[AAVSO-HEN] GRB090217: XRT analysis

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  8907
SUBJECT: GRB090217: XRT analysis 
DATE:    09/02/18 21:38:10 GMT
FROM:    Olivier Godet at U.of Leicester  <og19 at star.le.ac.uk>

O. Godet (U. Leicester) on behalf the Swift-XRT team

The Swift-XRT started observing the field of GRB090217 (GCN Circ. 8903) 39ks
after the LAT trigger (T0) using an early LAT position (RA,Dec (J2000) =
204.436 deg, -8.858 deg and a 90% confidence error radius of 0.454 deg) which
is 39 arcmin away from that quoted in Ohno et al. (GCN Circ. 8903).

We analysed 7.5ks of Photon Counting (PC) data collected from T0+39ks to
T0+62.8ks. The LAT error circle is larger than the XRT field of view. Three
X-ray sources with a signal-to-noise ratio larger than 3 were found at
(J2000):

S1: RA, Dec, err = 13 37 18.11,  -08 45 28.5, 5.5 arcsec

S2: RA, Dec, err = 13 37 40.35   -09 01 29.7, 4.5 arcsec

S3: RA, Dec, err = 13 37 39.49   -09 02 26.6, 4.4 arcsec

The XRT error radii are quoted at 90% confidence level.

The position S3 is consistent with the AGN HE 1335-0847 previously detected by
ROSAT. The position S2 is consistent with that of a star from the USNO-B1
catalog, while the position S1 is 6.7 arcsec away from a USNO-B1 source.

The data for S1 and S2 are too sparse to check for any variability during the
observation.  Nevertheless, none of these sources are likely to be the X-ray
afterglow of GRB 090217.

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