//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30897 SUBJECT: GRB 210930A: Swift detection of a burst DATE: 21/09/30 02:58:45 GMT FROM: Mike Siegel at PSU/Swift MOC V. D'Elia (SSDC & INAF-OAR), E. Ambrosi (INAF-IASFPA), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (U Tampa), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 02:46:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210930A (trigger=1075565). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 197.435, +48.623 which is RA(J2000) = 13h 09m 44s Dec(J2000) = +48d 37' 22" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 15 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~8 sec after the trigger. The XRT began observing the field at 02:49:12.3 UT, 140.1 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 197.40185, 48.62853 which is equivalent to: RA(J2000) = 13h 09m 36.44s Dec(J2000) = +48d 37' 42.7" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 81 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (9.55 x 10^19 cm^-2, Willingale et al. 2013), with an excess column of 6.4 (+3.87/-3.20) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 143 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.010. Burst Advocate for this burst is V. D'Elia (valerio.delia AT ssdc.asi.it). 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: 30900 SUBJECT: GRB 210930A: Enhanced Swift-XRT position DATE: 21/09/30 09:19:07 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 1714 s of XRT Photon Counting mode data and 2 UVOT images for GRB 210930A, 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 = 197.40188, +48.62856 which is equivalent to: RA (J2000): 13h 09m 36.45s Dec (J2000): +48d 37' 42.8" with an uncertainty of 2.4 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: 30901 SUBJECT: Swift GRB 210930A: Global MASTER-Net observations report DATE: 21/09/30 16:36:24 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 210930A ( V. D'Elia et al., GCN 30897) errorbox 48786 sec after notice time and 48953 sec after trigger time at 2021-09-30 16:22:45 UT, with upper limit up to 17.2 mag. Observations started at twilight. The observations began at zenith distance = 59 deg. The sun altitude is -11.0 deg. The galactic latitude b = 68 deg., longitude l = 114 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1737711 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 32055 | MASTER- | C | 1 | 14.1 | 32055 | MASTER- | C | 1 | 15.1 | 36978 | MASTER- | C | 180 | 20.0 | 49043 | MASTER-Tavrida | C | 180 | 17.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30902 SUBJECT: GRB 210930A: Swift-XRT refined Analysis DATE: 21/09/30 19:47:41 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and V. D'Elia report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 210930A (D'Elia et al. GCN Circ. 30897), from 143 s to 52.5 ks after the BAT trigger. The data comprise 63 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 30900). The light curve can be modelled with a power-law decay with a decay index of alpha=0.71 (+0.09, -0.08). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 4.04 (+0.30, -0.27). The best-fitting absorption column is 1.46 (+0.18, -0.16) x 10^22 cm^-2, in excess of the Galactic value of 9.6 x 10^19 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.2 (+0.4, -0.3) and a best-fitting absorption column of 6.1 (+2.4, -2.0) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (7.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 6.1 (+2.4, -2.0) x 10^21 cm^-2 Galactic foreground: 9.6 x 10^19 cm^-2 Excess significance: 5.0 sigma Photon index: 2.2 (+0.4, -0.3) If the light curve continues to decay with a power-law decay index of 0.71, the count rate at T+24 hours will be 6.7 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x 10^-13 (5.0 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01075565. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30903 SUBJECT: GRB 210930A: Swift/UVOT Upper Limits DATE: 21/09/30 22:33:53 GMT FROM: Alexander Belles at PSU/Swift A. Belles (PSU) and V. D'Elia (SSDC & INAF-OAR) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210930A 144 s after the BAT trigger (D'Elia et al., GCN Circ. 30897). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 30900) 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 144 293 147 >19.9 u_FC 302 551 246 >19.6 white 144 1722 411 >20.6 v 631 1773 136 >18.7 b 559 1873 134 >19.6 u 302 1848 363 >19.7 w1 681 1824 136 >19.5 m2 655 1450 39 >18.7 w2 607 1747 117 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.010 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30909 SUBJECT: GRB 210930A: CAHA 2.2m telescope optical limit DATE: 21/10/01 04:35:31 GMT FROM: Youdong HU at IAA-CSIC Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M. D. Caballero-Garcia, R. Sanchez-Ramirez, M. A. Castro Tirado (IAA-CSIC) and I. Vico (CAHA) on behalf of a larger collaboration, report: Following the detection of GRB 210930A by Swift (V. D'Elia et al. GCNC 30897), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain). Images were gathered after the twilight starting on Sep. 30 18:56:50 UT (i.e. 16.2 hour post trigger) in Sloan-gri bands with 90 s exposure each. On the co-added r-band image (6x90s), no optical transient down to 22.6 mag is detected at the X-ray afterglow candidate position reported by Swift/XRT (V. D'Elia et al. GCNC 30897, J.P. Osborne et al. GCNC 30900). This non-detection is consistent with the report from A. Belles et al. (GCNC 30903) and V. Lipunov et al.(GCNC 30901). We thank the staff at Calar Alto observatory for their excellent support. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30917 SUBJECT: GRB 210930A: Swift-BAT refined analysis DATE: 21/10/01 18:22:49 GMT FROM: Amy Lien at GSFC H. A. Krimm (NSF), S. D. Barthelmy (GSFC), V. D'Elia (SSDC & INAF-OAR), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210930A (trigger #1075565) (D'Elia et al., GCN Circ. 30897). The BAT ground-calculated position is RA, Dec = 197.415, 48.630 deg which is RA(J2000) = 13h 09m 39.5s Dec(J2000) = +48d 37' 47.1" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a single-pulse structure that starts at ~T+6 s, peaks at ~T+9 s, and ends at ~T+20 s. T90 (15-350 keV) is 11.81 +- 1.94 sec (estimated error including systematics). The time-averaged spectrum from T+5.84 to T+19.24 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.58 +- 0.19. The fluence in the 15-150 keV band is 4.0 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+8.40 sec in the 15-150 keV band is 0.7 +- 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/1075565/BA/