//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29106 SUBJECT: Swift Trigger 1014012: possible GRB 201221C DATE: 20/12/21 19:07:16 GMT FROM: Kim Page at U.of Leicester K. L. Page (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 18:41:33 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 201221C (trigger=1014012). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 278.205, +34.411 which is RA(J2000) = 18h 32m 49s Dec(J2000) = +34d 24' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for image triggers, there is nothing significant in the real-time light curves. The XRT began observing the field at 18:43:46.4 UT, 132.7 seconds after the BAT trigger. No source was detected in 215 s of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 136 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 25% of the BAT 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 BAT 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 0.07. Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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: 29107 SUBJECT: GRB 201221C: MASTER optical observtion DATE: 20/12/21 19:41:01 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa,A.Kuznetsov,K.Zhirkov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov,A.Pozdnyakov, V.Topolev, 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 (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to the GRB201221.78 133 sec after notice time and 208 sec after trigger time at 2020-12-21 18:45:02 UT. On our 11-th (180s exposure) set , obtained 1451 sec after tigger time at 2020-12-21 19:05:45 UT, we haven`t found optical transient within Swift error-box (ra=278.204 dec=34.4108 r=0.05). The 5-sigma upper limit has been about 13.6mag The message may be cited. The galactic latitude b = 18 deg., longitude l = 63 deg. The observations made on zenith distance = 69 deg.The moon (48 % bright part) is 56 deg. above the horizon. The distance between moon and object is 87 Observations started at twilight. The sun altitude is -11.4 deg. The object can be observed till sunrise at 2020-12-22 07:52:15 The 5-sigma upper limit has been about 14.9mag The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29138 SUBJECT: Swift Trigger 1014012 (possible GRB 201221C) is likely not an astrophysical event DATE: 20/12/22 17:42:53 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: Using the full data set from recent downlinks, we report further ground data analysis for Swift trigger 1014012 (Page et al. GCN Circ. 29106). The BAT analysis uses data from T-239 to T+963 sec. The BAT image significance has now decreased to 5.2 sigma (15-350 keV). Also, the mask-weighted light curve does not show anything significant. There is no good evidence for an X-ray source in 4.7 ks data, to a 3 sigma upper limit of 2.3x10^-3 count s^-1 (corresponding to an observed flux of 1x10^-13 erg cm^-2 s^-1, assuming a typical power-law spectrum). We therefore conclude that this event is likely due to noise, and is not an astrophysical event.