K.L. Page, A.P. Beardmore (U. Leicester), S. Mereghetti (INAF - IASF
Milano), M. Feroci and M. Tavani (INAF/IASF Roma) report on behalf of the
Swift-XRT and AGILE teams:
Following a ToO request, Swift-XRT started observing the field of GRB
080514B at 20:12 on 14th May, about 37 ks after the trigger. Within the
SuperAGILE/IPN error box, there are two sources detected, one of which is
much brighter and appears to be fading. We therefore believe this to be
the X-ray afterglow of the GRB.
Using 925 s of overlapping XRT Photon Counting mode and UVOT data, 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 =
322.84426, 0.70843 which is equivalent to:
RA (J2000): 21 31 22.62
Dec (J2000): +00 42 30.3
with an uncertainty of 1.6 arcsec (radius, 90% confidence). This position
is 1.7 arcsec from the i-filter object mentioned by de Ugarte Postigo et
al., in GCN Circ. 7719.
A spectrum of the three orbits of Photon Counting (PC) mode data (6 ks of
data, spanning 37-49 ks after the trigger) can be modelled with an
absorbed power-law of Gamma = 2.06 +0.35/-0.31 and NH = (1.2
+0.8/-0.6)x10^21 cm^-2, which is slightly in excess of the Galactic value
of 3.75x10^20 cm^-2. The observed (unabsorbed) 0.3-10 keV flux is
2.34x10^-12 (3.14x10^-12) erg cm^-2 s^-1. This corresponds to an observed
counts to flux conversion of 1 count = 3.96x10^-11 erg cm^-2.
The light-curve can be fitted with a single power-law, with a slope of
alpha = 1.5 +/- 1.0. If the light-curve continues to follow this decay,
the count rate at 48 hours is predicted to be 6.6x10^-3 count s^-1 (an
observed flux of 2.6x10^-13 erg cm^-2 s^-1).
This circular is an official product of the Swift-XRT team.