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GCN Circular 20410

Subject
LIGO/Virgo G268556: Pan-STARRS1 observations and summary of transient sources
Date
2017-01-09T21:05:14Z (7 years ago)
From
S. J. Smartt at Queens U Belfast <s.smartt@qub.ac.uk>
S. J. Smartt, (QUB), K. W. Smith (QUB), M. E. Huber (IfA),
K. C. Chambers (IfA), 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)

Further to Chambers et al. GCN 20383, we report that we covered 632
square degrees on the first night (beginning 57758.3) . We estimate
this corresponds to a probability of containing the source of 33%.  We
have since reduced this area to the higher probability central region,
recovering 357 sq degrees and a containment probability of 26% (based
on the LALInference map, GCN 20385).

Images were taken in the Pan-STARRS i-band in a series of overlapping
45s exposures, with typically 4-8 images at each position.  These were
combined into stacks and subtracted from the Pan-STARRS1 3Pi reference
image (Chambers et al. arXiv:1612.05560, and available at
http://panstarrs.stsci.edu).

Using techniques discussed in Smartt et al. (2016, MNRAS, 462, 4094),
we have located and vetted transients with quality filters and a
machine learning algorithm on the images. We recover 6 iPTF objects
and 15 old transients known before the GW alert (given at the end for
completeness). ATLAS17aeu was recovered as discussed in Chambers et
al.  (GCN 20407)

In the following table, we give our 55 targets, sorted by magnitude.  The
lightcurve trend is given (LC trend), indicating the change in
magnitude between earliest and latest MJD of detection. To select
these targets we required a minimum of 2 detections over 2 separate
nights.

Our area is completely within the SDSS DR12 footprint, and we give the
redshifts (p for photometric and s for spectroscopic) of the host
galaxies.  Objects with no obvious host are labelled "hostless".  Some
targets are coincident with faint sources in SDSS for which
star/galaxy separation and photo-z estimates are not reliable and we
note these.  We have removed obvious AGN and candidate AGN (low level
variability associated with galaxy cores), as well as stellar
variables.

In the comments we note iPTF coincidences (Singer et al. GCN 20401;
Kasliwal et al. GCN 20364). A small number of candidates have a low
real-bogus (RB) machine learning factor and should be treated with
caution. All have been scanned by human reviewers. 

The photometric redshifts from SDSS should not be used as a robust
filtering for distance (see discussion in Smartt et al. 2016), but we
provide them as a guide.

We are targeting the objects with changing lightcurves with
Gemini+GMOS.

