//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15246 SUBJECT: GRB 130925A: Swift detection of a burst DATE: 13/09/25 04:26:41 GMT FROM: David Palmer at LANL A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC), M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 04:11:24 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130925A (trigger=571830). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 41.183, -26.134 which is RA(J2000) = 02h 44m 44s Dec(J2000) = -26d 08' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed that the burst was active during the pre-planned slew before the nominal trigger with an additional peak extending at least to T+170. The peak count rate was ~2700 counts/sec (15-350 keV), at ~110 sec after the trigger. The XRT began observing the field at 04:13:52.3 UT, 147.4 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 41.1766, -26.1544 which is equivalent to: RA(J2000) = +02h 44m 42.38s Dec(J2000) = -26d 09' 15.8" with an uncertainty of 5.1 arcseconds (radius, 90% containment). This location is 76 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. UVOT took a finding chart exposure of 150 seconds with the White filter starting 156 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. Results from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is A. Y. Lien (yarleen AT gmail.com). 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: 15247 SUBJECT: GRB 130925A: GROND afterglow candidate DATE: 13/09/25 06:05:22 GMT FROM: Vladimir Sudilovsky at MPE V. Sudilovsky (MPE Garching), D.A. Kann, and J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 130925A (Lien et al., GCN #15246) 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). The first epoch observation started at 04:18:52 UT on 25 Sept 2013, 7 minutes after the GRB trigger. They were performed at an average seeing of 0.7" and at an average airmass of 1.3. We do not find any sources within the revised 3".6 Swift XRT error circle. However, we do find an uncataloged red source 2" east of the error circle at position: RA (J2000.0) = 02:44:42.96 = 41.1790 Dec. (J2000.0) = -26:09:11.16 = -26.1531 with an uncertainty of 0.3" in each coordinate. Based on a total exposure of 4.4 minutes in g'r'i'z' and 4 minutes in JHK, we estimate preliminary magnitudes (all in AB) of g' > 21.5 mag, r' > 22 mag, i' = 21.8 ± 0.1 mag, z' = 21.3 ± 0.1 mag, J = 19.6 ± 0.1 mag, H = 18.6 ± 0.1 mag, and K = 18.0 ± 0.1 mag. The source is seen to be brightening in the first images before fading strongly. We suggest this source to be the afterglow of GRB 130925A. Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.02 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15248 SUBJECT: GRB 130925A: MAXI/GSC detection DATE: 13/09/25 08:31:49 GMT FROM: Satoshi Nakahira at JAXA/MAXI K. Suzuki, H. Sakakibara, H. Negoro (Nihon U.), S. Nakahira, H. Tomida, S. Ueno, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Morii, M. Serino, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Nakano (AGU), H. Tsunemi, M. Sasaki (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.), M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team: The MAXI/GSC Nova alert system triggered a bright uncatalogued X-ray transient source at UT 2013-09-25T05:13:41. Assuming that the source flux was constant over the transit, we obtain the source position at (41.38 deg, -25.91 deg) = (02 45 32, -25 54 54)(J2000) with a 90% C.L. statistical error of 0.2 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius). The position is consistent with that of GRB 130925A (Lien et al. GCN #15246), and apart from GRB 130925A by 0.30 deg. This detection is, however, about 1 hour after the Swift detection. The 2-20 keV flux was 290 (-51/+53) mCrab. An absorbed power-law fit to the burst spectrum gives a photon index 1.62 +/- 0.27. There was no significant excess flux in the previous transit at 03:41 UT and in the next transit at 06:47 UT with an upper limit of 20 mCrab for each. [GCN OPS NOTE(25sep13): Per author's request, the Lien citation of 12526 was changed to 15246.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15249 SUBJECT: GRB 130925A: VLT/UVES observations DATE: 13/09/25 10:45:42 GMT FROM: Paul Vreeswijk at Weizmann Inst of Science P. M. Vreeswijk (Weizmann), D. Malesani, J. P. U. Fynbo (DARK/NBI), A. De Cia (Weizmann) and C. Ledoux (ESO) report: GRB 130925A (Lien et al., GCN 15246; Suzuki et al., GCN 15248) was observed with UVES at the ESO-VLT, in Rapid Response Mode, starting at around 5 UT (50 minutes after the Swift trigger). A series of spectra were taken of the brightest object near the XRT error circle. We caution that the small field of view of the UVES acquisition camera and the lack of nearby bright stars does not allow us to identify this object unambiguously as the optical counterpart discovered by Sudilovsky et al. (GCN 15247). Preliminary analysis of the automatically reduced spectra reveals the presence of a very faint continuum in the red part and a pair of emission lines at 8845 A and 8873 A. These lines can be identified with Halpha and [NII] 6585 at a redshift of z=0.347. We are grateful for the excellent support at Paranal provided by Jonathan Smoker and Patricia Guajardo, and we thank D. A. Kann and the GROND team for showing us a finding chart of the afterglow field. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15250 SUBJECT: GRB 130925A: VLT/X-shooter redshift DATE: 13/09/25 11:07:01 GMT FROM: Sylvio Klose at TLS Tautenburg V. Sudilovsky, D.A. Kann, P. Schady (all MPE Garching), S. Klose (TLS Tautenburg), J. Greiner (MPE Garching), and T. Kruehler (ESO) report: We observed the optical/NIR afterglow (Sudilovsky et al., GCN 15247) of GRB 130925A (Swift trigger 571830, Lien et al., GCN 15246) using ESO/VLT UT2 equipped with the X-shooter spectrograph. Observations started at 07:42 UT on 2013-09-25, about 3.5 hr after the Swift trigger. A total exposure of 1.6 hr was obtained, covering the spectral range from 3000 to 20500 AA. In the spectrum we detect emission lines, which we interpret as being due to [O II](3726,3729), H_beta, [O III](4959), [O III](5007) and H_alpha at a common redshift of z = 0.35, in agreement with Vreeswijk et al. (GCN 15249). We thank the Paranal staff for excellent support, in particular Linda Schmidtobreick, Jonathan Smoker and Patricia. