Published June 10, 2024 | Version Published
Journal Article Open

Discovery of a Proto–White Dwarf with a Massive Unseen Companion

  • 1. ROR icon Johns Hopkins University
  • 2. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 3. ROR icon Institute for Advanced Study
  • 4. ROR icon Boston University
  • 5. ROR icon California Institute of Technology
  • 6. ROR icon University of Warwick
  • 7. ROR icon University of Illinois Urbana-Champaign

Abstract

We report the discovery of SDSS J022932.28+713002.7, a nascent extremely low-mass (ELM) white dwarf (WD) orbiting a massive (>1 M at 2σ confidence) companion with a period of 36 hr. We use a combination of spectroscopy, including data from the ongoing fifth-generation Sloan Digital Sky Survey (SDSS-V), and photometry to measure the stellar parameters of the primary pre-ELM WD. The lightcurve of the primary WD exhibits ellipsoidal variation, which we combine with radial velocity data and PHOEBE binary simulations to estimate the mass of the invisible companion. We find that the primary WD has mass M1 = 0.18_(−0.02)^(+0.02) M and the unseen secondary has mass M2 = 1.19_(−0.14)^(+0.21) M. The mass of the companion suggests that it is most likely a near-Chandrasekhar-mass WD or a neutron star. It is likely that the system recently went through a Roche lobe overflow from the visible primary onto the invisible secondary. The dynamical configuration of the binary is consistent with the theoretical evolutionary tracks for such objects, and the primary is currently in its contraction phase. The measured orbital period puts this system on a stable evolutionary path which, within a few gigayears, will lead to a contracted ELM WD orbiting a massive compact companion.

Copyright and License

© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

G.A.P. thanks W. Brown for useful comments. V.C. gratefully acknowledges a Peirce Fellowship from Harvard University. N.L.Z. acknowledges support by the JHU President's Frontier Award and by the seed grant from the JHU Institute for Data Intensive Engineering and Science. B.G. received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 101020057). Y.Z. gratefully acknowledge support from NASA grants NNH17ZDA001N, 80NSSC22K0494, 80NSSC21K0242, and 80NSSC19K0112. N.R.C. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE2139757. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Based on observations obtained with the Samuel Oschin 48 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility 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, 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 COO, IPAC, and UW.

This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

Funding for the Sloan Digital Sky Survey V has been provided by the Alfred P. Sloan Foundation, the Heising-Simons Foundation, the National Science Foundation, and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. SDSS telescopes are located at Apache Point Observatory, funded by the Astrophysical Research Consortium and operated by New Mexico State University, and at Las Campanas Observatory, operated by the Carnegie Institution for Science. The SDSS website is www.sdss.org.

SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration, including Caltech, The Carnegie Institution for Science, Chilean National Time Allocation Committee (CNTAC) ratified researchers, The Flatiron Institute, the Gotham Participation Group, Harvard University, Heidelberg University, The Johns Hopkins University, L'Ecole polytechnique fédérale de Lausanne (EPFL), Leibniz-Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Extraterrestrische Physik (MPE), Nanjing University, National Astronomical Observatories of China (NAOC), New Mexico State University, The Ohio State University, Pennsylvania State University, Smithsonian Astrophysical Observatory, Space Telescope Science Institute (STScI), the Stellar Astrophysics Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Illinois at Urbana-Champaign, University of Toronto, University of Utah, University of Virginia, Yale University, and Yunnan University.

Data Availability

The photometric data from GALEX, SDSS, Pan-STARRS, 2MASS, and CatWISE used in this paper are publicly available from the corresponding archives. The ZTF and TESS lightcurve data used are also publicly available (STScI 20192020; IRSA 2022). The SDSS-V data are not public but the reduced and calibrated data are made available in the online version of this article (see Figure 1). The APO data used in this work are also made available in the online version of this article.

Software References

astropy (Astropy Collaboration et al. 201320182022), numpy (Harris et al. 2020), scipy (Virtanen et al. 2020), matplotlib (Hunter 2007), lightkurve (Lightkurve Collaboration et al. 2018), eleanor (Feinstein et al. 2019), and PHOEBE (Prša 2018)

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Additional details

Identifiers

ISSN
1538-4357

Funding

Harvard University
Johns Hopkins University
European Research Council
101020057
National Aeronautics and Space Administration
NNH17ZDA001N
National Aeronautics and Space Administration
80NSSC22K0494
National Aeronautics and Space Administration
80NSSC21K0242
National Aeronautics and Space Administration
80NSSC19K0112
National Science Foundation
NSF Graduate Research Fellowship DGE-2139757
National Science Foundation
AST-1440341
California Institute of Technology
Zwicky Transient Facilitiy
Alfred P. Sloan Foundation
Heising-Simons Foundation

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