//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29662 SUBJECT: GRB 210318A: Swift detection of a burst DATE: 21/03/18 04:09:40 GMT FROM: Caryl Gronwall at PSU/Swift-UVOT E. Troja (NASA/GSFC/UMCP), C. Gronwall (PSU), J.D. Gropp (PSU), N. J. Klingler (PSU), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 03:54:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210318A (trigger=1037339). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 33.930, -37.789 which is RA(J2000) = 02h 15m 43s Dec(J2000) = -37d 47' 21" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 03:56:35.2 UT, 123.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 33.9263, -37.7772 which is equivalent to: RA(J2000) = 02h 15m 42.32s Dec(J2000) = -37d 46' 38.1" with an uncertainty of 3.2 arcseconds (radius, 90% containment). This location is 43 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 1.88 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 126 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 0.016. Burst Advocate for this burst is E. Troja (eleonora.troja AT 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/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29665 SUBJECT: Swift GRB 210318A: Global MASTER-Net observations report DATE: 21/03/18 18:04:28 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210318A ( E. Troja et al., GCN 29662) errorbox 50452 sec after notice time and 50501 sec after trigger time at 2021-03-18 17:56:12 UT, with upper limit up to 19.7 mag. Observations started at twilight. The observations began at zenith distance = 58 deg. The sun altitude is -14.2 deg. The galactic latitude b = -69 deg., longitude l = 248 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1570922 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 50591 | MASTER-SAAO | C | 180 | 19.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29669 SUBJECT: Swift GRB210318.13: Global MASTER-Net observations report DATE: 21/03/18 22:06:18 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB210318.13 (trigger No 1037335,17h 36m 55.88s , -35d 49m 19.2s, R=0.01) errorbox 65903 sec after trigger time at 2021-03-18 21:26:56 UT, with upper limit up to 17.3 mag. The observations began at zenith distance = 83 deg. The sun altitude is -52.2 deg. The galactic latitude b = -3 deg., longitude l = 354 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1571373 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 65934 | MASTER-SAAO | C | 60 | 14.1 | 66013 | MASTER-SAAO | C | 60 | 14.5 | 66093 | MASTER-SAAO | C | 60 | 14.9 | 67868 | MASTER-SAAO | C | 60 | 17.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29670 SUBJECT: GRB 210318A: Enhanced Swift-XRT position DATE: 21/03/19 01:16:18 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 1075 s of XRT Photon Counting mode data and 2 UVOT images for GRB 210318A, 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 = 33.92621, -37.77693 which is equivalent to: RA (J2000): 02h 15m 42.29s Dec (J2000): -37d 46' 36.9" 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: 29671 SUBJECT: GRB 210318A: Swift-XRT refined Analysis DATE: 21/03/19 04:20:47 GMT FROM: Phil Evans at U of Leicester B. Sbarufatti (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , D.N. Burrows (PSU), J. D. Gropp (PSU) and E. Troja report on behalf of the Swift-XRT team: We have analysed 3.1 ks of XRT data for GRB 210318A (Troja et al. GCN Circ. 29662), from 107 s to 45.6 ks after the BAT trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 29670). The light curve can be modelled with a power-law decay with a decay index of alpha=1.09 (+0.27, -0.29). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.8 (+0.6, -0.5). The best-fitting absorption column is 1.4 (+1.9, -1.2) x 10^21 cm^-2, consistent with the Galactic value of 1.9 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+1.9, -1.2) x 10^21 cm^-2 Galactic foreground: 1.9 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.8 (+0.6, -0.5) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01037339. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29672 SUBJECT: GRB 210318A: Swift-BAT refined analysis DATE: 21/03/19 12:04:17 GMT FROM: Hans Krimm at NSF/NASA-GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), E. Troja (NASA/GSFC, UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210318A (trigger #1037339) (Troja, et al., GCN Circ. 29662). The BAT ground-calculated position is RA, Dec = 33.892, -37.755 deg which is RA(J2000) = 02h 15m 34.0s Dec(J2000) = -37d 45' 17.7" with an uncertainty of 2.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%. The mask-weighted light curves shows a single broad FRED-shaped peak with some structure. The emission starts at ~T10 sec, peaks at T+5 sec, and falls to background by T+50 sec. T90 (15-350 keV) is 48.00 +- 22.63 sec (estimated error including systematics). The time-averaged spectrum from T-12.37 to T+35.63 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.48 +- 0.33. The fluence in the 15-150 keV band is 6.4 +- 1.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+11.13 sec in the 15-150 keV band is 0.3 +- 0.3 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/1037339/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29706 SUBJECT: GRB 210318A: Swift/UVOT Upper Limits DATE: 21/03/24 11:05:42 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210318A 127 s after the BAT trigger (Troja et al., GCN Circ. 29662). No optical afterglow consistent with the XRT position (Troja et al. GCN Circ. 29662) 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 127 277 147 >20.5 u_FC 285 535 246 >19.9 white 127 1188 353 >21.0 v 614 1064 58 >18.6 b 541 1163 58 >19.3 u 285 535 246 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.017 in the direction of the burst (Schlegel et al. 1998).