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1. Searches for Neutrinos in the Direction of Radio-bright Blazars with the ANTARES Telescope

Author

A. Albert, S. Alves, M. André, M. Ardid, S. Ardid, J.-J. Aubert, J. Aublin, B. Baret, S. Basa, Y. Becherini, 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, S. Campion, A. Capone, L. Caramete, F. Carenini, J. Carr, V. Carretero, S. Celli, L. Cerisy, M. Chabab, R. Cherkaoui El Moursli, T. Chiarusi, M. Circella, J. A. B. Coelho, A. Coleiro, R. Coniglione, P. Coyle, A. Creusot, A. S. M. Cruz, A. F. Díaz, B. De Martino, C. Distefano, I. Di Palma, A. Domi, C. Donzaud, D. Dornic, D. Drouhin, T. Eberl, T. van Eeden, D. van Eijk, S. El Hedri, N. El Khayati, A. Enzenhöfer, P. Fermani, G. Ferrara, F. Filippini, L. Fusco, S. Gagliardini, J. García, C. Gatius Oliver, P. Gay, N. Geißelbrecht, H. Glotin, R. Gozzini, R. Gracia Ruiz, K. Graf, C. Guidi, L. Haegel, 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, Y. A Kovalev, Y. Y Kovalev, I. Kreykenbohm, V. Kulikovskiy, R. Lahmann, M. Lamoureux, A. Lazo, 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, P. Migliozzi, A. Moussa, R. Muller, S. Navas, E. Nezri, B. Ó Fearraigh, E. Oukacha, A. Păun, G. E. Păvălaş, S. Peña-Martínez, M. Perrin-Terrin, V. Pestel, P. Piattelli, A. Plavin, C. Poirè, V. Popa, T. Pradier, A. Pushkarev, N. Randazzo, D. Real, S. Reck, G. Riccobene, A. Romanov, A. Sánchez-Losa, A. Saina, F. Salesa Greus, 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, S. Troitsky, B. Vallage, G. Vannoye, V. Van Elewyck, S. Viola, D. Vivolo, J. Wilms, S. Zavatarelli, A. Zegarelli, J. D. Zornoza, J. Zúñiga, ANTARES Collaboration, T. Hovatta, S. Kiehlmann, I. Liodakis, V. Pavlidou, A. C. S Readhead, and OVRO Collaboration

Subjects
Neutrino astronomy, Blazars, Astrophysics, QB460-466
Abstract

Active galaxies, especially blazars, are among the most promising extragalactic candidates for high-energy neutrino sources. To date, ANTARES searches included these objects and used GeV–TeV γ -ray flux to select blazars. Here, a statistically complete blazar sample selected by their bright radio emission is used as the target for searches of origins of neutrinos collected by the ANTARES neutrino telescope over 13 yr of operation. The hypothesis of a neutrino–blazar directional correlation is tested by pair counting and a complementary likelihood-based approach. The resulting posttrial p -value is 3.0% (2.2 σ in the two-sided convention). Additionally, a time-dependent analysis is performed to search for temporal clustering of neutrino candidates as a means of detecting neutrino flares in blazars. None of the investigated sources alone reaches a significant flare detection level. However, the presence of 18 sources with a pretrial significance above 3 σ indicates a p = 1.4% (2.5 σ in the two-sided convention) detection of a time-variable neutrino flux. An a posteriori investigation reveals an intriguing temporal coincidence of neutrino, radio, and γ -ray flares of the J0242+1101 blazar at a p = 0.5% (2.9 σ in the two-sided convention) level. Altogether, the results presented here suggest a possible connection of neutrino candidates detected by the ANTARES telescope with radio-bright blazars.

Published
2024
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2. Compact Symmetric Objects. III. Evolution of the High-luminosity Branch and a Possible Connection with Tidal Disruption Events

Author

A. C. S Readhead, V. Ravi, R. D. Blandford, A. G. Sullivan, J. Somalwar, M. C. Begelman, M. Birkinshaw, I. Liodakis, M. L. Lister, T. J. Pearson, G. B. Taylor, P. N. Wilkinson, N. Globus, S. Kiehlmann, C. R. Lawrence, D. Murphy, S. O’Neill, V. Pavlidou, E. Sheldahl, A. Siemiginowska, and K. Tassis

Subjects
Active galactic nuclei, Active galaxies, Relativistic jets, Tidal disruption, Astrophysics, QB460-466
Abstract

