[vsnet-grb-info 5495] Possible XRF in NGC 2770 - NOT observations of the optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7161
SUBJECT: Possible XRF in NGC 2770 - NOT observations of the optical counterpart
DATE:    08/01/11 05:07:06 GMT
FROM:    Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr  <cthoene at astro.ku.dk>

Christina C. Thoene, Daniele Malesani, Jens Hjorth (DARK), Pall Jakobsson
(Univ. of Hertfordshire), Matt Bayliss and Benjamin Koester (Univ. of
Chicago) report:

We observed the optical counterpart of the proposed XRF in NGC 2770
(Berger & Soderberg, GCN 7159; Deng & Zhu, GCN 7160) with NOT/StanCam on
Jan 11, starting at UT 00:05 in UBVRI.
The optical counterpart reported in Deng & Zhu GCN 7160 is clearly
detected in all bands. Based on archival photometric zeropoints from
the NOT webpages, we obtain the following magnitudes:

U   19.9
B   20.2
V   19.3
R   18.7
I   18.1

If the transient is a SN related to the XRF and associated to NGC 2770, it
would be about 3 mag fainter than SN 1998bw at the same epoch.
At the moment, however, we cannot determine any possible variability or
get any conclusive evidence on the nature of the transient. Spectroscopic
observations are on the way.