//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12885 SUBJECT: GRB 120121A: Swift detection of a burst DATE: 12/01/21 10:00:46 GMT FROM: David Palmer at LANL K. L. Page (U Leicester), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), J. A. Kennea (PSU), D. M. Palmer (LANL), M. H. Siegel (PSU), R. L. C. Starling (U Leicester) and B.-B. Zhang (PSU) report on behalf of the Swift Team: At 09:42:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120121A (trigger=512164). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 249.336, -23.954 which is RA(J2000) = 16h 37m 21s Dec(J2000) = -23d 57' 14" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked FRED structure with a duration of about 40 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 09:44:18.7 UT, 119.4 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 123 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 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.84. Burst Advocate for this burst is K. L. Page (kpa AT star.le.ac.uk). 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: 12886 SUBJECT: GRB 120121A: Swift-XRT position DATE: 12/01/21 10:58:57 GMT FROM: Kim Page at U.of Leicester K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Using promptly downlinked data we find an X-ray source with an enhanced position: RA,Dec = 249.3547, -23.9618 (degrees) which is equivalent to: RA (J2000.0) = 16 37 25.13 DEC (J2000.0) = -23 57 42.4 with an uncertainty of 3.2 arcsec (radius, 90% containment). This location is 67.6 arcseconds from the BAT onboard position, inside the BAT error circle. It is not yet possible to determine whether the source is fading. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12887 SUBJECT: GRB 120121A: ISON-NM optical observations DATE: 12/01/21 13:16:52 GMT FROM: Leonid Elenin at ISON L. Elenin (KIAM), A. Pozanenko (IKI), A. Volnova (SAI MSU), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 120121A (Page et al., GCN 12885) with 0.45-m telescope ISON-NM observatory on Jan. 21. We took several unfiltered images of 60 s exposure on Jan. 21, starting (UT) 12:29:25. We do not detect any object within the XRT error circle (Page et al., GCN 12886 ), down to 19.7m (calibrated against the USNO B1.0 catalog). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12888 SUBJECT: GRB 120121A: Enhanced Swift-XRT position DATE: 12/01/21 16:34:19 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1511 s of XRT Photon Counting mode data and 2 UVOT images for GRB 120121A, 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 = 249.35428, -23.96156 which is equivalent to: RA (J2000): 16h 37m 25.03s Dec (J2000): -23d 57' 41.6" with an uncertainty of 1.7 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: 12889 SUBJECT: GRB 120121A: Swift-BAT refined analysis DATE: 12/01/21 17:59:41 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120121A (trigger #512164) (Page, et al., GCN Circ. 12885). The BAT ground-calculated position is RA, Dec = 249.363, -23.963 deg which is RA(J2000) = 16h 37m 27.1s Dec(J2000) = -23d 57' 45.9" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 70%. The mask-weighted light curve shows several overlapping peaks starting at ~T-10 sec, peaking at ~T+2 sec, and ending at ~T+70 sec. T90 (15-350 keV) is 26.1 +- 3.1 sec (estimated error including systematics). The time-averaged spectrum from T-11.00 to T+18.33 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.23 +- 0.13. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.86 sec in the 15-150 keV band is 0.7 +- 0.2 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/512164/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12890 SUBJECT: GRB 120121A: Swift-XRT refined Analysis DATE: 12/01/21 20:02:06 GMT FROM: Kim Page at U.of Leicester K. L. Page (U Leicester) reports on behalf of the Swift-XRT team: We have analysed 9.8 ks of XRT data for GRB 120121A (Page et al. GCN Circ. 12885), from 130 s to 23.1 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 12888). The light curve can be modelled with a power-law decay with a decay index of alpha=0.88 (+0.09, -0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+0.7, -0.6). The best-fitting absorption column is 2.4 (+1.3, -0.9) x 10^22 cm^-2, in excess of the Galactic value of 1.2 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 7.5 x 10^-11 (2.0 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.4 (+1.3, -0.9) x 10^22 cm^-2 Galactic foreground: 1.2 x 10^21 cm^-2 Excess significance: 4.3 sigma Photon index: 2.0 (+0.7, -0.6) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00512164. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12891 SUBJECT: GRB 120121A: Swift/UVOT Upper Limits DATE: 12/01/21 20:11:24 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 120121A 124 s after the BAT trigger (Page et al., GCN Circ. 12885). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 12888) 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) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 124 273 147 >20.2 u_FC 336 585 246 >19.7 white 124 6777 673 >21.1 v 664 7188 510 >18.9 b 591 13219 1160 >20.2 u 336 18998 2078 >20.2 w1 714 18281 2108 >20.4 m2 16474 17374 886 >20.1 w2 1020 23198 1298 >21.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.87 in the direction of the burst (Schlegel et al. 1998).