Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 31635

ZTF22aabjpxh/AT2022cva: NICER X-ray detection is consistent with a GRB afterglow
2022-02-22T17:27:01Z (2 years ago)
Dheeraj R. Pasham at Mass. Inst. of Technology <>
Dheeraj Pasham (MIT), Keith Gendreau (NASA/GSFC), Elizabeth Ferrara
(NASA/GSFC),  Anna Ho (UC Berkeley)

NICER observed the rapidly fading transient AT2022cva (Ho et al. GCN 31619)
for 2.4 ks starting at 2022-02-21T22:56:03. X-rays are clearly detected
above the background in the 0.3-5.0 keV band with a mean
background-subtracted count rate of 0.92+-0.02 counts/seconds. We fit the
0.3-5 keV X-ray spectrum with a redshifted powerlaw modified by neutral
absorption in Milkway and host galaxy  (tbabs*ztbabs*zpow in XSPEC). Using
a Galactic nH value for tbabs (0.023e22 cm^2; HI4PI Collaboration, Bekhti
et al. 2016) and a redshift of 0.293 (Fremling et al., GCN 31619) gives a
good fit with a c-stat/degrees of freedom of 57/57. The best-fit power law
index and host column density values are 1.36(+0.14,-0.12) and <5e20 cm^-2,
respectively. The 0.3-5 keV observed flux is (2.24+-0.07)e-12 erg/s/cm^2.
This corresponds to an observed luminosity of 5.04(+0.03,-0.33)e44 erg/s at
a redshift of 0.293, which is typical for a GRB afterglow at a similar

NICER can carry out prompt follow-up observations of transients and is
planning to systematically follow up alerts from LIGO/Virgo and other X-ray
bright extra-galactic transients in the future.

NICER is a 0.2-12 keV X-ray telescope operating on the International Space
Station. The NICER mission and portions of the NICER science team
activities are funded by NASA.
Looking for U.S. government information and services? Visit