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GCN Circular 21543

Subject
LIGO/Virgo G298048: Galaxy-Targeted Optical Followup With Las Cumbres Observatory
Date
2017-08-18T04:54:23Z (7 years ago)
From
Iair Arcavi at LCOGT <iarcavi@lcogt.net>
I. Arcavi, D. A. Howell, C. McCully, G. Hosseinzadeh, S. Vasylyev (UCSB/Las
Cumbres Obs), M. Zalzman, D. Poznanski (TAU), L.P. Singer (NASA/GSFC), S.
Valenti (UC Davis), T. Piran (HUJI), D. Kasen, J. Barnes (UC Berkeley) and
W-f. Fong (UA) report on optical followup observations of the LIGO-Virgo
G298048 trigger using the Las Cumbres Observatory (LCO) worldwide telescope
network.

We target galaxies from the GLADE catalog and prioritize them by their
position in the LIGO/Virgo localization region, their mass (estimated from
their absolute B-band magnitude), and inversely by their distance.

Between 2017-08-17 17:04 and 18:42 UT we observed the following galaxies
using the two LCO 1-meter telescopes at the South African Astronomical
Observatory in the following filters with a 300s exposure per filter:

GLADE ID  RA          Dec         Dist [Mpc]  Galaxy B-mag  Filters Observed
2037      199.749649  -47.908653  40.926      11.8          g,r,i
564852    214.019012  -48.127373  54.444      11.69         g,r
621160    194.532623  -46.264214  29.3765     10.93         g,r,i
732352    204.16272   -33.965916  49.125      11.24         g,r,i
737707    213.977814  -48.114883  59.917      12.06         g,r,i
815140    193.363815  -48.749153  49.556      11.98         g,r,i
1306036   198.491943  -49.478775  45.278      11.47         g,r,i
1850978   194.305     -46.37728   46.9894     12.12         g,r,i

All r-band images were visually inspected for new sources compared to
archival DSS images. No obvious ones were found.
The above galaxies were chosen to also lie close to the FERMI localization
region. Following the revised LIGO/Virgo localization from Singer et al.
(LVC GCN 21513), we observed the following galaxies using the two LCO
1-meter telescopes at the Cerro Tololo Inter-American Observatory in Chile
in the following filters with a 300s exposure per filter:

GLADE ID  RA          Dec         Dist [Mpc]  Galaxy B-mag  Filters Observed
341075    197.018005  -23.796844  34.097      12.87         w
564852    214.019012  -48.127373  54.444      11.69         g,r,i
602087    196.774902  -23.67704   33.42       13.18         w
645472    196.907242  -23.57892   41.75       14.21         w
667146*   197.448776  -23.383831  33.806      12.87         w
770765    196.89064   -24.008606  43.944      12.68         w
773496    196.735474  -23.91707   33.653      13.07         w
777014    196.270554  -22.383947  30.479      13.98         w
1366038   197.691406  -23.865728  33.42       12.64         w
1478047   197.466     -24.23937   38.548      13.6          w
1486718   196.937     -22.85784   26.792      12.88         w
1486724   197.329     -24.38456   33.42       13.85         w
1850989   197.465     -24.24      42.2669     12.78         w

* GLADE 667146 is also NGC 4993 where we detect SSS17a / DLT17ck, the
possible optical counterpart reported by Coulter et al. (LVC GCN 21529),
Allam et al. (LVC GCN 21530), Yang et al. (LVC GCN 21531) and Melandri et
al. (LVC GCN 21532). See Arcavi et al. (LCV GCN 21538).

The w-band is wide filter covering the g+r+i-bands.

Analysis of all images obtained is ongoing.

The following GLADE galaxies have been submitted for observations starting
at 2017-08-18 08:32 UT using the two LCO 1-meter telescopes at the Siding
Spring Observatory in Australia with 300s w-band exposures:

GLADE ID  RA          Dec         Dist [Mpc]  Galaxy B-mag
7         192.519547  -14.73349   53.528      13.21
626       193.998657  -19.26899   41.944      13.27
3644      192.248566  -14.399235  49.583      12.55
420937    198.880432  -23.982388  35.3367     12.31675
557076    194.366257  -19.691298  44.75       12.68
635635    196.600052  -24.164007  33.431      13.78
645300    196.580811  -22.98033   39.361      15.71
646603    193.219254  -15.413292  56.139      13.09
684330    193.363464  -17.005495  54.417      12.76
708169    196.666443  -22.455793  42.222      15.15
795473    199.096786  -26.561554  44.319      13.95
977319    194.252274  -17.320408  54.444      13.97
1486596   193.107     -15.51722   50.431      14.25
1486614   193.706     -16.0522    46.375      14.95
1486713   196.719     -22.84175   33.958      14.67

A spectrum of SSS17a / DLT17ck has also been submitted to start at
2017-08-18 08:32 UT using the LCO 2-meter telescope at Siding Spring, as
well as g,r,i 300s imaging with one of the LCO 1-meter telescopes there.
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