Rani, M. Razzano, A. Reimer, O. Reimer, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, H. Tajima, K. Takagi, D. Tak, D. F. Torres, J. Valverde, K. Wood, R. Yamazaki, M. Yassine, S. Zhu, Z. Lucas Uhm, Bing Zhang, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Fermi-LAT, Ajello, M., Arimoto, M., Asano, K., Axelsson, M., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Berretta, A., Bissaldi, E., Blandford, R. D., Bonino, R., Bottacini, E., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Cameron, R. A., Caputo, R., Caraveo, P. A., Cavazzuti, E., Chen, S., Chiaro, G., Ciprini, S., Costantin, D., Cutini, S., D’Ammando, F., de la Torre Luque, P., de Palma, F., Di Lalla, N., Di Venere, L., Fana Dirirsa, F., Fegan, S. J., Franckowiak, A., Fukazawa, Y., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Green, D., Grenier, I. A., Grondin, M. -H., Guiriec, S., Hays, E., Horan, D., Jóhannesson, G., Kocevski, D., Kovac’Evic’, M., Kuss, M., Larsson, S., Latronico, L., Li, J., Liodakis, I., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Maldera, S., Manfreda, A., Martí-Devesa, G., Mazziotta, M. N., Mcenery, J. E., Mereu, I., Michelson, P. F., Mizuno, T., Monzani, M. E., Moretti, E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohno, M., Omodei, N., Orienti, M., Orlando, E., Palatiello, M., Paliya, V. S., Paneque, D., Pei, Z., Persic, M., Pesce-Rollins, M., Petrosian, V., Piron, F., Poon, H., Porter, T. A., Principe, G., Racusin, J. L., Rainò, S., Rando, R., Rani, B., Razzano, M., Reimer, A., Reimer, O., Serini, D., Sgrò, C., Siskind, E. J., Spandre, G., Spinelli, P., Tajima, H., Takagi, K., Tak, D., Torres, D. F., Valverde, J., Wood, K., Yamazaki, R., Yassine, M., Zhu, S., Lucas Uhm, Z., Zhang, Bing, and Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, Telescope, Spitzer Space Telescope, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, GRB131108A, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Gamma ray, Astronomy and Astrophysics, Light curve, 13. Climate action, Space and Planetary Science, ddc:520, Gamma-ray burst, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], gamma rays bursts, Fermi Gamma-ray Space Telescope, Flare
Abstract

GRB 131108A is a bright long Gamma-Ray Burst (GRB) detected by the Large Area Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses reveal three $\gamma$-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the GBM band (10 keV - 10 MeV). The high-energy light curve of GRB 131108A (100 MeV - 10 GeV) shows an unusual evolution: a steep decay, followed by three flares with an underlying emission, and then a long-lasting decay phase. The detailed analysis of the $\gamma$-ray flares finds that the three flares are 6 - 20 times brighter than the underlying emission and are similar to each other. The fluence of each flare, (1.6 $\sim$ 2.0) $\times$ 10$^{-6}$ erg cm$^{-2}$, is comparable to that of emission during the steep decay phase, 1.7 $\times$ 10$^{-6}$ erg cm$^{-2}$. The total fluence from three $\gamma$-ray flares is 5.3 $\times$ 10$^{-6}$ erg cm$^{-2}$. The three $\gamma$-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in $\sim$ 50\% of afterglows, in some cases well after the prompt emission. Also, the temporal and spectral indices during the early steep decay phase and the decaying phase of each flare show the consistency with a relation of the curvature effect ($\alpha$ = 2 + $\beta$), which is the first observational evidence of the high-latitude emission in the GeV energy band., Comment: ApJL, 10 pages, 3 figures, 2 tables

