Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 21626

LIGO/Virgo G298048: NuSTAR limits on X-ray emission
2017-08-21T04:33:27Z (7 years ago)
Mansi M. Kasliwal at Caltech <>
F. A. Harrison, K. Forster, J. Garcia, B. W. Grefenstette, M. Heida, M. M.
Kasliwal, K. K. Madsen,  H. Miyasaka, S. Pike, V. Rana, Y. Xu (Caltech)

We obtained X-ray imaging of the optical counterpart of SSS17a (Coulter et
al.; GCN21529), the candidate optical counterpart of G298048 (LVC; GCN
21509) in the 3 ��� 79 keV band with NuSTAR.  Observations began at
2017-08-18T05:26:09 UT and ended at 2017-08-18T19:46:09, with a total
exposure of 24 ksec.  We did not detect any X-ray emission in a circular
50������ extraction region centered on the position of the optical counterpart,
with a 3-sigma threshold of 1.4 x 10-14 erg/cm^2/s in the 3-10 keV band,
assuming an X-ray spectrum with a photon power law index of -2.   No source
was detected in the 10-60 keV band, however additional analysis is ongoing
to place limits on possible line emission from nuclear decays. We note that
the NuSTAR hard X-ray band is not sensitive to X-ray emission from star
formation in the host galaxy, and there is no known AGN activity in this

Further NuSTAR observations are planned.
Looking for U.S. government information and services? Visit