[vsnet-grb-info 15044] Chandra late-time observations of GRB140515A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16338
SUBJECT: Chandra late-time observations of GRB140515A
DATE:    14/05/28 19:03:45 GMT
FROM:    Raffaella Margutti at Harvard  <rmargutti at cfa.harvard.edu>

R. Margutti, E. Berger, R. Chornock, W. Fong, T. Laskar and A. Zauderer
(Harvard U.) report:

"We observed the location of GRB 140515A (D'Avanzo et al., GCN 16267)
at z=6.32 (Chornock et al., GCN 16269)
with the Chandra X-ray Observatory (Program 15508477, PI Margutti).
Our observations started on May 25th, 07:38:38 UT,  858.6 ks after the BAT
trigger.
No X-ray source is detected at the position of the optical and radio
afterglow
(Fong et al., GCN 16274, Laskar et al., GCN 16283),
with a 3-sigma count-rate limit of 1.5E-4 c/s (0.3-10 keV energy range,
total exposure time of 19.8 ks).

Adopting the best fitting parameters from the total PC-mode spectrum
(photon index Gamma=1.8, intrinsic neutral hydrogen column density
NHint=2.3E+22 cm-2 at z=6.32), we compute an observed flux limit of
1.5E-15 erg/s/cm2 (0.3-10 keV).  The Galactic hydrogen column density
in the direction of the burst is NHgal=2.5E+20 cm-2 (Kalberla et al.,
2005).
Our observations constrain the late-time (t> 100 ks) X-ray afterglow decay
to be steeper than t^-2.6.

We thank Belinda Wilkes and the entire Chandra team for making these
observations possible."