GCN Circular 9977
Subject
GRB 090929A: Swift-XRT non-detection
Date
2009-09-30T16:21:47Z (15 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team:
Swift performed a short Target of Opportunity observation of GRB 090929A
about 13 hours after the burst (Rau, GCN Circ. 9962; Cummings & Krimm, GCN
Circ. 9966; Golenetskii et al., GCN Circ. 9968). This area of sky was a
hot target for the XRT, so only a short observation was performed, with
1.4 ks of data being collected in Photon Counting mode.
We do not detect a source within the BAT error circle, to a 90% upper
limit of 0.015 count s^-1 over 0.3-10 keV. Assuming a typical counts to
flux conversion of 3.8 x 10^-11 erg cm^-2 ct^-1 (Evans et al., 2009,
MNRAS, 397, 1177), this corresponds to an observed flux of 5.7 x 10^-13
erg cm^-2 s^-1. We note that this is not a very constraining upper limit,
because of the greater than usual background caused by the high XRT CCD
temperature and the short exposure time.
Filtering out all photons below 1 keV, a more stringent upper limit of 9 x
10^-3 count s^-1 (1-10 keV; observed flux of ~3.4 x 10^-13 erg cm^-2 s^-1)
can be determined.
This circular is an official product of the Swift-XRT team.