We use a sample of 54 compact symmetric objects (CSOs) to confirm that there are two unrelated CSO classes: an edge-dimmed, low-luminosity class (CSO 1), and an edge-brightened, high-luminosity class (CSO 2). Using blind tests, we show that CSO 2s consist of three subclasses: CSO 2.0, having prominent hot spots at the leading edges of narrow jets and/or narrow lobes; CSO 2.2, without prominent hot spots and with broad jets and/or lobes; and CSO 2.1, which exhibit mixed properties. Most CSO 2s do not evolve into larger jetted active galactic nuclei (AGN), but spend their whole life cycle as CSOs of size ≲500 pc and age ≲5000 yr. The minimum energies needed to produce the radio luminosity and structure in CSO 2s range from ∼10 ^−4 M _⊙ c ^2 to ∼7 M _⊙ c ^2 . We show that the transient nature of most CSO 2s, and their birth rate, can be explained through ignition in the tidal disruption events of stars. We also consider possibilities of tapping the spin energy of the supermassive black hole, and tapping the energy of the accretion disk. Our results demonstrate that CSOs constitute a large family of AGN in which we have thus far studied only the brightest. More comprehensive CSO studies, with higher sensitivity, resolution, and dynamic range, will revolutionize our understanding of AGN and the central engines that power them.

Published
2024
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3. Compact Symmetric Objects. I. Toward a Comprehensive Bona Fide Catalog

Author

S. Kiehlmann, M. L. Lister, A. C. S Readhead, I. Liodakis, Sandra O’Neill, T. J. Pearson, Evan Sheldahl, Aneta Siemiginowska, K. Tassis, G. B. Taylor, and P. N. Wilkinson

Subjects
Active galactic nuclei, Relativistic jets, Active galaxies, Astrophysics, QB460-466
Abstract

Compact symmetric objects (CSOs) are jetted active galactic nuclei (AGN) with overall projected size 700 mJy is between (6.8 ± 1.6)% and (8.5 ± 1.8)%.

Published
2024
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4. Compact Symmetric Objects. II. Confirmation of a Distinct Population of High-luminosity Jetted Active Galaxies

Author

S. Kiehlmann, A. C. S. Readhead, S. O’Neill, P. N. Wilkinson, M. L. Lister, I. Liodakis, S. Bruzewski, V. Pavlidou, T. J. Pearson, E. Sheldahl, A. Siemiginowska, K. Tassis, and G. B. Taylor

Subjects
Active galactic nuclei, Active galaxies, Relativistic jets, Astrophysics, QB460-466
Abstract

Compact symmetric objects (CSOs) are compact (99%) of CSO 2s do not evolve into larger-scale radio sources. These CSO 2s belong to a distinct population of jetted AGN, which should be characterized as “short-lived,” as opposed to “young,” compared to the classes of larger jetted AGN. We show that there is a sharp upper cutoff in the CSO 2 size distribution at ≈500 pc. The distinct differences between most CSO 2s and other jetted AGN provides a crucial new time domain window on the formation and evolution of relativistic jets in AGN and the supermassive black holes that drive them.

Published
2024
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5. 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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6. 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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7. 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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9. RoboPol: a four-channel optical imaging polarimeter

Author

A N Ramaprakash, C V Rajarshi, H K Das, P Khodade, D Modi, G Panopoulou, S Maharana, D Blinov, E Angelakis, C Casadio, L Fuhrmann, T Hovatta, S Kiehlmann, O G King, N Kylafis, A Kougentakis, A Kus, A Mahabal, A Marecki, I Myserlis, G Paterakis, E Paleologou, I Liodakis, I Papadakis, I Papamastorakis, V Pavlidou, E Pazderski, T J Pearson, A C S Readhead, P Reig, A Słowikowska, K Tassis, and J A Zensus

Published
2019
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10. New Tests of Milli-lensing in the Blazar PKS 1413 + 135

Author

A. L. Peirson, I. Liodakis, A. C. S Readhead, M. L. Lister, E. S. Perlman, M. F. Aller, R. D. Blandford, K. J. B. Grainge, D. A. Green, M. A. Gurwell, M. W. Hodges, T. Hovatta, S. Kiehlmann, A. Lähteenmäki, W. Max-Moerbeck, T. Mcaloone, S. O’Neill, V. Pavlidou, T. J. Pearson, V. Ravi, R. A. Reeves, P. F. Scott, G. B. Taylor, D. J. Titterington, M. Tornikoski, H. K. Vedantham, P. N. Wilkinson, D. T. Williams, and J. A. Zensus

Published
2022
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11. 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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12. 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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13. 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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15. 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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16. 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

17. 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
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18. 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

19. Unresolved Gamma-Ray Sky through its Angular Power Spectrum

Author

M. Ackermann, M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, 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, D. Costantin, A. Cuoco, S. Cutini, F. D’Ammando, P. de la Torre Luque, F. de Palma, A. Desai, S. W. Digel, N. Di Lalla, M. Di Mauro, L. Di Venere, F. Fana Dirirsa, 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, L. Guillemot, S. Guiriec, D. Horan, G. Jóhannesson, M. Kuss, S. Larsson, L. Latronico, J. Li, I. Liodakis, F. Longo, F. Loparco, P. Lubrano, J. D. Magill, S. Maldera, D. Malyshev, A. Manfreda, M. N. Mazziotta, I. Mereu, P. F. Michelson, W. Mitthumsiri, T. Mizuno, M. E. Monzani, A. Morselli, I. V. Moskalenko, M. Negro, E. Nuss, M. Orienti, E. Orlando, M. Palatiello, V. S. Paliya, D. Paneque, M. Persic, M. Pesce-Rollins, V. Petrosian, F. Piron, T. A. Porter, G. Principe, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, D. Serini, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, D. J. Suson, H. Tajima, M. Takahashi, J. B. Thayer, L. Tibaldo, D. F. Torres, E. Troja, T. M. Venters, G. Vianello, K. Wood, M. Yassine, G. Zaharijas, S. Ammazzalorso, N. Fornengo, and M. Regis

