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Abdalla, Hassan E. ; Adam, R. ; Aharonian, Felix A. ; Benkhali, F. Ait ; Angüner, Ekrem Oǧuzhan ; Arakawa, M. ; Arcaro, C. ; Armand, C. ; Ashkar, H. ; Backes, M. ; Martins, V. Barbosa ; Barnard, M. ; Becherini, Y. ; Berge, D. ; Bernloehr, K. ; Bissaldi, E. ; Blackwell, R. ; Boettcher, M. ; Boisson, C. ; Bolmont, J. ; Bonnefoy, S. ; Bregeon, J. ; Breuhaus, M. ; Brun, F. ; Brun, P. ; Bryan, M. ; Buechele, M. ; Bulik, T. ; Bylund, T. ; Capasso, M. ; Caroff, S. ; Carosi, A. ; Casanova, Sabrina ; Cerruti, M. ; Chand, T. ; Chandra, S. ; Chen, A. ; Colafrancesco, S. ; Curylo, M. ; Davids, I. D. ; Deil, C. ; Devin, J. ; deWilt, P. ; Dirson, L. ; Djannati-Atai, A. ; Dmytriiev, A. ; Donath, A. ; Doroshenko, V ; Dyks, J. ; Egberts, Kathrin ; Emery, G. ; Ernenwein, J-P ; Eschbach, S. ; Feijen, K. ; Fegan, S. ; Fiasson, A. ; Fontaine, G. ; Funk, S. ; Fussling, Matthias ; Gabici, S. ; Gallant, Y. A. ; Gate, F. ; Giavitto, G. ; Giunti, L. ; Glawion, D. ; Glicenstein, J. F. ; Gottschall, D. ; Grondin, M-H ; Hahn, J. ; Haupt, M. ; Heinzelmann, G. ; Henri, G. ; Hermann, G. ; Hinton, J. A. ; Hofmann, W. ; Hoischen, Clemens ; Holch, T. L. ; Holler, M. ; Horns, D. ; Huber, D. ; Iwasaki, H. ; Jamrozy, M. ; Jankowsky, D. ; Jankowsky, F. ; Jardin-Blicq, A. ; Jung-Richardt, I ; Kastendieck, M. A. ; Katarzynski, K. ; Katsuragawa, M. ; Katz, U. ; Khangulyan, D. ; Khelifi, B. ; King, J. ; Klepser, S. ; Kluzniak, W. ; Komin, Nu ; Kosack, K. ; Kostunin, D. ; Kreter, M. ; Lamanna, G. ; Lemiere, A. ; Lemoine-Goumard, M. ; Lenain, J-P ; Leser, Eva ; Levy, C. ; Lohse, T. ; Lypova, I ; Mackey, J. ; Majumdar, J. ; Malyshev, D. ; Marandon, V ; Marcowith, Alexandre ; Mares, A. ; Mariaud, C. ; Marti-Devesa, G. ; Marx, R. ; Maurin, G. ; Meintjes, P. J. ; Mitchell, A. M. W. ; Moderski, R. ; Mohamed, M. ; Mohrmann, L. ; Moore, C. ; Moulin, Emmanuel ; Muller, J. ; Murach, T. ; Nakashima, S. ; de Naurois, M. ; Ndiyavala, H. ; Niederwanger, F. ; Niemiec, J. ; Oakes, L. ; Odaka, H. ; Ohm, S. ; Wilhelmi, E. de Ona ; Ostrowski, M. ; Oya, I ; Panter, M. ; Parsons, R. D. ; Perennes, C. ; Petrucci, P-O ; Peyaud, B. ; Piel, Q. ; Pita, S. ; Poireau, V ; Noel, A. Priyana ; Prokhorov, D. A. ; Prokoph, H. ; Puehlhofer, G. ; Punch, M. ; Quirrenbach, A. ; Raab, S. ; Rauth, R. ; Reimer, A. ; Reimer, O. ; Remy, Q. ; Renaud, M. ; Rieger, F. ; Rinchiuso, L. ; Romoli, C. ; Rowell, G. ; Rudak, B. ; Ruiz-Velasco, E. ; Sahakian, V ; Sailer, S. ; Saito, S. ; Sanchez, D. A. ; Santangelo, Andrea ; Sasaki, M. ; Schlickeiser, R. ; Schussler, F. ; Schulz, A. ; Schutte, H. M. ; Schwanke, U. ; Schwemmer, S. ; Seglar-Arroyo, M. ; Senniappan, M. ; Seyffert, A. S. ; Shafi, N. ; Shiningayamwe, K. ; Simoni, R. ; Sinha, A. ; Sol, H. ; Specovius, A. ; Spir-Jacob, M. ; Stawarz, L. ; Steenkamp, R. ; Stegmann, Christian ; Steppa, Constantin Beverly ; Takahashi, T. ; Tavernier, T. ; Taylor, A. M. ; Terrier, R. ; Tiziani, D. ; Tluczykont, M. ; Trichard, C. ; Tsirou, M. ; Tsuji, N. ; Tuffs, R. ; Uchiyama, Y. ; van der Walt, D. J. ; van Eldik, C. ; van Rensburg, C. ; van Soelen, B. ; Vasileiadis, G. ; Veh, J. ; Venter, C. ; Vincent, P. ; Vink, J. ; Voelk, H. J. ; Vuillaume, T. ; Wadiasingh, Z. ; Wagner, S. J. ; White, R. ; Wierzcholska, A. ; Yang, R. ; Yoneda, H. ; Zacharias, M. ; Zanin, R. ; Zdziarski, A. A. ; Zech, Alraune ; Ziegler, A. ; Zorn, J. ; Zywucka, N. ; de Palma, F. ; Axelsson, M. ; Roberts, O. J.
