GRB 201221C

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/)

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.

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
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 ).

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.