Published
2019

33. THE FIRST FERMI LAT SUPERNOVA REMNANT CATALOG

Author

F. Acero, M. Ackermann, M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, E. Bissaldi, R. D. Blandford, E. D. Bloom, R. Bonino, E. Bottacini, T. J. Brandt, J. Bregeon, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, R. Caputo, M. Caragiulo, P. A. Caraveo, J. M. Casandjian, E. Cavazzuti, C. Cecchi, A. Chekhtman, J. Chiang, G. Chiaro, S. Ciprini, R. Claus, J. M. Cohen, J. Cohen-Tanugi, L. R. Cominsky, B. Condon, J. Conrad, S. Cutini, F. D’Ammando, A. de Angelis, F. de Palma, R. Desiante, S. W. Digel, L. Di Venere, P. S. Drell, A. Drlica-Wagner, C. Favuzzi, E. C. Ferrara, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, G. A. Gomez-Vargas, I. A. Grenier, M.-H. Grondin, L. Guillemot, S. Guiriec, M. Gustafsson, D. Hadasch, A. K. Harding, M. Hayashida, E. Hays, J. W. Hewitt, A. B. Hill, D. Horan, X. Hou, G. Iafrate, T. Jogler, G. Jóhannesson, A. S. Johnson, T. Kamae, H. Katagiri, J. Kataoka, J. Katsuta, M. Kerr, J. Knödlseder, D. Kocevski, M. Kuss, H. Laffon, J. Lande, S. Larsson, L. Latronico, M. Lemoine-Goumard, J. Li, L. Li, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, J. Magill, S. Maldera, M. Marelli, M. Mayer, M. N. Mazziotta, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, M. E. Monzani, E. Moretti, A. Morselli, I. V. Moskalenko, S. Murgia, R. Nemmen, E. Nuss, T. Ohsugi, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, D. Paneque, J. S. Perkins, M. Pesce-Rollins, V. Petrosian, F. Piron, G. Pivato, T. A. Porter, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, M. Renaud, T. Reposeur, R. Rousseau, P. M. Saz Parkinson, J. Schmid, A. Schulz, C. Sgrò, E. J. Siskind, F. Spada, G. Spandre, P. Spinelli, A. W. Strong, D. J. Suson, H. Tajima, H. Takahashi, T. Tanaka, J. B. Thayer, D. J. Thompson, L. Tibaldo, O. Tibolla, D. F. Torres, G. Tosti, E. Troja, Y. Uchiyama, G. Vianello, B. Wells, K. S. Wood, M. Wood, M. Yassine, P. R. den Hartog, S. Zimmer, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Acero F, Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caputo R, Caragiulo M, Caraveo PA, Casandjian JM, Cavazzuti E, Cecchi C, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen JM, Cohen-Tanugi J, Cominsky LR, Condon B, Conrad J, Cutini S, DAmmando F, de Angelis A, de Palma F, Desiante R, Digel SW, Di Venere L, Drell PS, Drlica-Wagner A, Favuzzi C, Ferrara EC, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giommi P, Giordano F, Giroletti M, Glanzman T, Godfrey G, Gomez-Vargas GA, Grenier IA, Grondin MH, Guillemot L, Guiriec S, Gustafsson M, Hadasch D, Harding AK, Hayashida M, Hays E, Hewitt JW, Hill AB, Horan D, Hou X, Iafrate G, Jogler T, Johannesson G, Johnson AS, Kamae T, Katagiri H, Kataoka J, Katsuta J, Kerr M, Knodlseder J, Kocevski D, Kuss M, Laffon H, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Li J, Li L, Longo F, Loparco F, Lovellette MN, Lubrano P, Magill J, Maldera S, Marelli M, Mayer M, Mazziotta MN, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monzani ME, Moretti E, Morselli A, Moskalenko IV, Murgia S, Nemmen R, Nuss E, Ohsugi T, Omodei N, Orienti M, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Petrosian V, Piron F, Pivato G, Porter TA, Raino S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Renaud M, Reposeur T, Rousseau R, Parkinson PMS, Schmid J, Schulz A, Sgro C, Siskind EJ, Spada F, Spandre G, Spinelli P, Strong AW, Suson DJ, Tajima H, Takahashi H, Tanaka T, Thayer JB, Thompson DJ, Tibaldo L, Tibolla O, Torres DF, Tosti G, Troja E, Uchiyama Y, Vianello G, Wells B, Wood KS, Wood M, Yassine M, den Hartog PR, Zimmer S, ITA, Acero, F., Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., Cameron, R. A., Caputo, R., Caragiulo, M., Caraveo, P. A., Casandjian, J. M., Cavazzuti, E., Cecchi, C., Chekhtman, A., Chiang, J., Chiaro, G., Ciprini, S., Claus, R., Cohen, J. M., Cohen Tanugi, J., Cominsky, L. R., Condon, B., Conrad, J., Cutini, S., D'Ammando, F., Angelis, A. De, Palma, F. De, Desiante, R., Digel, S. W., Venere, L. Di, Drell, P. S., Drlica Wagner, A., Favuzzi, C., Ferrara, E. C., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giommi, P., Giordano, F., Giroletti, M., Glanzman, T., Godfrey, G., Gomez Vargas, G. A., Grenier, I. A., Grondin, M. H., Guillemot, L., Guiriec, S., Gustafsson, M., Hadasch, D., Harding, A. K., Hayashida, M., Hays, E., Hewitt, J. W., Hill, A. B., Horan, D., Hou, X., Iafrate, G., Jogler, T., Jóhannesson, G., Johnson, A. S., Kamae, T., Katagiri, H., Kataoka, J., Katsuta, J., Kerr, M., Knödlseder, J., Kocevski, D., Kuss, M., Laffon, H., Lande, J., Larsson, S., Latronico, L., Lemoine Goumard, M., Li, J., Li, L., Longo, Francesco, Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J., Maldera, S., Marelli, M., Mayer, M., Mazziotta, M. N., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Moiseev, A. A., Monzani, M. E., Moretti, E., Morselli, A., Moskalenko, I. V., Murgia, S., Nemmen, R., Nuss, E., Ohsugi, T., Omodei, N., Orienti, M., Orlando, E., Ormes, J. F., Paneque, D., Perkins, J. S., Pesce Rollins, M., Petrosian, V., Piron, F., Pivato, G., Porter, T. A., Rainò, S., Rando, R., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Renaud, M., Reposeur, T., Rousseau, R., Parkinson, P. M. Saz, Schmid, J., Schulz, A., Sgrò, C., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Strong, A. W., Suson, D. J., Tajima, H., Takahashi, H., Tanaka, T., Thayer, J. B., Thompson, D. J., Tibaldo, L., Tibolla, O., Torres, D. F., Tosti, G., Troja, E., Uchiyama, Y., Vianello, G., Wells, B., Wood, K. S., Wood, M., Yassine, M., Den Hartog, P. R., and Zimmer, S.

