//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28384 SUBJECT: GRB 200907B: Swift detection of a short burst DATE: 20/09/07 19:01:32 GMT FROM: David Palmer at LANL A. P. Beardmore (U Leicester), S. D. Barthelmy (GSFC), J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 18:51:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200907B (trigger=995004). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 89.013, +6.911 which is RA(J2000) = 05h 56m 03s Dec(J2000) = +06d 54' 38" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 1 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 18:52:31.3 UT, 80.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 89.02837, 6.90752 which is equivalent to: RA(J2000) = 05h 56m 06.81s Dec(J2000) = +06d 54' 27.1" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 56 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 https://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 consistent with the Galactic value of 4.23 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 83 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 0.61. 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/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28385 SUBJECT: GRB 200907B: Prompt enhanced Swift-XRT position DATE: 20/09/07 19:21:53 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 200907B, we find an enhanced XRT position of the afterglow: RA, Dec: 89.0289, 6.9063 which is equivalent to: RA (J2000) = 05 56 06.93 Dec (J2000) = +06 54 22.8 with an uncertainty of 2.2 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/995004. 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: 28388 SUBJECT: Correction to GCN 28387: GRB 200907B GROWTH-India optical upper limit DATE: 20/09/07 23:01:18 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar (IITB), P. Dorje (IIA), V. Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA), report on behalf of the GROWTH-India collaboration: We apologize for the confusion caused in GRB name. GROWTH-India Telescope followed-up GRB 200907B, not GRB 200907A. Here is the corrected GCN:- We observed GRB 200907B reported by Swift-BAT (A.P. Beardmore et al., GCN #28384, P.A. Evans et al., GCN #28385) with 0.7m GROWTH-India telescope. The field was observed in the SDSS r filter starting at 2020-09-07T20:59:05.36 UT i.e. ~2.1 hrs after the event detection by Swift-BAT. We didn’t find any new source in stacked image of 7*500 sec exposure, within an uncertainty region of 2.2 arcsec around RA(J2000) = 05:56:06.93, Dec(J2000)= +06:54:22.8 (GCN 28385) up to r > 20.83 mag (5-sigma) (calibrated against PanSTARRs PS1 data release, Flewelling et al., 2018). The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28391 SUBJECT: GRB 200907B: Enhanced Swift-XRT position DATE: 20/09/08 00:36:18 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 742 s of XRT Photon Counting mode data and 1 UVOT images for GRB 200907B, 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 = 89.02906, +6.90625 which is equivalent to: RA (J2000): 05h 56m 6.97s Dec (J2000): +06d 54' 22.5" 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: 28392 SUBJECT: Swift GRB 200907B: Global MASTER-Net observations report DATE: 20/09/08 01:15:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 200907B ( A. P. Beardmore et al., GCN 28384) errorbox 22142 sec after notice time and 22169 sec after trigger time at 2020-09-08 01:00:40 UT, with upper limit up to 17.6 mag. The observations began at zenith distance = 59 deg. The sun altitude is -23.0 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 200907B errorbox 22375 sec after notice time and 22402 sec after trigger time at 2020-09-08 01:04:33 UT, with upper limit up to 15.9 mag. The observations began at zenith distance = 73 deg. The sun altitude is -46.6 deg. The galactic latitude b = -8 deg., longitude l = 201 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1435309 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 22260 | MASTER-Tavrida | C | 180 | 17.3 | 22461 | MASTER-Tavrida | C | 180 | 17.6 | 22493 | MASTER-SAAO | C | 180 | 15.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28393 SUBJECT: GRB 200907B: MITSuME Okayama optical upper limits DATE: 20/09/08 01:35:11 GMT FROM: Ryohei Hosokawa at Tokyo Institute of Technology R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, N. Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai (TokyoTech) report on behalf of the MITSuME collaboration: We observed the field of GRB 200907B (Beardmore et al., GCN 28384; Evans et al., GCN 28385,28391) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Okayama Astrophysical Observatory, Okayama, Japan. The observation with a series of 60 sec exposures started at 2020-09−07 18:52:16UT. We did not find any new point sources within the enhanced Swift/XRT error circle (Evans et al., GCN 28391) in the 60 sec exposure images and the stacked images. We obtained the 5-sigma limits of the stacked images as follows. T0+[sec] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 65 2020-09-07T19:19:48 2100 g'>17.1, Rc>17.9, Ic>17.3 ------------------------------------------------------------------------------------------------ T0+: Elapsed time after the burst T-EXP: Total Exposure time We used the PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al., accepted for publication in PASJ, https://arxiv.org/abs/2008.11486; https://github.com/MNiwano/Eclaire). