TITLE:   GCN CIRCULAR
NUMBER:  18484
SUBJECT: LIGO/Virgo G194575: further Pan-STARRS observations of the RA=1hr localisation region
DATE:    15/10/27 10:20:18 GMT
FROM:    S. J. Smartt at Queens U Belfast  <s.smartt@qub.ac.uk>

K. W. Smith, D. Wright, S. J. Smartt (Queen’s University Belfast),  
K. Chambers, M. Huber, (IfA, University of Hawaii), E. Magnier, 
H. Flewelling, C. Waters, J. Tonry, A. Schultz, N. Primak, A. Heinze, 
B. Stalder, L. Denneau, A. Sherstyuk (IfA), C. Stubbs, 
M. Coughlin (Harvard), A. Rest (STScI)

Further to GCN 18445, we report that 2 further transients were discovered within 
the 45% probability contour of the RA=1hr blob. These transients are listed
below along with their discovery dates. We also recovered LSQ15bjb on
MJD=57316 (i=19.55) and MJD=57317 (i=19.03), as PS transient PS15cog. 
Our first detection is 29.14 hrs before the GW trigger, hence although we
confirm the LSQ result that this is indeed a fast rising and bright transient, 
it exploded before the LIGO/Virgo detection trigger.

Name         RA (J2000)    Dec (J2000)   Disc. Date   Disc Mag  filter   Notes

LSQ15bjb   00 11 27.61   -06 25 38.4      20151021     19.55       i       (1)

PS15coe     00 29 00.31   -01 34 53.6     20151023     20.69       i       (2)

PS15cof      00 32 03.01   -05 51 46.9     20151023     21.02       i       (3)

(1) LSQ15bjb = PS15cog.  The PS1 photometry shows it to be visible 29.14 
hours prior to the G194575 event, hence can probably be ruled out as unrelated.  
SDSS DR12 reports that the likely host (12.34" away) is 
SDSS J001127.44-062549.5, with photometric redshift of ~0.06.
(2) DR12 reports that the likely host (2.2" away) is SDSS J002900.23-013451.7,
with photometric redshift of ~0.15.
(3) DR12 reports that the likely host (3.17" away) is SDSS J003203.21-055146.6, 
with photometric redshift of ~0.11.