Subjects
catalog, Acceleration of particles, Supernova Remnants, Astrophysics::High Energy Astrophysical Phenomena, Flux, Context (language use), Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 7. Clean energy, 01 natural sciences, law.invention, Telescope, law, 0103 physical sciences, Supernova remnant, ISM [gamma-rays], Cosmic rays, 010303 astronomy & astrophysics, acceleration of particle, cosmic ray, Astrophysics::Galaxy Astrophysics, gamma-rays: ISM, ISM: supernova remnants, Physics, radiation mechanisms: nonthermal, 010308 nuclear & particles physics, Astronomy and Astrophysics, nonthermal [radiation mechanisms], gamma-rays, Astronomy and Astrophysic, catalogs, cosmic rays, Space and Planetary Science, Radio, Supernova, [SDU]Sciences of the Universe [physics], 13. Climate action, ddc:520, supernova remnant [ISM], Longitude, acceleration of particles – catalogs – cosmic rays – gamma-rays: ISM – ISM: supernova remnants – radiation mechanisms: nonthermal, Fermi Gamma-ray Space Telescope
Abstract

International audience; To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope (LAT). Based on the spatial overlap of sources detected at GeV energies with SNRs known from radio surveys, we classify 30 sources as likely GeV SNRs. We also report 14 marginal associations and 245 flux upper limits. A mock catalog in which the positions of known remnants are scrambled in Galactic longitude allows us to determine an upper limit of 22% on the number of GeV candidates falsely identified as SNRs. We have also developed a method to estimate spectral and spatial systematic errors arising from the diffuse interstellar emission model, a key component of all Galactic Fermi LAT analyses. By studying remnants uniformly in aggregate, we measure the GeV properties common to these objects and provide a crucial context for the detailed modeling of individual SNRs. Combining our GeV results with multiwavelength (MW) data, including radio, X-ray, and TeV, we demonstrate the need for improvements to previously sufficient, simple models describing the GeV and radio emission from these objects. We model the GeV and MW emission from SNRs in aggregate to constrain their maximal contribution to observed Galactic cosmic rays.

Published
2016

34. Identifying the 3FHL Catalog. I. Archival Swift Observations and Source Classification.

Author

A. Kaur, M. Ajello, S. Marchesi, and N. Omodei

Subjects
TELESCOPES, ASTRONOMICAL observations, FERMI level, MACHINE learning, RADIO sources (Astronomy), QUASARS
Abstract

We present the results of an identification campaign of unassociated sources from the Fermi Large Area Telescope 3FHL catalog. Out of 200 unidentified sources, we selected 110 sources for which archival Swift-XRT observations were available, 52 of which were found to have exactly one X-ray counterpart within the 3FHL 95% positional uncertainty. In this work, we report the X-ray, optical, IR, and radio properties of these 52 sources using positional associations with objects in various catalogs. The Wide-field Infrared Survey Explorer color–color plot for sources suggests that most of these belong to the blazar class family. The redshift measurements for these objects range from z = 0.277 to z = 2.1. Additionally, under the assumption that the majority of these sources are blazars, three machine-learning algorithms are employed to classify the sample into flat spectrum radio quasars or BL Lacertae objects. These suggest that the majority of the previously unassociated sources are BL Lac objects, in agreement with the fact the BL Lac objects represent by far the most numerous population detected above 10 GeV in 3FHL. [ABSTRACT FROM AUTHOR]

Published
2019
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35. The Bright and the Slow—GRBs 100724B and 160509A with High-energy Cutoffs at ≲100 MeV.

Author

G. Vianello, R. Gill, J. Granot, N. Omodei, J. Cohen-Tanugi, and F. Longo

Subjects
HIGH energy astronomy observatories, GAMMA ray bursts, PHENOMENOLOGY, LORENTZ force, BAND spectra
Abstract

We analyze the prompt emission of GRB 100724B and GRB 160509A, two of the brightest gamma-ray bursts (GRBs) observed by Fermi at ≲MeV energies but surprisingly faint at ≳100 MeV energies. Time-resolved spectroscopy reveals a sharp high-energy cutoff at energies Ec ∼ 20–60 MeV for GRB 100724B and Ec ∼ 80–150 MeV for GRB 160509A. We first characterize phenomenologically the cutoff and its time evolution. We then fit the data to two models where the high-energy cutoff arises from intrinsic opacity to pair production within the source (τγγ): (i) a Band spectrum with τγγ from the internal-shocks-motivated model of Granot et al. (2008) and (ii) the photospheric model of Gill & Thompson (2014). Alternative explanations for the cutoff, such as an intrinsic cutoff in the emitting electron energy distribution, appear to be less natural. Both models provide a good fit to the data with very reasonable physical parameters, providing an estimate of bulk Lorentz factors in the range Γ ∼ 100–400, on the lower end of what is generally observed in Fermi GRBs. Surprisingly, their lower cutoff energies Ec compared to other Fermi/LAT GRBs arise not only predominantly from the lower Lorentz factors, but also at a comparable level from differences in variability time, luminosity, and high-energy photon index. Finally, particularly low Ec values may prevent detection by Fermi/LAT, thus introducing a bias in the Fermi/LAT GRB sample against GRBs with low Lorentz factors or variability times. [ABSTRACT FROM AUTHOR]

Published
2018
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36. A Statistical Study to Determine the Origin of Long-duration Gamma-Ray Flares.

