//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20337 SUBJECT: GRB 161224A: Swift-BAT refined analysis DATE: 16/12/25 18:23:24 GMT FROM: Amy Lien at GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), A. Cholden-Brown (PSU), J. R. Cummings (CPI), N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 161224A (trigger #728268) (Cholden-Brown et al., GCN Circ. 20335). The BAT ground-calculated position is RA, Dec = 204.820, -18.028 deg which is RA(J2000) = 13h 39m 16.9s Dec(J2000) = -18d 01' 41.7" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%. The mask-weighted light curve shows a single pulse structure that starts at ~ T+12 s, peaks at ~T+33 s, and ends at ~T+65 s. T90 (15-350 keV) is 47.04 +- 12.12 sec (estimated error including systematics). The time-averaged spectrum from T+12.46 to T+65.18 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index -0.21 +- 1.56, and Epeak of 34.5 +- 5.6 keV (chi squared 44.84 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is (8.2 +- 1.3) x 10^-7 erg/cm2 and the 1-sec peak flux measured from T+32.88 sec in the 15-150 keV band is 0.8 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.21 +- 0.21 (chi squared 57.66 for 57 d.o.f.). 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/728268/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20338 SUBJECT: GRB 161224A: Swift-XRT refined Analysis DATE: 16/12/26 06:15:37 GMT FROM: Aaron Cholden-Brown at PSU/Swift A. Cholden-Brown (PSU) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: We have analysed 4.9 ks of XRT data for GRB 161224A, from 28.3 ks to 52.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. A fading X-ray source is found in the BAT error region. Using 617 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 204.81579, -18.02909 which is equivalent to: RA (J2000): 13h 39m 15.79s Dec(J2000): -18d 01' 44.7" with an uncertainty of 4.1 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=2.8 (+0.8, -2.1). If the light curve continues to decay with a power-law decay index of 2.8, the count rate at T+24 hours will be 8.4 x 10^-4 count s^-1 The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00728268. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20339 SUBJECT: GRB 161224A: Swift/UVOT Upper limits DATE: 16/12/26 12:12:17 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and A. Cholden-Brown (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 161224A 28.3ks after the BAT trigger after a Sun constraint (Cholden-Brown et al., GCN Circ. 20335). At the position of the XRT source (Cholden-Brown and Evans, GCN Circ. 20338) no uv-optical source was found to the upper limits below. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 44266.0 44786.3 508 >19.99 v 28322.2 50899.7 1770 >19.90 uvw1 35223.6 41032.4 786 >19.91 uvw2 46285.0 46772.6 480 >19.88 uvm2 29234.3 35216.6 1198 >20.48 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.096 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20340 SUBJECT: GRB 161224A: TSHAO optical observations DATE: 16/12/26 13:04:31 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 161224A (Swift trigger=728268, Cholden-Brownet al., GCN 20333) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory. We obtained several images in R filter starting on Dec. 25 (UT) 00:13:31 and Dec. 25 (UT) 23:45:12. We do not detect any evident variable source in the BAT ground-calculated position (Ukwatta al., GCN 20337). Within enhanced XRT position (Cholden-Brownet al., GCN 20338) we not detected any source. Preliminary photometry of the field is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2016-12-25 00:13:31 0.10201 R 16*180 n/d n/d 21.1 2016-12-25 23:45:12 1.07646 R 11*180 n/d n/d 20.7 Photometry is based on nearby USNO-B1.0 stars 0719-0341418 17.14 0720-0349085 17.50 0720-0348989 16.94 0719-0341338 15.94 A finding chart can be found in http://grb.rssi.ru/GRB161224A/GRB161224A_20161225_TSHAO_fc.png