Published
2018
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20. The Unanticipated Phenomenology of the Blazar PKS 2131-021: A Unique Supermassive Black Hole Binary Candidate

Author

S. O’Neill, S. Kiehlmann, A. C. S. Readhead, M. F. Aller, R. D. Blandford, I. Liodakis, M. L. Lister, P. Mróz, C. P. O’Dea, T. J. Pearson, V. Ravi, M. Vallisneri, K. A. Cleary, M. J. Graham, K. J. B. Grainge, M. W. Hodges, T. Hovatta, A. Lähteenmäki, J. W. Lamb, T. J. W. Lazio, W. Max-Moerbeck, V. Pavlidou, T. A. Prince, R. A. Reeves, M. Tornikoski, P. Vergara de la Parra, J. A. Zensus, California Institute of Technology, University of Crete, University of Michigan, Ann Arbor, Stanford University, University of Turku, Purdue University, University of Warsaw, University of Manitoba, Jet Propulsion Laboratory, University of Manchester, Metsähovi Radio Observatory, Department of Electronics and Nanoengineering, Universidad de Chile, Universidad de Concepción, Max Planck Institute for Radio Astronomy, Aalto-yliopisto, and Aalto University

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

Most large galaxies host supermassive black holes in their nuclei and are subject to mergers, which can produce a supermassive black hole binary (SMBHB), and hence periodic signatures due to orbital motion. We report unique periodic radio flux density variations in the blazar PKS~2131$-$021, which strongly suggest an SMBHB with an orbital separation of $\sim 0.001-0.01$ pc. Our 45.1-year radio light curve shows two epochs of strong sinusoidal variation with the same period and phase to within $, Comment: 24 pages, 13 figure, 3 Tables, accepted for publication in APJL

