GCN Circular 36063

T. M. Parsotan (GSFC), S. Dichiara (PSU),
R. A. J. Eyles-Ferris (U Leicester), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), K. L. Page (U Leicester),
B. Sbarufatti (INAF-OAB), M. H. Siegel (PSU) and M. A. Williams (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 15:32:54 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240411B (trigger=1221183).  Swift slewed immediately to the burst. 
No further BAT information is available at this time due to a
telemetry gap.  Further information will be available after the
next telemetry pass over a ground station. 

The XRT began observing the field at approximately 15:35:54 UT, around 180
seconds after the BAT trigger. Using promptly downlinked data we find an 
uncatalogued X-ray source with an enhanced position: RA, Dec 231.54236, 
-2.14609 which is equivalent to:
   RA(J2000)  = 15h 26m 10.17s
   Dec(J2000) = -02d 08' 45.9"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). 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 consistent with the Galactic value of 1.11
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 190 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 0.138. 

Burst Advocate for this burst is T. M. Parsotan (parsotat AT umbc.edu). 
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/)