Author

L. M. Winter, V. Bernstein, N. Omodei, and M. Pesce-Rollins

Subjects
SOLAR flares, PARTICLE acceleration, SOFT X rays, CORONAL mass ejections, GAMMA ray spectrometer, SHOCK waves
Abstract

Two scenarios have been proposed to account for sustained ≥30 MeV gamma-ray emission in solar flares: (1) prolonged particle acceleration/trapping involving large-scale magnetic loops at the flare site, and (2) precipitation of high-energy (>300 MeV) protons accelerated at coronal/interplanetary shock waves. To determine which of these scenarios is more likely, we examine the associated soft X-ray flares, coronal mass ejections (CMEs), and solar energetic proton events for (a) the long-duration gamma-ray flares (LDGRFs) observed by the Large Area Telescope on Fermi, and (b) delayed and/or spatially extended high-energy gamma-ray flares observed by the Gamma-ray Spectrometer on the Solar Maximum Mission, the Gamma-1 telescope on the Gamma satellite, and the Energetic Gamma-Ray Experiment Telescope on the Compton Gamma-Ray Observatory. For the Fermi data set of 11 LDGRFs with >100 MeV emission lasting for ≥∼2 hr, we search for associations and reverse associations between LDGRFs, X-ray flares, CMEs, and SEPs, i.e., beginning with the gamma-ray flares and also, in turn, with X-class soft X-ray flares, fast (≥1500 km s−1) and wide CMEs, and intense (peak flux ≥2.67 × 10−3 protons cm−2 s−1 sr−1, with peak to background ratio >1.38) >300 MeV SEPs at 1 au. While LDGRFs tend to be associated with bright X-class flares, we find that only one-third of the X-class flares during the time of Fermi monitoring coincide with an LDGRF. However, nearly all fast, wide CMEs are associated with an LDGRF. These preliminary association analyses favor the proton precipitation scenario, although there is a prominent counter-example of a potentially magnetically well-connected solar eruption with >100 MeV emission for ∼10 hr for which the near-Earth >300 MeV proton intensity did not rise above background. [ABSTRACT FROM AUTHOR]

Published
2018
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37. A Luminous and Highly Variable Gamma-Ray Flare Following the 2017 Periastron of PSR B1259–63/LS 2883.

Author

T. J. Johnson, K. S. Wood, M. Kerr, R. H. D. Corbet, C. C. Cheung, P. S. Ray, and N. Omodei

Subjects
VARIABLE stars, PULSARS, BE stars, SPACE telescopes, SOLAR flares, GAMMA rays
Abstract

Three periastron passages of the PSR B1259−63/LS 2883 binary system, consisting of a 48 ms rotation-powered pulsar and a Be star, have been observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, in 2010, 2014, and 2017. During the most recent periastron passage, sustained low-level gamma-ray emission was observed over a ∼3-week-long interval immediately after periastron, which was followed by an interval of no emission. Sporadic flares were detected starting 40 days post-periastron and lasted approximately 50 days, during which the emission displayed significant spectral curvature, variability on timescales as short as 1.5 minutes, and peak flux levels well in excess of the pulsar spin-down power. By contrast, during the 2010 and 2014 periastron passages, significant gamma-ray emission was not observed with the LAT until 30 and 32 days post-periastron, respectively. The previous flares did not exhibit spectral curvature, showed no short term variability, and did not exceed the pulsar spin-down power. The high flux and short timescales observed in 2017 suggest significant beaming of the emission is required and constrain the size of the emission region. The flares occur long enough after periastron that the neutron star should already have passed through the extended disk-like outflow, thus constraining options for target material and seed photon sources for inverse Compton models. [ABSTRACT FROM AUTHOR]

Published
2018
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38. Probing the EBL Evolution at High Redshift Using GRBs Detected with the Fermi-LAT.

Author

A. Desai, M. Ajello, N. Omodei, D. H. Hartmann, A. Domínguez, V. S. Paliya, K. Helgason, J. Finke, and M. Meyer

Subjects
REDSHIFT, METAPHYSICAL cosmology, BLACK holes, PHOTONS, SPECTRUM analysis
Abstract

The extragalactic background light (EBL), from ultraviolet to infrared wavelengths, is predominantly due to emission from stars, accreting black holes and reprocessed light due to Galactic dust. The EBL can be studied through the imprint it leaves, via γ–γ absorption of high-energy photons, in the spectra of distant γ-ray sources. The EBL has been probed through the search for the attenuation it produces in the spectra of BL Lacertae (BL Lac) objects and individual γ-ray bursts (GRBs). GRBs have significant advantages over blazars for the study of the EBL especially at high redshifts. Here we analyze a combined sample of 22 GRBs, detected by the Fermi Large Area Telescope between 65 MeV and 500 GeV. We report a marginal detection (at the ∼2.8σ level) of the EBL attenuation in the stacked spectra of the source sample. This measurement represents a first constraint of the EBL at an effective redshift of ∼1.8. We combine our results with prior EBL constraints and conclude that Fermi-LAT is instrumental to constrain the UV component of the EBL. We discuss the implications on existing empirical models of EBL evolution. [ABSTRACT FROM AUTHOR]

Published
2017
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41. Discovery of Gamma Rays from the Quiescent Sun with HAWC.

