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 27936

GRB 200613A: Swift-XRT afterglow detection
2020-06-14T04:46:25Z (4 years ago)
Kim Page at U.of Leicester <>
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri
(INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 200613A (Ohno et al. GCN Circ. 27931),
collecting 4.9 ks of Photon Counting (PC) mode data between T0+43.6 ks
and T0+67.6 ks. 

Seven uncatalogued X-ray sources are detected, of which one ("Source
2") is above the RASS limit, and is therefore likely the GRB afterglow.
Using 4079 s of PC mode data and 4 UVOT images, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 153.04199, +45.75408 which is
equivalent to:

RA (J2000): 10h 12m 10.08s
Dec(J2000): +45d 45' 14.7"

with an uncertainty of 1.4 arcsec (radius, 90% confidence). This
position is 5.8 arcmin from the Fermi/LAT position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.6 (+/-0.5).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.89 (+0.14, -0.13). The
best-fitting absorption column is  2.3 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 8.4 x 10^19 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.5 x 10^-11 (4.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.3 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 8.4 x 10^19 cm^-2
Excess significance: 7.5 sigma
Photon index:	     1.89 (+0.14, -0.13)

The results of the XRT-team automatic analysis are available at
The results of the full analysis of the XRT observations are available

This circular is an official product of the Swift-XRT team.
Looking for U.S. government information and services? Visit