//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6027 SUBJECT: GRB 070126?: Swift detection of a possible burst DATE: 07/01/26 03:04:26 GMT FROM: Loredana Vetere at PSU L. Vetere (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), S. T. Holland (CRESST/GSFC/USRA), S. Immler (GSFC/USRA), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), J. L. Racusin (PSU), J. L. Racusin (PSU), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester) and E. Troja (INAF-IASFPA) report on behalf of the Swift Team: At 02:33:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible source (trigger=257741). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 33.460, -73.523 which is RA(J2000) = 02h 13m 50s Dec(J2000) = -73d 31' 23" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows no significant variation, which is not uncommon for image triggers. We will have to wait for ground analysis to determine if this is a real source. The XRT began observing the field at 02:35:21 UT, 116 seconds after the BAT trigger. XRT centroided on a cosmic ray and no source is visible in the field of view up to an exposure time of 203s. The UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 123 seconds after the BAT trigger. The quickly available image does not cover any portion of the BAT error circle. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6037 SUBJECT: Possible GRB 070126: Swift/UVOT Upper Limit DATE: 07/01/26 17:22:58 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (NASA/USRA) and L. Vetere (PSU) report on the behalf of the Swift UVOT team: The Swift/UVOT began observing the field of the possible burst GRB 070126 123 seconds after the BAT trigger (Vetere et al., GCN 6027). No optical afterglow candidate is detected in the BAT error circle within the first 100 s White exposure or in a coadded 590 s image, down to a limiting magnitude of 21.0 (3-sigma). The other UVOT filters only cover a small fraction (around 25%) of the BAT error circle. No correction has been made for the expected extinction corresponding to E(B-V) = 0.05 mag (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6040 SUBJECT: GRB 070126, Swift-BAT refined analysis of a very faint burst DATE: 07/01/26 20:25:16 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift E. Fenimore (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), L. Vetere (PSU) on behalf of the Swift-BAT team: Using the data set from T-240 to T+500 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070126 (trigger #257741) (Veter, et al., GCN Circ. 6027). The BAT ground-calculated position is RA, Dec = 33.579, -73.532 deg which is RA(J2000) = 2h 14m 18.9s Dec(J2000) = -73d 31' 54" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted lightcurve shows a broad, weak, and soft bump from T_zero to ~T+60 sec. T90 (15-350 keV) is 51 +- 5 sec (estimated error including systematics). The time-averaged spectrum from T+1.0 to T+56.0 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.9 +- 0.5. The fluence in the 15-150 keV band is 1.6 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+10.00 sec in the 15-150 keV band is 0.2 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The flux of this burst is at the lower limit of the BAT sensitivity. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6045 SUBJECT: GRB070126: Swift-XRT possible detection of an afterglow DATE: 07/01/28 10:26:47 GMT FROM: Loredana Vetere at PSU L. Vetere, J. Racusin (PSU) reports on behalf of Swift XRT Team: We analysed the first 28ks of XRT data of the faint burst GRB 070126 (Vetere et al., GCN 6027). We do find in the BAT error circle (Fenimore et al., GCN 6040) a detection of a faint uncatalogued X-ray source at the following coordinates: RA(J2000) = 2h 14m 09.78s Dec(J2000) = -73d 32' 06.7" with an estimated uncertainty of 4.4 arcseconds (90% containment). This position lies 0.7 arcmin from the BAT refined position reported by Fenimore et al. (GCN 6040). The PSF corrected count rate is (7.1 +/- 2.3)e-4 cts/s. No other point source is detected above the 3 sigma upper limit of 1.0e-3 cts/s inside BAT error circle. Due to the small number of counts, we are unable to determine whether the source is decaying at this time. Observations are continuing and further analysis regarding the fading nature of this source will be issued as the data become available. This circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6046 SUBJECT: GRB 070126: VLT observations DATE: 07/01/28 12:00:08 GMT FROM: Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center D. Malesani (Dark/NBI), P.M. Vreeswijk (ESO), P. Jakobsson (Herfordshire), J.P.U. Fynbo (Dark/NBI), report on behalf of a larger collaboration: We observed the field of the faint GRB 070126 (Vetere et al., GCN 6027) with the ESO VLT + FORS2 on 2006 Jan 26.17 UT (1.52 hr after the GRB). Short exposures (~1 min) were acquired in BVRIz. Inside the XRT error circle (Vetere \& Racusin, GCN 6045) we detect a single, extended source, which is present in the USNO-B1 catalog and in the DSS images, at the coordinates (0.5" error): RA(J2000) = 02:14:10.03 Dec(J2000) = -73:32:05.7 Given the lack of evidence for variability of the X-ray source, the possible association of this galaxy with the GRB or the X-ray source is at present unclear. Our images cover ~80% of the refined BAT error circle (Fenimore et al., GCN 6040). No new sources brighter than the DSS limits (R~20.5) are seen across the whole observed region. We acknowledge excellent support from the ESO staff at Paranal, in particular Hugues Sana, Thomas Rivinius, Leonardo Vanzi and Dominique Naef. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6052 SUBJECT: GRB 070126: Swift/UVOT refined analysis DATE: 07/01/29 17:37:37 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (NASA/USRA) and L. Vetere (PSU) report on the behalf of the Swift UVOT team: An extended source is found at the position reported by Malesani et al. (GCN 6046) in UVOT images of GRB 070126, consistent with the position of the XRT source (Vetere & Racusin, GCN 6045). The source is also present in DSS images and could be the host galaxy of the faint burst. The table below gives the measured UVOT magnitudes. The position of the burst is outside the UVOT field-of-view for all other filters. Filter T_start T_end Exposure Mag Error WHITE 123 6146 590 21.8 0.4 UVW1 3900 40895 3592 21.0 0.3 UVM2 5128 40337 3333 21.5 0.3 UVW2 4719 6214 2588 >20.4 (3-sigma UL) T_start and T_end are the start and stop times of the summed exposures in seconds from the trigger. No correction has been made for the expected extinction corresponding to E(B-V) = 0.05 mag (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6068 SUBJECT: GRB070126: Swift-XRT Observation DATE: 07/02/02 00:06:37 GMT FROM: Loredana Vetere at PSU L. Vetere, J. Racusin, D.N. Burrows, C. Pagani (PSU) report on behalf of Swift XRT Team: We have re-observed the field of GRB 070126 (Vetere et al., GCN 6027) from 2007-01-30 00:49:07.62 (~340ks after BAT trigger) to 2007-02-01 14:10:17.0 for a total exposure of ~27.2ks. The possible afterglow candidate that we reported in GCN 6045 is still present and shows a slightly increased count rate (1.4 +/- 0.3)E-03 cts/sec compared to (0.76 +/- 0.23) E-03 cts/sec obtained with the first 28ks of observation. We thus conclude that the object reported is not the X-ray afterglow of GRB 070126. No other point sources are detected above the 3 sigma upper limit of 1.0e-3 cts/s inside BAT error circle. This circular is an official product of the Swift XRT Team.