J/A+A/568/A75          GRB 130925A GROND light curves          (Greiner+, 2014)

GROND coverage of the main peak of gamma-ray burst 130925A. Greiner J., Yu H.-F., Kruhler T., Frederiks D.D., Beloborodov A., Bhat P.N., Bolmer J., van Eerten H., Aptekar R.L., Elliott J., Golenetskii S.V., Graham J.F., Hurley K., Kann D.A., Klose S., Nicuesa Guelbenzu A., Rau A., Schady P., Schmidl S., Sudilovsky V., Svinkin D.S., Tanga M., Ulanov M.V., Varela K., von Kienlin A., Zhang X.-L. <Astron. Astrophys. 568, A75 (2014)> =2014A&A...568A..75G 2014A&A...568A..75G
ADC_Keywords: Gamma rays ; Photometry, infrared ; Photometry, ugriz Keywords: gamma rays: stars - radiation mechanisms: non-thermal Abstract: Prompt or early optical emission in gamma-ray bursts (GRBs) is notoriously difficult to measure, and observations of the dozen cases show a large variety of properties. Yet, such early emission promises to help us achieve a better understanding of the GRB emission process(es). We performed dedicated observations of the ultra-long duration (T90 about 7000s) Swift GRB 130925A in the optical/near-infrared with the 7-channel Gamma-Ray burst Optical and Near-infrared Detector (GROND) at the 2.2m MPG/ESO telescope. We detect an optical/near-infrared flare with an amplitude of nearly 2mag which is delayed with respect to the keV-MeV prompt emission by about 300-400s. The decay time of this flare is shorter than the duration of the flare (500s) or its delay. While we cannot offer a straightforward explanation, we discuss the implications of the flare properties and suggest ways toward understanding it. Description: GROND exposures automatically started 350s after the arrival of the Swift/BAT trigger. Simultaneous imaging in g'r'i'z'JHKs continued for nearly 6 hrs, with the last exposures done only in the NIR channels due to morning twilight (after 09:36 UT). Further observations were done in the mornings of Sep. 26, 27 and 29, with one late-time deep host imaging on Oct. 6. Seven files are provided, one for each GROND filter band (g'r'i'z'JHK). The values are as observed, no correction for foreground or intrinsic extinction has been applied. Objects: -------------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------------- 02 44 42.38 -26 09 15.8 GRB 130925A = GRB 130925A -------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file g_ab.dat 48 10 GROND filter band g' r_ab.dat 48 10 GROND filter band r' i_ab.dat 48 16 GROND filter band i' z_ab.dat 48 18 GROND filter band z' j_ab.dat 48 27 GROND filter band J h_ab.dat 48 28 GROND filter band H k_ab.dat 48 27 GROND filter band Ks -------------------------------------------------------------------------------- See also: J/A+A/562/A29 : GRB 100814A GROND and UVOT light curves (Nardini+, 2014) Byte-by-byte Description of file: *_ab.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1 A1 --- Band [grizJHK] Observed band 3- 11 F9.1 s Tmid Mid-time of exposure after Swift trigger 13- 18 F6.1 s Texp Half of exposure length 20- 24 F5.2 mag mag [16.5/23] Magnitude in Band in AB system, not corrected for foreground or intrinsic extinction 26- 29 F4.2 mag e_mag [0.03/0.3] Magnitude error (1σ) 31- 36 F6.2 uJy Flux Flux in Band, not corrected for foreground or intrinsic extinction 38- 42 F5.2 uJy e_Flux Negative flux error (1-σ) 44- 48 F5.2 uJy E_Flux Positive flux error (1-σ) -------------------------------------------------------------------------------- Acknowledgements: Jochen Greiner, jcg(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 16-Jul-2014
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