[vsnet-grb-info 24889] GRB200120A: SRG/eROSITA discovery of X-ray afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26988
SUBJECT: GRB200120A: SRG/eROSITA discovery of X-ray afterglow
DATE:    20/02/05 15:50:25 GMT
FROM:    Arne Rau at MPE  <arau at mpe.mpg.de>

P. Weber (FAU), A. Rau (MPE), Th. Dauser (FAU), I. Kreykenbohm (FAU), J. 
Wilms (FAU) report:

The location of the Fermi/GBM long duration GRB 200120A (#26831, #26840, 
#26851, #26856, #26857, #26974) was observed by SRG/eROSITA as part of 
its all-sky survey between UTC 2020 Jan 16th and Jan 24th.  Throughout 
this period, the instrument scanned over the position with a cadence of 4hr.

On UTC Jan 20th 23:18:15 (820 seconds after the Fermi/GBM trigger) we 
detected a bright and quickly fading X-ray source localized to

RA(J2000) =   09:08:32.1 (137.13364 deg)
Dec(J2000) = -70:25:11   (-70.43628 deg)

with an uncertainty of ~4" arcsec radius. This position is consistent 
with the Fermi/GBM (#26831) and IPN (#26856) localizations, suggesting 
the source to be the X-ray afterglow of GRB200120A.

At the time of discovery, the source was detected with a count rate of 
44+/-2 cnt/s in the 0.2-10keV band, corresponding to a flux of approx. 
1x10E-10 erg/cm^2/s. The source was also found during the next scan 4hr 
later. By then, it had faded to 2.8+/-0.5 cnt/s (approx. 6x10E-12 
erg/cm^2/s). Further detections were obtained in the following three 
scans with count rates of ~1+/-0.3 cnt/s. Nothing was seen in the scans 
prior to the Fermi/GBM detection.