//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4859 SUBJECT: GRB 060312: Swift detection of a burst DATE: 06/03/12 02:07:45 GMT FROM: David Palmer at LANL D. Grupe (PSU), S. Barthelmy (GSFC), D. Burrows (PSU), N. Gehrels (GSFC), S. Hunsberger (PSU), C. Pagani (PSU), D. Palmer (LANL) on behalf of the Swift team: At 01:36:12 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060312 (trigger=201391). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 45.768, +12.820 {03h 03m 04s, +12d 49' 12"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 30 sec. The peak count rate was 1300 counts/sec (15-350 keV), at ~6 sec after the trigger. The XRT began observing the burst position at 01:37:03 UT (51 s after the BAT trigger). The XRT found a bright, uncataloged, fading source located at RA(J2000) = 3h 03m 06.1s Dec(J2000) = +12d 50' 04" with an uncertainty of 5.0 arcseconds (90% confidence radius). This is 58 arcseconds from the BAT position. The initial flux was 1.8E-9 ergs/cm2/s. The UVOT is currently in a state where it is unable to take data. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4860 SUBJECT: GRB 060312: ROTSE-III Optical Limits DATE: 06/03/12 02:34:29 GMT FROM: Brad Schaefer at LSU B. E. Schaefer (Louisiana State), F. Yuan (U Mich), S.A. Yost (U Mich), R. Quimby (U Texas), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 060312 (Swift trigger 201391; D. Grupe et al. 2005, GCN 4859), producing images beginning 6.0 s after the GCN notice time. An automated response took the first image at 01:36:33.0 UT, 20.3 s after the burst trigger. We took 10 5-sec, 10 20-sec and 74 60-sec eposures; with ongoing imaging. The first 25 images were taken with moderate twilight and thin clouds, but after this there appears to be no problem with the sky conditions. These unfiltered images are calibrated relative to USNO A2.0 (R). Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma error circle, for both single images and coadding into sets of 10; the field is not crowded. In particular, we see no source at the location of the XRT fading transient (Grupe et al. 2005). Individual images have limiting magnitudes ranging from 14.4-17.5; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 01:36:33.0 01:36:38.0 5 14.6 20.3 N 01:47:39.9 01:52:22.2 282 17.1 687.2 Y 01:57:23.3 02:02:06.5 283 18.3 1270.6 Y //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4862 SUBJECT: GRB 060312: Swift XRT team refined analysis DATE: 06/03/12 08:30:49 GMT FROM: Dirk Grupe at PSU/Swift-XRT Subject: GRB 060312: Swift XRT team refined analysis Dirk Grupe (PSU), David N. Burrows (PSU), Claudio Pagani (PSU), on behalf of the Swift XRT team: We report on the analysis of the first three orbits of X-ray data of the Swift discovered GRB 060312. The XRT began observing the field of GRB 060312 01:36:12 UT, 51 seconds after the BAT trigger. The following refined position was obtained: RA(J2000) = 03h 03m 06.12s Dec(J2000)= =12d 50' 03.5" with an estimated uncertainty of 3.7 arcsec (90% containment). This is 0.5 arcsec from the XRT position given in GCN 4859 (Grupe et al.), and 87 arcsec from the BAT position reported in the same circular. The X-ray spectrum of the Windowed Timing (WT) data can be fitted by a single absorbed power low with a photon index Gamma=2.17+/-0.10 and an absorption column density NH=(2.3+/_0.3)e21 cm-2. This column density is above the Galactic value (1.4e21; Dickey & Lockman 1990) and suggests that the burst is intrinsically absorbed. The photon counting (pc) mode data are consistent with this result. The light curve shows several flares in the first orbit. The underlying afterglow decay slope withing the first 10 ks after the burst is alpha=0.60+/-0.13. Assuming this decay slope the prediction for the flux 24 hours after the trigger is 4e-13 ergs/s/cm2. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4864 SUBJECT: GRB 060312: Refined analysis of the Swift-BAT burst DATE: 06/03/12 17:09:19 GMT FROM: Scott Barthelmy at NASA/GSFC H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), D. Hullinger (BYU-Idaho), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-300 to T+302 sec from the recent telemetry downlink, we report further analysis of BAT GRB 060312 (trigger #201391) (Grupe, et al., GCN 4859). The BAT ground-calculated position is RA,Dec = 45.777,+12.825 deg {3h 3m 6.5s,+12d 49' 29.6"} (J2000) +- 0.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted lightcurve shows two main peaks at T-27 and T+7 sec. The first peak starts at T-35 sec and the second ends at ~T+30 sec. T90 (15-350 keV) is 43 +- 3 sec (estimated error including systematics). The time-averaged spectrum from T-29.4 to T+22.0 is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.35 +- 0.34, and Epeak of 62.8 +- 21.5 keV (chi squared 46.33 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.8 +- 0.1 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+5.63 sec in the 15-150 keV band is 1.5 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.85 +- 0.08 (chi squared 52.99 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4865 SUBJECT: GRB060312: Swift UVOT observation DATE: 06/03/12 18:40:37 GMT FROM: Sally Hunsberger at PSU/Swift S. D. Hunsberger (PSU), D. Grupe (PSU), and F. Marshall (GSFC) on behalf of the Swift UVOT team: The UVOT took a finding chart exposure of 200 seconds with the V filter starting 14.4 hours after the BAT trigger. No afterglow candidate has been found in the 2.7'x2.7' sub-image which covers 100% of the XRT error circle. The 3-sigma UL at the XRT position is 0.9 cps or 18.0 mag. No correction has been made for the expected extinction of about 0.6 magnitudes.