Published
2022

21. Cherenkov Telescope Array : the World’s largest VHE gamma-ray observatory

Author

Roberta Zanin, H. Abdalla, H. Abe, S. Abe, A. Abusleme, F. Acero, A. Acharyya, V. Acin Portella, K. Ackley, R. Adam, C. Adams, S.S. Adhikari, I. Aguado Ruesga, I. Agudo, R. Aguilera, A. Aguirre Santaella, F. Aharonian, A. Alberdi, R. Alfaro, J. Alfaro, C. Alispach, R. Aloisio, R. Alves Batista, J.P. Amans, L. Amati, E. Amato, L. Ambrogi, G. Ambrosi, M. Ambrosio, R. Ammendola, J. Anderson, M. Anduze, E.O. Anguner, L.A. Antonelli, V. Antonuccio, P. Antoranz, R. Anutarawiramkul, J. Aragunde Gutierrez, C. Aramo, A. Araudo, M. Araya, A. Arbet Engels, C. Arcaro, V. Arendt, C. Armand, T. Armstrong, F. Arqueros, L. Arrabito, B. Arsioli, M. Artero, K. Asano, Y. Ascasibar, J. Aschersleben, M. Ashley, P. Attina, P. Aubert, C. B. Singh, D. Baack, A. Babic, M. Backes, V. Baena, S. Bajtlik, A. Baktash, C. Balazs, M. Balbo, O. Ballester, J. Ballet, B. Balmaverde, A. Bamba, R. Bandiera, A. Baquero Larriva, P. Barai, C. Barbier, V. Barbosa Martins, M. Barcelo, M. Barkov, M. Barnard, L. Baroncelli, U. Barres de Almeida, J.A. Barrio, D. Bastieri, P.I. Batista, I. Batkovic, C. Bauer, R. Bautista González, J. Baxter, U. Becciani, J. Becerra González, Y. Becherini, G. Beck, J. Becker Tjus, W. Bednarek, A. Belfiore, L. Bellizzi, R. Belmont, W. Benbow, D. Berge, E. Bernardini, M.I. Bernardos, K. Bernlöhr, A. Berti, M. Berton, B. Bertucci, V. Beshley, N. Bhatt, S. Bhattacharyya, W. Bhattacharyya, B. Y. Bi, G. Bicknell, N. Biederbeck, C. Bigongiari, A. Biland, R. Bird, E. Bissaldi, J. Biteau, M. Bitossi, O. Blanch, M. Blank, J. Blazek, J. Bobin, C. Boccato, F. Bocchino, C. Boehm, M. Bohacova, C. Boisson, J. Boix, J.P. Bolle, J. Bolmont, G. Bonanno, C. Bonavolontà, L. Bonneau Arbeletche, G. Bonnoli, P. Bordas, J. Borkowski, R. Bose, D. Bose, Z. Bosnjak, E. Bottacini, Markus Böttcher, M.T. Botticella, C. Boutonnet, F. Bouyjou, V. Bozhilov, E. Bozzo, L. Brahimi, C. Braiding, S. Brau Nogue, S. Breen, J. Bregeon, M. Breuhaus, A. Brill, W. Brisken, E. Brocato, A.M. Brown, K. Brügge, P. Brun, F. Brun, L. Brunetti, G. Brunetti, P. Bruno, A. Bruno, A. Bruzzese, N. Bucciantini, J. H. Buckley, R. Bühler, A. Bulgarelli, T. Bulik, M. Bünning, M. Bunse, M. Burton, A. Burtovoi, M. Buscemi, S. Buschjager, G. Busetto, J. Buss, K. Byrum, A. Caccianiga, F. Cadoux, A. Calanducci, C. Calderon, J. Calvo Tovar, R. A. Cameron, P. Campana, R. Canestrari, F. Cangemi, B. Cantlay, M. Capalbi, M. Capasso, M. Cappi, A. Caproni, R. Capuzzo Dolcetta, P. Caraveo, V. Cárdenas, L. Cardiel, M. Cardillo, C. Carlile, S. Caroff, R. Carosi, A. Carosi, E. Carquin, M. Carrere, J.M. Casandjian, S. Casanova, F. Cassol, F. Catalani, O. Catalano, D. Cauz, A. Ceccanti, C. Celestino Silva, K. Cerny, M. Cerruti, E. Chabanne, P. Chadwick, Y. Chai, P. Chambery, C. Champion, S. Chaty, A. Chen, K. Cheng, M. Chernyakova, G. Chiaro, A. Chiavassa, M. Chikawa, V.R. Chitnis, J. Chudoba, L. Chytka, S. Cikota, A. Circiello, P. Clark, M. Colak, E. Colombo, S. Colonges, A. Comastri, A. Compagnino, V. Conforti, E. Congiu, R. Coniglione, J. Conrad, F. Conte, J.L. Contreras, P. Coppi, R. Cornat, J. Coronado Blazquez, J. Cortina, A. Costa, H. Costantini, G. Cotter, B. Courty, S. Covino, S. Crestan, P. Cristofari, R. Crocker, J. Croston, K. Cubuk, O. Cuevas, X. Cui, G. Cusumano, S. Cutini, G. D'Amico, F. D'Ammando, P. D'Avanzo, P. Da Vela, M. Dadina, S. Dai, M. Dalchenko, M. Dall'Ora, M.K. Daniel, J. Dauguet, I. Davids, J. Davies, B. Dawson, A. De Angelis, A.E. de Araujo Carvalho, M. de Bony de Lavergne, G. De Cesare, F. de Frondat, I. de la Calle, E. de Gouveia Dal Pino, B. De Lotto, A. De Luca, D. De Martino, M. de Naurois, E. de