Author

Albert A, Alfaro R, Alvarez C, Arteaga-Velázquez JC, Avila Rojas D, Ayala Solares HA, Babu R, Belmont-Moreno E, Brisbois C, Caballero-Mora KS, Capistrán T, Carramiñana A, Casanova S, Chaparro-Amaro O, Cotti U, Cotzomi J, Coutiño de León S, De la Fuente E, Diaz Hernandez R, Dingus BL, DuVernois MA, Durocher M, Díaz-Vélez JC, Ellsworth RW, Engel K, Espinoza C, Fan KL, Fang K, Fernández Alonso M, Fleischhack H, Fraija N, García-González JA, Garfias F, González MM, Goodman JA, Harding JP, Hernandez S, Hinton J, Huang D, Hueyotl-Zahuantitla F, Hüntemeyer P, Iriarte A, Joshi V, Kaufmann S, Lee J, Linnemann JT, Longinotti AL, Luis-Raya G, Malone K, Martinez O, Martínez-Castro J, Matthews JA, Miranda-Romagnoli P, Morales-Soto JA, Moreno E, Mostafá M, Nayerhoda A, Nellen L, Nisa MU, Noriega-Papaqui R, Olivera-Nieto L, Omodei N, Pérez Araujo Y, Pérez-Pérez EG, Rho CD, Rosa-González D, Ruiz-Velasco E, Salazar H, Salazar-Gallegos D, Sandoval A, Schneider M, Serna-Franco J, Smith AJ, Son Y, Springer RW, Tibolla O, Tollefson K, Torres I, Torres-Escobedo R, Turner R, Ureña-Mena F, Varela E, Villaseñor L, Wang X, Watson IJ, Willox E, Yun-Cárcamo S, Zhou H, de León C, Beacom JF, Linden T, Ng KCY, Peter AHG, and Zhou B

Abstract

We report the first detection of a TeV γ-ray flux from the solar disk (6.3σ), based on 6.1 years of data from the High Altitude Water Cherenkov (HAWC) observatory. The 0.5-2.6 TeV spectrum is well fit by a power law, dN/dE=A(E/1  TeV)^{-γ}, with A=(1.6±0.3)×10^{-12}  TeV^{-1} cm^{-2} s^{-1} and γ=3.62±0.14. The flux shows a strong indication of anticorrelation with solar activity. These results extend the bright, hard GeV emission from the disk observed with Fermi-LAT, seemingly due to hadronic Galactic cosmic rays showering on nuclei in the solar atmosphere. However, current theoretical models are unable to explain the details of how solar magnetic fields shape these interactions. HAWC's TeV detection thus deepens the mysteries of the solar-disk emission.

Published
2023
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42. X-ray polarization evidence for a 200-year-old flare of Sgr A .

Author

Marin F, Churazov E, Khabibullin I, Ferrazzoli R, Di Gesu L, Barnouin T, Di Marco A, Middei R, Vikhlinin A, Costa E, Soffitta P, Muleri F, Sunyaev R, Forman W, Kraft R, Bianchi S, Donnarumma I, Petrucci PO, Enoto T, Agudo I, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Cavazzuti E, Chen CT, Ciprini S, De Rosa A, Del Monte E, Di Lalla N, Doroshenko V, Dovčiak M, Ehlert SR, Evangelista Y, Fabiani S, Garcia JA, Gunji S, Hayashida K, Heyl J, Ingram A, Iwakiri W, Jorstad SG, Kaaret P, Karas V, Kitaguchi T, Kolodziejczak JJ, Krawczynski H, La Monaca F, Latronico L, Liodakis I, Maldera S, Manfreda A, Marinucci A, Marscher AP, Marshall HL, Massaro F, Matt G, Mitsuishi I, Mizuno T, Negro M, Ng CY, O'Dell SL, Omodei N, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Pilia M, Possenti A, Poutanen J, Puccetti S, Ramsey BD, Rankin J, Ratheesh A, Roberts OJ, Romani RW, Sgrò C, Slane P, Spandre G, Swartz D, Tamagawa T, Tavecchio F, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov SS, Turolla R, Vink J, Weisskopf MC, Wu K, Xie F, and Zane S

Abstract

The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A * (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei 1 . Reflection of X-rays from Sgr A * by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years 2 . The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A * are consistent with the reflection scenario 3-5 . If this interpretation is correct, the reflected continuum emission should be polarized 6 . Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of -48° ± 11°. The polarization angle is consistent with Sgr A * being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A * was briefly comparable to that of a Seyfert galaxy., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2023
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43. Vela pulsar wind nebula X-rays are polarized to near the synchrotron limit.

