TITLE:   GCN CIRCULAR
NUMBER:  21653
SUBJECT: LIGO/Virgo G298048: ESO/VLT optical observations
DATE:    17/08/23 07:52:38 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo, A. Melandri, S. Covino (INAF-OAB), M. G. Bernardini (LUPM/INAF-OAB), M. Branchesi (GSSI), 
S. Campana (INAF-OAB), V. D'Elia (INAF-ASDC), M. Della Valle (INAF-OAC), Y. Z. Fan (PMO, Nanjing),
G. Ghirlanda, G. Ghisellini (INAF-OAB), L. Nava (INAF-OATs/INAF-OAB), E. Palazzi (INAF-IAFS Bo), 
A. Pescalli (Univ. Insubria/INAF-OAB), T. Piran (HUJI), S. Piranomonte (INAF-OAR), 
O. S. Salafia (Univ. Bicocca/INAF-OAB), R. Salvaterra (INAF-IASF Mi), G. Stratta (Urbino University/INFN Firenze), 
G. Tagliaferri (INAF-OAB), E. Troja (NASA-GSFC), S. D. Vergani (Obs. Paris/CNRS/INAF-OAB), Z. P. Zhin (PMO, Nanjing), 

and

G. Greco (Urbino University/INFN Firenze), D. Fugazza (INAF-OAB), L. Amati (INAF-IASF Bo), L. A. Antonelli, (INAF-OAR), 
S. Ascenzi (INAF-OAR), S. Benetti (INAF-OAPD), M.T. Botticella (INAF-OAC),  E. Cappellaro (INAF-OAPD),  
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), L. Pulone (INAF-OAR), A. Rossi (INAF-IASF Bo), V. Testa (INAF-OAR), L . Tomasella (INAF-OAPD), 
S. Yang (INAF-OAPD), E. Brocato (INAF-OAR) on behalf of GRavitational Wave Inaf TeAm report:


We observed the transient SSS17a in NGC 4993 reported by Coulter et al. (LVC GCN 21529) with the ESO/VLT UT1 
equipped with the FORS2 camera. Imaging observations were carried out on 2017 Aug 21 starting at 23:23:10 UT 
during twilight (about 4.5 days after the LIGO/Virgo event; LVC GCNs 21509) with the B, V, R, I and z filters. 
The source is detected in all bands, showing a red color. From preliminary photometry (likely contaminated by the host 
galaxy light) we measure the following AB magnitudes:

R = 19.4 +/- 0.2
z = 18.5 +/- 0.2 

calibrated against the USNOB1 and PAN-STARRS catalogues. 


We acknowledge excellent support from the from the ESO observing staff in Paranal, in particular Jesus M. Corral-Santana 
and Stephane Brillant.