Ona Wilhelmi, F. De Palma Persio, N. De Simone, V. de Souza Valle, E. Delagnes, G. Deleglise Reznicek, C. Delgado, A.G. Delgado Giler, J. Delgado Mengual Valle, Domenico Della Volpe, D. Depaoli, J. Devin, T. Di Girolamo, C. Di Giulio Pierro, L. Di Venere, C. Díaz, C. Dib, S. Diebold, S. Digel, A. Djannati Atai, J. Djuvsland, A. Dmytriiev, K. Docher, A. Domínguez, D. Dominis Prester, A. Donini, D. Dorner, M. Doro, Rita Cassia dos Anjos, J.L. Dournaux, T. Downes, G. Drake, H. Drass, D. Dravins, C. Duangchan, A. Duara, G. Dubus, L. Ducci, C. Duffy, D. Dumora, K. Dundas Mora, A. Durkalec, V.V. Dwarkadas, J. Ebr, C. Eckner, J. Eder, E. Edy, K. Egberts, S. Einecke, C. Eleftheriadis, D. Elsässer, G. Emery, D. Emmanoulopoulos, J.P. Ernenwein, M. Errando, P. Escarate, J. Escudero, C. Espinoza, S. Ettori, A. Eungwanichayapant, P. Evans, C. Evoli, M. Fairbairn, D. Falceta Goncalves, A. Falcone, V. Fallah Ramazanı, R. Falomo, K. Farakos, G. Fasola, A. Fattorini, Y. Favre, R. Fedora, E. Fedorova, K. Feijen, Q. Feng, G. Ferrand, G. Ferrara, O. Ferreira, M. Fesquet, E. Fiandrini, A. Fiasson, M. Filipovic, D. Fink, J.P. Finley, V. Fioretti, D.F.G. Fiorillo, M. Fiorini, S. Flis, H. Flores, L. Foffano, C. Fohr, M.V. Fonseca, L. Font, G. Fontaine, O. Fornieri, P. Fortin, L. Fortson, N. Fouque, B. Fraga, A. Franceschini, F.J. Franco, L. Freixas Coromina, L. Fresnillo, D. Fugazza, Y. Fujita, S. Fukami, Y. Fukazawa, D. Fulla, S. Funk, A. Furniss, S. Gabici, D. Gaggero, G. Galanti, P. Galdemard, Y. A. Gallant, D. Galloway, S. Gallozzi, V. Gammaldi, R. Garcia, L. E. García-Muñoz, E. Garcia Lopez, F. Gargano, C. Gargano, S. Garozzo, D. Gascon, T. Gasparetto, D. Gasparrini, H. Gasparyan, M. Gaug, N. Geffroy, A. Gent, S. Germani, A. Ghalumyan, A. Ghedina, G. Ghirlanda, F. Gianotti, S. Giarrusso, M. Giarrusso, G. Giavitto, B. Giebels, N. Giglietto, V. Gika, F. Gillardo, R. Gimenes, F. Giordano, E. Giro, M. Giroletti, Andrea Giuliani, M. Gjaja, J.F. Glicenstein, P. Gliwny, H. Goksu, P. Goldoni, J.L. Gomez, M.M. Gonzalez, Juan Manuel Gonzalez, K.S. Gothe, D. Gotz Coelho, T. Grabarczyk, R. Graciani, P. Grandi, G. Grasseau, D. Grasso, D. Green, J. Green, T. Greenshaw, P. Grespan, A. Grillo, M.H. Grondin, J. Grube, V. Guarino, B. Guest, O. Gueta, M. Günduz, S. Gunji, G. Gyuk, J. Hackfeld, D. Hadasch, L. Hagge, A. Hahn, J.E. Hajlaoui, A. Halim, P. Hamal, W. Hanlon, Y. Harada, M.J. Hardcastle, M. Harvey Collado, T. Haubold, A. Haupt, M. Havelka, K. Hayashi, M. Hayashida, H. He, L. Heckmann, M. Heller, F. Henault, Gilles Henri, G. Hermann, S. Hernández Cadena, J. Herrera Llorente, O. Hervet, J. Hinton, A. Hiramatsu, K. Hirotani, B. Hnatyk, R. Hnatyk, J.K. Hoang, D. H.H. Hoffmann, C. Hoischen, J. Holder, M. Holler, B. Hona, D. Horan, Dieter Horns, P. Horvath, J. Houles, M. Hrabovsky, D. Hrupec, Y. Huang, J.‑M. Huet, G. Hughes, G. Hull, T.B. Humensky, M. Hütten, M. Iarlori, J.M. Illa, R. Imazawa, T. Inada, F. Incardona, A. Ingallinera, S. Inoue, T. Inoue, Y. Inoue, F. Iocco, K. Ioka, M. Ionica, S. Iovenitti, A. Iriarte, K. Ishio, W. Ishizaki, Y. Iwamura, J. Jacquemier, M. Jacquemont, M. Jamrozy, P. Janecek, F. Jankowsky, A. JardinBlicq, C. Jarnot, P. Jean Martínez, L. Jocou, N. Jordana, M. Josselin, I. JungRichardt, F.J.P.A. Junqueira, C. Juramy Gilles, P. Kaaret, L.H.S. Kadowaki, M. Kagaya, R. Kankanyan, D. Kantzas, V. Karas, A. Karastergiou, S. Karkar, J. Kasperek, H. Katagiri, J. Kataoka, K. Katarzynski, S. Katsuda, N. Kawanaka, D. Kazanas, D. Kerszberg, B. Khélifi, M.C. Kherlakian, T.P. Kian, D.B. Kieda, T. Kihm, S. Kim, S. Kisaka, R. Kissmann, R. Kleijwegt, G. Kluge, W. Kluźniak, J. Knapp, A. Kobakhidze, Y. Kobayashi, B. Koch, J. Kocot, K. Kohri, N. Komin, A. Kong, K. Kosack, F. Krack, M. Krause, F. Krennrich, H. Kubo, V. N. Kudryavtsev, S. Kunwar, J. Kushida, P. Kushwaha, Barbera