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Published January 2021 | Submitted + Supplemental Material
Journal Article Open

Optical follow-up of the neutron star–black hole mergers S200105ae and S200115j

Abstract

LIGO and Virgo's third observing run revealed the first neutron star–black hole (NSBH) merger candidates in gravitational waves. These events are predicted to synthesize r-process elements creating optical/near-infrared 'kilonova' emission. The joint gravitational wave and electromagnetic detection of an NSBH merger could be used to constrain the equation of state of dense nuclear matter, and independently measure the local expansion rate of the Universe. Here, we present the optical follow-up and analysis of two of the only three high-significance NSBH merger candidates detected to date, S200105ae and S200115j, with the Zwicky Transient Facility. The Zwicky Transient Facility observed ~48% of S200105ae and ~22% of S200115j's localization probabilities, with observations sensitive to kilonovae brighter than −17.5 mag fading at 0.5 mag d⁻¹ in the g- and r-bands; extensive searches and systematic follow-up of candidates did not yield a viable counterpart. We present state-of-the-art kilonova models tailored to NSBH systems that place constraints on the ejecta properties of these NSBH mergers. We show that with observed depths of apparent magnitude ~22 mag, attainable in metre-class, wide-field-of-view survey instruments, strong constraints on ejecta mass are possible, with the potential to rule out low mass ratios, high black hole spins and large neutron star radii.

Additional Information

© 2020 Nature Publishing Group. Received 14 April 2020; Accepted 20 July 2020; Published 14 September 2020. This work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation under PIRE grant no. 1545949. GROWTH is a collaborative project among California Institute of Technology (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Texas Tech University (USA), San Diego State University (USA), University of Washington (USA), Los Alamos National Laboratory (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Indian Institute of Technology Bombay (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), Liverpool John Moores University (UK) and University of Sydney (Australia). This work was based on observations obtained with the 48-inch Samuel Oschin Telescope and the 60-inch Telescope at the Palomar Observatory as part of the ZTF project. ZTF is supported by the National Science Foundation under grant no. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington (UW), Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee and Lawrence Berkeley National Laboratories. Operations are conducted by Caltech Optical Observatories, IPAC, and UW. The work is partly based on the observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. The KPED team (M.W.C., R.G.D., D.A.D., M.F., S.R.K., E.S. and R.R.) thanks the National Science Foundation and the National Optical Astronomical Observatory for making the Kitt Peak 2.1-m telescope available. We thank the observatory staff at Kitt Peak for their efforts to assist Robo-AO KP operations. The KPED team thanks the National Science Foundation, the National Optical Astronomical Observatory, the Caltech Space Innovation Council and the Murty family for support in the building and operation of KPED. In addition, they thank the CHIMERA project for use of the Electron Multiplying CCD (EMCCD). SED Machine is based upon work supported by the National Science Foundation under grant no. 1106171 The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). M.W.C. acknowledges support from the National Science Foundation with grant no. PHY-2010970. S.A. gratefully acknowledges support from a GROWTH PIRE grant (1545949). Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. E.C.K. acknowledges support from the G.R.E.A.T. research environment and the Wenner-Gren Foundations. F.F. gratefully acknowledges support from NASA through grant 80NSSC18K0565, from the NSF through grant PHY-1806278, and from the DOE through CAREER grant DE-SC0020435. Data availability: The data that support the plots within this paper and other findings of this study are available from the corresponding authors on reasonable request. Code availability: The code (primarily in python) used to produce the figures is available from the corresponding authors on reasonable request. These authors contributed equally: Shreya Anand, Michael W. Coughlin. Author Contributions: S.A. and M.W.C. were the primary authors of the manuscript. M.M.K. is the PI of GROWTH and the ZTF EM-GW programme. M.B., A.S.C. and F.F. led the theory and modelling. T.A., M.A., N.G., I.A. and L.P.S. support the development of the GROWTH TOO Marshal and the associated programme. T.A., R. Stein, J.S., S.B.C., V.Z.G., A.K.H.K., H.K., E.C.K., P.M. and S.R. contributed to candidate scanning, vetting and classification. E.C.B. leads the ZTF scheduler and associated interfacing with the TOO programme. B.B. interpreted the asteroid candidates. M.D.C.-G., A.J.C.-T., Y.H., R. Sánchez-Ramírez and A.F.V. provided GTC data and associated analysis. K.D. and M.J.H. provided P200 follow-up. R.G.D., D.A.D., M.F., S.R.K., E.S. and R.R. provided KPED data. M.R. and R.W. provided SEDM data. C.F., M.J.G., R.R.L., F.J.M., P.M, M.P., P.R., B.R., D.L.S., R. Smith, M.T.S. and R.W. are ZTF builders. All authors contributed to editing the manuscript. The authors declare no competing interests. Peer review information: Nature Astronomy thanks Aaron Zimmerman and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Attached Files

Submitted - 2020NatAs_Optical_follow_up_of_the_neutron_star_black_hole_mergers_S200105ae_and_S200115j.pdf

Supplemental Material - 41550_2020_1183_Fig10_ESM.webp

Supplemental Material - 41550_2020_1183_Fig11_ESM.webp

Supplemental Material - 41550_2020_1183_Fig12_ESM.webp

Supplemental Material - 41550_2020_1183_Fig13_ESM.webp

Supplemental Material - 41550_2020_1183_Fig5_ESM.webp

Supplemental Material - 41550_2020_1183_Fig6_ESM.webp

Supplemental Material - 41550_2020_1183_Fig7_ESM.webp

Supplemental Material - 41550_2020_1183_Fig8_ESM.webp

Supplemental Material - 41550_2020_1183_Fig9_ESM.webp

Supplemental Material - 41550_2020_1183_MOESM1_ESM.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 20, 2023