{
  "bibcode": "2019GCN.24096....1S",
  "body": "K. W. Smith, D. R. Young, M. Huber, K. C. Chambers, S. J. Smartt,\nO. McBrien, J. Gillanders. S. Srivastav, D. O'Neil,  P. Clark, \nS. Sim (QUB), E. Magnier, A. Schultz, (IfA, Univ. Hawaii), \nL. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland,  \nA. Rest (STScI),  B. Stalder (LSST), C. Stubbs (Harvard)\n\nWe report observations of the BAYESTAR skymap of the BBH event S190804an \n(The LIGO Scientific Collaboration and the Virgo Collaboration, GCN \n24069) with the Pan-STARRS1 telescope (Chambers et al. 2016, \narXiv:1612.05560C). Images were taken in the PS1 w,z and y-bands \n(Tonry et al. 2012, ApJ 750, 99) in the standard NEO search sequence. \nAt each pointing position a sequence of quads (4 x 45 sec) was taken.\nThis observing sequence ensures exactly the same pointing position \nfor each of the quads. We estimate that the active \npixel area covered 72 square degrees and a summed probability of \n11% of the BAYESTAR skymap. We began taking data at 2019-04-09\n14:30 (UTC) 20hrs after the GW trigger.\n\nThe images were processed with the IPP (Magnier et al. 2016, \narXiv:1612.05240) and difference images were produced using \nthe Pan-STARRS1 Science Consortium 3Pi images as reference \nframes. Transient candidates were run through our standard \nfiltering procedures, combined with a machine learning algorithm \n(Wright et al. 2015, MNRAS, 449, 451) were applied and all candidates were\nspatially cross-matched with known minor planets, and major \nstar, galaxy, AGN and multi-wavelength catalogues (as described in \nSmartt et al. 2016, MNRAS, 462 4094). \n\nWe find 3 new transients. None of which appear to possess any \npeculiar feature that indicates any link to S190804an. \n\nbPC denotes the percentage probability contour within which \nthe transient is found according to the bayestar.fits map. \n\nObject RA         DEC        Disc Mag  filt MJD         z      bPC  Notes\n-------------------------------------------------------------------------\nPS19pn 339.15090  +33.16465  20.40 0.21  w  58582.6099  -      60%  (1)\nPS19pm 337.33525  +25.26419  19.87 0.14  w  58582.6061  ~0.195 80%  (2)\nPS19pl 335.17707  +31.17752  19.44 0.12  w  58582.6086  ~0.083 90%  (3)  \n\n(1) Orphan, no host object \n(2) Nuclear Transient coincident with SDSS J222920.46+251551.0; an r=18.31 \nmag galaxy found in the SDSS DR12 PhotoObjAll Table catalogue. It's located \n0.2\" from the galaxy core. A host photoZ=0.195 (��0.031) implies absolute\nmag of M = -20. There is some variability history at similar flux levels in \nPan-STARRS data.\n(3) Probably associated with SDSS J222042.60+311038.3; an r=17.26 mag\ngalaxy found in the SDSS DR12 PhotoObjAll Table catalogue. It's located\n0.69\" N, 1.35\" W from the galaxy centre. A host photoZ=0.083 (��0.020)\nimplies an absolute mag of M = -18.5",
  "circularId": 24096,
  "createdOn": 1554942640000,
  "email": "k.w.smith@qub.ac.uk",
  "subject": "LIGO/Virgo S190408an: Pan-STARRS observations and transients in the skymap",
  "submitter": "Ken Smith at Queen's University Belfast  <k.w.smith@qub.ac.uk>",
  "eventId": "LIGO/Virgo S190408an"
}