[AAVSO-HEN] GRB 070724B: Swift-XRT afterglow candidates

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  6669
SUBJECT: GRB 070724B: Swift-XRT afterglow candidates
DATE:    07/07/25 23:50:43 GMT
FROM:    Pat Romano at OAB-Swift  <patrizia.romano at brera.inaf.it>

P. Romano(Uni-Bicocca and OAB), J.A. Kennea(PSU), C. Guidorzi(Uni-Bicocca and OAB),
D. Burrows report on behalf of the Swift-XRT team:

We have analysed the first two orbits of Swift-XRT data obtained for
GRB 070724B detected by SuperAGILE (Feroci et al., GCN Circ. 6668),
which include 3971s of Photon Counting (PC) mode data, beginning
on 2007-07-25 18:32:39 UT, 17.1 hours after the burst trigger time.
Using the PC data we found two sources within the SuperAGILE error circle,
at the following positions:

1) RA, Dec=17.48574, 57.67613, which is equivalent to
RA(J2000)  =  01 09 56.58
Dec(J2000) = +57 40 34.1
with an estimated error radius of 4.5 arcsec (90% confidence).
This position lies 4.6 arcmin  from the SuperAGILE position
(GCN Circ. 6668). The current observed 0.3-10 keV count rate is
(3.9+/-0.4)E-02 counts/s, which translates into a 0.3-10 keV flux of
~2E-12 erg/cm2/s (assuming a power-law with photon index=2 absorbed
by a column of NH=E21 cm-2).

2) RA, Dec= 17.51024, 57.81898, which is
RA(J2000)  =  01 10 02.46
Dec(J2000) = +57 49 08.3
with an estimated error radius of 6.1 arcsec (90% confidence).
This position lies 9.5 arcmin  from the SuperAGILE position.
The current observed 0.3-10 keV count rate is (0.6+/-0.2)E-03
counts/s, which translates into a 0.3-10 keV flux of ~3E-13 erg/cm2/s.

More data are being collected and a new circular will be issued
when the fading nature of these objects is established.

This circular is an official product of the XRT team.