Parola, G. La Rosa, R. Lahmann, A. Lamastra, M. Landoni, D. Landriu, R.G. Lang, J. Lapington, P. Laporte, P. Lason, J. Lasuik, J. Lazendic Galloway, T. Le Flour, P. Le Sidaner, S. Leach, S.H. Lee, W.H. Lee, S. Lee Oliveira, A. Lemiere, M. Lemoine Goumard, J.P. Lenain, F. Leone, V. Leray, G. Leto, F. Leuschner, R. Lindemann, E. Lindfors, L. Linhoff, I. Liodakis, A. Lipniacka, M. Lobo, Thomas Lohse, S. Lombardi, A. Lopez, M. Lopez, R. Lopez Coto, F. Louis, M. Louys, F. Lucarelli, H. Ludwig Boudi, P.L. Luque Escamilla, M.C. Maccarone, E. Mach, A.J. Maciejewski, J. Mackey, P. Maeght, C. Maggio, G. Maier, P. Majumdar, M. Makariev, M. Mallamaci, R. Malta Nunes de Almeida, D. Malyshev, D. Mandat, G. Maneva, M. Manganaro, P. Manigot, K. Mannheim, N. Maragos, D. Marano, M. Marconi, A. Marcowith, M. Marculewicz, B. Marcun, J. Marin, N. Marinello, P. Marinos, S. Markoff, P. Marquez, G. Marsella, J. M. Martin, P. G. Martin, M. Martinez, G. Martinez, O. Martinez, H. Martinez Huerta, C. Marty, R. Marx, N. Masetti, P. Massimino, H. Matsumoto, N. Matthews, G. Maurin, W. Max Moerbeck, N. Maxted, M.N. Mazziotta, S.M. Mazzola, J.D. Mbarubucyeye, L. Mc Comb, I. McHardy, S. McKeague, S. McMuldroch, E. Medina, D. Medina Miranda, A. Melandri, C. Melioli, D. Melkumyan, S. Menchiari, S. Mereghetti, G. Merino Arevalo, E. Mestre, J.L. Meunier, T. Meures, S. Micanovic, M. Miceli, M. Michailidis, J. Michalowski, T. Miener, I. Mievre, J. D. Miller, T. Mineo, M. Minev, J.M. Miranda, A. Mitchell, T. Mizuno, B. A. Mode, R. Moderski, L. Mohrmann, E. Molinari, T. Montaruli, I. Monteiro, C. Moore, A. Moralejo, D. Morcuende Parrilla, E. Moretti, K. Mori, P. Moriarty, K. Morik, P. Morris, A. Morselli, K. Mosshammer, R. Mukherjee, J. Muller, C. Mundell, J. Mundet, T. Murach, A. Muraczewski, H. Muraishi, I. Musella, A. Musumarra, A. Nagai, S. Nagataki, T. Naito, T. Nakamori, K. Nakashima, K. Nakayama, N. Nakhjiri, G. Naletto, D. Naumann, L. Nava, M.A. Nawaz, H. Ndiyavala, D. Neise, L. Nellen, R. Nemmen, N. Neyroud, K. Ngernphat, T. Nguyen Trung, L. Nicastro, L. Nickel, J. Niemiec, D. Nieto, C. Nigro, M. Nikołajuk, D. Ninci, K. Noda, Y. Nogami, S. Nolan, R. P. Norris, D. Nosek, M. Nöthe, V. Novotny, S. Nozaki, F. Nunio, P. O'Brien, K. Obara, Y. Ohira, M. Ohishi, S. Ohm, T. Oka, N. Okazaki, A. Okumura, C. Oliver, G. Olivera, B. Olmi, M. Orienti, R. Orito, M. Orlandini, E. Orlando, J.P. Osborne, M. Ostrowski, N. Otte, E. Ovcharov, E. Owen, I. Oya, A. Ozieblo, M. Padovani, A. Pagliaro, A. Paizis, M. Palatiello, M. Palatka, E. Palazzi, J.‑L. Panazol, D. Paneque, S. Panny, Francesca Romana Pantaleo, M. Panter, M. Paolillo, A. Papitto, A. Paravac, J.M. Paredes, G. Pareschi, N. Parmiggiani, R.D. Parsons, P. Paśko, S. R. Patel, B. Patricelli, L. Pavletic, S. Pavy, A. Peer, M. Pecimotika, M.G. Pellegriti, P. Peñil Del Campo, A. Pepato, S. Perard, C. Perennes, M. Peresano, A. Perez Aguilera, J. Perez Romero, M.A. Perez Torres, M. Persic, P. O. Petrucci, O. Petruk, B. Peyaud, K. Pfrang, E. Pian, P. Piatteli, E. Pietropaolo, R. Pillera, D. Pimentel, F. Pintore, C. Pio Garcia, G. Pirola, F. Piron, S. Pita, M. Pohl, V. Poireau, A. Pollo, M. Polo, C. Pongkitivanichkul, J. Porthault, J. Powell, D. Pozo, R.R. Prado, E. Prandini, J. Prast, K. Pressard, G. Principe, N. Produit, D. Prokhorov, H. Prokoph, H. Przybilski, E. Pueschel, G. Pühlhofer, I. Puljak, M.L. Pumo, M. Punch, F. Queiroz, J. Quinn, A. Quirrenbach, P.J. Rajda, R. Rando, S. Razzaque, S. Recchia, P. Reichherzer, O. Reimer, A. Reisenegger, Q. Remy, M. Renaud, T. Reposeur, B. Reville, J.M. Reymond, J. Reynolds, D. Ribeiro, M. Ribo, G. Richards, J. Rico, F. Rieger, L. Riitano, M. Riquelme, D. Riquelme, S. Rivoire, V. Rizi, E. Roache, M. Roche, J. Rodriguez, G. Rodriguez