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15251 SUBJECT: GRB 130925A: Enhanced Swift-XRT position DATE: 13/09/25 11:55:00 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 614 s of XRT Photon Counting mode data and 2 UVOT images for GRB 130925A, 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 = 41.17877, -26.15300 which is equivalent to: RA (J2000): 02h 44m 42.91s Dec (J2000): -26d 09' 10.8" 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: 15252 SUBJECT: GRB 130925A: TAROT La Silla observatory optical observations DATE: 13/09/25 13:27:30 GMT FROM: Alain Klotz at IRAP-CNRS-OMP Klotz A. (IRAP-CNRS-OMP), Gendre B. (IRAP-CNRS-OMP), Boer M., Siellez K., Dereli H., Bardho O. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report: We imaged the field of GRB 130925A detected by SWIFT (trigger 571830) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile. The observations started 88.1s after the GRB trigger (13.0s after the notice). The elevation of the field increased from 50 degrees above horizon and weather conditions were good. We do not detect the afterglow discovered by Sudilovsky et al. (GCNC 15247, GCNC 15250) and confirmed by Vreeswijk et al. (GCNC 15249). However, the observations of TAROT give upper optical limits of the early afterglow. The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39): t0+88.1s to t0+148.1s : Rlim = 17.5 We co-added a series of exposures with diurnal drift: t0+477s to t0+1081s : Rlim = 19.2 Magnitudes were estimated with the nearby NOMAD1 stars and are not corrected for galactic dust extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15253 SUBJECT: GRB 130925A: Initial Similarities to Swift J1644+57 DATE: 13/09/25 14:59:41 GMT FROM: S. Bradley Cenko at Caltech D. N. Burrows (PSU), D. Malesani (DARK/NBI), A. Y. Lien (NASA/GSFC/ORAU), S. B. Cenko (NASA/GSFC), and N. Gehrels (NASA/GSFC) report: At 04:11:24 UT on 25 September 2013, the Swift BAT triggered on an object denoted as GRB 130925A on the assumption that it is a gamma-ray burst (Lien et al., GCN 15246). Here we note that this source presents several unusual features that are atypical of GRBs. The initial XRT observations show extremely rapid and dramatic flaring over the first 10^4 s, far in excess of what we typically see in GRBs. The high X-ray flux at these relatively late times is likely what resulted in the detection of this source by MAXI ~ 1 hour after the GRB (Suzuki et al., GCN 15248). The Swift/XRT light curve is available at the following URL: http://www.swift.ac.uk/xrt_curves/00571830/ We note that this behavior is at first glance similar to the highly variable soft X-ray light curve observed from Swift J1644+57 (GRB 110328A), which has been interpreted as a newly formed relativistic jet resulting from the tidal disruption of a star by a super-massive black hole (Burrows et al. 2011; Levan et al. 2011; Zauderer et al. 2011; Bloom et al. 2011). Like Swift J1644+57, GRB 130925A is a BAT image trigger, is associated with highly absorbed optical/NIR transient emission (Sudilovsky et al., GCN 15247), and lies at a relatively low redshift (z = 0.347; Vreeswijk et al., GCN 15249; Sudilovsky et al., GCN 15250). We encourage observations at all wavelengths to help determine the nature of this interesting source. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15254 SUBJECT: GRB 130925A: Swift-XRT refined Analysis DATE: 13/09/25 15:27:05 GMT FROM: Phil Evans at U of Leicester P.A. Evans, C. Pagani, K.L. Page, A.P. Beardmore, R.L.C. Starling (U. Leicester) and A. Y. Lien (NASA/GSFC/ORAU) report on behalf of the Swift-XRT team: We have analysed 4.7 ks of XRT data for GRB 130925A (Lien et al. GCN Circ. 15246), from 151 s to 12.0 ks after the BAT trigger. The data comprise 3.2 ks 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 15251). The light curve behaviour is dominated by sharp, bright flares. The initial decay follows a power-law with an index of 2.70 (+/- 0.03) and then breaks at T0+464 (+9,-6) to a virtually flat segment, with a formal decay index of 0.16 (+0.11, -0.17). At this point the XRT count rate is 47 ct/sec (approx 2.1e-9 erg cm^-2 s^-1, 0.3-10 keV). Then at T0+750 a flare begins, which peaks at T0+1000 s at a count rate of ~100 ct/sec. This flare fades steeply to ~8 ct/sec at T0+1240 s at which point a second, steep and bright flare begins. This peaks at T0+1380 s at a count rate of ~150 ct/sec. The Swift observations were interrupted at T0+1503 s as the GRB entered Earth-eclipse; the count-rate by this time had fallen to ~50 ct/sec. The MAXI detection (Suzuki et al., GCN Circ. 15248) took place while the GRB was thus unobservable by Swift and corresponds to an XRT count rate of ~80 ct/sec. Swift began observing the GRB again at T0+4.75 ks; the count rate was ~8 ct/sec, but rapidly rising due to another flare which peaked 200 s later at ~130 ct/sec, and then faded to ~3 ct/sec by T0+6.1 ks. Another flare began shortly after, at T0+6.6 ks and peaked at T0+7.1 ks at 150 ct/sec. Observations were interrupted soon after this as the GRB again went into eclipse. The next observation began at T0+10.5 ks at which time the count rate was ~5 ct/sec but again rising in a flare which peaked at T0+11.2 ks, at a count rate of ~20 ct/sec. This decayed to ~5 ct/sec by T0+11.6ks and then began to rise again, but the Swift observations stopped just after this. Further observations are planned. The time-averaged WT mode spectrum can be