Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 17288

GRB 150101B / Swift J123205.1-105602: 9.8 GHz VLA observations
2015-01-09T16:06:35Z (9 years ago)
Wen-fai Fong at U of Arizona <>
W. Fong (U. Arizona) reports on behalf of a larger collaboration:

"We observed the field of the short/soft GRB 150101B (Cummings; GCN
17267) with the Karl G. Jansky Very Large Array (VLA) beginning on
2015 Jan 07.378 UT (5.73 days post-burst) at a mean frequency of 9.8
GHz. These observations are contemporaneous with the WSRT observations
at 4.9 GHz (van der Horst et al.; GCN 17286) and cover the
BAT position (90% containment). In 1 hour of observations, we detect
two sources within the BAT position also identified by WSRT.

The first source coincides with the galaxy 2MASX J12320498-1056010,
the XRT position (Cummings et al.; GCN 17268) and the bright source at
4.9 GHz (van der Horst et al.; GCN 17286). The 9.8 GHz flux density is
3.15 +/- 0.02 milliJy which translates to nuLnu ~ 1.5e40 erg/s (at
z=0.134; Levan et al.; GCN 17281), consistent with the interpretation
that this source is an AGN (Fong et al.; GCN 17285).

The second, fainter source is located at:

RA(J2000) = 12:32:08.19
Dec(J2000) = -10:56:14.2

with an uncertainty of 1" in each coordinate, and coincides with the
WSRT position (van der Horst et al.; GCN 17286). This
source has a 9.8 GHz flux density of 0.45 +/- 0.01 milliJy. Assuming a
single power law between 4.9 and 9.8 GHz, we calculate a spectral
index of -1.13 +/- 0.25 for this source. We note that there is no
optical source at this position in our Magellan r-band observations
(Fong et al.; GCN 17285) or in deeper r-band imaging we
obtained with Gemini-South/GMOS (17x90-sec) at 5.67 days post-burst.

We do not detect any other radio sources within the BAT position to a
3-sigma limit of 27 microJy.

We thank the VLA staff for quickly executing these observations."
Looking for U.S. government information and services? Visit