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28394 SUBJECT: GRB 200907B: Swift-XRT refined Analysis DATE: 20/09/08 01:38:21 GMT FROM: Phil Evans at U of Leicester M. Capalbi (INAF-IASFPA), M. Perri (ASDC), V. D'Elia (ASDC), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester) and A.P. Beardmore report on behalf of the Swift-XRT team: We have analysed 6.7 ks of XRT data for GRB 200907B (Beardmore et al. GCN Circ. 28384), from 83 s to 18.0 ks after the BAT trigger. The data comprise 5 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. 28385). The light curve can be modelled with a power-law decay with a decay index of alpha=2.09 (+/-0.18). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.5, -0.4). The best-fitting absorption column is 5.7 (+3.0, -1.4) x 10^21 cm^-2, consistent with the Galactic value of 4.2 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (7.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.7 (+3.0, -1.4) x 10^21 cm^-2 Galactic foreground: 4.2 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.9 (+0.5, -0.4) If the light curve continues to decay with a power-law decay index of 2.09, the count rate at T+24 hours will be 1.3 x 10^-6 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x 10^-17 (9.2 x 10^-17) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00995004. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28395 SUBJECT: GRB 200907B: AstroSat CZTI detection DATE: 20/09/08 20:42:51 GMT FROM: Soumya Gupta at IUCAA/ASTROSAT S. Gupta, V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (IUCAA/TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed a weak detection of a short GRB 200907B, which was also detected by Swift (Beardmore A. et al., GCN #28384), Swift-XRT (Evans P. et al., GCN #28385), GROWTH-India optical (Kumar H. et al., GCN #28388), Global MASTER-Net (Lipunov V. et al., GCN #28392), and MITSuME Okayama optical (Hosokawa R. et al., GCN #28393). The source was clearly detected in the 40-200 keV energy range. The light curve showed a single peak of emission peaking at 2020-09-07 18:51:10.019 UT. The measured peak count rate associated with the burst is 160 +/- 24 cts/s above the background in the combined data of four quadrants, with a total of 259 +/- 3 cts. The local mean background count rate was 515+/- 1 cts/s. Using cumulative rates, we measure a T90 of 1.60 +/- 0.01 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single peak of emission peaking at 2020-09-07 18:51:09.00 UT. The measured peak count rate is 513 +/- 44 cts/s above the background in the combined Veto data of four quadrants, with a total of 560 +/- 5 cts. The local mean background count rate was 1494 +/- 2 cts/s. We measure a T90 of 1.48 +/- 0.06 s from the cumulative Veto light curve. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28398 SUBJECT: GRB 200907B: Swift-BAT refined analysis DATE: 20/09/08 22:17:25 GMT FROM: Amy Lien at GSFC H. A. Krimm (NSF), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), J. R. Cummings (CPI), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200907B (trigger #995004) (Beardmore et al., GCN Circ. 28384). The BAT ground-calculated position is RA, Dec = 89.019, 6.905 deg which is RA(J2000) = 05h 56m 04.5s Dec(J2000) = +06d 54' 17.7" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%. The mask-weighted light curve shows a multi-peaked structure that starts at ~T-0.6 and ends at ~T+0.3 s. The main peak occurs at ~T+0.1 s. T90 (15-350 keV) is 0.83 +- 0.13 sec (estimated error including systematics). The time-averaged spectrum from T-0.64 to T+0.28 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.68 +- 0.25. The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.68 sec in the 15-150 keV band is 1.5 +- 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/995004/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 28400 SUBJECT: GRB 200907B: Swift/UVOT Upper Limits DATE: 20/09/09 03:50:55 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200907B 84 s after the BAT trigger (Beardmore et al., GCN Circ. 28384). No optical afterglow consistent with the XRT position (Evans GCN Circ. 28385) 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 84 233 147 >20.4 u_FC 296 546 246 >19.7 white 84 4892 383 >21.0 v 625 819 39 >17.7 b 551 4687 236 >19.4 u 296 4482 462 >20.4 w1 675 4277 216 >19.2 m2 650 670 19 >18.3 w2 601 5048 186 >19.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.61 in the direction of the burst (Schlegel et al. 1998).