//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13525 SUBJECT: GRB 120728A: Swift detection of a burst DATE: 12/07/28 22:37:55 GMT FROM: Scott Barthelmy at NASA/GSFC J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC), M. M. Chester (PSU), H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL), C. B. Markwardt (NASA/GSFC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 22:25:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120728A (trigger=529021). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 137.100, -54.437, which is RA(J2000) = 09h 08m 24s Dec(J2000) = -54d 26' 13" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a peak with structure with a total duration of about 20 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~3 sec after the trigger. The XRT began observing the field at 22:27:38.8 UT, 147.8 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 137.09412, -54.43783 which is equivalent to: RA(J2000) = 09h 08m 22.59s Dec(J2000) = -54d 26' 16.2" with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 12 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 5.18 x 10^21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 250 seconds with the U filter starting 148 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. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain extinction expected. Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.nasa.gov). 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: 13526 SUBJECT: GRB 120728A: GROND observations DATE: 12/07/29 02:20:44 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann, S. Klose (both TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 120728A (Swift trigger 529021; Cummings et al., GCN 13525) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Observations started at 23:05 UT on 2012-07-28, 41 minutes after the GRB trigger. Observations were obtained in twilight, at high (2.5) airmass and bad seeing (2".7 in the r' band). Based on an exposure of 9.4 minutes in the optical and 16 minutes in the NIR we do not detect any source within the Swift/XRT error circle at coordinates RA, Dec(J2000)= 09:08:22.69, -54:26:17.7, error 3".6. (SPER data) At the edge of the error circle, we find two sources. One, at RA (J2000) = 09:08:23.20, Dec. (J2000) = -54:26:18.8, is a star also visible in the DSS. The other may be marginally detected in the DSS, and likely consists of two sources, centered at (+/- 0".5) RA (J2000) = 09:08:22.82, Dec. (J2000) = -54:26:13.1 and RA (J2000) = 09:08:22.55, Dec. (J2000) = -54:26:14.2. We are unable to make any statements about the variability of these objects at this time, but given the crowded field this close to the Galactic plane, it is likely neither is associated with the GRB. Preliminary limiting magnitudes (AB mags) are: g' > 21.6 r' > 21.9 i' > 21.3 z' > 21.1 J > 19.5 H > 19.9 Ks > 19.3. Magnitudes are derived based on GROND zeropoints (g'r'i'z') and 2MASS stars (JHKs). No correction for the high Galactic reddening along the line of sight (E(B-V)=0.57 mag; Schlegel et al. 1998) has been applied. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13528 SUBJECT: GRB 120728A: Enhanced Swift-XRT position DATE: 12/07/29 09:02:12 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 4986 s of XRT Photon Counting mode data and 6 UVOT images for GRB 120728A, 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 = 137.09469, -54.43760 which is equivalent to: RA (J2000): 09h 08m 22.73s Dec (J2000): -54d 26' 15.4" 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: 13529 SUBJECT: GRB 120728A: Swift-XRT refined Analysis DATE: 12/07/29 10:38:05 GMT FROM: Phil Evans at U of Leicester V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), J.P. Osborne (U. Leicester), V. Mangano (INAF-IASFPA) and J.R. Cummings report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 120728A (Cummings et al. GCN Circ. 13525), from 161 s to 24.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 13528). The late-time light curve (from T0+5.1 ks) can be modelled with a power-law decay with a decay index of alpha=0.98 (+/-0.25). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.67 (+0.25, -0.10). The best-fitting absorption column is consistent with the Galactic value of 5.2 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 3.4 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 0 (+2.2, -0) x 10^20 cm^-2 Galactic foreground: 5.2 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.67 (+0.25, -0.10) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00529021. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13533 SUBJECT: GRB 120728A: Swift/UVOT Upper Limits DATE: 12/07/29 13:31:20 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) and J. R. Cummings (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 120728A 148 s after the BAT trigger (Cummings et al., GCN Circ. 13525). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ.13528) 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 u_FC 148 398 246 >19.5 v 456 17454 1356 >20.6 b 404 24174 2261 >22.3 u 148 23261 2438 >21.0 w1 505 19107 1200 >20.8 m2 480 18359 1357 >21.0 w2 430 24878 1735 >21.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.53 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13535 SUBJECT: GRB 120728A, Swift-BAT refined analysis DATE: 12/07/29 16:13:33 GMT FROM: Hans Krimm at NASA-GSFC C. B. Markwardt (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), 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-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120728A (trigger #529021) (Cummings, et al., GCN Circ. 13525). The BAT ground-calculated position is RA, Dec = 137.085, -54.437 deg which is RA(J2000) = 09h 08m 20.3s Dec(J2000) = -54d 26' 12.4" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 13%. The mask-weighted light curve shows a broad FRED-like peak of total duration ~25 seconds with three subsidiary peaks superimposed. The T90 (15-350 keV) is 22.06 +- 2.59 sec (estimated error including systematics). The time-averaged spectrum from T+0.56 to T+26.46 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.13. The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+12.12 sec in the 15-150 keV band is 2.4 +- 0.5 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/529021/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13542 SUBJECT: GRB 120728A: GROND Afterglow discovery DATE: 12/07/30 10:09:43 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann, S. Klose (both TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed again the field of GRB 120728A (Swift trigger 529021; Cummings et al., GCN 13525) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Compared to our first epoch (Kann et al., GCN 13526), seeing conditions significantly improved to 1".5 in the r' band. We obtained 7 minutes of optical observations and 12 minutes of NIR observations centered 1.035 days after the GRB. We achieve limiting magnitudes which are 0.5 mag deeper in all optical bands compared to our first epoch, but shallower in the NIR. The enhanced Swift-XRT position (Osborne et al., GCN 13528) does not include the bright DSS source in the south-east anymore, but still overlaps with the two northern sources (Kann et al., GCN 13526). Upon close inspection, the eastern source is also detected in the DSS, whereas the western source is not. This source is furthermore not present anymore in our second epoch, which we confirm by image subtraction. We therefore propose this source to be the optical afterglow of GRB 120728A, and derive a position: RA (J2000) = 09:08:22.62, DEC (J2000) = -54:26:14.5 with an error of 0".8. The preliminary magnitude is r' = 20.80 +/- 0.16 (statistical) +/- 0.27 (systematic) against the USNO-B1.0 catalog in the first epoch, 0.0377 days after the GRB. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13595 SUBJECT: GRB 120728A: Fermi GBM observation DATE: 12/08/06 17:24:10 GMT FROM: Shaolin Xiong at UAH Shaolin Xiong (UAH) reports on behalf of the Fermi GBM Team: "At 22:25:13.737 UT on 28 July 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120728A (trigger 365207115 / 120728934) which was also detected by the Swift/BAT (Cummings et al. 2012, GCN 13525). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 110 degrees. The GBM light curve consists of multiple pulses with a duration (T90) of about 32.8 s (50-300 keV). The time-averaged spectrum from T0-1.0 s to T0+23.6 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.66 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 119.80 +/- 30.80 keV. The event fluence (10-1000 keV) in this time interval is (5.29 +/- 0.27)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+13.12 s in the 10-1000 keV band is 3.58 +/- 0.28 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."