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GCN Circular 20699

Subject
LIGO/Virgo G274296: Pan-STARRS imaging and discovery of 70 transients
Date
2017-02-19T13:56:33Z (7 years ago)
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),
D. R. Young, S. J. Smartt, (QUB), M. Coughlin (Harvard), T.-W. Chen
(MPE), L. Denneau, H. Flewelling, A. Heinze, E. Kankare (QUB),
T. Lowe, 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, M. Willman (IfA), D. E. Wright (QUB)

We report that we covered 501 square degrees on the first night
following the release of the G274296 alert. We began taking data at
2017-02-18.29 UT (57802.29; 25hrs after the event detection).  We
estimate that this first night of data coverage corresponds to a
probability of containing the source of 44.7%, (based on the cWB map
skyprobcc_cWB.fits ; GCN 20689). Maps will be posted on GraceDB.

Images were taken in the Pan-STARRS i-band filter in a series of
overlapping 45s exposures, with typically 4-8 images at each position.
Difference images were produced by subtracting the Pan-STARRS1 3Pi
reference image from these separate 45s exposures (Chambers et
al. arXiv:1612.05560, and available at http://panstarrs.stsci.edu).
We reach i ~ 21 - 21.5 in the individual exposures. 

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 difference images.  

In the following table, we give our 70 targets, sorted by magnitude.
To select these targets we required a minimum of 2 detections in these
sets of images. There are 10 transients in galaxies with redshifts
(from SDSS DR12), and these are listed first. The rest of the
transients are not obviously associated with a galaxy with a redshift.
The closest transient is PS17bfl (i=21.06) 2.9" offset from 2MASX
J11504136+3715422 : z=0.035, mu=35.8, D=140 Mpc, M_i = -14.8.  With
this relatively faint  absolute magnitude, spectroscopic classification of
this transient in particular is recommended.

Variable sources which are likely AGN/QSOs or variable stars have, as
far as possible, been removed from this transient list.  We remove
likely AGN/QSOs either from catalogues, SDSS DR12 spectra, or nuclear
transients which are in galaxies with previous core variability seen
in Pan-STARRS general survey mode. Similarly variable stars or stellar
outbursts are removed through catalogue matching. The following list
is composed of SN-like transients, as far as we can tell from current
data.

We found 10 transients which are previously known transients or 
supernovae found in preceding weeks or months before G274296, and 
we list them here for reference. 

Name    RA          DEC         MJD-Disc                mag(i)      z
Transients with host spectroscopic redshifts :
PS17bda 09:30:36.08 +11:29:53.6 57802.32131  19.41   0.090
PS17bel 10:50:34.63 +30:25:30.7 57802.30825  20.09   0.116
PS17bew 11:13:30.66 +29:40:02.9 57802.38998  20.14   0.046
PS17bdt 10:17:28.88 +22:24:57.4 57802.30240  20.26   0.048
PS17bfg 11:45:39.79 +33:23:38.9 57802.41584  20.67   0.141
PS17bdr 10:11:35.41 +19:15:46.7 57802.30099  20.74   0.078
PS17bfy 12:06:57.57 +35:25:36.9 57802.40619  21.01   0.081
PS17bfl 11:50:41.38 +37:15:45.0 57802.40490  21.06   0.035
PS17bdz 10:27:42.90 +28:21:20.3 57802.30500  21.06   0.161
PS17bef 10:38:13.94 +25:49:24.6 57802.30435  21.19   0.078

