//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20570 SUBJECT: GRB 170131A detected in Swift/BAT ground processing DATE: 17/02/01 19:19:04 GMT FROM: David Palmer at LANL GRB 170131A detected in Swift/BAT ground processing David Palmer (LANL), on behalf of the Swift team, reports: At 23:15:13 UT on 2017-01-31, the Swift Burst Alert Telescope (BAT) detected a marginal peak in a rate-triggered image (Swift Trigger #736107). Because it was below the image significance threshold, it did not yield a GRB follow-up. However, ground analysis shows that it is at the same location as a Fermi/GBM trigger (#507597304). KONUS/WIND also reported a trigger at the same time. The BAT on-board calculated location is RA, Dec 341.447, 64.006, which is RA(J2000) = 22h 45m 55s Dec(J2000) = +64d 00' 22" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a ~30 s long FRED structure starting at ~T-20 (consistent with the Fermi/GBM trigger time) superimposed with a ~5 second peak near the BAT trigger time. The peak count rate was ~3000 counts/sec (15-350 keV), at ~3 sec after the BAT trigger. A Swift ToO observation has been scheduled. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20571 SUBJECT: GRB 170131A: Swift ToO observations DATE: 17/02/01 20:34:18 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Swift/BAT GRB 170131A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020738 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Swift/BAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20572 SUBJECT: GRB 170131A: Fermi GBM observation DATE: 17/02/01 23:24:55 GMT FROM: Bagrat Mailyan at UAH B. Mailyan (UAH) and O.J Roberts (NASA-MSFC/USRA) report on behalf of the Fermi GBM Team: "At 23:14:59.36 UT on January 31st 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170131A (trigger 507597304 /170131969) which was also detected by the Swift/BAT (Palmer, GCN 20570). The GBM on-ground location is consistent with the Swift-BAT position. The angle from the Fermi LAT boresight at the GBM trigger time using the Swift-BAT position is 18 degrees. The GBM light curve shows a FRED-like burst with overlapping pulses with a duration (T90) of about 23 s (50-300 keV). The time-averaged spectrum from T0-1.0 s to T0+18.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.37+/-0.06 and the cutoff energy, parameterized as Epeak, is 209 +/- 34 keV. The event fluence (10-1000 keV) in this time interval is (4.56 +/- 0.27)E-06 erg/cm^2. The 1 s peak photon flux measured starting from T0+15.4 s in the 10-1000 keV band is 4.9 +/- 0.3 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: 20573 SUBJECT: GRB 170131A: Swift-XRT observations DATE: 17/02/02 08:41:10 GMT FROM: Phil Evans at U of Leicester A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Cholden-Brown (PSU), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 170131A (David Palmer et al. GCN Circ. 20570), collecting 4.9 ks of Photon Counting (PC) mode data between T0+78.4 ks and T0+96.6 ks. One uncatalogued X-ray source has been detected consistent with being within 296 arcsec of the Swift/BAT position, it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 341.3994 = 22:45:35.85 Dec (J2000.0): +64.0090 = +64:00:32.6 Error: 5.8 arcsec (radius, 90% conf.) Count-rate: (2.19 [+0.93, -0.75])e-3 ct s^-1 Distance: 75 arcsec from Swift/BAT position. Flux: (6.2 [+2.6, -2.1])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) A uncatalogued source was also detected, however this was too far from the GRB position to be the afterglow. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020738. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20574 SUBJECT: GRB 170131A: Swift/UVOT Upper Limits DATE: 17/02/02 14:21:17 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL), M. Stamatikos (OSU) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170131A 78368 s after the BAT trigger (Palmer, GCN Circ. 20570) using the UVW2 filter only. No optical afterglow consistent with the XRT source 1 position (Melandri et al., GCN Circ. 20573) is detected in the initial UVOT exposures. However, there is a USNO-B1.0 source at this position (USNO-B1.0 1540-029147), but it is not detected in the UVW2 filter. The preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures is: Filter T_start(s) T_stop(s) Exp(s) Mag w2 78368 96539 4888 >21.2 The magnitude in the table is not corrected for the large, but uncertain Galactic extinction due to the reddening of E(B-V) = 1.19 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20600 SUBJECT: GRB 170131A: POLAR Observation DATE: 17/02/04 03:20:19 GMT FROM: Zhao Yi at POLAR Yi Zhao (IHEP), Xing Wen (IHEP), Yuanhao Wang (IHEP) report on behalf of the POLAR collaboration: At 2017-01-31T23:14:59.00 UT (T0), during a routine on-ground search of data, POLAR detected the GRB 170131A, which was also detected by the Fermi/GBM (trigger 507597304/170131969, Circ 20572), Swift (Circ 20570) and Konus-Wind. The POLAR light curve consists of multiple peaks, with a duration (T90) of 21.88 s measured from T0-1.21 s. The 1-s peak rate measured from T0+16.00 s is 888.4 cnts/s. The total counts is about 7085 cnts. The above measurements are in the energy range of about 20-500 keV. LC_URL: http://polar.ihep.ac.cn/grb/2017/01/GRB170131A/lc/POLAR_lc_grb170131A.png Using the best location from the Swift/BAT, which is (J2000): RA: 341.447 [deg] Dec: +64.006 [deg] Err: 3.00 [arcmin] the incident angle in POLAR coordinate at T0 is: theta: 76.5 [deg] phi: 22.2 [deg] All analysis results presented above are preliminary. POLAR is a dedicated Gamma-Ray Burst polarimeter (50-500 keV) on-board the Chinese space laboratory Tiangong-2 launched on Sep 15,2016. More information about POLAR can be found at http://polar.ihep.ac.cn/en/ , http://isdc.unige.ch/polar/ and http://polar.psi.ch/pub/.