{
  "bibcode": "2019GCN.25801....1B",
  "body": "F. E. Bauer (PUC), A. S. Fruchter (STScI), J. Gonzalez Lopez (UDP), J. \nHjorth (DARK/NBI), T. Kangas (STScI), S. Kim (PUC), A. J. Levan (Radboud \nUniv.), D. B. Malesani (DTU Space), M. J. Michalowski (AMU), B. \nMilvang-Jensen (DAWN/NBI), R. Paladino (INAF/IRA), S. Schulze (WIS), A. \nde Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), report on behalf of the \nENGRAVE collaboration:\n\nWe observed the host galaxy of the radio transient ASKAP 005547-270433 / \nAT 2019osy (Stewart et al., GCN 25487) on 2019 Sep 17.9 UT using the \nF140W (1.4 micron) broadband filter of the Wide-Field Camera 3 on the \nHubble Space Telescope and at 109 and 242 GHz in the configuration C43-7 \n(beam size of 0.21'' at 100 GHz) with ALMA on 2019 Sep 5.2 UT.\n\nA point source is detected by ALMA at 109 GHz consistent with the \nlocation reported by ASKAP (Stewart et al., GCN 25496), for which we \nmeasure these refined coordinates (~0.05\" error):\n\nRA(J2000) = 00:55:47.417\nDec(J2000) = -27:04:33.14\n\nWe aligned the HST data to the Gaia catalog (to be consistent with the \nALMA astrometry) using four stars in common inside the HST field of \nview. While we resolve a small elongated nucleus at the center of the \nhost, we see no clear evidence of a point source superposed on the \napparently normal structure of an edge-on spiral. Nonetheless, the \nposition of the ALMA source aligns with the peak of the light in the \nnucleus to within its positional error of ~0.05\". This result agrees \nwith the finding of Mooley et al. (GCN 25539), who reported an alignment \nbetween the optical centroid of the host obtained from ground-based \nimaging and a VLA position at the 0.1\" level.\n\nWhile the galaxy nucleus is not detected by ALMA at 242 GHz, a separate \nsource is marginally detected approximately 1.5\" away (not visible at \n109 GHz), at a position still overlaying the stellar extent of the host \ngalaxy and consistent with the ASKAP position of AT 2019osy (Stewart et \nal., GCNs 25487, 25496). The lack of detections by both ALMA at 109 GHz \nand by the VLA at 1-10 GHz (on Aug 28; Mooley et al., GCN 25539) makes \nit unlikely to be associated with AT 2019osy. It could be a noise peak, \nan unrelated background source, or a star-forming region inside the galaxy.\n\nCutouts from the HST image, both wide-field and zoomed-in, can be seen \nat http://www.engrave-eso.org/AT2019osy_host_images .\n\nThis circular is based on data collected under ALMA program \n2018.1.01652.T, and on HST GO program #15664. We thank the staffs of \nSTScI (in particular Alison Vick) and of the ALMA observatory for their \nassistance with these time-constrained observations. For further \ninformation on ENGRAVE, see http://www.engrave-eso.org/.",
  "circularId": 25801,
  "createdOn": 1569089002000,
  "email": "malesani@space.dtu.dk",
  "subject": "LIGO/Virgo S190814bv: HST and ALMA observations of the host galaxy of ASKAP J005547-270433 / AT 2019osy",
  "submitter": "Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>",
  "eventId": "LIGO/Virgo S190814bv"
}