{
  "bibcode": "2019GCN.24107....1W",
  "body": "H. Weiland (IfA, Univ. of Hawaii), K. W. Smith, D. R. Young, (Queen's \nUniversity Belfast), L. Denneau, H. Flewelling, A. Heinze, J. Tonry \n(IfA), S. Smartt,  O. McBrien, J. Gillanders,nS. Srivastav, D. O'Neil,  \nP. Clark, S. Sim (QUB), A. Rest (STScI),  B. Stalder (LSST), \nC. Stubbs (Harvard), E. Magnier, A. Schultz, , M. Huber, \nK. C. Chambers (IfA)\n\nWe report observations of the BAYESTAR skymap of the BBH event S190412m \n(The LIGO Scientific Collaboration and the Virgo Collaboration, GCN \n24098) with the ATLAS telescope system (Tonry et al. 2018, PASP, 13, \n164505). ATLAS is a twin 0.5m telescope system on \nHaleakala and Mauna Loa employing two filters cyan and orange. \nWhile carrying out the primary mission for Near Earth Objects, we\ncan adjust the schedule rapidly to point at LVC gravitational wave \nskymaps. \n\nSequences of 30 sec images were taken in the ATLAS o/c bands, and \nat each pointing position a sequence of quads (4 x 30 sec) was taken.\nThe images were processed with the ATLAS pipeline and reference images \nsubtracted from each one. Transient candidates were run through our \nstandard filtering procedures, combined with machine learning algorithms \n(e.g. Wright et al. 2015, MNRAS, 449, 451). Candidates were \nspatially cross-matched with known minor planets, and \nstar, galaxy, AGN and multi-wavelength catalogues (as described in \nSmartt et al. 2016, MNRAS, 462 4094, Stalder et al. 2017, ApJ, 850, \n149). \n\nWe covered 137 square degrees of the bayestar map 90% credible \nregion and covered a sky region totalling 91% of the event���s \nfull localisation likelihood. Data acquisition began at 58585.300570\nor 2019-04-12 07:12:49 (UTC), 41 mins after the PRELIMINARY notice \nand 102 mins after the GW merger event. All data acquisition finished\napproximately 4hrs later. \n\nWe found no new transients to magnitudes of o < 19.1 (the median of\nthe 5 sigma limits of the individual 30 sec images) between \n~40 to ~240 minutes after the BBH merger. \n\nThis work has made use of data from the Asteroid Terrestrial-impact \nLast Alert System (ATLAS) project. ATLAS is primarily funded to search \nfor near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, \nand 80NSSC18K1575; byproducts of the NEO search include images and \ncatalogs from the survey area. The ATLAS science products have been \nmade possible through the contributions of the University of Hawaii \nInstitute for Astronomy, the Queen's University Belfast, and the \nSpace Telescope Science Institute.",
  "circularId": 24107,
  "createdOn": 1555081023000,
  "email": "s.smartt@qub.ac.uk",
  "subject": "LIGO/Virgo S190408an: ATLAS observations of the S190412m skymap",
  "submitter": "Stephen Smartt at Queen's U/Belfast  <s.smartt@qub.ac.uk>",
  "eventId": "LIGO/Virgo S190408an"
}