Author

Xie F, Di Marco A, La Monaca F, Liu K, Muleri F, Bucciantini N, Romani RW, Costa E, Rankin J, Soffitta P, Bachetti M, Di Lalla N, Fabiani S, Ferrazzoli R, Gunji S, Latronico L, Negro M, Omodei N, Pilia M, Trois A, Watanabe E, Agudo I, Antonelli LA, Baldini L, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Capitanio F, Castellano S, Cavazzuti E, Ciprini S, De Rosa A, Del Monte E, Di Gesu L, Donnarumma I, Doroshenko V, Dovčiak M, Ehlert SR, Enoto T, Evangelista Y, Garcia JA, Hayashida K, Heyl J, Iwakiri W, Jorstad SG, Karas V, Kitaguchi T, Kolodziejczak JJ, Krawczynski H, Liodakis I, Maldera S, Manfreda A, Marin F, Marinucci A, Marscher AP, Marshall HL, Massaro F, Matt G, Mitsuishi I, Mizuno T, Ng CY, O'Dell SL, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Petrucci PO, Possenti A, Poutanen J, Puccetti S, Ramsey BD, Ratheesh A, Sgró C, Slane P, Spandre G, Tamagawa T, Tavecchio F, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Tsygankov SS, Turolla R, Vink J, Weisskopf MC, Wu K, and Zane S

Abstract

Pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. The Vela pulsar wind nebula is powered by a young pulsar (B0833-45, aged 11,000 years) 1 and located inside an extended structure called Vela X, which is itself inside the supernova remnant 2 . Previous X-ray observations revealed two prominent arcs that are bisected by a jet and counter jet 3,4 . Radio maps have shown high linear polarization of 60% in the outer regions of the nebula 5 . Here we report an X-ray observation of the inner part of the nebula, where polarization can exceed 60% at the leading edge-approaching the theoretical limit of what can be produced by synchrotron emission. We infer that, in contrast with the case of the supernova remnant, the electrons in the pulsar wind nebula are accelerated with little or no turbulence in a highly uniform magnetic field., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2022
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44. Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1.

Author

Krawczynski H, Muleri F, Dovčiak M, Veledina A, Rodriguez Cavero N, Svoboda J, Ingram A, Matt G, Garcia JA, Loktev V, Negro M, Poutanen J, Kitaguchi T, Podgorný J, Rankin J, Zhang W, Berdyugin A, Berdyugina SV, Bianchi S, Blinov D, Capitanio F, Di Lalla N, Draghis P, Fabiani S, Kagitani M, Kravtsov V, Kiehlmann S, Latronico L, Lutovinov AA, Mandarakas N, Marin F, Marinucci A, Miller JM, Mizuno T, Molkov SV, Omodei N, Petrucci PO, Ratheesh A, Sakanoi T, Semena AN, Skalidis R, Soffitta P, Tennant AF, Thalhammer P, Tombesi F, Weisskopf MC, Wilms J, Zhang S, Agudo I, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Castellano S, Cavazzuti E, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Gesu L, Di Marco A, Donnarumma I, Doroshenko V, Ehlert SR, Enoto T, Evangelista Y, Ferrazzoli R, Gunji S, Hayashida K, Heyl J, Iwakiri W, Jorstad SG, Karas V, Kolodziejczak JJ, La Monaca F, Liodakis I, Maldera S, Manfreda A, Marscher AP, Marshall HL, Mitsuishi I, Ng CY, O'Dell SL, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Pilia M, Possenti A, Puccetti S, Ramsey BD, Romani RW, Sgrò C, Slane P, Spandre G, Tamagawa T, Tavecchio F, Taverna R, Tawara Y, Thomas NE, Trois A, Tsygankov S, Turolla R, Vink J, Wu K, Xie F, and Zane S

Abstract

A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a polarimetric observation of the XRB Cygnus X-1 using the Imaging X-ray Polarimetry Explorer. The electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray-emitting region. The polarization degree is 4.01 ± 0.20% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. These observations reveal that hot x-ray-emitting plasma is spatially extended in a plane perpendicular to, not parallel to, the jet axis.

Published
2022
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45. Polarized x-rays from a magnetar.

Author

Taverna R, Turolla R, Muleri F, Heyl J, Zane S, Baldini L, González-Caniulef D, Bachetti M, Rankin J, Caiazzo I, Di Lalla N, Doroshenko V, Errando M, Gau E, Kırmızıbayrak D, Krawczynski H, Negro M, Ng M, Omodei N, Possenti A, Tamagawa T, Uchiyama K, Weisskopf MC, Agudo I, Antonelli LA, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Cavazzuti E, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Gesu L, Di Marco A, Donnarumma I, Dovčiak M, Ehlert SR, Enoto T, Evangelista Y, Fabiani S, Ferrazzoli R, Garcia JA, Gunji S, Hayashida K, Iwakiri W, Jorstad SG, Karas V, Kitaguchi T, Kolodziejczak JJ, La Monaca F, Latronico L, Liodakis I, Maldera S, Manfreda A, Marin F, Marinucci A, Marscher AP, Marshall HL, Matt G, Mitsuishi I, Mizuno T, Ng SC, O'Dell SL, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Pilia M, Poutanen J, Puccetti S, Ramsey BD, Ratheesh A, Romani RW, Sgrò C, Slane P, Soffitta P, Spandre G, Tavecchio F, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov SS, Vink J, Wu K, and Xie F

Abstract

Magnetars are neutron stars with ultrastrong magnetic fields, which can be observed in x-rays. Polarization measurements could provide information on their magnetic fields and surface properties. We observed polarized x-rays from the magnetar 4U 0142+61 using the Imaging X-ray Polarimetry Explorer and found a linear polarization degree of 13.5 ± 0.8% averaged over the 2- to 8-kilo-electron volt band. The polarization changes with energy: The degree is 15.0 ± 1.0% at 2 to 4 kilo-electron volts, drops below the instrumental sensitivity ~4 to 5 kilo-electron volts, and rises to 35.2 ± 7.1% at 5.5 to 8 kilo-electron volts. The polarization angle also changes by 90° at ~4 to 5 kilo-electron volts. These results are consistent with a model in which thermal radiation from the magnetar surface is reprocessed by scattering off charged particles in the magnetosphere.

