TITLE:   GCN CIRCULAR
NUMBER:  20383
SUBJECT: LIGO/Virgo G268556:  Pan-STARRS1 observations of the skymap 
DATE:    17/01/06 20:08:36 GMT
FROM:    S. J. Smartt at Queens U Belfast  <s.smartt@qub.ac.uk>

K. C. Chambers (IfA), K. W. Smith (QUB), M. E. Huber (IfA),
S. J. Smartt, D. R. Young, D. E. Wright (QUB), M. Coughlin (Harvard),
L. Denneau, H. Flewelling, A. Heinze, E. A. Magnier (IfA), A. Rest
(STScI), B. Stalder (IfA), A. S. B. Schultz, C. W. Stubbs (Harvard)
J. Tonry, C. Waters, R. J. Wainscoat, H. Weiland (IfA) 

We report observations of the localisation skymap for LIGO/Virgo
G268556 with the Pan-STARRS1 telescope (see Chambers et
al. arXiv:1612.05560) and our search for transients (Smartt et
al. 2016, MNRAS, 462, 4094).
 
The alert for G268556 came too close to sunrise for immediate
observations at the time of the event release and we started observing
the LIGO/VIRGO localisation region at 57758.309 (2017-01-05 07:34:57
UT), beginning at RA=114 DEC=+5 and scanning the error lobe
north and eastwards to approximately R=140, DEC=+65.
A plot of the footprints has been uploaded to GraceDB. 

The images were taken in the Pan-STARRS i-band in a series of
overlapping 45s exposures, with typically 4 images at each position.
These were combined into stacks and subtracted from the Pan-STARRS1
3Pi reference image (as discussed in Chambers et al. arXiv:1612.05560,
and available at http://panstarrs.stsci.edu). The combined images typically 
reach i~21. 

We have located several tens of transient candidates and will report these in
a GCN after a further nights observing on 57759, and confirmation of
stationary sources.