Transients with no host spectroscopic redshifts :
PS17bgn 11:31:52.98 +29:59:45.1 57802.41391  18.33   bright nuclear transient 
PS17bfc 11:29:33.54 +34:12:07.1 57802.39565  19.42   
PS17beo 10:53:24.67 +28:51:27.1 57802.30825  19.51   
PS17bgt 11:58:09.80 +34:04:38.0 57802.40426  19.81   
PS17bek 10:47:41.90 +26:50:06.0 57802.30629  19.85   
PS17bcv 09:16:27.70 +03:35:25.1 57802.28975  19.90   
PS17bgf 10:59:22.27 +29:44:11.3 57802.41064  19.91   
PS17bed 10:31:52.14 +24:26:31.0 57802.35657  20.10   
PS17bep 10:57:33.56 +31:05:16.0 57802.42273  20.17   
PS17bdv 10:21:15.87 +23:38:53.3 57802.30370  20.23   
PS17bem 10:51:31.88 +26:29:10.4 57802.30760  20.29   
PS17bgm 11:28:24.06 +30:06:26.5 57802.39965  20.31   
PS17bgx 09:20:37.00 +12:53:17.8 57802.48646  20.37   
PS17bgz 10:29:39.67 +26:38:57.9 57802.43359  20.45   
PS17bdm 10:05:41.12 +22:31:24.9 57802.35248  20.47   
PS17bev 11:11:17.74 +31:28:53.4 57802.39824  20.57   
PS17bfh 11:46:47.23 +31:34:13.4 57802.40169  20.63   
PS17bcs 09:02:44.47 +02:12:41.1 57802.44885  20.65   
PS17bdn 10:05:43.77 +22:31:05.8 57802.29958  20.66   
PS17bff 11:42:16.34 +32:36:01.9 57802.40169  20.70   
PS17bgu 12:04:37.88 +32:07:42.4 57802.31211  20.74   
PS17bgp 11:42:27.80 +31:02:12.5 57802.40169  20.74   
PS17bfm 11:55:15.38 +35:50:48.6 57802.40490  20.80   
PS17beg 10:40:17.22 +27:47:37.2 57802.30629  20.82   
PS17bgr 11:47:04.86 +35:13:14.0 57802.40490  20.85   
PS17bgd 10:28:30.41 +22:30:23.2 57802.30370  20.90   
PS17beh 10:42:02.04 +29:51:18.1 57802.30564  20.97   
PS17bgs 11:55:32.52 +29:55:29.7 57802.40362  20.99   
PS17bgo 11:33:14.22 +30:53:06.1 57802.39965  21.02   
PS17bdx 10:22:58.46 +24:38:17.0 57802.35590  21.02   
PS17bgc 10:22:36.15 +21:12:37.9 57802.30163  21.03   
PS17bgw 12:09:21.73 +36:46:08.2 57802.40619  21.05   
PS17beb 10:31:19.80 +26:56:54.5 57802.33322  21.05   
PS17bcx 09:24:03.25 +08:04:33.8 57802.34338  21.05   
PS17bgi 11:12:46.03 +28:38:50.4 57802.41131  21.10   
PS17bfz 09:16:10.00 +08:37:10.4 57802.45144  21.12   
PS17bdu 10:20:34.54 +20:12:51.4 57802.30163  21.13   
PS17bgb 09:46:52.25 +10:39:51.1 57802.29491  21.13   
PS17bei 10:42:41.75 +25:35:06.8 57802.35990  21.15   
PS17bdw 10:22:57.59 +24:38:22.1 57802.38244  21.15   
PS17bdb 09:32:00.94 +15:00:40.2 57802.29362  21.16   
PS17bcu 09:15:24.05 +03:45:37.4 57802.34263  21.16   
PS17bee 10:34:00.57 +26:56:00.3 57802.35723  21.17   
PS17bfk 11:50:33.88 +35:33:45.1 57802.40490  21.19   
PS17bge 10:57:22.95 +30:22:03.4 57802.38805  21.19   
PS17bfo 11:57:44.78 +32:54:59.9 57802.39192  21.20   
PS17bgq 11:43:47.66 +32:44:07.0 57802.40169  21.21   
PS17bgg 11:03:12.23 +31:56:23.9 57802.33709  21.21   
PS17bgl 11:24:07.20 +36:13:14.2 57802.40233  21.36   
PS17bds 10:16:57.14 +24:34:18.8 57802.30240  21.40   
PS17bfb 11:24:05.27 +33:26:57.0 57802.40105  21.42   
PS17bgh 11:12:08.04 +30:21:11.1 57802.38998  21.45   
PS17bet 11:08:34.19 +30:03:46.3 57802.38934  21.46   
PS17bgy 09:32:17.63 +13:36:14.5 57802.48711  21.50   
PS17bgv 12:08:20.09 +38:45:20.8 57802.40554  21.53   
PS17bdl 10:04:29.91 +22:01:20.9 57802.32850  21.54   
PS17bgk 11:15:17.75 +30:53:09.5 57802.42537  21.57   
PS17bgj 11:15:16.28 +32:14:05.4 57802.39062  21.64   
PS17bga 09:16:19.41 +00:47:06.0 57802.44950  21.69   
PS17bfe 11:41:34.79 +30:39:15.2 57802.40169  21.73   


Already known objects : 
PS17bhc 09:47:26.75 +19:36:31.1 57789.49854  21.00   
PS17bhb 09:44:33.28 +15:15:42.4 57789.50327  21.61   
PS17bha 09:27:42.08 +12:00:14.1 57789.47490  20.78   
PS17beu 11:10:52.80 +28:16:27.8 57802.30954  19.18   AT2017nf
PS17bfw 12:01:07.05 +38:52:35.0 57802.40554  20.66   CSS160514-120107+385236
PS17abg 10:50:24.61 +23:59:21.5 57802.35990  21.24   AT2017qh
PS17bdp 10:06:29.10 +22:26:43.9 57802.32850  16.89   SN2016idl
PS17gn 10:01:11.46 +19:29:43.2 57802.29814  20.91   AT2016ieg
PS17bdj 10:00:18.25 +19:23:05.1 57802.29814  19.85   MLS160217-100018+192305
PS17m 09:34:55.90 +06:17:27.0 57802.29169  20.01   AT2017D
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