//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12980 SUBJECT: GRB 120224A: Swift detection of a burst DATE: 12/02/24 04:51:10 GMT FROM: David Palmer at LANL C. J. Saxton (UCL-MSSL), J. R. Cummings (NASA/UMBC), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (NASA/GSFC/ORAU), O. M. Littlejohns (U Leicester), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), C. J. Mountford (U Leicester), S. R. Oates (UCL-MSSL), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU), C. A. Swenson (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 04:39:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120224A (trigger=515976). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 40.975, -17.793 which is RA(J2000) = 02h 43m 54s Dec(J2000) = -17d 47' 32" 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 10 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 04:41:45.6 UT, 109.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 40.94380, -17.75959 which is equivalent to: RA(J2000) = 02h 43m 46.51s Dec(J2000) = -17d 45' 34.5" with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 160 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 in excess of the Galactic value (2.45 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 3.6 (+4.34/-3.51) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 114 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 none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT 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 0.04. Burst Advocate for this burst is C. J. Saxton (cjs2 AT mssl.ucl.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: 12981 SUBJECT: GRB 120224A: Enhanced Swift-XRT position DATE: 12/02/24 08:48:09 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1421 s of XRT Photon Counting mode data and 2 UVOT images for GRB 120224A, 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 = 40.94221, -17.76130 which is equivalent to: RA (J2000): 02h 43m 46.13s Dec (J2000): -17d 45' 40.7" with an uncertainty of 1.8 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: 12983 SUBJECT: GRB 120224A: Swift-BAT refined analysis DATE: 12/02/24 13:26:41 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), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), C. J. Saxton (UCL-MSSL), 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+326 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120224A (trigger #515976) (Saxton, et al., GCN Circ. 12980). The BAT ground-calculated position is RA, Dec = 40.937, -17.779 deg, which is RA(J2000) = 02h 43m 44.8s Dec(J2000) = -17d 46' 42.6" with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 29%. The mask-weighted light curve shows two peaks, the first starting at ~T-20 sec, peaking at ~T-6 sec. The second (and stronger peak) starts at ~T-3 sec, peaks at ~T+1 sec, and ends at ~T+13 sec. T90 (15-350 keV) is 8.13 +- 1.99 sec (estimated error including systematics). The time-averaged spectrum from T-1.08 to T+8.26 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.25 +- 0.36. The fluence in the 15-150 keV band is 2.4 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.24 sec in the 15-150 keV band is 0.9 +- 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/515976/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12984 SUBJECT: GRB 120224A: Swift/UVOT Upper Limits DATE: 12/02/24 16:39:22 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (MSSL-UCL) and C. J. Saxton (UCL-MSSL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 120224A 115 s after the BAT trigger (Saxton et al., GCN Circ. 12980). No optical afterglow consistent with the enhanced XRT position (Osborne et al., GCN Circ. 12981) 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 115 264 147 >20.7 u_FC 273 522 246 >20.5 white 115 1547 392 >21.2 v 602 1424 97 >19.4 b 529 1522 97 >20.2 u 273 1497 304 >20.4 w1 1107 1127 19 >19.6 m2 1254 1448 39 >19.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12986 SUBJECT: GRB 120224A: Swift-XRT refined Analysis DATE: 12/02/24 19:51:03 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU) and C.J. Saxton report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 120224A (Saxton et al. GCN Circ. 12980), from 95 s to 34.0 ks after the BAT trigger. The data comprise 6 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 12981). The late-time light curve (from T0+5.3 ks) can be modelled with a power-law decay with a decay index of alpha=0.99 (+/-0.11). