TITLE: GCN CIRCULAR NUMBER: 25495 SUBJECT: LIGO/Virgo S190814bv: DESGW non-detection of AT2019osy/ASKAP 005547-270433 DATE: 19/08/27 22:14:55 GMT FROM: Ken Herner at Fermi Nat Accelerator Lab LIGO/Virgo S190814bv: DESGW non-detection of AT2019osy/ASKAP 005547-270433 Ken Herner, Marcelle Soares-Santos, James Annis, Antonella Palmese on behalf of the DESGW Team* We cannot confirm the optical detection in DECam data reported by Andreoni et al. in GCN 25488, said to be spatially coincident with AT2019osy/ASKAP 005547-270433 (Stewart et al., GCN 25487). Between MJD 58716.19 and 58716.36 we imaged the candidate area three times in both i and z band. We did not record any detections in our difference imaging pipeline within 3" of the coordinates reported in GCN 25487 (ra,dec = 13.945833,-27.075833) either in the individual images or in the coadded analysis (where we combine images in a given bandpass from the same night; see Soares-Santos et al. GCN 25486). We also did not record any detections at that location in our first four nights of observations. We have a single low-significance detection in one bandpass in the coadded images from MJD 58716.19 to 58716.36, but it does not pass our most basic quality cuts. Also, there is a 3.2" separation between our detection (ra,dec=13.946664, -27.076167) and the transient coordinates in TNS. We visually inspected the DES Year 5 coadded image at the position of ASKAP 005547-270433 (GCN 25487) and there is definitely light from the nearby edge-on dusty spiral galaxy at that location. *The DESGW Collaboration: Sahar Allam (Fermilab), James Annis (Fermilab), Iair Arcavi (Tel Aviv U), Tristan Bachmann (U Chicago), Paulo Barchi (INPE & Brandeis U), Thomas Beatty (U of Arizona) Keith Bechtol (U of Wisconsin-Madison), Federico Berlfein (Brandeis U), Antonio Bernardo (U of Sao Paulo), Dillon Brout (U Penn), Robert Butler (Indiana U), Melissa Butner, (Fermilab), Annalisa Calamida (STScI), Hsin-Yu Chen (Harvard U), Chris Conselice (U of Nottingham), Carlos Contreras (STScI), Jeff Cooke (Swinburne U), Chris D’Andrea (U Penn), Tamara Davis (U Queensland), Reinaldo de Carvalho (UNICSUL), H. Thomas Diehl (Fermilab), Zoheyr Doctor (U Chicago), Alex Drlica-Wagner (Fermilab), Maria Drout (U Toronto), Maya Fishbach (U Chicago), Francisco Forster (U de Chile), Ryan Foley (UCSC), Joshua Frieman (Fermilab & U Chicago), Chris Frohmaier (U of Portsmouth), Ori Fox (STScI), Alyssa Garcia (Brandeis U), Juan Garcia-Bellido (U Autonoma de Madrid), Mandeep Gill (SLAC & Stanford U), Robert Gruendl (NCSA), Will Hartley (U College London), Kenneth Herner (Fermilab), Daniel Holz (U Chicago), Jorge Horvath (U of Sao Paulo), D. Andrew Howell (Las Cumbres Observatory), Richard Kessler (U Chicago), Charles Kilpatrick (UCSC), Nikolay Kuropatkin (Fermilab), Ofer Lahav (U College London), Huan Lin (Fermilab), Andrew Lundgren (U of Portsmouth), Martin Makler (CBPF), Clara Martinez-Vazquez (CTIO/NOAO), Curtis McCully (Las Cumbres Observatory), Mitch McNanna (U of Wisconsin-Madison), Robert Morgan (U of Wisconsin-Madison), Gautham Narayan (STScI), Eric Neilsen (Fermilab), Robert Nichol (U of Portsmouth), Antonella Palmese (Fermilab), Francisco Paz-Chinchon (NCSA & UIUC), Matthew Penny (OSU), Maria Pereira (Brandeis U), Sandro Rembold (UFSM), Armin Rest (STScI & JHU), Livia Rocha (U Sao Paulo), Russell Ryan (STScI), Masao Sako (U Penn), Samir Salim (Indiana U), David Sand (U of Arizona), Luidhy Santana-Silva (Valongo Observatory), Daniel Scolnic (Duke U), Nora Sherman (Fermilab), J. Allyn Smith (Austin Peay State U), Mathew Smith (U of Southampton), Marcelle Soares-Santos (Brandeis U), Lou Strolger (STScI), Riccardo Sturani (UFRN), Mark Sullivan (U of Southampton), Masaomi Tanaka (NAOJ), Nozomu Tominaga (Konan U), Douglas Tucker (Fermilab), Yousuke Utsumi (Stanford U), Stefano Valenti (UC Davis), Kathy Vivas (NOAO/CTIO), Alistair Walker (NOAO/CTIO), Sara Webb (Swinburne U), Matt Wiesner (Benedictine U), Brian Yanny (Fermilab), Michitoshi Yoshida (NAOJ), Alfredo Zenteno (NOAO/CTIO)