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GCN Circular 21160

Subject
LIGO/Virgo G268556: optical observations and classification of Pan-STARRS1 transients
Date
2017-05-28T21:05:39Z (7 years ago)
From
Alexei Pozanenko at IKI,Moscow <grbgw.iki@gmail.com>
A. Pozanenko (IKI), A. Volnova (IKI), E. Mazaeva (IKI), E. Klunko 
(ISTP), A. Kusakin (AFIF), I. Reva (AFIF) on behalf of IKI-GW follow-up 
collaboration:

We report results of photometric observations and possible 
classifications of Pan-STARRS1 transients PS17dp, PS17fl, PS17fn, PS17gl 
(Smartt et al, GCN 20410) detected  in  the LIGO G268556 localizations 
(LIGO Scientific Collaboration, GCN 20364). Observations were conducted 
using telescopes/observatories AZT-33IK/Mondy and  Zeiss-1000/TSHAO.

===============

PS17dp	
RA   09:00:51.09
Dec +45:26:44.3

We observed the source PS17dp taking 5 observational sets in different 
epochs between Jan. 19 and 24. All observations were performed with 
filter R. The photometry is based on nearby SDSS stars.

Date		UT start	Filter	MJD		mag 	err
2017-01-19	18:24:02	R	57770.77716	16.93	0.04
2017-01-21	17:56:26	R	57774.75795	16.91	0.05
2017-01-22	17:40:22	R	57775.74680	16.90	0.05
2017-01-23	17:04:07	R	57776.72092	16.93	0.05
2017-01-24	21:17:52	R	57777.89783	17.02	0.04

The source is fading during our observations. There is an SDSS galaxy 
J090050.96+452642.7 at the position of the source with r = 17.280 +/- 
0.006 and R = 17.050 +/- 0.015 (Lupton 2005 transformation equations) 
which might be a host galaxy of the transient. At the last observational 
epoch the source faded to the host galaxy level within 1 sigma.

===============

PS17fl	
RA   08:02:09.73
Dec +28:49:44.7

We observed the source PS17fl taking 9 observational sets in different 
epochs between January 17 and March 28. All observations were performed 
with filter R.  The photometry is based on nearby SDSS stars.

Date		UT start	Filter	MJD		mag 	err
2017-01-17	16:24:04	R	57770.69727	18.15	0.10
2017-01-19	16:52:12	R	57772.71590	18.16	0.02
2017-01-21	15:21:07	R	57774.65356	18.20	0.02
2017-01-22	15:47:17	R	57775.66825	18.18	0.02
2017-01-23	15:39:48	R	57776.66306	18.17	0.02
2017-01-24	19:43:15	R	57777.82865	18.21	0.03
2017-01-25	16:24:35	R	57778.69277	18.18	0.03
2017-01-28	18:32:47	R	57781.78667	18.12	0.02
2017-03-28	17:18:32	R	57840.73404	18.22	0.03

The brightness of the source slowly decreases and in our last 
observational set has a magnitude consistent within 2 sigma with that of 
its host galaxy SDSS J080209.69+284945.3 (Chambers  et al. GCN 20437) 
with r = 18.47 +/- 0.01 and R = 18.29 +/- 0.02 (Lupton 2005 
transformation equations). If SN Ib/Ic (suggested by Chambers  et al. 
GCN 20437) then maximum can be between MJD 57761.4876 and  57770.69727 
and therefore could be related to G268556 event.

===============

PS17fn	
RA   08:05:51.40
Dec +28:42:51.9

We observed the source PS17fn taking 8 observational sets in different 
epochs between Jan. 17 and 28. All observations were performed with 
filter R.   The photometry is based on nearby SDSS stars.

Date		UT start	Filter	MJD		mag 	err
2017-01-17	17:52:24	R	57770.75515	19.51	0.16
2017-01-19	17:34:47	R	57772.74354	19.18	0.04
2017-01-21	16:15:49	R	57774.68807	19.11	0.04
2017-01-22	16:19:52	R	57775.69088	19.15	0.04
2017-01-23	16:32:34	R	57776.69970	19.15	0.40
2017-01-24	20:05:57	R	57777.84441	19.31	0.05
2017-01-25	16:53:02	R	57778.71114	19.33	0.04
2017-01-28	19:15:36	R	57781.80806	19.31	0.07

There is an SDSS galaxy J080209.69+284945.3 at the position of the 
source with r = 19.801 +/- 0.032 and R = 19.612 +/- 0.063 (Lupton 2005 
transformation equations) which might be a host galaxy of the transient. 
The source is rising above the host level for more then 3 sigma, than 
fading.The photometry of the source might be contaminated by a nearby 
galaxy J080551.85+284253.6 in 6 arcseconds to the East of the source. 
The temporal behavior of the transient allows to confirm it to be a 
supernova (Chambers  et al. 20437) with the maximum around of MJD = 
57774.68807 and therefore the source is inconsistent with the G268556 
trigger.


===============

PS17gl	
RA   08:34:50.85
Dec +61:13:02.2

We observed the source PS17fl taking 5 observational sets in different 
epochs between Jan. 19 and 25. All observations were performed with 
filter R. The photometry is based on nearby SDSS stars.

Date		UT start	Filter	MJD		mag 	err
2017-01-19	18:59:34	R	57772.80185	17.38	0.03
2017-01-21	16:48:39	R	57774.71087	17.39	0.03
2017-01-22	16:57:34	R	57775.71707	17.40	0.03
2017-01-24	20:36:10	R	57777.87095	17.56	0.02
2017-01-25	18:51:56	R	57778.79509	17.57	0.02

There is an SDSS galaxy J083450.96+611258.7 at the position of the 
source with r = 17.704 +/- 0.009 and R = 17.502 +/- 0.020 (Lupton 2005 
transformation equations) which might be a host galaxy of the transient. 
The source is fading during our observations down to the level of the 
host galaxy within 2 sigma. This may be a supernova or a GRB afterglow.
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