modelled with an absorbed power-law with a photon index of 1.73 (+/-0.02) and an absorption column of 6.8e21 cm^-2 at z=0.347 (Vreeswijk et al., GCN Circ. 15249) in addition to the Galactic value of 0.17e21 cm^-2 (Kalberla et al, 2005). However as is typical during flaring episodes, there is strong spectral evolution during the XRT observations. We therefore extracted a further 4 spectra, one before the flares and one during each of them. These spectra were fitted above 0.5 keV to avoid possible instrumental effects at low energies caused by the accumulation of charge traps due to radiation damage since the release of the current CALDB WT gain file (version 13). In the spectra for the first 2 flares there is evidence for additional soft emission above the simple power-law. There are known calibration issues which can cause bumps such as these to appear artificially (see http://www.swift.ac.uk/analysis/xrt/digest_cal.php#abs) so we extracted the spectra using only single-pixel events, however the soft component is still present. It can be well modelled by adding in a thermal component (reducing the cstat of the fits by ~120). In the first flare this has a temperature of 33 (+/-3) eV, and in the second flare 45 (+/- 6) eV. Details of the power-law fits are given below (for the first two flare spectra these are the fits which include the soft component); note that it is likely that some spectral evolution occurred during the flares, thus these are still aggregated values. As for the time-averaged fit, the Galactic column was fixed to 0.17e21 cm^-2 (Kalberla et al 2005) and the free absorber was set to have a redshift of z=0.347 (GCN Circ. 15249) Pre-flare (T0+ 150-500 s): NH = 1.66 (+/- 0.05) e22 cm^-2 Gamma = 1.70 (+/- 0.04) Flare 1 (T0+ 1240-1500 s) NH = 2.2 (+/- 0.1) e22 cm^-2 Gamma = 2.28 (+/- 0.06) Flare 2 (T0+ 4650-6100 s) NH = 1.59 (+/- 0.07) e22 cm^-2 Gamma = 2.03 (+/- 0.04) Flare 3 (T0+ 6700-7300 s) NH = 1.66 (+/- 0.06) e22 cm^-2 Gamma = 1.79 (+/- 0.03) Flare 4 (T0+11.5-12.9 ks) NH = 1.3 (+/- 0.2) e22 cm^-2 Gamma = 2.39 (+/- 0.2) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00571830. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15255 SUBJECT: Fermi GBM detection of GRB 130925A and a possible precursor DATE: 13/09/25 16:13:06 GMT FROM: Gerard Fitzpatrick at UCD Gerard Fitzpatrick (UCD) reports on behalf of the Fermi GBM Team: At 04:09:26.73 UT on 25 September 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB130925A (trigger 401774969/130925173), which was also detected approximately 2 minutes later by Swift (Lien et al., GCN 15246). The on-ground calculated location is consistent with the Swift location. The GBM data show that the event was still in progress at the time of the Swift trigger. The burst was sufficiently bright that a Fermi Automatic Repointing Request (ARR) was triggered. This event may not actually be a GRB, as indicated by Burrows et al. (GCN 15253). Downlink of the full data set for this event was delayed due to the ARR; more details will be provided when the data are available. At 03:56:23.29 UT, 15 minutes prior to the GBM detection of GRB130925A, GBM triggered and located GBM trigger 401774186/130925164. The on-ground calculated location, using the GBM trigger data, is RA = 48.3 , DEC = -21.8 (J2000 degrees, equivalent to 03h 13m, -21d 42.0'), with an uncertainty of 12.8 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). This is also consistent with the Swift location of GRB130925A (Lien et al., GCN 15246). The temporal and positional coincidence indicate that this may be a precursor pulse to GRB130925A. The GBM light curve for this possible precursor consists of a single peak with a duration (T90) of about 6.6 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+2.5 s is adequately fit by a simple power law function with index -2.25 +/- 0.07 The event fluence (10-1000 keV) in this time interval is (6.9 +/- 0.6)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-3 s in the 10-1000 keV band is 3.0 +/- 0.2 ph/s/cm^2. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15256 SUBJECT: GRB 130925A: Historical non-detection from Rosat-HRI DATE: 13/09/25 17:03:21 GMT FROM: Jonathan Gelbord at PSU/Swift J. M. Gelbord (Eureka Scientific) reports: Historical X-ray data covering the position of GRB 130925A (Evans et al., GCN Circ 15246) is available from the ROSAT archive at HEASARC. The deepest data set is a 5.5 ks observation with the ROSAT HRI taken 1997-07-01, in which the position of GRB 130925A is 9' off axis. There is no trace of an X-ray source at this position. Using a source extraction region of 24" and a concentric annular background region from 80" to 240", formally I find 0.2 +/- 3.6 counts in the HRI band. The three sigma upper limit is 14.8 counts (using the Bayesian approach of Kraft, Burrows & Nousek 1991, ApJ 374, 344). Given the nominal exposure time of 5.5 ks, this translates to 2.7E-03 HRI counts per sec. We use WebPIMMS ( http://heasarc.gsfc.nasa.gov/Tools/w3pimms.html ) to convert the 3-sigma HRI count rate limit to a limit in the Swift-XRT band. Assuming the auto-generated spectral model for GRB 130925A (available from http://www.swift.ac.uk/xrt_products/00571830 ) fitted to the XRT PC-mode data for GRB 130925A (through T0+29.8 ks; NH (intrinsic) = 9.4E+21, Gamma = 2.61), together with NH (Galactic) = 1.66E+20 and z=0.347 (Vreeswijk et al., GCN Circ 15249 and Sudilovsky et al., GCN Circ 15250), the 3-sigma HRI count rate limit translates to an XRT count rate of 5.7E-3 counts per second. If we instead adopt the harder spectral model resulting from the fit to the WT-mode data (NH (Intrinsic) = 6.8E+21 and Gamma = 1.73), the equivalent XRT count rate would be 7.8E-3 counts per second. Thus, the Rosat HRI upper limit reveals that GRB 130925A at T0+200s was at least 10^6 times brighter and at T0+30ks was still at least 100 times brighter than any X-ray source at this position in July 1997. