TITLE:   GCN CIRCULAR
NUMBER:  21889
SUBJECT: LIGO/Virgo G298048: Danish Telescope Observations of SSS17a/DLT17ck
DATE:    17/09/15 16:40:07 GMT
FROM:    Zach Cano at U of Iceland  <zewcano@gmail.com>

​Z. Cano (IAA-CSIC), U. G. Jorgensen (Univ. of Copenhagen), G. Hodosan
(IAA-CSIC, Univ. of St Andrews), R. Figuera Jaimes (Univ. of St Andrews),
Y. I. Fujii (Univ. of Copenhagen; Nagoya Univ.), and M. Rabus (Pontificia
Univ. Catolica de Chile, MPIA)

We report on observations obtained with the 1.54-m Danish Telescope located
at La Silla, Chile, of the GW counterpart SSS17a/DLT17ck (Coulter et al.,
LVC GCN 21529). Observations were obtained on 2017, August 19th, 21st and
22nd in the I-band (all three dates), and z-band (19th only). A summary of
the observations follows:

Date        UT Start    Exposure time (s)    Filter
----------------------------------------------------------------------
19-August    23:41:45.6    6 x 150            I
19-August    23:44:49.9    6 x 150            z
21-August    23:17:51.8    25 x 100        I
22-August    23:23:57.3    40 x 100        I

Image subtraction of the co-added I-band images obtained during the first
two nights reveals a residual transient at the following position:

RA, Dec (J2000): 13:09:48.11 -23:22:53.0

With an estimated uncertainty of ~0.5''. This position is consistent with
that found by other groups within its uncertainty radius.

Further analysis of the images is currently underway, including the precise
photometric calibration of the optical transient.​