GROWTH on S190425z: Searching Thousands of Square Degrees to Identify an Optical or Infrared Counterpart to a Binary Neutron Star Merger with the Zwicky Transient Facility and Palomar Gattini-IR

Abstract

The third observing run by LVC has brought the discovery of many compact binary coalescences. Following the detection of the first binary neutron star merger in this run (LIGO/Virgo S190425z), we performed a dedicated follow-up campaign with the Zwicky Transient Facility (ZTF) and Palomar Gattini-IR telescopes. The initial skymap of this single-detector gravitational wave (GW) trigger spanned most of the sky observable from Palomar Observatory. Covering 8000 deg 2 of the initial skymap over the next two nights, corresponding to 46% integrated probability, ZTF system achieved a depth of ≈21 m AB in g-and r-bands. Palomar Gattini-IR covered 2200 square degrees in J-band to a depth of 15.5 mag, including 32% integrated probability based on the initial skymap. The revised skymap issued the following day reduced these numbers to 21% for the ZTF and 19% for Palomar Gattini-IR. We narrowed 338,646 ZTF transient "alerts" over the first two nights of observations to 15 candidate counterparts. Two candidates, ZTF19aarykkb and ZTF19aarzaod, were particularly compelling given that their location, distance, and age were consistent with the GW event, and their early optical light curves were photometrically consistent with that of kilonovae. These two candidates were spectroscopically classified as young core-collapse supernovae. The remaining candidates were ruled out as supernovae. Palomar Gattini-IR did not identify any viable candidates with multiple detections only after merger time. We demonstrate that even with single-detector GW events localized to thousands of square degrees, systematic kilonova discovery is feasible.

Measuring the Hubble constant with a sample of kilonovae

“…Here, we focus on the kilonova observation happening in coincidence with sGRBs. This type of analysis is particularly prescient given the difficulty of searches for GW counterparts during Advanced LIGO and Advanced Virgo's third observing run (O3) 20 . AT2017gfo, synthesized by the radioactive decay of r-process elements in neutron-rich matter ejected during the merger 21,22 , is certainly the best sampled kilonova observation to date.…”

Searching for electromagnetic counterparts to gravitational-wave merger events with the prototype Gravitational-Wave Optical Transient Observer (GOTO-4)

“…Numerous wide-field follow-up missions have tiled GW error boxes searching for transients, including the All-Sky Automated Survery for Supernovae (ASASSN; Shappee et al 2014), the Asteroid Terrestrial impact Last Alert System (ATLAS; Tonry et al 2018), the Deca-Degree Optical Transient Imager (DDOTI; Watson et al 2016), the Dark Energy Survey (DES; Dark Energy Survey Collaboration et al 2016), the Global Rapid Advanced Network Devoted to the Multimessenger Addicts (GRANDMA; Antier et al 2020b), KMT-Net (Kim et al 2016), the Mobile Astronomical System of TElescope Robots (MASTER; Lipunov et al 2010), MeerLICHT (Bloemen et al 2016), PanSTARRS (Kaiser et al 2010), Searches After Gravitational waves Using ARizona Observatories (SAGUARO; Lundquist et al 2019), the Télescope à Action Rapide pour les Objets Transitoires (TAROT; Boër 2001), the Visible and Infrared Survey Telescope for Astronomy (VISTA;Sutherland et al 2015), the VLT Survey Telescope (VST; Capaccioli & Schipani 2011) and the Zwicky Transient Facility (ZTF; Bellm et al 2019). No associated transients were identified (Anand et al 2020;Antier et al 2020b,a;Coughlin et al 2020;Sagués Carracedo et al 2020), but constraining limits were placed on a number of milestone events, including S190814bv, the first NSBH merger candidate identified in GW (Dobie et al 2019;Gomez et al 2019;LIGO Scientific Collaboration & Virgo Collaboration 2019;Ackley et al 2020;Andreoni et al 2020;Vieira et al 2020;Watson et al 2020), and several candidate BNS systems (Goldstein et al 2019;Hosseinzadeh et al 2019;Lundquist et al 2019), including the unusually massive GW190425 (Coughlin et al 2019;Hosseinzadeh et al 2019;Lundquist et al 2019;Abbott et al 2020b).…”

Constraints on the Physical Properties of GW190814 through Simulations Based on DECam Follow-up Observations by the Dark Energy Survey

“…The field of multimessenger astrophysics has experienced dramatic growth in the past few years, thanks to the development and increased sensitivities of instruments like the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO; Aasi et al 2015), the Virgo Interferometer (Acernese et al 2014), IceCube (Achterberg et al 2006), and ANTARES (Ageron et al 2011). Furthermore, real-time alert streams of detections made by instruments such as the Astrophysical Multimessenger Observatory Network (AMON; Smith et al 2013;Keivani et al 2017) and the Gamma-ray Coordination Network (GCN; Barthelmy et al 1998) have made it possible for the astronomical community to target the sources of gravitational waves (Coughlin et al 2019a;Doctor et al 2019;Hosseinzadeh et al 2019;Andreoni et al 2020;Garcia et al 2020, among several others from the previous LIGO/Virgo observing runs) and high-energy neutrinos (Abbasi et al 2012;Aartsen et al 2015;The IceCube Collaboration et al 2018;Kankare et al 2019;Morgan et al 2019;Stein et al 2020, among several others) in search of an electromagnetic signal within hours of the first detection of astrophysical events.…”