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15257 SUBJECT: GRB 130925A Swift-BAT refined analysis DATE: 13/09/26 00:03:46 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift 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), A. Y. Lien (NASA/GSFC/ORAU), D. M. Palmer (LANL), T. Sakamoto (AGU), 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+7152 sec from recent telemetry downlinks, we report further analysis of BAT GRB 130925A (trigger #571830) (Lien, et al., GCN Circ. 15246). The BAT ground-calculated position is RA, Dec = 41.186, -26.146 deg which is RA(J2000) = 02h 44m 44.5s Dec(J2000) = -26d 08' 47.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 9%. The mask-weighted light curve covers only a small part of this exceptionally long GRB (if indeed it is a GRB at all). As reported by the Fermi-GBM team (Fitzpatrick, GCN Circ. # 15255) the event may have begun 17 minutes prior to the BAT trigger, and the source was still detected in BAT at T+2 hours. Thus we cannot estimate a T90 at this time. There were multiple peaks and several late-time flares. In the current analysis, the burst was first detected by BAT at T-59 sec, when the target entered the BAT field of view already emitting, and last detected by BAT in a survey interval ending at T+7152 sec. BAT also detected a flux increase during the first flare detected by XRT (Evans et al. GCN Circ. # 15254) that peaked at about T+1000 seconds. BAT did not see a significant increase at the time of the next flare (brightest in XRT), peaking at about T+1380 seconds, though the source was still detected. BAT did strongly detect increases during the XRT-observed flares that peaked at approximately T+4950 and T+7100 seconds. BAT did not detect emission during another, smaller, flare observed by XRT that peaked at about T+11000 seconds. BAT has not detected significant flux from this location in the 15-50 keV band prior to the current event. The time-averaged spectrum from T-59 to T+903 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.85 +- 0.14, and Epeak of 33.4 +- 20.0 keV (chi squared 38.18 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 4.1 +- 0.1 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-35.64 sec in the 15-150 keV band is 7.3 +- 0.6 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.09 +- 0.04 (chi squared 45.62 for 57 d.o.f.). The flares at T+4950 and T+7100 seconds have photon indices in simple power-law fits of 2.19 +- 0.36 and 2.34 +- 0.28 respectively. 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/571830/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15258 SUBJECT: GRB 130925A: RATIR Optical and NIR Observations DATE: 13/09/26 01:55:31 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 130925A (Lien, et al., GCN 15246) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2013/09 25.27 to 2013/09 25.50 UTC (2.30 to 7.81 hours after the BAT trigger), obtaining a total of 3.67 hours exposure in the r and i bands and 1.43 hours exposure in the Z, Y, J, and H bands. We find an uncatalogued source in the enhanced Swift-XRT error circle (Evans et al., GCN 15251). In comparison with USNO-B1 and 2MASS, we obtain the following detections and upper limits (3-sigma): r 22.26 +/- 0.11 i 21.75 +/- 0.10 Z 20.25 +/- 0.06 Y 20.77 +/- 0.14 J 19.98 +/- 0.07 H 19.85 +/- 0.12 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The source is spatially coincident and about as bright as the source reported by Sudilovsky et al. (GCN 15247), which was observed minutes rather than hours after the GRB. Further observations are planned. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15259 SUBJECT: Observation of possible GRB/TDE 130925A by INTEGRAL/SPI-ACS: three activity episodes DATE: 13/09/26 08:07:55 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve V. Savchenko, V. Beckmann (APC), C. Ferrigno, E. Bozzo, M. Beck (ISDC), J. Borkowski (CAMK/Torun), D. Götz (CEA/Saclay), S. Mereghetti (INAF/IASF-Milano), A. von Kienlin, A. Rau (MPE), and K. Hurley (SSL/Berkeley) The possible GRB or tidal disruption event (Burrows et al, GCN 15253, 15257) 130925A, detected by Swift/BAT (Lien et al. GCN 15246, Markwardt et al GCN 15257) and Fermi/GBM (Fitzpatrick et al, GCN 15255), has been independently detected by the SPI Anti-Coincidence System (ACS) on-board INTEGRAL. The SPI-ACS light curve reveals rich multi-peak structure with a total duration of about 5000 seconds and evolution on a time scale as small as 2 seconds. The initial burst, detected by Fermi/GBM at 2013-09-25T04:09:26, also triggered SPI-ACS at 04:09:25 (T0 hereafter). The light curve displays two fast-rise slow-decay pulses, typical for a GRB, lasting a total of about 200 seconds and reaching a peak count rate of about 3500 counts/s (approximately corresponding to 3.5e-7 erg/cm2/s in the 75 keV-1 MeV range, Vigano' and Mereghetti 2009, arXiv:0912.5329, assuming a GRB-like spectrum) over 1s at T0+13s. The second episode is brighter. It starts at about T0+1800s, (04:42:00) and lasts for ~1700 seconds with a peak count rate of about 5000 counts/s (approximately 5e-7 erg/cm2/s) over 1s at T0+2770s (04:55:10). We note that this episode was not observed by Swift. The last, weaker, episode spans from ~T0+4000 to ~T0+4500 seconds with a peak count rate of ~1000 count/s (1e-7 erg/cm2/s). A possible precursor observed by Fermi/GBM at 03:56:23.29 (T0-900) is not visible in the SPI-ACS data. (note, however, that Fermi/GBM is more sensitive to photons below 100keV than SPI-ACS). Since SPI-ACS has no imaging capabilities, it is not possible to conclude with absolute certainty that all three episodes, spanning over almost 5000 seconds, belong to the same source. However, a chance temporal coincidence of these events in the SPI-ACS data is unlikely. No strong solar activity was reported at the time of the event. Rapid X-ray flaring detected by XRT (Evans et al, GCN 15251, Burrows et al, GCN 15253) for at least 10000 seconds strengthens the hypothesis that this source was active much longer than a typical GRB. The SPI-ACS light curve of this burst, in 10s bins is available: http://www.apc.univ-paris7.fr/~savchenk/grb130925a/grb130925a_spiacs.png Zoomed on the first and the second peaks: http://www.apc.univ-paris7.fr/~savchenk/grb130925a/grb130925a_spiacs_peak1.png http://www.apc.univ-paris7.fr/~savchenk/grb130925a/grb130925a_spiacs_peak2.png The original SPI-ACS light curve of this event is available at: http://www.apc.univ-paris7.fr/~savchenk/grb130925a/grb130925a_spiacs.txt.gz Arbitrary interval of the SPI-ACS light curve can be accessed with: http://isdc.unige.ch/~savchenk/spiacs-online/spiacs-ipnlc.pl All SPI-ACS light curves are available (both as images and data files) at http://isdc.unige.ch/Soft/ibas/ibas_acs_web.cgi. The light curves, binned at 50 ms, are derived from 91 independent detectors with different lower energy thresholds (mainly between 50 keV and 150 keV). SPI-ACS has no upper energy threshold and can detect photons with energies up to at least 100 MeV. The ACS response varies as a function of the GRB incident angle. For these reasons we caution that the count rates cannot be easily translated into physical flux units. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15260 SUBJECT: Konus-Wind observation of GRB 130925A DATE: 13/09/26 15:36:02 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline, on behalf of the Konus-Wind team, report: The very long GRB 130925A (Swift-BAT trigger #571830: Lien et al., GCN 15246; Markwardt et al., GCN 15257; MAXI/GSC detection: Suzuki et al., GCN 15248; Fermi/GBM detection: Fitzpatrick, GCN 15255; INTEGRAL/SPI-ACS observation: Savchenko et al., GCN 15259) was detected by Konus-Wind in the waiting mode. The light curve shows several multi-peaked pulses separated by long periods of a low-level emission with a total duration of ~4500 s. At least three major emission episodes can be distingushed: the first one, which triggered BAT, started at ~T0(BAT)-130 s and lasted until ~T0(BAT)+170 s; the second, more fluent episode, from ~T0(BAT)+1750 s to ~T0(BAT)+2950 s; and the third, the weakest one, which onset corresponds to the MAXI detection, from ~T0(BAT)+3730 s to ~T0(BAT)+4360 s. The possible precursor detected by GBM is clearly seen at ~T0(BAT)-900 s in the softest KW energy band. As observed by Konus-Wind, the burst had a fluence of (5.0 ± 0.1)x10^-4 erg/cm2 and a 2.944-s peak energy flux, measured from T0(BAT)+2548.858, of (1.0 ± 0.03)x10^-6 erg/cm2 (both in the 20 - 10000 keV energy range). The emission shows no signs of strong spectral variability. Modeling the KW 3-channel time-integrated spectrum (from T0(BAT)-120 s to T0(BAT)+4340 s) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.42 ± 0.04, and Ep = 181 ± 10 keV. Assuming z = 0.347 (Vreeswijk et al., GCN 15249) and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release E_iso = (1.50 ± 0.03)x10^53 erg, the peak isotropic luminosity L_iso = (4.0 ± 0.1)x10^50 erg, and Ep_rest is 244 ± 13 keV. Thus, the prompt gamma-ray emission properties of this GRB: fluence, Ep, and E_iso are similar to those observed in other long energetic GRBs; the only outstanding feature of the burst is its huge duration. In that, it resembles other ultra-long bursts: GRB 111209A at z=0.677 (with total duration of ~10000 s: Golenetskii et al., GCN 12663) and GRB 121027A at z=1.77 (with a total duration of >4000 s: Starling et al., in preparation). Therefore, we suggest that the extremely rapid and dramatic X-ray flaring observed over the first 10^4 s after the BAT trigger (Evans et al., GCN 15254) at least partially corresponds to the burst prompt emission. All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary. The K-W light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB130925A/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15261 SUBJECT: GRB 130925A: Fermi GBM Detection DATE: 13/09/26 15:42:20 GMT FROM: Peter Jenke at MSFC P. Jenke (UAH) reports on behalf of the Fermi GBM Team: "At 04:09:26.73 UT on September 25 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130925A (trigger 401774969/130925173), which was also detected by Swift (Lien et al. GCN 15246) and MAXI (Suzuki et al., GCN 15248). The trigger resulted in an Autonomous Repoint Request (ARR) that was accepted and the LAT slewed to the GBM in-flight location which was consistent with the Swift/XRT position (Evans et al. GCN 15251). The angle from the Fermi LAT boresight is 22 deg from Swift/XRT position. The GBM light curve consists of multiple peaks with a duration (T90) of about 212 s (50-300 keV). The time-averaged spectrum from T0-6 s to T0+288 s is best fit with a power law function with an exponential high-energy cutoff parameterized as Epeak = 107 +/- 3 keV and an Index = -1.50 +/- 0.05. The event fluence (10-1000 keV) in this time interval is (2.83 +/- 0.06)E-07 erg/cm^2. The 1.0-sec peak photon flux measured starting from T0+83 s in the 10-1000 keV band is 11.5 +/- 0.3 ph/s/cm^2. This event, although initially classified as a GRB, has been shown to exhibit behavior consistent with a Tidal Disruption Event (Burrows et al. GCN 15253). Its location suggests that it is the same source as GBM trigger 401774186/130925164 (G. Fitzpatrick GCN 15255). