[AAVSO-HEN] GRB 090916: Swift-XRT upper limit

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  9925
SUBJECT: GRB 090916: Swift-XRT upper limit
DATE:    09/09/18 15:44:29 GMT
FROM:    Andy Beardmore at U Leicester  <apb at star.le.ac.uk>

A. P. Beardmore, K. L. Page (U. Leicester) and E. Troja (NASA/GSFC/ORAU)
report on behalf of the Swift-XRT team :

Due to a Moon constraint, the Swift-XRT could not observe the field of
the BAT short GRB 090916 (Troja et al., GCN Circ. 9913) until 9.3
hours after the trigger. In 12.3 ks of Photon Counting mode data (from
33.5 to 126.6 ks after the trigger) we do not detect any source
within the BAT refined error circle of Barthelmy et al. (GCN Circ. 9915).
The 3 sigma upper limit 0.3-10 keV count rate is 8 x 10^-4 count s^-1,
which corresponds to an observed flux limit of 3 x 10^-14 erg cm^-2 s^-1
(assuming a typical count-to-observed flux conversion factor of
3.8 x 10^-11 erg cm^-2 ct^-1, Evans  et al., 2009, MNRAS, 397, 1177).

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