Gamma-ray bursts (GRBs) are brief flashes of gamma-rays and are considered to be the most energetic explosive phenomena in the Universe(1). The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow-produced by the interaction between the ejected matter and the circumburst medium-slows down, and a gradual decrease in brightness is observed(2). GRBs typically emit most of their energy via.-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments(3). However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elusive(4). Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow-ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and gamma-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies.
Abdalla, Hassan E. ; Adam, R. ; Aharonian, Felix A. ; Benkhali, F. Ait ; Angüner, Ekrem Oǧuzhan ; Arakawa, M. ; Arcaro, C. ; Armand, C. ; Ashkar, H. ; Backes, M. ; Martins, V. Barbosa ; Barnard, M. ; Becherini, Y. ; Berge, D. ; Bernloehr, K. ; Blackwell, R. ; Böttcher, M. ; Boisson, C. ; Bolmont, J. ; Bonnefoy, S. ; Bregeon, J. ; Breuhaus, M. ; Brun, F. ; Brun, P. ; Bryan, M. ; Büchele, M. ; Bulik, T. ; Bylund, T. ; Capasso, M. ; Caroff, S. ; Carosi, A. ; Casanova, Sabrina ; Cerruti, M. ; Chand, T. ; Chandra, S. ; Chen, A. ; Colafrancesco, S. ; Curylo, M. ; Davids, I. D. ; Deil, C. ; Devin, J. ; DeWilt, P. ; Dirson, L. ; Djannati-Ata, A. ; Dmytriiev, A. ; Donath, A. ; Doroshenko, V ; Dyks, J. ; Egberts, Kathrin ; Emery, G. ; Ernenwein, J-P ; Eschbach, S. ; Feijen, K. ; Fegan, S. ; Fiasson, A. ; Fontaine, G. ; Funk, S. ; Füßling, Matthias ; Gabici, S. ; Gallant, Y. A. ; Gate, F. ; Giavitto, G. ; Glawion, D. ; Glicenstein, J. F. ; Gottschall, D. ; Grondin, M-H ; Hahn, J. ; Haupt, M. ; Heinzelmann, G. ; Henri, G. ; Hermann, G. ; Hinton, James Anthony ; Hofmann, W. ; Hoischen, Clemens ; Holch, Tim Lukas ; Holler, M. ; Horns, D. ; Huber, D. ; Iwasaki, H. ; Jamrozy, M. ; Jankowsky, D. ; Jankowsky, F. ; Jardin-Blicq, A. ; Jung-Richardt, I ; Kastendieck, M. A. ; Katarzynski, K. ; Katsuragawa, M. ; Katz, U. ; Khangulyan, D. ; Khelifi, B. ; King, J. ; Klepser, S. ; Kluzniak, W. ; Komin, Nu ; Kosack, K. ; Kostunin, D. ; Kraus, M. ; Lamanna, G. ; Lau, J. ; Lemiere, A. ; Lemoine-Goumard, M. ; Lenain, J-P ; Leser, Eva ; Levy, C. ; Lohse, T. ; Lypova, I ; Mackey, J. ; Majumdar, J. ; Malyshev, D. ; Marandon, V ; Marcowith, Alexandre ; Mares, A. ; Mariaud, C. ; Marti-Devesa, G. ; Marx, R. ; Maurin, G. ; Meintjes, P. J. ; Mitchell, A. M. W. ; Moderski, R. ; Mohamed, M. ; Mohrmann, L. ; Moore, C. ; Moulin, Emmanuel ; Muller, J. ; Murach, T. ; Nakashima, S. ; de