[vsnet-grb-info 20943] NuSTAR observations of GRB 180720B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23041
SUBJECT: NuSTAR observations of GRB 180720B
DATE:    18/07/26 16:39:39 GMT
FROM:    Eric C Bellm at UW  <ecbellm at uw.edu>

E. C. Bellm (UW) and S. B. Cenko (GSFC) report:

We have analyzed 38 ksec of NuSTAR data for GRB 180720B (M. H. Siegel et
al., GCN Circ. 22973), from 243 ksec to 318 ksec after the BAT trigger.
NuSTAR detects emission from the X-ray afterglow to approximately 30 keV.

The NuSTAR spectrum can be well-modeled from 3-30 keV by an absorbed power
law with spectral index 1.80+/-0.06, consistent with the value reported
by XRT (K.  L. Page et al., GCN Circ. 22984).  The 3-30 keV flux was
4.8+/-0.2 x 10^-12 erg cm^-2 s^-1.

We thank Karl Forster and the NuSTAR operations team for their assistance
executing these TOO observations.