Fernandez, J.C. Rodriguez Ramirez, J.J. Rodriguez Vazquez, G. Rojas, P. Romano, G. Romeo Lobato, C. Romoli, M. Roncadelli, J. Rosado, A. Rosales de Leon, G. Rowell, A. Rugliancich, J.E. Ruiz del Mazo, C. Rulten, C. Russell, F. Russo Hatlen, S. Safi Harb, L. Saha, V. Sahakian, S. Sailer, T. Saito, N. Sakaki, S. Sakurai, G. Salina, H. Salzmann, D. Sanchez, H. Sandaker, A. Sandoval, P. Sangiorgi, M. Sanguillon, H. Sano, M. Santander, A. Santangelo, R. Santos Lima, A. Sanuy, L. Sapozhnikov, T. Saric, S. Sarkar, H. Sasaki, N. Sasaki, Y. Sato, F.G. Saturni, M. Sawada, J. Schaefer, A. Scherer, J. Scherpenberg, P. Schipani, B. Schleicher, J. Schmoll, M. Schneider, H. Schoorlemmer, P. Schovanek, F. Schussler, B. Schwab, U. Schwanke, J. Schwarz, E. Sciacca, S. Scuderi, M. Seglar Arroyo, I. Seitenzahl, D. Semikoz, O. Sergijenko, J.E. Serna Franco, Karol Seweryn, V. Sguera, A. Shalchi, R.Y. Shang, P. Sharma, L. Sidoli, J. Sieiro, H. Siejkowski, A. Sillanpaa, B.B. Singh, K.K. Singh, A. Sinha, C. Siqueira, J. Sitarek, P. Sizun, V. Sliusar, D. Sobczynska, R.W. Sobrinho, H. Sol, G. Sottile, H. Spackman, S. Spencer, G. Spengler, D. Spiga, W. Springer, A. Stamerra, S. Stanic, R. Starling, Ł. Stawarz, Stanislav Stefanik, C. Stegmann, A. Steiner, S. Steinmassl, C. Stella, R. Sternberger, M. Sterzel, C. Stevens, B. Stevenson, T. Stolarczyk, G. Stratta, U. Straumann, J. Striskovic, M. Strzys, R. Stuik, M. Suchenek, Y. Sunada, Tiina Suomijarvi, T. Suric, H. Suzuki, P. Swierk, T. Szepieniec, K. Tachihara, G. Tagliaferri, H. Tajima, N. Tajima, D. Tak, H. Takahashi, M. Takahashi, J. Takata, R. Takeishi, T. Tam, M. Tanaka, T. Tanaka, S. Tanaka, M. Tavani, F. Tavecchio, T. Tavernier, A. Russ Taylor, L.A. Tejedor, P. Temnikov, K. Terauchi, J.C. Terrazas, R. Terrier, T. Terzic, M. Teshima, D. Thibaut, F. Thocquenne, W. Tian, L. Tibaldo, A. Tiengo, M. Tluczykont, C.J. Todero Peixoto, K. Toma, L. Tomankova, J. Tomastik, M. Tornikoski, D.F. Torres, E. Torresi, G. Tosti, L. Tosti, N. Tothill, F. Toussenel, G. Tovmassian, C. Trichard, M. Trifoglio, A. Trois, S. Truzzi, A. Tsiahina, B. Turk, A. Tutone, Y. Uchiyama, P. Utayarat, L. Vaclavek, M. Vacula, V. Vagelli, F. Vagnetti, J.A. Valdivia, M. Valentino, A. Valio, B. Vallage, P. Vallania Quispe, A.M. van den Berg, W. van Driel, C. van Eldik, C. van Rensburg, Brian van Soelen, J. Vandenbroucke, G. Vasileiadis, V. Vassiliev, M. Vazquez Acosta, M. Vecchi, A. Vega, J. Veh, P. Veitch, C. Venter, S. Ventura, S. Vercellone, V. Verguilov, G. Verna, S. Vernetto, V. Verzi, G.P. Vettolani, C. Veyssiere, I. Viale, A. Viana, N. Viaux, J. Vignatti, C.F. Vigorito, J. Villanueva, V. Vitale, V. Vittorini, V. Vodeb, N. Vogel, V. Voisin, S. Vorobiov, M. Vrastil, T. Vuillaume, S.J. Wagner, P. Wagner, K. Wakazono, S.P. Wakely, M. Ward, D. Warren, J. Watson, M. Wechakama, P. Wegner, A. Weinstein, C. Weniger, F. Werner, H. Wetteskind, M. L. White, A. Wierzcholska, S. Wiesand, R. Wijers, M. Wilkinson, M. Will, J. Williams, T. J. Williamson, A. Wolter, Y.W. Wong, M. Wood, T. Yamamoto, H. Yamamoto, Y. Yamane, R. Yamazaki, S. Yanagita, L. Yang, S. Yoo, T. Yoshida, T. Yoshikoshi, P. Yu, A. Yusafzai, Michael Zacharias, B. Zaldivar, L. Zampieri, R. Zanin, R. Zanmar Sanchez, D. Zaric, M. Zavrtanik, D. Zavrtanik, Andrzej Zdziarski, A. Zech, H. Zechlin, A. Zenin, A. Zerwekh, K. Ziętara, A. Zink, J. Ziolkowski, M. Zivec, A. Zmija, Współautorami artykułu są członkowie CTA Observatory, CTA Consortium i LST Collaboration w liczbie 1139, Astronomy, Research unit Nuclear & Hadron Physics, and Research unit Astroparticle Physics

