{
  "bibcode": "2017GCN.21617....1C",
  "body": "K. C. Chambers (IfA), M. E. Huber (IfA),K. W. Smith (QUB),\nS. J. Smartt, (QUB), D. R. Young, M. Coughlin (Harvard), T.-W. Chen\n(MPE), J. Bulger, L. Denneau, H. Flewelling, A. Heinze, E. Kankare\n(QUB), T. Lowe, E. A. Magnier (IfA), A. Rest (STScI), B. Stalder\n(IfA), A. S. B. Schultz, C. W. Stubbs (Harvard) J. Tonry, C. Waters,\nR. J. Wainscoat, H. Weiland, M. Willman (IfA), D. E. Wright (QUB)\n\nWe report continued Pan-STARRS imaging of the transient SSS17a/DLT17ck\nin NGC4339 in filters i, z and y (see Chambers et al. GCN 21553 for\nmore details of filters, photometry, methods etc).\n\nOur reference stack and calibrations provide rapid reliable photometry\nwith the host removed and we will continue to post updates while it is\nvisible from Hawaii.  A series of short exposures to avoid sky\nsaturation in twilight in each of i, z, and y provide average nightly\nmagnitudes (AB) of \n\nMJD             i       err \n57983.23\t17.24\t0.06\n57984.24\t17.91\t0.05\n57985.24\t18.47\t0.08\n\nMJD             z       err \n57983.23\t17.26\t0.06\n57984.24\t17.80\t0.05\n57985.24\t18.31\t0.06\n\nMJD             y       err \n57983.23\t17.38\t0.10\n57984.24\t17.59\t0.07\n57985.24\t18.08\t0.07\n\nThe decline rate 0.6 mag per day is still consistent with some of the\nkilonova models (Kasen et al. 2015, Barnes & Kasen 2013, Tanaka et\nal. 2014). \n\nThe very rapid decline (and weak high energy emission) may explain why\ntransients of these types have not been recovered and recognised\nindependently in ground-based wide-field surveys to date, before the\nLIGO-Virgo era.\n\nFor example at d=100Mpc, this transient would fade from around i=19.2\nto 21.7 in four days in i-band (and would be fainter and faster in g,\nr and broad composite filters).  Making it difficult to recover and\nrecognise over multiple nights in \"~10^3 deg per night\" surveys such\nas PTF, Pan-STARRS, La Silla Quest, Skymapper, CRTS.  And well beyond\nthe wider, shallower, ASASSN and ATLAS sensitivities.",
  "circularId": 21617,
  "createdOn": 1503237590000,
  "email": "s.smartt@qub.ac.uk",
  "subject": "LIGO/Virgo G298048: Pan-STARRS izy photometry monitoring of SSS17a/DLT17ck",
  "submitter": "S. J. Smartt at Queens U Belfast  <s.smartt@qub.ac.uk>",
  "eventId": "LIGO/Virgo G298048"
}