GCN Circular 23985

S. D. Barthelmy (GSFC), P. A. Evans (U Leicester), J.D. Gropp (PSU),
J. A. Kennea (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC) and
B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 10:56:25 UT, the Swift Burst Alert Telescope (BAT) triggered 
on an event in the vicinity of GRO J2058+42. Because of a gap 
in the telemetry no BAT position or lightcurve were received, 
so we are unable to determine a BAT position or the 
lightcurve characteristics. 

The BAT transient monitor of this source shows hints of recent 
flaring: https://swift.gsfc.nasa.gov/results/transients/weak/GROJ2058p42/

Using promptly downlinked data we find a bright, uncatalogued X-ray
source located at RA, Dec 314.69874, 41.77432 which is equivalent to:
   RA(J2000)  = 20h 58m 47.70s
   Dec(J2000) = +41d 46' 27.6"
with an uncertainty of 4.6 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at http://www.swift.ac.uk/sper/894268

This position is 10.6 arcseconds from a known X-ray source: 1SXPS
J205847.2+414637. This source is in the Swift XRT 1SXPS catalogue with
a mean 0.3-10 keV count-rate of 1.350 +/- 0.043 ct/sec; see
http://www.swift.ac.uk/1SXPS/1SXPS%20J205847.2%2B414637 for details of
these previous observations. 

The initial flux in the 2.5 s image was 6.86e-10 erg cm-2 s-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the U filter starting
873 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 19.2 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 18.0 mag. No
correction has been made for the large, but uncertain, extinction expected.