Subjects
Physics, Observatory, Gamma ray, Astronomy
Abstract

Very-high Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations over the past decade have surprisingly revealed almost two hundred VHE emitters which appear to act as cosmic particle accelerators. These sources are an important component of the Universe, influencing the evolution of stars and galaxies. At the same time, they also act as a probe of physics in the most extreme environments known - such as in supernova explosions, and around or after the merging of black holes and neutron stars. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. A deeper understanding of the TeV sky requires a significant improvement in sensitivity at TeV energies, a wider energy coverage from tens of GeV to hundreds of TeV and a much better angular and energy resolution with respect to the currently running facilities. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will present this upcoming observatory from its design to the construction, and its potential science exploitation. CTAO will allow the entire astronomical community to explore a new discovery space that will likely lead to paradigm-changing breakthroughs. In particular, CTA has an unprecedented sensitivity to short (sub-minute) timescale phenomena, placing it as a key instrument in the future of multi-messenger and multi-wavelength time domain astronomy. I will conclude the talk presenting the first scientific results obtained by the LST-1, the prototype of one CTAO telescope type - the Large-Sized Telescope, that is currently under commission., PoS: Proceedings of Science, 395, ISSN:1824-8039, Proceedings of 37th International Cosmic Ray Conference (ICRC2021)

Published
2022

22. 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

23. 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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24. Optical polarization from colliding stellar stream shocks in a tidal disruption event.

Author

Liodakis I, Koljonen KII, Blinov D, Lindfors E, Alexander KD, Hovatta T, Berton M, Hajela A, Jormanainen J, Kouroumpatzakis K, Mandarakas N, and Nilsson K

Abstract

A tidal disruption event (TDE) occurs when a supermassive black hole rips apart a passing star. Part of the stellar material falls toward the black hole, forming an accretion disk that in some cases launches a relativistic jet. We performed optical polarimetry observations of a TDE, AT 2020mot. We find a peak linear polarization degree of 25 ± 4%, consistent with highly polarized synchrotron radiation, as is typically observed from relativistic jets. However, our radio observations, taken up to 8 months after the optical peak, do not detect the corresponding radio emission expected from a relativistic jet. We suggest that the linearly polarized optical emission instead arises from shocks that occur during accretion disk formation, as the stream of stellar material collides with itself.

Published
2023
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25. 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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26. 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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27. 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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28. 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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29. Unresolved Gamma-Ray Sky through its Angular Power Spectrum.

Author

Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Burns E, Buson S, Cameron RA, Caputo R, Caraveo PA, Cavazzuti E, Chen S, Chiaro G, Ciprini S, Costantin D, Cuoco A, Cutini S, D'Ammando F, de la Torre Luque P, de Palma F, Desai A, Digel SW, Di Lalla N, Di Mauro M, Di Venere L, Fana Dirirsa F, Favuzzi C, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Guillemot L, Guiriec S, Horan D, Jóhannesson G, Kuss M, Larsson S, Latronico L, Li J, Liodakis I, Longo F, Loparco F, Lubrano P, Magill JD, Maldera S, Malyshev D, Manfreda A, Mazziotta MN, Mereu I, Michelson PF, Mitthumsiri W, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Negro M, Nuss E, Orienti M, Orlando E, Palatiello M, Paliya VS, Paneque D, Persic M, Pesce-Rollins M, Petrosian V, Piron F, Porter TA, Principe G, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Serini D, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Suson DJ, Tajima H, Takahashi M, Thayer JB, Tibaldo L, Torres DF, Troja E, Venters TM, Vianello G, Wood K, Yassine M, Zaharijas G, Ammazzalorso S, Fornengo N, and Regis M

Abstract

The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi -large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission [unresolved gamma-ray background (UGRB)] below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This Letter presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi-LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with ∼3.7σ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55±0.23 and 1.86±0.15.

Published
2018
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