Published
2022
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46. Polarized blazar X-rays imply particle acceleration in shocks.

Author

Liodakis I, Marscher AP, Agudo I, Berdyugin AV, Bernardos MI, Bonnoli G, Borman GA, Casadio C, Casanova VC, Cavazzuti E, Rodriguez Cavero N, Di Gesu L, Di Lalla N, Donnarumma I, Ehlert SR, Errando M, Escudero J, Garcı A-Comas M, Agı S-González B, Husillos C, Jormanainen J, Jorstad SG, Kagitani M, Kopatskaya EN, Kravtsov V, Krawczynski H, Lindfors E, Larionova EG, Madejski GM, Marin F, Marchini A, Marshall HL, Morozova DA, Massaro F, Masiero JR, Mawet D, Middei R, Millar-Blanchaer MA, Myserlis I, Negro M, Nilsson K, O'Dell SL, Omodei N, Pacciani L, Paggi A, Panopoulou GV, Peirson AL, Perri M, Petrucci PO, Poutanen J, Puccetti S, Romani RW, Sakanoi T, Savchenko SS, Sota A, Tavecchio F, Tinyanont S, Vasilyev AA, Weaver ZR, Zhovtan AV, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Marco A, Doroshenko V, Dovčiak M, Enoto T, Evangelista Y, Fabiani S, Ferrazzoli R, Garcia JA, Gunji S, Hayashida K, Heyl J, Iwakiri W, Karas V, Kitaguchi T, Kolodziejczak JJ, La Monaca F, Latronico L, Maldera S, Manfreda A, Marinucci A, Matt G, Mitsuishi I, Mizuno T, Muleri F, Ng SC, Oppedisano C, Papitto A, Pavlov GG, Pesce-Rollins M, Pilia M, Possenti A, Ramsey BD, Rankin J, Ratheesh A, Sgró C, Slane P, Soffitta P, Spandre G, Tamagawa T, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov S, Turolla R, Vink J, Weisskopf MC, Wu K, Xie F, and Zane S

Abstract

Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization-the only range available until now-probe extended regions of the jet containing particles that left the acceleration site days to years earlier 1-3 , and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree Π X of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock., (© 2022. The Author(s).)

Published
2022
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47. Constraints on Lorentz Invariance Violation from HAWC Observations of Gamma Rays above 100 TeV.

Author

Albert A, Alfaro R, Alvarez C, Angeles Camacho JR, Arteaga-Velázquez JC, Arunbabu KP, Avila Rojas D, Ayala Solares HA, Baghmanyan V, Belmont-Moreno E, BenZvi SY, Brisbois C, Caballero-Mora KS, Capistrán T, Carramiñana A, Casanova S, Cotti U, Cotzomi J, Coutiño de León S, De la Fuente E, de León C, Dingus BL, DuVernois MA, Díaz-Vélez JC, Ellsworth RW, Engel K, Espinoza C, Fleischhack H, Fraija N, Galván-Gámez A, Garcia D, García-González JA, Garfias F, González MM, Goodman JA, Harding JP, Hernandez S, Hona B, Huang D, Hueyotl-Zahuantitla F, Hüntemeyer P, Iriarte A, Joshi V, Lara A, Lee WH, León Vargas H, Linnemann JT, Longinotti AL, Luis-Raya G, Lundeen J, López-Coto R, Malone K, Marinelli SS, Martinez-Castellanos I, Martínez-Castro J, Martínez-Huerta H, Matthews JA, Miranda-Romagnoli P, Morales-Soto JA, Moreno E, Nayerhoda A, Nellen L, Newbold M, Nisa MU, Noriega-Papaqui R, Omodei N, Peisker A, Pérez-Pérez EG, Rho CD, Rivière C, Rosa-González D, Rosenberg M, Ruiz-Velasco E, Salazar H, Salesa Greus F, Sandoval A, Schneider M, Schoorlemmer H, Sinnis G, Smith AJ, Springer RW, Surajbali P, Tabachnick E, Tanner M, Tibolla O, Tollefson K, Torres I, Torres-Escobedo R, Weisgarber T, Yodh G, Zepeda A, and Zhou H

Abstract

Because of the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV). Superluminal LIV enables the decay of photons at high energy. The high altitude water Cherenkov (HAWC) observatory is among the most sensitive gamma-ray instruments currently operating above 10 TeV. HAWC finds evidence of 100 TeV photon emission from at least four astrophysical sources. These observations exclude, for the strongest of the limits set, the LIV energy scale to 2.2×10^{31}  eV, over 1800 times the Planck energy and an improvement of 1 to 2 orders of magnitude over previous limits.

Published
2020
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48. Observation of inverse Compton emission from a long γ-ray burst.

