{
  "bibcode": "2017GCN.21914....1A",
  "body": "Giambattista Aresu, Matteo Bachetti, Franco Buffa, Marta Burgay, Marco \nButtu, Teresa Caria, Ettore Carretti, Paola Castangia, Giuseppe Carboni, \nSilvia Casu, Raimondo Concu, Alessandro Corongiu, Gianluigi Deiana, \nElise Egron, Antonietta Fara, Francesco Gaudiomonte, Vincenzo Gusai, \nAdelaide Ladu, Sara Loru, Silvia Leurini, Lino Marongiu, Andrea Melis, \nPino Melis, Carlo Migoni, Sabrina Milia, Alessandro Navarrini, Andrea \nOrlati, Pierluigi Ortu, Stefano Palmas, Alberto Pellizzoni, Delphine \nPerrodin, Maura Pilia, Tonino Pisanu, Sergio Poppi, Andrea Possenti, \nAndrea Saba, Giampaolo Serra, Mauro Serrau, Gabriele Surcis, Alessio \nTrois, Valentina Vacca, Gian Paolo Vargiu - all from INAF Osservatorio \nAstronomico di Cagliari\nViviana Casasola - INAF Osservatorio Astrofisico di Arcetri\nGiancarlo Ghirlanda - INAF Osservatorio Astronomico di Brera\nSimona Righini, Matteo Stagni - INAF Istituto di Radioastronomia di Bologna\non behalf of GRAvitational Wave Inaf TeAm (GRAWITA) report:.\n\nFollowing the VLA detection of a radio source (Mooley et al., LVC GCN \n21814; Corsi et al., LVC GCN 21815) coincident with the optical \ntransient SSS17a/DLT17ck (Coulter et al. LVC GCN 21529; Allam et al., \nLVC GCN 21530; Yang et al., LVC GCN 21531), the possible counterpart of \nG298048 (LVC, LVC GCN 21505) in NGC 4993, we carried out observations of \nthe field with the Sardinia Radio Telescope at 7.2 GHz (central \nfrequency, with a bandwidth of 680 MHz). Observations were conducted on \nthe days 2017-09-07, 2017-09-08, 2017-09-09, and 2017-09-19, for a total \nof approximately 18 hours of on-the-fly mapping over the entire \nregion and about 8 minutes of on-source time. The target was observed at \nlow elevations (<27 degrees) and the weather conditions were suboptimal \nfor a large fraction of the observing time.\n\nData were taken to image a field of 0.3x0.3 deg^2 centred on the position\nof the source that was reported to be detected with the VLA on 2017-09-03.\nCalibration and analysis were conducted following two different\napproaches:\n\n- according to the procedures described in Egron et al. (2017,MNRAS, 470, 1329), we did\nnot detect any source and find an upper limit for a steady source at the\nposition of the target of 1.5 mJy (1 sigma) and a global rms of the image\nof 0.9 mJy/beam (1 sigma);\n\n- by using the map-making software described in Carretti et al. (2010, MNRAS, 405, 1670), \n we did not detect any source at that position, at an upper limit of\n0.5 mJy rms (1 sigma) as computed for a steady source.\n\nAccording to the condition of each single observation, we find an upper\nlimit ranging between at most 1 and 3 mJy for each observing session. At\npresent a refinement of the analysis is ongoing and observations at\nsubsequent epochs and at higher frequencies are planned.\n\n-- \nEnzo Brocato\nINAF - Osservatorio Astronomico di Roma\nVia di Frascati 33,  \nI-00040 Monteporzio Catone, Italy\nPhone:  +39 0694286438 Fax: +39 06 9447243\nskype: enzo.brocato\nURL: SpoT Group Homepage: www.oa-teramo.inaf.it/SPoT",
  "circularId": 21914,
  "createdOn": 1506107204000,
  "email": "enzo.brocato@oa-roma.inaf.it",
  "subject": "LIGO/Virgo G298048: SRT observations of SSS17a in NGC 4993",
  "submitter": "Enzo Brocato at INAF-OA Roma  <enzo.brocato@oa-roma.inaf.it>",
  "eventId": "LIGO/Virgo G298048"
}