//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17261 SUBJECT: GRB 150101A: Swift detection of a short burst DATE: 15/01/01 06:53:33 GMT FROM: Hans Krimm at NASA-GSFC A. Vargas (PSU), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (NASA/UMBC), H. A. Krimm (CRESST/GSFC/USRA), B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 06:28:53 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150101A (trigger=623158). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 312.631, +36.728 which is RA(J2000) = 20h 50m 31s Dec(J2000) = +36d 43' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.1 sec. The peak count rate was ~3700 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 06:29:54.4 UT, 60.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 312.6038, 36.7334 which is equivalent to: RA(J2000) = 20h 50m 24.91s Dec(J2000) = +36d 44' 00.3" with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 80 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 4.62 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 65 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain extinction expected. Burst Advocate for this burst is A. Vargas (vargas.09242011.angie AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17262 SUBJECT: GRB 150101A: Enhanced Swift-XRT position DATE: 15/01/01 09:49:05 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 1496 s of XRT Photon Counting mode data and 2 UVOT images for GRB 150101A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 312.60337, +36.73318 which is equivalent to: RA (J2000): 20h 50m 24.81s Dec (J2000): +36d 43' 59.5" with an uncertainty of 2.7 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17263 SUBJECT: GRB 150101A: Swift/UVOT Upper Limits DATE: 15/01/01 16:27:00 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and A. Vargas (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150101A 65 s after the BAT trigger (Vargas et al., GCN Circ. 17261). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 17262) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 65 215 147 >21.4 u_FC 277 527 246 >20.6 white 65 1524 392 >22.1 v 607 1574 117 >20.1 b 533 1500 97 >20.4 u 277 1475 324 >21.0 w1 656 1451 97 >19.4 m2 631 1425 97 >19.9 w2 583 1550 117 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.52 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17264 SUBJECT: GRB 150101A: Swift-XRT refined Analysis DATE: 15/01/01 18:53:05 GMT FROM: Phil Evans at U of Leicester B. Sbarufatti (INAF-OAB/PSU), V. Mangano (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and A. Vargas report on behalf of the Swift-XRT team: We have analysed 8.5 ks of XRT data for GRB 150101A (Vargas et al. GCN Circ. 17261), from 68 s to 18.8 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 17262). The source is fading with alpha >0.6. If the light curve continues to decay with a power-law decay index of , the count rate at T+24 hours will be 7.9 x 10^-5 count s^-1 The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00623158. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17265 SUBJECT: GRB 150101A: Fermi GBM detection DATE: 15/01/01 19:47:05 GMT FROM: Oliver Roberts at UCD/Fermi O.J. Roberts (UCD) reports on behalf of the Fermi GBM Team: "At 06:28:53.76 UT on the 1st of January 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150101A (trigger 441786536 / 150101270). The GBM on-ground location, using the Fermi GBM trigger data, is consistent with the enhanced Swift XRT position (Goad et al. 2015, GCN 17262). The angle from the Fermi LAT boresight is about 12 degrees. The GBM light curve consists of a single quick pulse with a duration (T90) of about 0.24 s (50-300 keV). The time-averaged spectrum from T0-0.13 s to T0+13 s is adequately fit by a power law function. The power law index is -1.5 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (9.9 +/- 2.0)E-08 erg/cm^2. The 64 ms peak photon flux measured starting from T0-0.1 s in the 10-1000 keV band is 5.3 +/- 1.1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17266 SUBJECT: GRB 150101A Swift-BAT refined analysis of the short hard burst DATE: 15/01/02 21:19:17 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings, N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec, we report further analysis of BAT GRB 150101A (trigger #623158) (Vargas, et al., GCN Circ. 17261). The BAT ground-calculated position is RA, Dec = 312.599, 36.669 deg which is RA(J2000) = 20h 50m 23.6s Dec(J2000) = +36d 40' 07.8" with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 91%. The mask-weighted light curve shows a single peak. T90 (15-350 keV) is 0.060 +- 0.005 sec (estimated error including systematics). The time-averaged spectrum from T+0.0 to T+0.68 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.26 +- 0.31. The fluence in the 15-150 keV band is (2.3 +- 0.5) x 10^-08 erg/cm2. The 1-sec peak photon flux measured from T-0.46 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/623158/BA/