We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Gamma similar to 500-550.

MULTIWAVELENGTH OBSERVATIONS OF GRB 110731A: GeV EMISSION FROM ONSET TO AFTERGLOW

D'AMMANDO, FILIPPO;
2013

Abstract

We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Gamma similar to 500-550.
2013
Ackermann M; Ajello M; Asano K; Baldini L; Barbiellini G; Baring MG; Bastieri D; Bellazzini R; Blandford RD; Bonamente E; Borgland AW; Bottacini E; Bregeon J; Brigida M; Bruel P; Buehler R; Buson S; Caliandro GA; Cameron RA; Caraveo PA; Cecchi C; Charles E; Chaves RCG; Chekhtman A; Chiang J; Ciprini S; Claus R; Cohen-Tanugi J; Conrad J; Cutini S; DAmmando F; de Angelis A; de Palma F; Dermer CD; Silva EDE; Drell PS; Drlica-Wagner A; Favuzzi C; Fegan SJ; Focke WB; Franckowiak A; Fukazawa Y; Fusco P; Gargano F; Gasparrini D; Gehrels N; Giglietto N; Giordano F; Giroletti M; Glanzman T; Godfrey G; Granot J; Greiner J; Grenier IA; Grove JE; Guiriec S; Hadasch D; Hanabata Y; Hayashida M; Hays E; Hughes RE; Jackson MS; Jogler T; Johannesson G; Johnson AS; Knodlseder J; Kocevski D; Kuss M; Lande J; Larsson S; Latronico L; Longo F; Loparco F; Lovellette MN; Lubrano P; Mazziotta MN; McEnery JE; Mehault J; Meszaros P; Michelson PF; Mitthumsiri W; Mizuno T; Monte C; Monzani ME; Moretti E; Morselli A; Moskalenko IV; Murgia S; Naumann-Godo M; Norris JP; Nuss E; Nymark T; Ohno M; Ohsugi T; Omodei N; Orienti M; Orlando E; Paneque D; Perkins JS; Pesce-Rollins M; Piron F; Pivato G; Racusin JL; Raino S; Rando R; Razzano M; Razzaque S; Reimer A; Reimer O; Romoli C; Roth M; Ryde F; Sanchez DA; Sgro C; Siskind EJ; Sonbas E; Spinelli P; Stamatikos M; Takahashi H; Tanaka T; Thayer JG; Thayer JB; Tibaldo L; Tinivella M; Tosti G; Troja E; Usher TL; Vandenbroucke J; Vasileiou V; Vianello G; Vitale V; Waite AP; Winer BL; Wood KS; Yang Z; Gruber D; Bhat PN; Bissaldi E; Briggs MS; Burgess JM; Connaughton V; Foley S; Kippen RM; Kouveliotou C; McBreen S; McGlynn S; Paciesas WS; Pelassa V; Preece R; Rau A; van der Horst AJ; von Kienlin A; Kann DA; Filgas R; Klose S; Kruhler T; Fukui A; Sako T; Tristram PJ; Oates SR; Ukwatta TN; Littlejohns O
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/595728
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