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15262 SUBJECT: GRB 130925A: Continued RATIR Optical and NIR Observations DATE: 13/09/26 17:50:25 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 130925A (Lien, et al., GCN 15246) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2013/09 26.28 to 2013/09 26.51 UTC (26.43 to 31.98 hours after the BAT trigger), obtaining a total of 3.66 hours exposure in the r and i bands and 1.12 hours exposure in the Z, Y, J, and H bands. For the uncatalogued source in the enhanced Swift-XRT error circle (Evans et al., GCN 15251) reported previously (Butler et al., GCN 15258), in comparison with 2MASS, we obtain the following detections and upper limit (3-sigma): r 22.29 +/- 0.16 i 21.36 +/- 0.13 Z > 21.5 Y 21.28 +/- 0.29 J 19.69 +/- 0.06 H 20.02 +/- 0.17 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Compared to our observations the night before (GCN 15258), the source has apparently remained approximately constant in flux in all bands. We cannot determine, as did Sudilovsky et al. (GCN 15247), that the source is fading. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15263 SUBJECT: GRB 130925A: optical upper limit DATE: 13/09/27 10:43:49 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), N. Minikulov (Institute of Astrophysics), S. Abdulaev (Institute of Astrophysics), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 130925A (Lien, et al., GCN 15246) with AZT-8 (0.7m) telescope of Gissar observatory in R filter starting on Sep. 25 (UT) 22:15. We do not detect optical afterglow (Sudilovsky et al., GCN 15247). A preliminary photometry of combined image is following T_start T0+ Filter, Exposure, OT, UL(3 sigma) (UT) (mid, d) (s) 2013-09-25T22:16:55 0.7766 R 60x60 n/d 19.9 The photometry is based on the reference star USNO-B1.0 0638-0038928 RA 02:45:02.36 Dec -26:10:50.2 (J2000), assuming R = 17.07 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15264 SUBJECT: GRB 130925A: sub-mm non-detection with SMA DATE: 13/09/27 10:47:02 GMT FROM: Ashley Zauderer at CfA A. Zauderer, E. Berger (Harvard), and G. Petitpas (SMA) report on behalf of a larger collaboration: "We observed the position of GRB 130925A (Lien et al., GCN 15246) beginning 2013 Sep 26.31 UT (dt = 1.1 d) with the SMA at a mean frequency of 230 GHz. We find no significant radio emission at the position of the enhanced Swift-XRT position (Evans et al., GCN 15250) to a 3-sigma limit of 1.89 mJy. Observations are ongoing. We thank the SMA staff for prompt execution of these observations." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15266 SUBJECT: GRB 130925A: Swift/UVOT Upper Limits DATE: 13/09/27 11:37:03 GMT FROM: Stephen Holland at STScI S. T. Holland (STScI) and A. Y. Lien (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130925A 157 s after the BAT trigger (Lien et al. 2013, GCNC 15246). We do not detect any new source consistent with the GROND afterglow position (Sudilovsky et al. 2013, GCNC 15247) in any of the UVOT exposures. Preliminary 3-sigma upper limits, using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373), for the finding chart and summed exposures are presented below. --------------------------------------------------- Filter TSTART TSTOP Exposure Mag --------------------------------------------------- white (FC) 157 306 147 >21.4 u (FC) 315 564 246 >20.6 --------------------------------------------------- v 645 7269 381 >20.0 b 571 6121 170 >20.6 u 719 5983 274 >20.4 uvw1 5579 11,956 701 >21.1 uvm2 5374 11,436 1082 >21.2 uvw2 4964 7136 393 >20.7 white 595 6929 618 >22.0 --------------------------------------------------- The quoted upper limits have not been corrected for the expected extinction due to the Galactic reddening along the line of sight to this burst of E(B-V) = 0.02 mag (Schlafly et al. 2011, ApJS, 737, 103). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15267 SUBJECT: GRB 130925A: Swift/UVOT Detection of the Host Galaxy DATE: 13/09/27 18:22:43 GMT FROM: Stephen Holland at STScI S. T. Holland (STScI) reports on behalf of the Swift/UVOT team: Deep Swift/UVOT imaging taken between 157 s and 184.8 ks after the BAT trigger (Lien et al, 2013, GCNC 15246) shows a faint source at the location of the GROND detection (Sudilovsky et al. 2013, GCNC 15247). This source has a preliminary magnitude, on the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373), of white = 22.9 +/- 0.3 mag and is detected with a significance of 4.7 sigma. This magnitude has not been corrected for the expected extinction due to the Galactic reddening along the line of sight to this burst of E(B-V) = 0.02 mag (Schlafly et al. 2011, ApJS, 737, 103). The total white exposure time is 18 ks. There is no evidence for variability. The probability of finding a galaxy of this apparent luminosity within the UVOT-enhanced XRT error circle (Evans et al. 2013, GCNC 15251) is 0.01 using the method of Bloom et al. (2002, AJ, 423, 1111). The positional coincidence and lack of variability suggest that this is the host galaxy of GRB 130925A. There is no evidence in the UVOT data that this source has any extended structure. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15268 SUBJECT: Fermi LAT Upper Limits on GRB 130925A DATE: 13/09/28 00:03:12 GMT FROM: Daniel Kocevski at SLAC D. Kocevski, J. Racusin (NASA/GSFC), G. Vianello (Stanford), M. Axelsson (Stockholm University), Nicola Omodei (Stanford) report on behalf of the Fermi-LAT team: A preliminary examination of the Fermi LAT data of the field containing GRB 130925A (Lien, et al., GCN 15246) has revealed no significant emission above 40 MeV. The GRB was located ~22 degrees away from the LAT boresight at the time of the first GBM detected emission associated with this burst at 03:56:23.29 UT on 25 September 2013 (GCN 15255), hereafter T0(GBM), and the subsequent autonomous repoint ensured that the source remained in the field-of-view for the next ~2000s until it was occulted by the Earth. Using an unbinned likelihood analysis, we estimate the following LAT upper limits at 95% confidence for three separate time intervals, one covering the entire 2000s that the source stayed in the LAT field-of-view, and two of which correspond to the first and third emission episodes detected by INTEGRAL/SPI-ACS (GCN 15259) and Konus-Wind (GCN 15260). We note that the source was not in the LAT field-of-view during the second interval reported in GCNs 15259 & 15260. Interval 1: T0(GBM) to T0(GBM)+2000 = 7.3e-07 photons cm-2 s-1 (4.8e-10 ergs cm-2 s-1) Interval 2: T0(GBM)+900s to T0(GBM)+1100s = 5.5e-06 photons cm-2 s-1 (3.6e-09 ergs cm-2 s-1) Interval 3: T0(GBM)+4900 to T0(GBM)+5400 = 2.5e-06 photons cm-2 s-1 (1.6e-09 ergs cm-2 s-1) This analysis covers an energy range of 0.1 to 10 GeV with a 12 deg extraction region centered on the best known source position (GCN 15246). The upper limits are computed using the P7SOURCE_V6 instrument response functions, where we assume a power-law source spectrum fixed to a photon index of -2.1, reflecting a typical value for high-energy emission in GRBs. For reference, T0(GBM) = T0(BAT)-900s. The Fermi LAT point of contact for this burst is Magnus Axelsson ( magnusa@astro.su.se). