TITLE:   GCN CIRCULAR
NUMBER:  20776
SUBJECT: LIGO/Virgo G275697: REM optical/NIR observations
DATE:    17/02/28 22:10:50 GMT
FROM:    Andrea Melandri at INAF-OAB  <andy.melandri@gmail.com>

A. Melandri, P. D'Avanzo (INAF-OAB), G. Greco (Urbino University/INFN Firenze), D. Fugazza, S. Covino, (INAF-OAB), E. Palazzi (INAF-IASF Bo), M. Branchesi (Urbino University/INFN Firenze), L. Amati (INAF-IASF Bo), L. A. Antonelli, (INAF-OAR), S. Ascenzi (INAF-OAR), M.T. Botticella (INAF-OAC),  S. Campana (INAF-OAB), E. Cappellaro (INAF-OAPD), V. D'Elia (INAF-ASDC), F. Getman (INAF-OAC), A. Grado (INAF-OAC), L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), L. Nicastro (INAF-IASF Bo), E. Pian (SNS-Pisa), S. Piranomonte (INAF-OAR), L. Pulone (INAF-OAR), A. Rossi (INAF-IASF Bo), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR), L . Tomasella (INAF-OAPD), S. Yang (INAF-OAPD), E. Brocato (INAF-OAR) on behalf of GRavitational Wave Inaf TeAm (GRAWITA) report:

We carried out optical/NIR follow-up observations of the LIGO/Virgo GW trigger G275697 (LVC GCN Circ. 20763) with the 60-cm robotic telescope REM located at the La Silla Observatory (Chile). The observations were carried out on 2017 Feb 28 from 00:12:54 UT to 04:59:04 UT (from 5.25 to 10.04 hours after T0, LVC GCN Circ. 20763), simultaneously in the g, r, i, z and H bands. 

We observed the twenty brightest (according to the B magnitude reported in the GLADE catalogue) galaxies within the bayestar probability sky map visible from La Silla. The galaxies with a catalogued distance in the range 80-280 Mpc (evaluated on the basis of directional distance information, Singer et al. 2016, ApJL 829, 15) and brighter than absolute B_Mag ~ -21.3 were selected within the 30% containment  probability contour of the sky map using the GWsky script (https://github.com/ggreco77/GWsky).


RA(J2000)  Dec(J2000) Dist(Mpc) Mag(B)
-------------------------------------------------------
174.160   -38.3830    275.633  -22.09
163.889   -28.5261    112.893  -22.04
171.471   -35.3945    136.773  -21.97
171.850   -35.0727    153.462  -21.90
164.899   -29.5633    86.5000  -21.87
164.007   -28.3702    257.040  -21.84
171.087   -35.0165    240.991  -21.65
164.058   -28.9641    277.971  -21.64
175.374   -38.4629    246.604  -21.56
168.117   -32.1972    243.220  -21.49
170.986   -34.8010    242.103  -21.47
175.459   -37.9629    259.418  -21.46
172.862   -37.4394    269.153  -21.43
174.692   -37.7118    133.660  -21.41
168.150   -33.3339    140.605  -21.40
160.274   -24.4960    230.144  -21.40
165.627   -29.8585    248.886  -21.34
164.473   -28.3671    215.774  -21.31
171.862   -34.9971    276.694  -21.30
173.608   -36.8816    236.592  -21.29


A preliminary analysis reveals no obvious optical/NIR candidate counterpart in the above galaxies down to the following magnitudes: r > 19.3, H > 16.5 (AB, 3sigma upper limit, calibrated against the APASS and 2MASS catalogues, respectively).
 
Further analysis is in progress.