Naurois, M. ; Ndiyavala, H. ; Niederwanger, F. ; Niemiec, J. ; Oakes, L. ; Odaka, H. ; Ohm, S. ; Wilhelmi, E. de Ona ; Ostrowski, M. ; Oya, I ; Panter, M. ; Parsons, R. D. ; Perennes, C. ; Petrucci, P-O ; Peyaud, B. ; Piel, Q. ; Pita, S. ; Poireau, V ; Priyana Noel, A. ; Prokhorov, D. A. ; Prokoph, H. ; Pühlhofer, G. ; Punch, M. ; Quirrenbach, A. ; Raab, S. ; Rauth, R. ; Reimer, A. ; Reimer, O. ; Remy, Q. ; Renaud, M. ; Rieger, F. ; Rinchiuso, L. ; Romoli, C. ; Rowell, G. ; Rudak, B. ; Ruiz-Velasco, E. ; Sahakian, V ; Saito, S. ; Sanchez, David M. ; Santangelo, Andrea ; Sasaki, M. ; Schlickeiser, R. ; Schüssler, F. ; Schulz, A. ; Schutte, H. ; Schwanke, U. ; Schwemmer, S. ; Seglar-Arroyo, M. ; Senniappan, M. ; Seyffert, A. S. ; Shafi, N. ; Shiningayamwe, K. ; Simoni, R. ; Sinha, A. ; Sol, H. ; Specovius, A. ; Spir-Jacob, M. ; Stawarz, L. ; Steenkamp, R. ; Stegmann, Christian ; Steppa, Constantin Beverly ; Takahashi, T. ; Tavernier, T. ; Taylor, A. M. ; Terrier, R. ; Tiziani, D. ; Tluczykont, M. ; Trichard, C. ; Tsirou, M. ; Tsuji, N. ; Tuffs, R. ; Uchiyama, Y. ; van Der Walt, D. J. ; van Eldik, C. ; van Rensburg, C. ; van Soelen, B. ; Vasileiadis, G. ; Veh, J. ; Venter, C. ; Vincent, P. ; Vink, J. ; Voisin, F. ; Voelk, H. J. ; Vuillaume, T. ; Wadiasingh, Z. ; Wagner, S. J. ; White, R. ; Wierzcholska, A. ; Yang, R. ; Yoneda, H. ; Zacharias, Michael ; Zanin, R. ; Zdziarski, A. A. ; Zech, Alraune ; Ziegler, A. ; Zorn, J. ; Zywucka, N. ; Meyer, M.
The flat spectrum radio quasar 3C 279 is known to exhibit pronounced variability in the high-energy (100MeV < E < 100 GeV) gamma-ray band, which is continuously monitored with Fermi-LAT. During two periods of high activity in April 2014 and June 2015 target-of-opportunity observations were undertaken with the High Energy Stereoscopic System (H.E.S.S.) in the very-high-energy (VHE, E > 100 GeV) gamma-ray domain. While the observation in 2014 provides an upper limit, the observation in 2015 results in a signal with 8 : 7 sigma significance above an energy threshold of 66 GeV. No VHE variability was detected during the 2015 observations. The VHE photon spectrum is soft and described by a power-law index of 4.2 +/- 0.3. The H.E.S.S. data along with a detailed and contemporaneous multiwavelength data set provide constraints on the physical parameters of the emission region. The minimum distance of the emission region from the central black hole was estimated using two plausible geometries of the broad-line region and three potential intrinsic spectra. The emission region is confidently placed at r greater than or similar to 1 : 7 X 1017 cm from the black hole, that is beyond the assumed distance of the broad-line region. Time-dependent leptonic and lepto-hadronic one-zone models were used to describe the evolution of the 2015 flare. Neither model can fully reproduce the observations, despite testing various parameter sets. Furthermore, the H.E.S.S. data were used to derive constraints on Lorentz invariance violation given the large redshift of 3C 279.
