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GCN Circular 24021

Subject
Swift Trigger 895479: Detection of GRO J2058+42
Date
2019-03-27T21:49:05Z (6 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
J. A. Kennea (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 21:27:45 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRO J2058+42 (trigger=895479).  Swift slewed immediately to the source. 
The BAT on-board calculated location is 
RA, Dec 314.705, +41.745 which is 
   RA(J2000) = 20h 58m 49s
   Dec(J2000) = +41d 44' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with an image trigger, the available
BAT light curve shows no significant structure. 

The XRT began observing the field at 21:30:58.4 UT, 193.0 seconds after
the BAT trigger. Using promptly downlinked data we find an X-ray source
with an enhanced position: RA, Dec 314.6977, 41.7766 which is
equivalent to:
   RA(J2000)  = 20h 58m 47.44s
   Dec(J2000) = +41d 46' 35.6"
with an uncertainty of 2.5 arcseconds (radius, 90% containment). This
location is 115 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. This position is 2.3 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/1SXPSJ205847.2%2B414637
for details of these previous observations. No spectrum from the
promptly downlinked event data is yet available to determine the column
density. 

UVOT took a finding chart exposure of 250 seconds with the U filter
starting  193 seconds after the BAT trigger. UVOT detects a 16th mag
source consistent with the XRT position. No  correction has been made
for the large, but uncertain, extinction expected. 

Swift-BAT previously triggered on this source on 2019 March 22 (GCN Circ. 23985Loading...
 
 )
and earlier today on 2019 March 27 (GCN Circ. 24017Loading...
 
 )

The BAT transient monitor of this source shows the source to be in outburst: 
https://swift.gsfc.nasa.gov/results/transients/weak/GROJ2058p42/