TITLE:   GCN CIRCULAR
NUMBER:  21648
SUBJECT: LIGO/Virgo G298048: Chandra X-ray observations
DATE:    17/08/22 18:06:23 GMT
FROM:    Raffaella Margutti at Northwestern U  <rafmargutti@gmail.com>

R. Margutti, W. Fong (Northwestern), E. Berger (Harvard), R. Chornock (Ohio
University), P. Cowperthwaite, K. D. Alexander (Harvard)

We observed the field of the EM counterpart to the LVC trigger G298048 with
the Chandra X-ray Observatory (CXO) starting on 2017-08-19T17:10:09UT  (PI
Fong).
We do not find evidence for significant X-ray emission at the location of
the optical transient (RA= 13:09:48.08, Dec= -23:22:53.2,  Coulter et al.
LVC GCN 21529; Allam et al., LVC GCN 21530; Sheng Yang et al., LVC GCN
21531; Chambers et al. LVC GCN 21553).

An extended X-ray source is clearly detected at:
RA= 13:09:47.7
dec= -23:23:02.0

This position is consistent with the radio source that we identified in
Alexander et al. (LVC GCN 21589) and it is centered on the host-galaxy
optical position. Based on preliminary analysis, we estimate a flux ~1e-14
erg/s/cm2 in the 0.3-10 keV band.

The CXO X-ray source lies outside the 90% containment, but within the
3-sigma containment, of the localization region of the Swift-XRT source
(Evans et al., LVC GCN 21612). The flux inferred by Evans et al., Fx=2.6
(+1.1, -0.9) e-14 erg/cm^2/s is also consistent with our results. We thus
suggest that the X-ray source identified by Swift-XRT is most likely
emission from the host galaxy.

We thank Belinda Wilkes and the entire Chandra team for their great support
with these observations.