//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13182 SUBJECT: GRB 120401A: Swift detection of a burst DATE: 12/04/01 05:33:59 GMT FROM: David Palmer at LANL A. P. Beardmore (U Leicester), W. H. Baumgartner (GSFC/UMBC), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), C. J. Mountford (U Leicester), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (NASA/UMBC), M. H. Siegel (PSU), R. L. C. Starling (U Leicester) and B.-B. Zhang (PSU) report on behalf of the Swift Team: At 05:24:15 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120401A (trigger=519043). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 58.068, -17.671 which is RA(J2000) = 03h 52m 16s Dec(J2000) = -17d 40' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for an image trigger, no activity is apparent in the immediately available light curve. The XRT began observing the field at 05:26:14.1 UT, 118.3 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 58.0835, -17.6349 which is equivalent to: RA(J2000) = +03h 52m 20.04s Dec(J2000) = -17d 38' 05.6" with an uncertainty of 5.4 arcseconds (radius, 90% containment). This location is 140 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 1.35e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 127 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 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 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 0.05. Burst Advocate for this burst is A. P. Beardmore (apb 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: 13183 SUBJECT: GRB 120401A: Prompt enhanced Swift-XRT position DATE: 12/04/01 06:16:27 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Using promptly downlinked XRT event data for GRB 120401A, we find an enhanced XRT position of the afterglow: RA, Dec: 58.0819, -17.6359 which is equivalent to: RA (J2000) = 03 52 19.67 Dec (J2000) = -17 38 09.2 with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/519043. Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13184 SUBJECT: GRB 120401A: Enhanced Swift-XRT position DATE: 12/04/01 10:53:59 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 2418 s of XRT Photon Counting mode data and 3 UVOT images for GRB 120401A, 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 = 58.08251, -17.63577 which is equivalent to: RA (J2000): 03h 52m 19.80s Dec (J2000): -17d 38' 08.8" with an uncertainty of 1.6 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: 13186 SUBJECT: GRB 120401A: Swift-BAT refined analysis DATE: 12/04/01 15:53:31 GMT FROM: Scott Barthelmy at NASA/GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), 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 120401A (trigger #519043) (Beardmore, et al., GCN Circ. 13182). The BAT ground-calculated position is RA, Dec = 58.057, -17.658 deg, which is RA(J2000) = 03h 52m 13.8s Dec(J2000) = -17d 39' 29.6" with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows the burst was occuring when the location came into the BAT FoV at T-100 sec during a preplanned slew. There was a decline, then a increase around T+0, and the a decline again returning to baseline around T+180 sec. We are not quoting a T90 because we did not observe the burst in its entirety. The time-averaged spectrum from T-92.97 to T+52.72 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.66 +- 0.23. The fluence in the 15-150 keV band is 9.1 +- 1.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-85 sec in the 15-150 keV band is 0.12 +- 0.04 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/519043/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13187 SUBJECT: GRB 120401A: Swift-XRT refined Analysis DATE: 12/04/01 17:34:05 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), A. Maselli (INAF-IASFPA), V. Mangano (INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU) and A.P. Beardmore report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 120401A (Beardmore et al. GCN Circ. 13182), from 124 s to 24.8 ks after the BAT trigger. The data comprise 519 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 13183). The late-time light curve (from T0+5.0 ks) can be modelled with a power-law decay with a decay index of alpha=1.2 (+0.4, -0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.29 (+0.07, -0.06). The best-fitting absorption column is 1.27 (+0.13, -0.12) x 10^21 cm^-2, in excess of the Galactic value of 3.2 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.75 (+0.11, -0.10) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 0 (+1.5, -0) x 10^20 cm^-2 Galactic foreground: 3.2 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.75 (+0.11, -0.10) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00519043. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13219 SUBJECT: GRB 120401A: GROND Detection of an optical/NIR afterglow candidate DATE: 12/04/04 23:27:18 GMT FROM: Vladimir Sudilovsky at MPE V. Sudilovsky, J. Elliott, J. Greiner (all MPE Garching), T. Kruehler (DARK) and A. Rau (also MPE Garching), report on behalf of the GROND team: We observed the field of GRB120401A (Swift trigger 519043; Beardmore et al., GCN #13182) 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 23:32 UT on 2012-04-01, 18.1 hours after the GRB trigger. For an exposure time of 18.76 min in g'r'i'z' and 15 min in JHK performed at an average seeing of 1".8 and at an average airmass of 2.1, we find a single point source within the 1".6 enhanced Swift-XRT error circle reported by Evans et al. (GCN #13184) at RA (J2000.0) = 03:52:19.82 = 58.08258 Dec. (J2000.0) = -17:38:08.5 = -17.63569 with an uncertainty of 0.3" in each coordinate. We estimate preliminary magnitudes (all in AB) of g' > 23, r' = 22.7 +/- 0.2 i' = 21.5 +/- 0.1 z' = 21.0 +/- 0.1 J = 20.7 +/- 0.2, H > 20.7, and K > 18.5 The SED, constructed from the Galactic foreground extinction (E_(B-V)=0.053 mag, Schlegel et al. 1998) corrected magnitudes of the object gives a photometric redshift of z=4.5 ± 0.5, while intrinsic or host galaxy extinction alone cannot account for the r'-i' colour. A second observation began at 23:29 UT on 2012-04-02, 1.75 days after the GRB trigger. Due to telescope pointing problems, JHK were the only filters to cover the GRB location. For an exposure time of 38.3 min in JHK at an average seeing of 1".4 and at an average airmass of 2.0, we do not detect the source. With an upper limit of J (AB) > 21.4, it suggests a decay of at least 0.7 mag. Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars.