GRANDMA observations of advanced LIGO’s and advanced Virgo’s third observational campaign

Abstract

GRANDMA is a network of 25 telescopes of different sizes, including both photometric and spectroscopic facilities. The network aims to coordinate follow-up observations of gravitational-wave candidate alerts, especially those with large localisation uncertainties, to reduce the delay between the initial detection and the optical confirmation. In this paper, we detail GRANDMA’s observational performance during Advanced LIGO/Advanced Virgo Observing Run 3 (O3), focusing on the second part of O3; this includes summary statistics pertaining to coverage and possible astrophysical origin of the candidates. To do so, we quantify our observation efficiency in terms of delay between gravitational-wave candidate trigger time, observations, and the total coverage. Using an optimised and robust coordination system, GRANDMA followed-up about 90% of the gravitational-wave candidate alerts, i.e. 49 out of 56 candidates. This led to coverage of over 9000 deg2 during O3. The delay between the gravitational-wave candidate trigger and the first observation was below 1.5 hour for 50% of the alerts. We did not detect any electromagnetic counterparts to the gravitational-wave candidates during O3, likely due to the very large localisation areas (on average thousands of degrees squares) and relatively large distance of the candidates (above 200 Mpc for 60% of BNS candidates). We derive constraints on potential kilonova properties for two potential binary neutron star coalescences (GW190425 and S200213t), assuming that the events’ locations were imaged.

Implications of the search for optical counterparts during the second part of the Advanced LIGO’s and Advanced Virgo’s third observing run: lessons learned for future follow-up observations

“…While it was the first BNS alert during the second half of the O3 campaign, the response to this alert was relatively tepid, likely due to the scattered light contamination. However, 53 report circulars have been distributed for this event due to the presence of an interesting transient found by the Pan-STARRS Collaboration PS19hgw/AT2019wxt, finally classified as supernovae IIb due to the photometry evolution and spectroscopy characterization (McBrien et al 2019b;Vallely 2019;Antier et al 2020b). In total, three neutrinos, one VHE, eight γ -rays, two X-rays, 19 optical, and one radio groups participated to the S191213g campaign (see the list of GCNs for S191213g).…”

“…The MASTERnetwork covered ≈43 per cent down to 19.5 in clear and within 144 h (Lipunov et al 2020a). The telescope network was already observing at the time of the trigger and because its routine observations were compatible with the sky localization of S200105ae, the delay was limited to 3 h. GRANDMA-TCA telescope was triggered as soon as the notice comes out, and the full GRANDMA network totalized 12.5 per cent of the full LALInference skymap down to 17 mag in clear and within 60 h (Antier et al 2020b). The Zwicky Transient Facility covered ≈52 per cent of the LALInference skymap down to 20.2 in both g and r bands (Stein et al 2020;Kasliwal et al 2020a) and with a delay of 10 h. There were 23 candidate transients reported by ZTF, as well as one candidate from the Gaia Alerts team (Kostrzewa-Rutkowska et al 2020) out of which ZTF20aaervoa and ZTF20aaertpj were both quite interesting due to their red colours (g − r = 0.66 and 0.35, respectively), and absolute magnitudes (−16.4 and −15.9, respectively) (Stein et al 2020).…”

“…S200213t was identified by H1, L1, and V1 at 2020-02-13 at 04:10:40 UTC (LIGO Scientific Collaboration & Virgo Collaboration 2020g). , and 48 h (bottom row) after the GW trigger time by ZTF (Bhalerao et al 2020;Kasliwal et al 2020b) and GRANDMA, including the TAROT (TCA, TCH, and TRE) network and OAJ (Antier et al 2020b). The LALInference localization probabilities are shown in shaded red.…”

“…1 Amongst the wide field-of-view telescopes, ATLAS (McBrien et al 2019a;Smartt et al 2019a, b;Srivastav et al 2019), ASAS-SN (Shappee et al 2019), CNEOST (Li et al 2019;Xu et al 2019b, c), Dabancheng/HMT (Xu et al 2019d), DESGW-DECam (Soares-Santos et al 2019), DDOTI/OAN (Dichiara et al 2019;Pereyra et al 2019;Watson et al 2019b), GOTO (Ackley et al 2019a, b;Steeghs et al 2019a, b;Gompertz et al 2020), GRANDMA (Antier et al 2020a;Antier et al 2020b), GRAWITA-VST (Grado et al 2019a, b), GROWTH-DECAM (Andreoni et al 2019a;Goldstein et al 2019), GROWTH-Gattini-IR (De et al 2019;Hankins et al 2019a, b), GROWTH-INDIA (Bhalerao et al 2019), HSC (Yoshida et al 2019), J-GEM (Niino et al 2019), KMTNet (Im et al 2019;Kim et al 2019), MASTERnetwork (Lipunov et al 2019a, b, c, d, e, f, g, h), MeerLICHT (Groot et al 2019), Pan-STARRS (Smith et al 2019;Smartt et al 2019a), SAGUARO (Lundquist et al 2019), SVOM-GWAC (Wei et al 2019), Swope (Kilpatrick et al 2019), Xinglong-Schmidt (Xu et al 2019a;Zhu et al 2019), and the Zwicky Transient Facility (Anand et al 2019;Coughlin et al 2019d;Kasliwal et al 2019a, b;Kool et al 2019;Singer et al 2019;…”

GWSkyNet: A Real-time Classifier for Public Gravitational-wave Candidates

“…5 For compact binaries, the information released in Open Public Alerts (OPA) included 6 : the false-alarm rate (FAR) estimated by the search pipelines, the inferred sky position and distance of the source (Singer & Price 2016;Singer et al 2016a), the probability of astrophysical origin with classification according to different mass regions (Kapadia et al 2020), and the probability of neutron star matter content (Foucart et al 2018;Chatterjee et al 2020). Rapid and public information release enabled every astronomer with access to telescopes or neutrino detectors to search for counterparts to the GW candidates (Andreoni et al 2019;Antier et al 2020;Coughlin 2020;Coughlin et al 2020;Graham et al 2020;Hussain et al 2020;Kasliwal et al 2020;Vieira et al 2020).…”