[AAVSO-HEN] 1E1547.0-5408: Swift detection of dust halo

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  8848
SUBJECT: 1E1547.0-5408: Swift detection of dust halo
DATE:    09/01/24 00:52:59 GMT
FROM:    Sandro Mereghetti at IASF/CNR  <sandro at iasf-milano.inaf.it>

A.Tiengo, S.Mereghetti, G.Vianello, P.Esposito (INAF-IASF Milano), 
G.L.Israel (INAF-OAR), N.Rea (Amsterdam Univ.), D.Gotz (CeA Saclay), on 
behalf of a larger collaboration report:

A Swift/XRT observation performed on January 23 from 15:23 to 15:51 UT in 
Photon Counting mode shows the presence of a dust scattering halo around 
the position of the Anomalous X-ray Pulsar 1E1547.0-5408.

A bright ring with a radius of about 1 arcmin is clearly visible, but the 
observation is too short to detect expansion.

Assuming that this ring is due to the bright burst detected on Jan 22 at 
06:48:04 UT (Mereghetti et al. GCN 8841), and that the distance of 
1E1547.0-5408 is 10 kpc, the distance inferred for the dust layer 
responsible for the scattering is about 7 kpc.

Further observations to measure the time evolution of the dust scattering 
rings can provide tighter constraints.