Observational constraints on the optical and near-infrared emission from the neutron star–black hole binary merger candidate S190814bv^⋆

¹ School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
² INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
³ INAF / Brera Astronomical Observatory, Via Bianchi 46, 23807 Merate, LC, Italy
⁴ INFN – Sezione di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, MI, Italy
⁵ University of Milano-Bicocca, Department of Physics “G. Occhialini”, Piazza della Scienza 3, 20126 Milano, Italy
⁶ Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Uni versidad Católica de Chile, Casilla 306, Santiago 22, Chile
⁷ Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sótero Sanz 100, Providencia, Santiago, Chile
⁸ Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
⁹ INAF, Osservatorio Astronomico di Padova, 35122 Padova, Italy
¹⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹¹ INAF Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
¹² Gran Sasso Science Institute, Viale F. Crispi 7, 67100 L’Aquila, AQ, Italy
¹³ INFN – Laboratori Nazionali del Gran Sasso, 67100 L’Aquila, AQ, Italy
¹⁴ INAF, Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monteporzio Catone, RM, Italy
¹⁵ INAF – Osservatorio Astronomico d’Abruzzo, Via M. Maggini snc, 64100 Teramo, Italy
¹⁶ DARK, Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, 2100 Copenhagen Ø, Denmark
¹⁷ Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 106 91 Stockholm, Sweden
¹⁸ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁹ Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
²⁰ APC, Univ Paris Diderot, CNRS/IN2P3, CEA/Irfu, Obs de Paris, Sorbonne Paris Cité, France
²¹ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
²² The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
²³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
²⁴ INFN, Sezione di Padova, 35131 Padova, Italy
²⁵ Astrophysics Research Institute, IC2 building, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
²⁶ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
²⁷ INAF – Istituto di radioastronomia Bologna, Bologna, Italy
²⁸ ASI Science Data Centre, Via del Politecnico snc, 00133 Rome, Italy
²⁹ Faculty of Science, Department of Astronomy and Space Sciences, Istanbul University, Beyazıt, 34119 Istanbul, Turkey
³⁰ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
³¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
³² Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193 Barcelona, Spain
³³ School of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
³⁴ Physics and Astronomy Department Galileo Galilei, University of Padova, Padova, Italy
³⁵ School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland
³⁶ Cosmic Dawn Center (DAWN), Copenhagen Ø, Denmark
³⁷ Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, 2100 Copenhagen Ø, Denmark
³⁸ Departamento de Física Teórica y del Cosmos, Universidad de Granada, 18071 Granada, Spain
³⁹ Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK
⁴⁰ University of Nova Gorica, Center for Astrophysics and Cosmology, Vipavska 13, 5000 Nova Gorica, Slovenia
⁴¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁴² CENTRA-Centro de Astrofíisica e Gravitação and Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal
⁴³ Università degli Studi di Urbino “Carlo Bo”, 61029 Urbino, Italy
⁴⁴ INFN, Sezione di Firenze, 50019 Sesto Fiorentino, Firenze, Italy
⁴⁵ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
⁴⁶ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁴⁷ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
⁴⁸ South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
⁴⁹ The Inter-University Institute for Data Intensive Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
⁵⁰ Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
⁵¹ Department of Physics and Astronomy, University of Turku, Vesilinnantie 5, Turku 20014, Finland
⁵² Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík, Iceland
⁵³ School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
⁵⁴ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
⁵⁵ Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China
⁵⁶ SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁵⁷ School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
⁵⁸ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁵⁹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
⁶⁰ Finnish Centre for Astronomy with ESO (FINCA), 20014 University of Turku, Finland
⁶¹ DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kongens Lyngby, Denmark
⁶² Università degli Studi di Trieste and INFN, Sezione di Trieste, 34127 Trieste, Italy
⁶³ School of Physics, Trinity College Dublin, University of Dublin, College Green, Dublin 2, Ireland
⁶⁴ Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁶⁵ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
⁶⁶ Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK
⁶⁷ Istituto di Astrofisica e Planetologia Spaziali (INAF), Via del Fosso del Cavaliere 100, Roma 00133, Italy
⁶⁸ Universitá di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy
⁶⁹ INFN – Sezione di Pisa, Largo B. Pontecorvo 3, 56127 Pisa, Italy
⁷⁰ Department of Physics, Trento University, Via Sommarive 14, 38123 Povo, Trento, Italy
⁷¹ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁷² Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, Chile
⁷³ National Astronomical Research Institute of Thailand, Ministry of Science and Technology, Chiang Mai 50180, Thailand
⁷⁴ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, CA, Italy
⁷⁵ University of Cagliari, Dept of Physics, S.P. Monserrato-Sestu Km 0, 700, 09042 Monserrato, CA, Italy
⁷⁶ Dipartimento di Fisica e Astronomia “E. Majorana”, Università degli studi di Catania, Via Santa Sofia 64, 95123 Catania, Italy
⁷⁷ INFN – Laboratori Nazionali del Sud, Via Santa Sofia 62, 95123 Catania, Italy
⁷⁸ INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia Edificio 6, 80126 Napoli, Italy
⁷⁹ Department of Physics, Via Cinthia, 80126 Fuorigrotta, Naples, Italy
⁸⁰ Armagh Observatory and Planetarium, Armagh BT61 9DG, UK
⁸¹ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
⁸² Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstrasse 25/8, 6020 Innsbruck, Austria
⁸³ The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
⁸⁴ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via A. Corti 12, 20133 Milano, Italy
⁸⁵ Physics Department, University of Calabria, Via P. Bucci, 87036 Rende, Italy
⁸⁶ European Southern Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile
⁸⁷ Department of Physics, University of Bath, Bath BA2 7AY, UK
⁸⁸ Department of Physics, Harvard University, Cambridge, MA 02138, USA
⁸⁹ Department of Physics, The George Washington University, 725 21st Street NW, Washington, DC 20052, USA
⁹⁰ Astronomy, Physics, and Statistics Institute of Sciences (APSIS), The George Washington University, Washington, DC 20052, USA
⁹¹ GEPI, Observatoire de Paris, PSL University, CNRS, 5 Place Jules Janssen, 92190 Meudon, France