Name 	RA	                 DEC          LC trend	  Earliest mjd	mag	         Latest mjd  z       Comment
PS17df	08:50:02.42	+46:39:48.8  fading 00.09 57758.43699	18.39	57759.4911  0.038 s iPTF17bo		
PS17fg	08:48:46.25	+44:00:24.6  fading 00.15 57758.42737	18.89	57761.4882  0.060 s iPTF17bq		
PS17fr	08:11:52.10	+25:25:21.4  rising 00.57 57758.43263	19.19	57761.4619  0.199 p iPTF17cf	
PS17fe	09:00:21.22	+63:50:49.8  fading 00.09 57758.39189	19.60	57759.4726  0.245 p	
PS17du	09:14:30.59	+54:28:34.4  fading 00.04 57758.42705	19.75	57759.4660  0.045 s 0.6" from core		
PS17dp	09:00:51.09	+45:26:44.3  rising 00.06 57758.39978	19.97	57759.5043  0.051 s 		
PS17gl	08:34:50.85	+61:13:02.2  rising 00.07 57758.39093	20.04	57759.4635  0.038 s 	
PS17ft	08:16:52.72	+26:27:25.3  fading 00.05 57758.44356	20.05	57761.4790  0.042 s 	
PS17fs	08:14:47.53	+27:50:12.2  fading 00.11 57758.45845	20.09	57761.4891  0.118 p iPTF17ch	
PS17bz	08:04:49.22	+29:19:48.8  fading 00.08 57758.40250	20.23	57761.4809  0.047 s 	
PS17fb	08:49:18.13	+44:38:31.1  rising 00.01 57758.41320	20.30	57759.4831  0.151 p	
PS17fh	07:55:14.13	+26:25:11.5  fading 00.14 57758.39608	20.32	57761.4492  0.119 p	
PS17fw	08:19:05.64	+23:20:42.8  fading 00.04 57758.40905	20.35	57761.4478  0.034 p	
PS17gb	08:21:17.00	+51:10:17.1  rising 00.13 57758.38839	20.36	57759.4635  0.197 p 	
PS17fa	08:47:22.51	+51:08:17.4  fading 00.02 57758.44371	20.41	57759.4865  0.497 p 	
PS17en	08:40:22.10	+38:43:25.0  fading 00.07 57758.44053	20.41	57761.4923  0.673 p iPTF17fa
PS17dy	08:13:00.78	+41:18:26.9  rising 00.00 57758.42812	20.43	57761.4760  0.282 p iPTF17fb	
PS17er	08:41:57.26	+40:55:07.7  rising 00.36 57758.45114	20.44	57761.4854  0.296 p 	
PS17fj	07:59:30.67	+28:27:03.8  fading 00.37 57758.41011	20.46	57761.4771  hostless 		
PS17fl	08:02:09.73	+28:49:44.7  rising 00.32 57758.42406	20.47	57761.4876  0.080 p	
PS17dw	07:49:25.36	+20:28:00.6  fading 00.05 57758.38695	20.48	57759.4846  0.171 p	
PS17fv	08:18:15.52	+43:45:03.4  fading 00.06 57758.45210	20.56	57761.5017  0.188 s
PS17gf	08:24:43.98	+35:29:45.8  rising 00.14 57758.46042	20.62	57761.4786  0.362 p 	
PS17gr	08:20:14.14	+27:13:44.2  fading 00.20 57759.47191	20.64	57761.4792  hostless 	
PS17gk	08:33:00.93	+38:51:04.7  fading 00.18 57758.43419	20.68	57761.4721  0.163 p	
PS17fy	08:19:47.91	+42:39:45.9  fading 00.09 57758.41450	20.73	57761.4678  0.166 p 	
PS17gv	08:54:41.22	+57:10:45.9  rising 00.08 57758.46079	20.82	57759.5027  0.076 p	
PS17gm	08:35:15.00	+48:27:06.2  fading 00.04 57758.44909	20.83	57759.4940  0.159 p 	
PS17fx	08:19:36.86	+48:06:38.9  fading 00.04 57758.42693	20.84	57759.4803  hostless		
PS17dk	08:55:48.76	+46:55:04.8  rising 00.10 57758.42465	20.85	57759.4746  0.567 p 	
PS17fp	08:06:52.00	+34:18:04.4  fading 00.22 57758.43602	20.85	57761.4726  0.193 p 	
PS17fm	08:02:26.56	+26:20:07.5  fading 00.05 57758.42467	20.85	57761.4661  hostless low RB factor		
PS17dj	08:54:13.87	+48:19:42.7  rising  00.05 57758.44299	20.86	57759.4844  0.382 p 		
PS17ea	08:30:11.01	+32:57:35.8  rising  00.32 57758.43602	20.88	57761.5046  0.110 p 	
PS17fn	08:05:51.40	+28:42:51.9  rising  00.59 57758.44882	20.88	57761.4973  0.072 p 	
PS17ga	08:20:47.13	+30:24:47.9  fading 00.03 57758.45271	20.90	57761.4895  r=22.35, faint source	
PS17fo	08:06:49.10	+28:16:05.9  rising  00.27 57758.44882	20.92	57761.4804  0.179 p 	
PS17gg	08:30:06.42	+48:28:34.4  fading 00.17 57758.43638	20.93	57759.4841  0.144 p  low RB factor	
PS17cj	08:10:23.04	+23:59:52.6  fading 00.10 57758.39319	20.94	57761.4614  r=22.9, faint source		
PS17dh	08:50:43.44	+56:42:44.0  rising  00.06 57758.43403	20.95	57759.4998  hostless  		
PS17fu	08:17:35.59	+47:05:06.3  rising  00.23 57758.41830	20.95	57761.4746  0.040 s		
PS17ei	08:37:00.85	+38:42:47.2  fading 00.01 57758.44228	20.98	57761.4775  hostless 		
PS17fz	08:19:57.24	+45:12:59.8  fading 00.17 57758.44267	21.14	57761.4625  0.175 p 	
PS17gj	08:32:56.15	+41:12:22.3  rising  00.08 57758.44494	21.17	57761.4882  0.276 p 		
PS17ec	08:35:47.59	+46:25:09.4  rising  00.11 57758.46003	21.24	57759.4855  0.403 p 	
PS17dx	08:05:30.92	+36:26:24.8  fading 00.08 57758.40284	21.33	57761.4500  hostless		
PS17dz	08:24:48.80	+30:53:37.3  fading 00.10 57759.48293	21.35	57761.4982  0.308 p 	
PS17el	08:39:41.07	+39:24:30.2  fading 00.03 57758.45160	21.37	57761.4788  hostless	
PS17gt	08:11:47.50	+37:44:39.4  rising  00.12 57759.47465	21.42	57761.4739  0.348 s		
PS17cw	08:38:37.02	+42:57:05.4  fading 00.12 57758.44623	21.46	57761.4923  0.35  p		
PS17gw	08:48:29.00	+43:24:48.4  rising  00.05 57759.47696	21.54	57761.4915  hostless 
PS17gd	08:23:08.94	+43:55:57.1  rising  00.06 57758.44611	21.56	57761.4711  r=22.4, faint source		
PS17b	08:23:44.47	+36:53:39.2  rising  00.15 57759.49179	21.62       57761.4837  0.224 p 
PS17gs	08:11:41.68	+38:28:22.4  fading 00.06 57759.47749	21.63	57761.4760  r=22.45, faint source 		
PS17gu	08:11:48.78	+37:18:50.3  fading 00.19 57759.46588	21.99	57761.4715  r=22,faint source		


This object was only detected on one night (we have no coverage of the
specific area afterwards), but has a high RB factor and is coincident
with a starforming galaxy. Hence it appears real, but we caution that
we do not have multiple night detections.

PS17co	08:13:46.29	+18:59:02.4  rising 00.02 57758.40522	18.30	57758.4070  0.124 s 	

The following transients were all recovered in our imaging, but were
discovered and reported well before G268556 was discovered.

AT2017M      08:23:09.79	+25:53:22.9 aka MLS150212-082310+255323	
AT2017N      08:25:42.74	+39:19:00.6		
PS1-14amh    07:55:40.63	+26:46:18.0	
SN2016hrv    08:33:21.92	+52:31:50.4	
ASASSN-16el  08:56:39.07	+52:06:08.0	
AT2016iyx    08:43:24.73	+37:32:45.8
AT2016jax    08:32:53.76	+42:08:01.6
SN2016gil    08:10:13.72	+33:57:25.6 
SN2016ins    08:07:27.35	+25:07:47.3
AT2016jau    08:00:40.94	+28:19:31.8
SN2016hqh    07:57:05.78	+23:08:55.2
AT2016jci    07:56:05.83	+28:22:35.3	
AT2016jay    09:21:43.35	+61:31:59.6	
AT2016hys    08:14:42.11	+38:24:08.5
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