GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for ~24.5 s (in the GBM) and had a peak flux of (5.7 ± 0.2) × 10-5 erg s-1 cm-2. The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 ± 2 MeV, which is the highest value ever detected in a GRB. This measurement was made possible by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100 MeV coverage. The peak energy later decreased as a power law in time with an index of -1.89 ± 0.10. The temperature of the blackbody component also decreased, starting from ~80 keV, and the decay showed a significant break after ~2 s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.
GRB110721A: An Extreme Peak Energy and Signatures of the Photosphere / M., Axelsson; L., Baldini; BARBIELLINI AMIDEI, Guido; M. G., Baring; R., Bellazzini; J., Bregeon; M., Brigida; P., Bruel; R., Buehler; G. A., Caliandro; R. A., Cameron; P. A., Caraveo; C., Cecchi; R. C., G.; A., Chekhtman; J., Chiang; R., Claus; J., Conrad; S., Cutini; F., D'Ammando; Palma, F.; C. D., Dermer; E. d., C.; P. S., Drell; C., Favuzzi; S. J., Fegan; E. C., Ferrara; W. B., Focke; Y., Fukazawa; P., Fusco; F., Gargano; D., Gasparrini; N., Gehrels; S., Germani; N., Giglietto; M., Giroletti; G., Godfrey; S., Guiriec; D., Hadasch; Y., Hanabata; M., Hayashida; X., Hou; S., Iyyani; M. S., Jackson; D., Kocevski; M., Kuss; J., Larsson; S., Larsson; Longo, Francesco; F., Loparco; C., Lundman; M. N., Mazziotta; J. E., Mcenery; T., Mizuno; M. E., Monzani; E., Moretti; A., Morselli; S., Murgia; E., Nuss; T., Nymark; M., Ohno; N., Omodei; M., Pesce Rollins; F., Piron; G., Pivato; J. L., Racusin; S., Rain\`o; M., Razzano; S., Razzaque; A., Reimer; M., Roth; F., Ryde; D. A., Sanchez; C., Sgr\`o; E. J., Siskind; G., Spandre; P., Spinelli; M., Stamatikos; L., Tibaldo; M., Tinivella; T. L., Usher; J., Vandenbroucke; V., Vasileiou; G., Vianello; V., Vitale; A. P., Waite; B. L., Winer; K. S., Wood; J. M., Burgess; P. N., Bhat; Bissaldi, Elisabetta; M. S., Briggs; V., Connaughton; G., Fishman; G., Fitzpatrick; S., Foley; D., Gruber; R. M., Kippen; C., Kouveliotou; P., Jenke; S., Mcbreen; S., Mcglynn; C., Meegan; W. S., Paciesas; V., Pelassa; R., Preece; D., Tierney; Kienlin, A.; C., Wilson Hodge; S., Xiong; A., Pe'Er. - In: THE ASTROPHYSICAL JOURNAL LETTERS. - ISSN 2041-8205. - 757:(2012), pp. L31-1-L31-6. [10.1088/2041-8205/757/2/L31]
GRB110721A: An Extreme Peak Energy and Signatures of the Photosphere
BARBIELLINI AMIDEI, GUIDO;LONGO, FRANCESCO;BISSALDI, ELISABETTA;
2012-01-01
Abstract
GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for ~24.5 s (in the GBM) and had a peak flux of (5.7 ± 0.2) × 10-5 erg s-1 cm-2. The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 ± 2 MeV, which is the highest value ever detected in a GRB. This measurement was made possible by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100 MeV coverage. The peak energy later decreased as a power law in time with an index of -1.89 ± 0.10. The temperature of the blackbody component also decreased, starting from ~80 keV, and the decay showed a significant break after ~2 s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.Pubblicazioni consigliate
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