GCN Circular 16013
Subject
GRB 140320B: Swift-XRT detection of the afterglow
Date
2014-03-20T21:57:31Z (10 years ago)
From
Claudio Pagani at U of Leicester <cp232@star.le.ac.uk>
C. Pagani, K.L. Page, R.L.C. Starling, (U. Leicester) report on behalf
of the Swift-XRT team:
We have analysed 4 ks of XRT data for the INTEGRAL detected GRB 140320B
(Mereghetti et al. GCN Circ. 16004), from 11.6 s to 23.1 ks after the
trigger. The data are entirely in Photon Counting (PC) mode. An
uncatalogued, fading X-ray source is detected inside the INTEGRAL error
circle.
Using 3683 s of XRT PC data and 4 UVOT images, 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 =
145.55932, 60.26822 which is equivalent to:
RA (J2000): 09 42 14.24
Dec (J2000): +60 16 05.6
with an uncertainty of 1.7 arcsec (radius, 90% confidence). This is
consistent with the optical position reported by Guidorzi et al. (GCN
16003) and Elenin et al. (GCN 16005).
The light curve can be modelled with a power-law decay with an index of
alpha=1.12 (+1.21, -0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+0.4, -0.3). The
best-fitting absorption column is 6 (+8, -6) x 10^20 cm^-2, consistent
with the Galactic value of 2.4 x 10^20 cm^-2 (Kalberla et al. 2005). The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 2.8 x 10^-11 (3.0 x 10^-11) erg cm^-2
count^-1.
If the light curve continues to decay with a power-law decay index of
1.12, the count rate at T+24 hours will be 7.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x
10^-14 (2.3 x 10^-14) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.