TITLE:   GCN CIRCULAR
NUMBER:  29834
SUBJECT: GRB 210419C: Swift detection of a burst
DATE:    21/04/20 00:45:40 GMT
FROM:    Michael Moss at George Washington U  <mikejmoss3@gmail.com>

M. J. Moss (GWU), V. D'Elia (SSDC & INAF-OAR), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU),
N. P. M. Kuin (UCL-MSSL), S. Laha (GSFC/UMBC/CRESST),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. H. Siegel (PSU)
and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 23:27:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210419C (trigger=1044236).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 212.968, 35.999 which is 
   RA(J2000) = 14h 11m 52s
   Dec(J2000) = +35d 59' 56"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). Currently, we only have limited BAT light curve data. 
The available light curve from ~T+110 s to ~T+400 s does
not show any significant structure. 

Due to lack of data, we do not have an accurate XRT position. However our current
best estimate for the GRB position is RA/Dec(J2000) = 212.96009,
+36.0096, which is equivalent to:

RA(J2000): 14h 11m 50.4s
Dec(J2000): 36d 00m 34.6s

Uncertainty of this position is unclear. We await ground
processed data to report an accurate position for this GRB. 

UVOT took a finding chart exposure of ​95​ seconds with the ​U​ filter
starting​ around 340 ​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
0.0​1​. 

Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). 
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/)