Abdalla, H. ; Adam, R. ; Aharonian, Felix A. ; Benkhali, F. Ait ; Angüner, Ekrem Oǧuzhan ; Arcaro, C. ; Armand, C. ; Armstrong, T. ; Ashkar, H. ; Backes, M. ; Baghmanyan, V. ; Martins, V. Barbosa ; Barnacka, A. ; Barnard, M. ; Becherini, Y. ; Berge, D. ; Bernlohr, K. ; Bi, B. ; Bottcher, M. ; Boisson, C. ; Bolmont, J. ; de Lavergne, M. de Bony ; Bordas, Pol ; Breuhaus, M. ; Brun, F. ; Brun, P. ; Bryan, M. ; Buchele, M. ; Bulik, T. ; Bylund, T. ; Caroff, S. ; Carosi, A. ; Casanova, Sabrina ; Chand, T. ; Chandra, S. ; Chen, A. ; Cotter, G. ; Curylo, M. ; Mbarubucyeye, J. Damascene ; Davids, I. D. ; Davies, J. ; Deil, C. ; Devin, J. ; deWilt, P. ; Dirson, L. ; Djannati-Atai, A. ; Dmytriiev, A. ; Donath, A. ; Doroshenko, V. ; Duffy, C. ; Dyks, J. ; Egberts, Kathrin ; Eichhorn, F. ; Einecke, S. ; Emery, G. ; Ernenwein, J. -P. ; Feijen, K. ; Fegan, S. ; Fiasson, A. ; de Clairfontaine, G. Fichet ; Fontaine, G. ; Funk, S. ; Fussling, Matthias ; Gabici, S. ; Gallant, Y. A. ; Giavitto, G. ; Giunti, L. ; Glawion, D. ; Glicenstein, J. F. ; Gottschall, D. ; Grondin, M. -H. ; Hahn, J. ; Haupt, M. ; Hermann, G. ; Hinton, J. A. ; Hofmann, W. ; Hoischen, Clemens ; Holch, T. L. ; Holler, M. ; Horbe, M. ; Horns, D. ; Huber, D. ; Jamrozy, M. ; Jankowsky, D. ; Jankowsky, F. ; Jardin-Blicq, A. ; Joshi, V. ; Jung-Richardt, I. ; Kasai, E. ; Kastendieck, M. A. ; Katarzynski, K. ; Katz, U. ; Khangulyan, D. ; Khelifi, B. ; Klepser, S. ; Kluzniak, W. ; Komin, Nu. ; Konno, R. ; Kosack, K. ; Kostunin, D. ; Kreter, M. ; Lamanna, G. ; Lemiere, A. ; Lemoine-Goumard, M. ; Lenain, J. -P. ; Levy, C. ; Lohse, T. ; Lypova, I. ; Mackey, J. ; Majumdar, J. ; Malyshev, D. ; Malyshev, D. ; Marandon, V. ; Marchegiani, P. ; Marcowith, Alexandre ; Mares, A. ; Marti-Devesa, G. ; Marx, R. ; Maurin, G. ; Meintjes, P. J. ; Meyer, M. ; Mitchell, A. ; Moderski, R. ; Mohamed, M. ; Mohrmann, L. ; Montanari, A. ; Moore, C. ; Morris, P. ; Moulin, Emmanuel ; Muller, J. ; Murach, T. ; Nakashima, K. ; Nayerhoda, A. ; de Naurois, M. ; Ndiyavala, H. ; Niederwanger, F. ; Niemiec, J. ; Oakes, L. ; O'Brien, Patrick ; Odaka, H. ; Ohm, S. ; Olivera-Nieto, L. ; Wilhelmi, E. de Ona ; Ostrowski, M. ; Oya, I. ; Panter, M. ; Panny, S. ; Parsons, R. D. ; Peron, G. ; Peyaud, B. ; Piel, Q. ; Pita, S. ; Poireau, V. ; Noel, A. Priyana ; Prokhorov, D. A. ; Prokoph, H. ; Puhlhofer, G. ; Punch, M. ; Quirrenbach, A. ; Raab, S. ; Rauth, R. ; Reichherzer, P. ; Reimer, A. ; Reimer, O. ; Remy, Q. ; Renaud, M. ; Rieger, F. ; Rinchiuso, L. ; Romoli, C. ; Rowell, G. ; Rudak, B. ; Ruiz-Velasco, E. ; Sahakian, V. ; Sailer, S. ; Sanchez, D. A. ; Santangelo, Andrea ; Sasaki, M. ; Scalici, M. ; Schussler, F. ; Schutte, H. M. ; Schwanke, U. ; Schwemmer, S. ; Seglar-Arroyo, M. ; Senniappan, M. ; Seyffert, A. S. ; Shafi, N. ; Shiningayamwe, K. ; Simoni, R. ; Sinha, A. ; Sol, H. ; Specovius, A. ; Spencer, S. ; Spir-Jacob, M. ; Stawarz, L. ; Sun, L. ; Steenkamp, R. ; Stegmann, C. ; Steinmassl, S. ; Steppa, C. ; Takahashi, T. ; Tavernier, T. ; Taylor, A. M. ; Terrier, R. ; Tiziani, D. ; Tluczykont, M. ; Tomankova, L. ; Trichard, C. ; Tsirou, M. ; Tuffs, R. ; Uchiyama, Y. ; van der Walt, D. J. ; van Eldik, C. ; van Rensburg, C. ; van Soelen, B. ; Vasileiadis, G. ; Veh, J. ; Venter, C. ; Vincent, P. ; Vink, J. ; Volk, H. J. ; Vuillaume, T. ; Wadiasingh, Z. ; Wagner, S. J. ; Watson, J. ; Werner, F. ; White, R. ; Wierzcholska, A. ; Wong, Yu Wun ; Yusafzai, A. ; Zacharias, M. ; Zanin, R. ; Zargaryan, D. ; Zdziarski, A. A. ; Zech, Alraune ; Zhu, S. J. ; Ziegler, A. ; Zorn, J. ; Zouari, S. ; Zywucka, N.
The unidentified very-high-energy (VHE; E > 0.1 TeV) gamma -ray source, HESS J1826-130, was discovered with the High Energy Stereoscopic System (HESS) in the Galactic plane. The analysis of 215 h of HESS data has revealed a steady gamma -ray flux from HESS J1826-130, which appears extended with a half-width of 0.21 degrees +/- 0.02 <br /> (stat)degrees <br /> stat degrees +/- 0.05 <br /> (sys)degrees sys degrees . The source spectrum is best fit with either a power-law function with a spectral index Gamma = 1.78 +/- 0.10(stat) +/- 0.20(sys) and an exponential cut-off at 15.2 <br /> (+5.5)(-3.2) -3.2+5.5 TeV, or a broken power-law with Gamma (1) = 1.96 +/- 0.06(stat) +/- 0.20(sys), Gamma (2) = 3.59 +/- 0.69(stat) +/- 0.20(sys) for energies below and above E-br = 11.2 +/- 2.7 TeV, respectively. The VHE flux from HESS J1826-130 is contaminated by the extended emission of the bright, nearby pulsar wind nebula, HESS J1825-137, particularly at the low end of the energy spectrum. Leptonic scenarios for the origin of HESS J1826-130 VHE emission related to PSR J1826-1256 are confronted by our spectral and morphological analysis. In a hadronic framework, taking into account the properties of dense gas regions surrounding HESS J1826-130, the source spectrum would imply an astrophysical object capable of accelerating the parent particle population up to greater than or similar to 200 TeV. Our results are also discussed in a multiwavelength context, accounting for both the presence of nearby supernova remnants, molecular clouds, and counterparts detected in radio, X-rays, and TeV energies.