[vsnet-grb-info 4270] GRB 070129: dust-scattered X-ray halo detected by Swift/XRT

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6065
SUBJECT: GRB 070129: dust-scattered X-ray halo detected by Swift/XRT
DATE:    07/01/31 14:31:35 GMT
FROM:    Sandro Mereghetti at IASF/CNR  <sandro at iasf-milano.inaf.it>

G. Vianello (INAF, IASF-Milano & Univ. dell'Insubria), A. Tiengo, S. 
Mereghetti (INAF, IASF-Milano) report:

We discovered a faint dust scattering halo in the Swift XRT Photon 
Counting mode data of GRB 070129. The halo consists of a partial ring of 
radius ~2 arcmin located to the North-West of the GRB afterglow position.

Analysis of the dynamical image (see Tiengo & Mereghetti 2006 A&A 449, 
203)  covering the period from T0+4700s to T0+7300s (where T0 is the BAT 
trigger time, as reported in GCN 6053) indicates that the halo is 
expanding and leads to an estimate of ~300 pc for the distance of the dust 
layer responsible for the scattering.

Dust maps (Schlegel, Finkbeiner, & Davis 1998, ApJ, 500, 525) show a 
diffuse structure in the direction indicated by the partial ring, and a 
total Galactic extinction of A_v~0.4.