Received: 5 February 2020
Accepted: 18 June 2020

Abstract

Context. Gravitational wave (GW) astronomy has rapidly reached maturity, becoming a fundamental observing window for modern astrophysics. The coalescences of a few tens of black hole (BH) binaries have been detected, while the number of events possibly including a neutron star (NS) is still limited to a few. On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv. A preliminary analysis of the GW data suggests that the event was likely due to the merger of a compact binary system formed by a BH and a NS.

Aims. In this paper, we present our extensive search campaign aimed at uncovering the potential optical and near infrared electromagnetic counterpart of S190814bv. We found no convincing electromagnetic counterpart in our data. We therefore use our non-detection to place limits on the properties of the putative outflows that could have been produced by the binary during and after the merger.

Methods. Thanks to the three-detector observation of S190814bv, and given the characteristics of the signal, the LIGO and Virgo Collaborations delivered a relatively narrow localisation in low latency – a 50% (90%) credible area of 5 deg² (23 deg²) – despite the relatively large distance of 267 ± 52 Mpc. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical and near infrared counterpart of the event. In addition, the ATLAS, GOTO, GRAWITA-VST, Pan-STARRS, and VINROUGE projects also carried out a search on this event. In this paper, we describe the combined observational campaign of these groups.

Results. Our observations allow us to place limits on the presence of any counterpart and discuss the implications for the kilonova (KN), which was possibly generated by this NS–BH merger, and for the strategy of future searches. The typical depth of our wide-field observations, which cover most of the projected sky localisation probability (up to 99.8%, depending on the night and filter considered), is r ∼ 22 (resp. K ∼ 21) in the optical (resp. near infrared). We reach deeper limits in a subset of our galaxy-targeted observations, which cover a total ∼50% of the galaxy-mass-weighted localisation probability. Altogether, our observations allow us to exclude a KN with large ejecta mass M ≳ 0.1 M_⊙ to a high (> 90%) confidence, and we can exclude much smaller masses in a sub-sample of our observations. This disfavours the tidal disruption of the neutron star during the merger.

Conclusions. Despite the sensitive instruments involved in the campaign, given the distance of S190814bv, we could not reach sufficiently deep limits to constrain a KN comparable in luminosity to AT 2017gfo on a large fraction of the localisation probability. This suggests that future (likely common) events at a few hundred megaparsecs will be detected only by large facilities with both a high sensitivity and large field of view. Galaxy-targeted observations can reach the needed depth over a relevant portion of the localisation probability with a smaller investment of resources, but the number of galaxies to be targeted in order to get a fairly complete coverage is large, even in the case of a localisation as good as that of this event.