[AAVSO-HEN] GRB 080514B: Swift-XRT analysis

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  7723
SUBJECT: GRB 080514B: Swift-XRT analysis
DATE:    08/05/15 08:19:04 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

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.