Author

Veres P, Bhat PN, Briggs MS, Cleveland WH, Hamburg R, Hui CM, Mailyan B, Preece RD, Roberts OJ, von Kienlin A, Wilson-Hodge CA, Kocevski D, Arimoto M, Tak D, Asano K, Axelsson M, Barbiellini G, Bissaldi E, Dirirsa FF, Gill R, Granot J, McEnery J, Omodei N, Razzaque S, Piron F, Racusin JL, Thompson DJ, Campana S, Bernardini MG, Kuin NPM, Siegel MH, Cenko SB, O'Brien P, Capalbi M, Daì A, De Pasquale M, Gropp J, Klingler N, Osborne JP, Perri M, Starling RLC, Tagliaferri G, Tohuvavohu A, Ursi A, Tavani M, Cardillo M, Casentini C, Piano G, Evangelista Y, Verrecchia F, Pittori C, Lucarelli F, Bulgarelli A, Parmiggiani N, Anderson GE, Anderson JP, Bernardi G, Bolmer J, Caballero-García MD, Carrasco IM, Castellón A, Segura NC, Castro-Tirado AJ, Cherukuri SV, Cockeram AM, D'Avanzo P, Di Dato A, Diretse R, Fender RP, Fernández-García E, Fynbo JPU, Fruchter AS, Greiner J, Gromadzki M, Heintz KE, Heywood I, van der Horst AJ, Hu YD, Inserra C, Izzo L, Jaiswal V, Jakobsson P, Japelj J, Kankare E, Kann DA, Kouveliotou C, Klose S, Levan AJ, Li XY, Lotti S, Maguire K, Malesani DB, Manulis I, Marongiu M, Martin S, Melandri A, Michałowski MJ, Miller-Jones JCA, Misra K, Moin A, Mooley KP, Nasri S, Nicholl M, Noschese A, Novara G, Pandey SB, Peretti E, Del Pulgar CJP, Pérez-Torres MA, Perley DA, Piro L, Ragosta F, Resmi L, Ricci R, Rossi A, Sánchez-Ramírez R, Selsing J, Schulze S, Smartt SJ, Smith IA, Sokolov VV, Stevens J, Tanvir NR, Thöne CC, Tiengo A, Tremou E, Troja E, de Ugarte Postigo A, Valeev AF, Vergani SD, Wieringa M, Woudt PA, Xu D, Yaron O, and Young DR

Abstract

Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission 1,2 . Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands 1-6 . The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock 7-9 . Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C 10,11 . Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10 -6 to 10 12 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.

Published
2019
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49. Investigating the Nature of Late-Time High-Energy GRB Emission Through Joint Fermi /Swift Observations.

Author

Ajello M, Baldini L, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Cameron RA, Caputo R, Caraveo PA, Chiaro G, Ciprini S, Cohen-Tanugi J, Costantin D, D'Ammando F, DE Palma F, DI Lalla N, DI Mauro M, DI Venere L, Domínguez A, Favuzzi C, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Guiriec S, Holt C, Horan D, Jóhannesson G, Kocevski D, Kuss M, LA Mura G, Larsson S, Li J, Longo F, Loparco F, Lubrano P, Magill JD, Maldera S, Manfreda A, Mazziotta MN, Michelson PF, Mizuno T, Monzani ME, Morselli A, Negro M, Nuss E, Omodei N, Orienti M, Orlando E, Paliya VS, Perkins JS, Persic M, Pesce-Rollins M, Piron F, Principe G, Racusin JL, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Tak D, Thayer JB, Torres DF, Tosti G, Valverde J, Vogel M, and Wood K

Abstract

We use joint observations by the Neil Gehrels Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveal that LAT non-detections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the non-detected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1-100 GeV energy range considered for this analysis.

Published
2018
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50. Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar.

Author

Clark CJ, Pletsch HJ, Wu J, Guillemot L, Kerr M, Johnson TJ, Camilo F, Salvetti D, Allen B, Anderson D, Aulbert C, Beer C, Bock O, Cuéllar A, Eggenstein HB, Fehrmann H, Kramer M, Kwang SA, Machenschalk B, Nieder L, Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buehler R, Burnett TH, Buson S, Cameron RA, Caputo R, Caraveo PA, Cavazzuti E, Cecchi C, Charles E, Chekhtman A, Ciprini S, Cominsky LR, Costantin D, Cutini S, D'Ammando F, De Luca A, Desiante R, Di Venere L, Di Mauro M, Di Lalla N, Digel SW, Favuzzi C, Ferrara EC, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Gomez-Vargas GA, Green D, Grenier IA, Guiriec S, Harding AK, Hewitt JW, Horan D, Jóhannesson G, Kensei S, Kuss M, La Mura G, Larsson S, Latronico L, Li J, Longo F, Loparco F, Lovellette MN, Lubrano P, Magill JD, Maldera S, Manfreda A, Mazziotta MN, McEnery JE, Michelson PF, Mirabal N, Mitthumsiri W, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Nuss E, Ohsugi T, Omodei N, Orienti M, Orlando E, Palatiello M, Paliya VS, de Palma F, Paneque D, Perkins JS, Persic M, Pesce-Rollins M, Porter TA, Principe G, Rainò S, Rando R, Ray PS, Razzano M, Reimer A, Reimer O, Romani RW, Saz Parkinson PM, Sgrò C, Siskind EJ, Smith DA, Spada F, Spandre G, Spinelli P, Thayer JB, Thompson DJ, Torres DF, Troja E, Vianello G, Wood K, and Wood M

Abstract

Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.

Published
2018
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