GCN Circular 18561

L. Tomasella, E. Cappellaro, (INAF-OAPd), E. Brocato (INAF-OAR), M. Branchesi (Urbino University/INFN Firenze),   L. A. Antonelli, (INAF-OAR), P. Astone (INFN-Roma), S. Campana (INAF-OAB), S. Covino (INAF-OAB), P. D'Avanzo,  V. D'Elia (INAF-ASDC), F. Getman (INAF-OAC), G. Giuffrida (INAF-ASDC), A. Grado (INAF-OAC), G.Greco (Urbino University/INFN Firenze), L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), S. Marinoni (INAF-ASDC), P. Marrese (INAF-ASDC), A. Melandri (INAF-OAB), L. Nicastro (INAF-IASF Bo), E. Palazzi (INAF-IAFS Bo), E. Pian (SNS-Pisa), S. Piranomonte, L. Pulone (INAF-OAR), F. Ricci (Sapienza University), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR) on behalf of the INAF Gravitational Astronomy group report: 


We report on the results of the observations of three optical transients from the list of Singer et al. (LIGO/Virgo Circular #18497), located in the skymap of the advanced LIGO and Virgo trigger G194575 (Singer et al., LIGO/Virgo Circular #18442).
Observation were obtained with the Asiago 1.82 m Copernico Telescope + AFOSC on 2015 Nov 4, under excellent sky conditions.

1- the spectrum of iPTF15dld (range 340-820 nm; resolution 1.4 nm) shows narrow emission lines of the H Balmer series, [OIII] doubled and SiII that are typical of Seyfert 2 at redshift z=0.046.  Preliminary photometry gives g=19.52(0.04), r=19.35(0.03), i=19.23(0.04).

2- the spectrum of  iPTF15dkv (same configuration as before) show  narrow Halpha/NII emissions consistent with that of a giant HII region at  redshift z=0.081 that indicates heavy contamination from the host galaxy.

3- photometry iPTF15dmq indicates a magnitude r~21.5. This is consistent with the magnitude reported by SDSS for SDDSJ233530.88+062710.7that is  r=21.63. Therefore, if  transient was present it already declined below our detection limit.