[vsnet-grb-info 4515] GRB 070412: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6287
SUBJECT: GRB 070412: Swift-XRT refined analysis
DATE:    07/04/12 12:50:16 GMT
FROM:    Pat Romano at OAB-Swift  <patrizia.romano at brera.inaf.it>

P. Romano (Univ. Bicocca & INAF-OAB), A. Moretti (INAF-OAB),
C. Guidorzi (Univ. Bicocca & INAF-OAB) report on behalf of the Swift Team:

We have analysed the first 4 orbits of XRT data from GRB 070412
(trigger=275119; Romano et al., GCN Circ. 6273), which include
40s in WT and 2.4ks in PC mode.
The refined XRT position is RA,Dec=181.5426 +40.1438:
RA(J2000)  =12h 06m 10.2s
Dec(J2000) =+40d 08' 37.8"
with an uncertainty of 4 arcsec (90% containment, see GCN Circ. 6282).

The 0.3-10 keV X-ray light curve can be fit with a simple power-law
with a decay slope of 0.98+/-0.05, although the initial descent could
be due to a flare or the tail of the prompt emission (slope of ~-3.5).

The X-ray spectrum from the XRT/WT data (40s starting from T+67.8) can be fit by an
absorbed power-law with a photon index
of 2.2+/-0.5 and column density of (1.8-0.9+1.1)E21 cm**-2, higher than the Galactic
column density in the direction of the source
(1.95E20 cm**-2). The unabsorbed (absorbed) 0.3-10 keV flux for this  spectrum is
3.3E-10 (2.2E-10) erg/cm**2/s.
The XRT/PC data (2.4ks starting from T+3386) can be fit by an absorbed  power-law with a
photon index of 2.3-0.5+0.6 and column density of  (2.5-1.2+1.4)E21 cm**-2, consistently
with the WT data.
The unabsorbed (absorbed) 0.3-10 keV flux for this
spectrum is 6.1E-12 (3.3E-12) erg/cm**2/s.

Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10
keV XRT count rate of 5.6E-3 count/s at T+24hr, which corresponds to an observed 0.3-10
keV flux of 2.8E-13 erg/cm**2/s.

This circular is an official product of the Swift XRT Team.

-- 
Pat Romano
INAF - Osservatorio Astronomico di Brera
Via Bianchi 46, 23807 Merate LC, Italy
Phone (+39)-039-9991126; Fax (+39)-039-9991160
http://www.merate.mi.astro.it/~romano/