[vsnet-grb-info 8672] GRB 091117: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10177
SUBJECT: GRB 091117: Swift XRT refined analysis
DATE:    09/11/19 15:58:16 GMT
FROM:    Valerio D'Elia at INAF-OAR  <delia at mporzio.astro.it>

V. D'Elia, G. Stratta, M. Perri (ASDC), P.A. Evans and M.R. Goad (U.  
Leicester),
J. Cummings (GSFC/CRESST), S. Campana (INAF-OAB) report on behalf of  
the Swift-XRT team:

We have analysed 3.85 ks of XRT data for GRB 091117 (Cummings et al.  
et al.
GCN Circ. 10171), from 96765 s to 119.4 ks after the Suzaku trigger. The
data are entirely in Photon Counting (PC) mode. Two sources are detected
at the edge of the BAT error circle.

Source #1:
using 722 s of XRT Photon Counting mode data and 1 UVOT
images, we find an astrometrically corrected X-ray position (using the
XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 30.97240, -16.97490 deg which is equivalent to:

RA (J2000):  02 03 53.38
Dec (J2000): -16 58 29.8

with an uncertainty of 3.6 arcsec (radius, 90% confidence).

This position may be improved as more data are received.  The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

The source is at a count rate level of (4.8+/-1.4)e-3 counts/s.
The light curve does not allow us to assess if the source is fading.

This source has been reported by Berger et al. (GCN Circ. 10173)
to be coincident with the DSS galaxy APMUKS B020129.84-171252.3
at redshift z=0.096 (Chornock & Berger 2009, GCN Circ. 10176)
We can't distinguish if this is nuclear emission from the AGN
discussed by Berger et al. (GCN Circ. 10176)

Source #2:
the other source has a count rate level of
(2.7+/-1.1)e-3 counts/s and is at RA, Dec= 30.988333, -16.948583 deg
which is equivalent to

RA (J2000): 02 03 57.2
Dec(J2000): -16 56 54.9

with an uncertainty of 7.7 arcsec (radius, 90% confidence).

The light curve does not allow us to assess if the source is fading.

We note that there is a known source (2MASX J02035665-1656585 at  
z=0.096220)
located 8.8 arcsec from Source #2.

Further observations are planned for this field.

This circular is an official product of the Swift-XRT team.