{
  "bibcode": "2019GCN.25445....1D",
  "body": "Dougal Dobie (University of Sydney/CSIRO), Adam Stewart (University of Sydney),\nZiteng Wang (University of Sydney), Tara Murphy (University of\nSydney),Emil Lenc (CSIRO),\nDavid Kaplan (UWM), Aidan Hotan (CSIRO), Kunal Mooley (NRAO, Caltech),\nGregg Hallinan (Caltech),\nDavid McConnell (CSIRO), Julie Banfield (CSIRO), Wasim Raja (CSIRO),\nMatthew Whiting (CSIRO),\nVanessa Moss (CSIRO), Igor Andreoni (Caltech) and the OzGrav, JAGWAR\nand GROWTH collaborations.\n\nWe report observations of the localisation region of S190814bv (LVC,\nGCN 25324) with the\nAustralian Square Kilometre Array Pathfinder (ASKAP) on 2019-08-16 at\na central frequency\nof 943 MHz with a bandwidth of 288 MHz.\n\nWe have observed a single 30 sq. deg. field centered on\n    RA = 00:50:37.5\n    Dec = -25:16:57.4\nwhich covers approximately 85% of the sky localisation from the\nLALInference skymap (GCN 25333),\nwith a median rms of 34 uJy.\n\nWe have searched for radio emission within 5 arcseconds of the\nlocation of the 124 optical transients\nreported on the Transient Name Server by the DECam-GROWTH and DESGW\nteams between 2019-08-16 and 2019-08-22\nas at 2019-08-22 03:00 UTC. We report coincident compact radio\nemission at the location of 14 of them:\n\n|       Name |         RA |       Dec | Int. Flux (uJy) | err. (uJy) | Notes |\n| AT 2019nqa | 00:52:39.1 | -25:00:15 |             258 |         30 |       |\n| AT 2019nqy | 00:56:23.2 | -24:41:11 |             393 |         29 |       |\n| AT 2019nqz | 00:46:46.5 | -24:20:12 |             870 |         30 |   (a) |\n| AT 2019nsr | 00:57:27.6 | -26:16:44 |             290 |         36 |   (c) |\n| AT 2019nto | 00:42:03.5 | -24:48:19 |             342 |         28 |   (c) |\n| AT 2019nuk | 00:54:57.9 | -26:08:03 |             233 |         28 |   (b) |\n| AT 2019nul | 00:55:16.4 | -26:56:35 |             204 |         28 |   (b) |\n| AT 2019nun | 00:56:48.7 | -24:54:31 |             377 |         29 | (b,c) |\n| AT 2019nuo | 00:56:03.9 | -23:18:15 |             388 |         36 |   (c) |\n| AT 2019nup | 00:55:04.3 | -26:46:12 |             446 |         33 |   (c) |\n| AT 2019nzj | 00:52:05.3 | -26:11:03 |             759 |         29 |       |\n| AT 2019nzn | 00:55:19.9 | -24:09:29 |             233 |         32 |   (c) |\n| AT 2019oay | 00:45:25.2 | -25:53:43 |             348 |         31 |       |\n| AT 2019ocs | 01:00:11.4 | -25:53:22 |             352 |         29 |       |\n\n(a) reported in GCN25391\n(b) reported in GCN25393\n(c) source possibly extended\n\n\nWe have also performed a preliminary search for transients using TraP\n(Swinbank et al. 2015) comparing this\nobservation to the Rapid ASKAP Continuum Survey (RACS, [1]) at a\ndetection threshold of 0.95 mJy, corresponding\nto 5 times the lowest rms of the RACS image. We find one candidate\ntransient located at\n    RA = 00:54:34.6 +/- 0.02 arcsec\n    Dec = -28:02:35.3 +/- 0.01 arcsec\nwhich we note is outside the 95% confidence region of S190814bv. We\nmeasure a flux density of 3.4 mJy in this\nobservation and a local rms noise of 0.25 mJy in the 888 MHz RACS\nimage observed on 2019-04-26. We measured an\nintegrated flux density of 0.74 mJy in the RACS image using TraP. We\nalso note that there is a radio source\ncoincident with this location in the image from the Very Large Array\nSky Survey (VLASS) observed on 2019-06-29\nwith a flux density of ~1.6 mJy at 3 GHz.\n\nWe conducted follow-up of this source with the Australia Telescope\nCompact Array (ATCA) on 2019-08-21 with two\n2048 MHz bands centered on 5.5 and 9 GHz. We measure preliminary flux\ndensities of 2.88 +/- 0.03 mJy and\n2.93 +/- 0.02 mJy at 5.5 and 9 GHz, with respective in-band spectral\nindices of +0.17 and -0.37.\n\nCombining the near-contemporaneous ATCA and ASKAP measurements we find\na flat spectral index. Based on these\nobservations this candidate is likely to be an unrelated AGN.\n\nThe ASKAP observation is publicly available on the CSIRO ASKAP Science\nData Archive [2] under Scheduling Block ID 9602.\n\nFurther analysis of this ASKAP observation is ongoing and further\nepochs are planned.\n\nThank you to CSIRO staff for supporting these observations.\n\n[1] https://www.atnf.csiro.au/content/racs\n[2] https://casda.csiro.au/",
  "circularId": 25445,
  "createdOn": 1566460640000,
  "email": "ddobie94@gmail.com",
  "subject": "LIGO/Virgo S190814bv: No radio counterpart detected in ASKAP observations",
  "submitter": "Dougal Dobie at VAST  <ddobie94@gmail.com>",
  "eventId": "LIGO/Virgo S190814bv"
}