{
  "bibcode": "2017GCN.21591....1M",
  "body": "D. Malesani (DARK/NBI), E. Pian (INAF-IASF Bo), J. Hjorth (DARK/NBI), D. \nJ. Watson (DARK/NBI), L. Amati (INAF-IASF Bo), L. A. Antonelli, \n(INAF-OAR), S. Ascenzi (INAF-OAR), S. Benetti (INAF-OAPD), M.T. \nBotticella (INAF-OAC), M. Branchesi (GSSI), S. Campana (INAF-OAB), E. \nCappellaro (INAF-OAPD), S. Covino (INAF-OAB), P. D'Avanzo (INAF-OAB), V. \nD'Elia (INAF-ASDC), D. Fugazza (INAF-OAB), F. Getman (INAF-OAC), A. \nGrado (INAF-OAC), G. Greco (Urbino University/INFN Firenze), L. Limatola \n(INAF-OAC), M. Lisi (INAF-OAR), A. Melandri (INAF-OAB), L. Nicastro \n(INAF-IASF Bo), E. Palazzi (INAF-IAFS Bo), S. Piranomonte (INAF-OAR), L. \nPulone (INAF-OAR), A. Rossi (INAF-IASF Bo), P. Schipani (INAF-OAC), G. \nStratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. \nTesta (INAF-OAR), L. Tomasella (INAF-OAPD), S. Yang (INAF-OAPD), E. \nBrocato (INAF-OAR) on behalf of GRavitational Wave Inaf TeAm report:\n\n\nWe observed object SSS17a (Coulter et al., GCN 21529; Allam et al., GCN \n21530; Yang et al., GCN 21531) possibly associated with the LIGO/Virgo \nevent G298048 (GCN 21509), using the Nordic Optical Telescope located in \nLa Palma (Canary Islands, Spain).\n\nObservations were carried out around Aug 18.85 UT (1.32 days after the \nGW event), and consisted of 9 min exposure in each of the J and K \nfilters. Conditions were difficult due to the large airmass (4.0 to 5.5) \nand the still bright twilight sky, which led to an unusually elongated \nPSF due to imperfect focusing.\n\nSSS17a is well visible in the J image and faintly detected in K. Based \non the 2MASS catalog, we provide preliminary magnitudes J = 16.23 +- \n0.11 and K = 15.88 +- 0.25 (both Vega). We note that an extra error may \narise from the non-circular PSF and the uneven background around the \nnearby NGC 4993.\n\nOur fluxes are earlier and fainter than the GROND measurements (Wiseman \net al., GCN 21584), confirming the brightening of SSS17a at NIR \nwavelengths and the overall cooling trend noted by several authors \n(e.g., Cenko et al., GCN 21572; Lyman et al., GCN 21582; Wiseman et al., \nGCN 21584).\n\nWe acknowledge excellent support of the NOT visiting observer, Auni \nSomero, in carrying out this difficult observation.",
  "circularId": 21591,
  "createdOn": 1503144005000,
  "email": "malesani@dark-cosmology.dk",
  "subject": "LIGO/Virgo G298048: NOT near-infrared observations of SSS17a",
  "submitter": "Daniele Malesani at DARK/NBI  <malesani@dark-cosmology.dk>",
  "eventId": "LIGO/Virgo G298048"
}