GCN Circular 21591
Subject
LIGO/Virgo G298048: NOT near-infrared observations of SSS17a
Date
2017-08-19T12:00:05Z (7 years ago)
From
Daniele Malesani at DARK/NBI <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), E. Pian (INAF-IASF Bo), J. Hjorth (DARK/NBI), D.
J. Watson (DARK/NBI), L. Amati (INAF-IASF Bo), L. A. Antonelli,
(INAF-OAR), S. Ascenzi (INAF-OAR), S. Benetti (INAF-OAPD), M.T.
Botticella (INAF-OAC), M. Branchesi (GSSI), S. Campana (INAF-OAB), E.
Cappellaro (INAF-OAPD), S. Covino (INAF-OAB), P. D'Avanzo (INAF-OAB), V.
D'Elia (INAF-ASDC), D. Fugazza (INAF-OAB), F. Getman (INAF-OAC), A.
Grado (INAF-OAC), G. Greco (Urbino University/INFN Firenze), L. Limatola
(INAF-OAC), M. Lisi (INAF-OAR), A. Melandri (INAF-OAB), L. Nicastro
(INAF-IASF Bo), E. Palazzi (INAF-IAFS Bo), S. Piranomonte (INAF-OAR), L.
Pulone (INAF-OAR), A. Rossi (INAF-IASF Bo), P. Schipani (INAF-OAC), 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 report:
We observed object SSS17a (Coulter et al., GCN 21529; Allam et al., GCN
21530; Yang et al., GCN 21531) possibly associated with the LIGO/Virgo
event G298048 (GCN 21509), using the Nordic Optical Telescope located in
La Palma (Canary Islands, Spain).
Observations were carried out around Aug 18.85 UT (1.32 days after the
GW event), and consisted of 9 min exposure in each of the J and K
filters. Conditions were difficult due to the large airmass (4.0 to 5.5)
and the still bright twilight sky, which led to an unusually elongated
PSF due to imperfect focusing.
SSS17a is well visible in the J image and faintly detected in K. Based
on the 2MASS catalog, we provide preliminary magnitudes J = 16.23 +-
0.11 and K = 15.88 +- 0.25 (both Vega). We note that an extra error may
arise from the non-circular PSF and the uneven background around the
nearby NGC 4993.
Our fluxes are earlier and fainter than the GROND measurements (Wiseman
et al., GCN 21584), confirming the brightening of SSS17a at NIR
wavelengths and the overall cooling trend noted by several authors
(e.g., Cenko et al., GCN 21572; Lyman et al., GCN 21582; Wiseman et al.,
GCN 21584).
We acknowledge excellent support of the NOT visiting observer, Auni
Somero, in carrying out this difficult observation.