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.22 (+0.16, -0.15). The best-fitting absorption column is 3.0 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 2.4 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (6.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.0 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 2.4 x 10^20 cm^-2 Excess significance: 9.3 sigma Photon index: 2.22 (+0.16, -0.15) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00515976. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12988 SUBJECT: GRB 120224A: GROND detection of the afterglow candidate DATE: 12/02/27 01:33:33 GMT FROM: Jonny Elliott at MPE/GROND J. Elliott (MPE Garching), S. Klose (TLS Tautenburg) and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB120224A (Swift trigger 515976; Saxton et al., GCN #12980) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). First observations started at 00:14 UT on 25 February 2012, 19.58 hrs after the GRB trigger. They were perfomed at an average seeing of 1".27 and at an average airmass of 1.4. After an exposure time of 4.72 min in g'r'i'z' and 8 min JHK, no source was detected. Second observations started at 00:48 UT on 26 February 2012, 1.84 days after the GRB trigger. They were performed at an average seeing of 0".96 and at an average airmass of 2.0. We find a single point source within the 1".8 refined Swift-XRT error circle reported by Osborne et al. (GCN #12981) at RA (J2000.0) = 02:43:46.15 = 40.94230 Dec. (J2000.0) = -17:45:42.0 = -17.76169 with an uncertainty of 0".5 in each coordinate. Based on total exposures of 36 min in JHK, we estimate preliminary magnitude (AB) of, J = 20.9 +/- 0.2 The given magnitude is calibrated against 2MASS field stars and is not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V)=0.04 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12990 SUBJECT: GRB 120224A: optical observation in Mondy observatory DATE: 12/02/27 19:44:55 GMT FROM: Alexei Pozanenko at IKI, Moscow A.Volnova (SAI MSU), E. Klunko (ISTP), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed the field of GRB 120224A (Saxton et al., GCN 12980) with AZT-33IK telescope of Sayan observatory (Mondy) on Feb. 24 between (UT) 12:49:39 - 13:22:16 (mean time 8.44 hrs after burst trigger) in R filter under mean FWHM of 4.5" and at high airmass of ~ 4 . In a combined image we do not detect the afterglow candidate (Elliott et al., GCN 12988). A photometry is based on the USNO-B1.0 star USNO-B1.0 0722-0043384 (02:43:36.48 -17:47:18.1) assuming R = 18.57: : T0+, Filter, Exposure, OT, UpperLimit (3 sigma) (mid, d) (s) 0.3518 R 37 x 60 n/d 20.3 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12991 SUBJECT: GRB 120224A: VLT/X-shooter observations DATE: 12/02/27 21:45:20 GMT FROM: Klaas Wiersema at U Leicester K. Wiersema (Leicester), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), J. P. U. Fynbo (DARK/NBI), N. R. Tanvir (U. Leicester), D. Malesani (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), S. D. Vergani (INAF/OAB), S. Covino (INAF/OAB), H. Flores (Obs. Paris) report on behalf of the X-shooter GTO GRB collaboration: We observed the position of the afterglow of GRB 120224A (Saxton et al., GCN 12980) using the X-shooter spectrograph mounted on the VLT. Observations started on 00:30 UT on 25 February 2012, i.e. 19.83 hours after burst. In the acquisition images, 5 x 150 seconds in R filter, we find a faint source, consistent with the candidate afterglow reported by Elliott et al (GCN 12988). We find a preliminary magnitude of R=22.3 using the USNO-B star 0722-0043411 (R=16.65). The detection of the afterglow in the R band places a limit on the redshift of approximately z < 5. We performed spectroscopy of this source, under poor seeing and high airmass. We detect a faint continuum in the near-infrared arm over the whole wavelength range, at low signal to noise. In the visual arm data we detect a very faint continuum at the red end of the wavelength range. No emission lines are detected. Because of the low signal to noise we are not able to identify absorption features. The non- detection of continuum emission below ~600 nm may be indicative of a moderately high redshift for this burst, though alternatives, such as a reddened spectrum (note that the X-ray afterglow shows considerable absorption; Osborne et al. GCN 12986), can not be excluded at present. We are grateful for the excellent support from the Paranal Observatory staff, in particular Myriam Rodrigues and Ivo Saviane.