Search

Your search keyword '"D, Costantin"' showing total 5 results
Start Over Author "D, Costantin" Journal the astrophysical journal
5 results on '"D, Costantin"'

1. 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. Dominguez, 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. Hays, 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. Mirabal, 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. Raino', R. Rando, B. Rani, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, F. K. Schinzel, D. Serini, C. Sgro', 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
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°). 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
Full Text
View/download PDF

2. 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
Full Text
View/download PDF

3. 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

Published
2020
Full Text
View/download PDF

4. 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

5. Variability and Period Analysis for BL Lac AO 0235+164

Author

Sofia O. Kurtanidze, Y. H. Yuan, J. H. Yang, Yi Liu, Xin Liu, Jun-Hui Fan, H. T. Wang, G. M. Richter, O. M. Kurtanidze, A. Y. Zhou, M. G. Nikolashvili, Mahito Sasada, C. Lin, Y. T. Zhang, and D. Costantin

Subjects
Physics, 010308 nuclear & particles physics, Space and Planetary Science, Climatology, 0103 physical sciences, Period Analysis, Astronomy and Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences
Published
2017
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results