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15278 SUBJECT: IPN Observations of GRB 130925A DATE: 13/09/30 22:05:33 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the IPN team, S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline, on behalf of the Konus-Wind team, I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team, W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, D. M. Smith, J. McTiernan, R. Schwartz, W. Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, and K. Makishima on behalf of the Suzaku WAM team, S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, J. Goldsten, on behalf of the MESSENGER NS GRB team, and V. Connaughton, M. S. Briggs, C. Meegan, and V. Pelassa, on behalf of the Fermi GBM team, report: Eight IPN spacecraft observed GRB 130925A (Lien et al. GCN 15246, Markwardt et al. 15247). When the responses of all the spacecraft are considered, the IPN had an uninterrupted view of this event from roughly 900 s before the Swift BAT trigger, to ~7100 s after it. Constraints on the arrival directions of the four main emission episodes strengthen the case for their common origin, as suggested by Savchenko et al. (GCN 15259). The following table details the observations. The times are relative to the BAT trigger at 15084 s UT (04:11:24). N/O means the episode was not observable. ---------------------------------------------------------------------------- Instrument/ | Precursor | 1st | 2nd | 3rd spacecraft | -900 s | episode | episode | episode* | | -130 -> +170 s|+1750 -> +2950 s|+3730 -> +4360 s ---------------------------------------------------------------------------- Swift BAT No Trig N/O No Fermi GBM Trig Trig N/O No INTEGRAL SPI-ACS No Yes Yes Yes Konus Wind Yes Yes Yes Yes MESSENGER No Yes Yes No Mars Odyssey No N/O Yes No Suzaku WAM No No Yes No RHESSI Yes Yes N/O No ------------------------------------------------------------------------------ *also observed and localized by MAXI (Suzuki et al. GCN 15248) We conclude from these observations that the total duration of this event in >25 keV gamma-rays above the IPN flux/fluence threshold was at least 5260 s, and ~7150 s long when the later episodes, observed only by BAT (GCN 15257), are included. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15280 SUBJECT: GRB 130925A: continuing Swift/XRT monitoring DATE: 13/10/01 17:52:33 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK/NBI), S. B. Cenko (NASA/GSFC), D. N. Burrows (PSU), A. Y. Lien (NASA/GSFC/ORAU), P. A. Evans (U. Leicester), and N. Gehrels (NASA/GSFC) report: Swift has been continuously monitoring the X-ray counterpart of GRB 130925A (Lien et al., GCN 15246), with data currently extending up to 512 ks after the trigger. The intense X-ray flaring activity reported by Burrows et al. (GCN 15253) and Evans et al. (GCN 15254) ceased between 12 and 28 ks after the trigger. The X-ray light curve from 27.9 to 512.4 ks can be modelled with an initial power-law decay with an index of alpha = 0.84 +/- 0.03, followed by a possible break at 310 (+60, -50) ks to an alpha of 1.38 (+0.47, -0.23). The updated X-ray light curve is available at the following URL: http://www.swift.ac.uk/xrt_curves/00571830/ While the duration of the prompt emission and the flaring activity are extraordinary among GRBs (Suzuki et al., GCN 15248; Fitzpatrick, GCN 15255; Markwardt et al., GCN 15257; Savchenko et al., GCN 15259; Golenetskii et al., GCN 15260; Jenke, GCN 15261; Hurley et al., GCN 15278), the late-time behaviour is typical of long-duration GRB afterglows, and quite different from that of the TDE Swift J1644+57, which showed continuous flares and dips, with no regular power-law decay (e.g. Burrows et al. 2011, Nat, 476, 421). There is also no prior detection of the source in BAT before the trigger (Markwardt et al., GCN 15257). The extremely long-lived high-energy emission coupled with the relatively steady power-law X-ray decay at t > 20 ks is reminiscent of the so-called "ultra-long" GRBs (Levan et al. 2013, arXiv:1302.2352), including GRB 101225A (Thoene et al. 2011, Nat, 480, 72; Campana et al. 2011, Nat, 480, 69), GRB 111209A (Gendre et al. 2013, ApJ, 766, 30), and GRB 121027A. The origin of these events and their relation to traditional long-duration GRBs (i.e., the core-collapse of a massive star) remain controversial, so we encourage continued multi-wavelength follow-up of this object. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15286 SUBJECT: NuSTAR observations of GRB 130925A DATE: 13/10/02 15:16:42 GMT FROM: Eric Bellm at Caltech E. C. Bellm, F. A. Harrison, K. Forster, K. K. Madsen, V. Rana (Caltech), S. E. Boggs, J. Tomsick (U.C. Berkeley), J. M. Miller (Michigan), and S. B. Cenko (NASA/GSFC) report on behalf of the NuSTAR collaboration: NuSTAR observed the unusual ultra-long GRB/TDE candidate GRB 130925A (GCN 15246) beginning 44.3 hours after the Swift trigger for a total of 39.2 ksec exposure time. NuSTAR detects the source to >20 keV; the average 3-20 keV flux over the interval was 1.3E-12 erg/cm^-2/s^-1. The data may be fit with an absorbed power law with spectral index Gamma ~ 3. NuSTAR observes a broad absorption feature centered near 6 keV. Simultaneous Swift-XRT spectra support the existence of this feature at lower SNR. An F-test of a Gaussian absorption feature fit to the combined data sets yields a detection significance of 5.5 sigma. Preliminary searches for features in the early-time XRT data have not identified any clear signatures; additional tests are ongoing. Further observations are in progress; we encourage continued monitoring of this interesting event at all wavelengths. We thank the NuSTAR Mission Operations Team for the rapid turnaround that enabled this observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15299 SUBJECT: GRB 130925A/Sw J0244-2609: mm observations at PdBI DATE: 13/10/03 20:02:01 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia A. J. Castro-Tirado (IAA-CSIC Granada and Univ. de Málaga), M. Bremer, J.-M. Winters and S. Koenig (IRAM Grenoble), on behalf of a large collaboration, report: "Following the detection of the extraordinarily long event GRB 130925A/Sw J0244-2609 by Swift (Lien et al. 2013, GCN 15247) we attempted on Oct 1 (00:30 UT) millimetre observations with the Plateu de Bure Interferometer (PdBI) in the French Alps, in 6-antenna compact D configuration. Due to the low declination, the source was lost for two antennas due to shadowing effects by other antenna. No mm source is detected, with a 3 sigma limit of 0.58 mJy at 86 GHz. This value is a factor of 30 times less than the measured flux density for the tidal disruption flare candidate GRB 110328A/Sw J1644+5734 with PdBI one week post burst (Castro-Tirado et al. 2013, RMxAC 42, 36)." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15301 SUBJECT: GRB 130925A: 3mm observations with CARMA DATE: 13/10/04 16:39:51 GMT FROM: Ashley Zauderer at CfA B. A. Zauderer, E. Berger, T. Laskar (Harvard) report on behalf of a larger collaboration as part of the CARMA Key Project "A Millimeter View of the Transient Universe": "We observed the position of GRB 130925A (Lien et al., GCN 15246) with the Combined Array for Research in Millimeter Astronomy (CARMA) beginning 2013 Sep 26.36 (dt = 1.19 d) at a mean frequency of 93 GHz. Observations were conducted in the compact E configuration, with significant flagging for shadowed antennas required. We do not detect any significant radio emission to a 3-sigma limit of 0.6 mJy at the position of the Swift-XRT position (Evans et al., GCN 15251). We thank the CARMA observers and staff for prompt execution of these observations." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15322 SUBJECT: GRB 130925A: Possible signatures of binary nature in the afterglow - Request for observations DATE: 13/10/10 14:57:27 GMT FROM: Remo Rufinni at ICRA R. Ruffini, C.L. Bianco, M. Enderli, M. Muccino, A.V. Penacchioni, G.B. Pisani, J.A. Rueda, N. Sahakyan, Y. Wang, L.Izzo report: The observed X-ray emission in the afterglow of GRB 130925A (Lien et al., GCN 15247; Fitzpatrick et al., GCN 15255) presents an unprecedented sequence of flares departing from the canonical single power law decay (L \propto t^{-1.5}) observed in energetic GRBs-SNe (the "golden sample", Pisani et al. 2013, A&A 552, L5, arXiv:1304.1764). Correspondingly the X-ray Luminosity after 2*10^4 s in the rest-frame of the burst is almost constant (L \propto t^{-0.3}) and the energy emitted is a factor 30 larger than in the golden sample. In the Induced Gravitational Collapse (IGC) paradigm, after the "input" due to a supernova explosion and the Black Hole formation (Ruffini 2013, IJMPD, 22, 1360009, arXiv:1310.1836), the "output" of a newly born Neutron Star from the Supernova and the Black Hole may remain bound in an elliptical orbit. This can explain the repeated flaring activity and the source of the larger observed energy. In the canonical IGC scenario at z = 0.35 (Sudilovsky et al., GCN 15250, Vreeswijk et al., GCN 15249), assuming a 1998bw-like SN, a supernova should be expected to peak around the 10 - 16 October. It is crucial to perform optical observations in order to find out if the presence of the above mentioned binary nature in the "output" can modify the canonical scenario. Periodicities on time scales down to few minutes should be explored. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15489 SUBJECT: GRB 130925A: HST imaging DATE: 13/11/16 09:22:23 GMT FROM: Nial Tanvir at U.Leicester N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), R. Hounsell, A. S. Fruchter (STScI), S. B. Cenko (NASA/GSFC), D. A. Perley (Caltech), P. T. O'Brien (U. Leicester) report: We imaged the location of GRB 130925A (Evans et al. GCN 15251; Sudilovsky et al. GCN 15247) with HST at two epochs, at 20 days and 47 days post-burst respectively, in the F814W (I-band), F110W (J-band) and F160W (H-band) filters. The host galaxy is well resolved and appears to be an almost edge-on spiral. The galaxy shows signs of disturbance: specifically the disk shows asymmetry and the bulge appears to be extended perpendicular to the disk, suggestive of a polar-ring morphology. Image subtraction reveals evidence of faint transient light in the first epoch in all three filters. The location is in good agreement with that from prior ground-based imaging of the GRB. The transient position is close to the disk plane, which likely accounts for the high extinction and X-ray column for this event (Evans et al. GCN 15254). It is, however, slightly offset from the nucleus of the galaxy by about 0.12 arcsec (~600pc in projection). This would initially seem to be in conflict with a possible tidal disruption origin for this event, although if the galaxy morphology is indicative of a recent major merger, then it is plausible that the system currently contains more than one super-massive black hole. Further analysis is ongoing. We thank the staff at STScI for approving and expediting these ToO observations.