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Munday, J. orcid.org/0000-0002-1872-5398, Marsh, T.R. orcid.org/0000-0002-2498-7589, Hollands, M. orcid.org/0000-0003-0089-2080 et al. (15 more authors) (2022) Two decades of optical timing of the shortest-period binary star system HM Cancri. Monthly Notices of the Royal Astronomical Society, 518 (4). pp. 5123-5139. ISSN 0035-8711
Abstract
The shortest-period binary star system known to date, RX J0806.3+1527 (HM Cancri), has now been observed in the optical for more than two decades. Although it is thought to be a double degenerate binary undergoing mass transfer, an early surprise was that its orbital frequency, f0, is currently increasing as the result of gravitational wave radiation. This is unusual since it was expected that the mass donor was degenerate and would expand on mass loss, leading to a decreasing f0. We exploit two decades of high-speed photometry to precisely quantify the trajectory of HM Cancri, allowing us to find that f¨0 is negative, where f¨0 = (−5.38±2.10)×10−27 Hz s−2. Coupled with our positive frequency derivative, we show that mass transfer is counteracting gravitational-wave dominated orbital decay and that HM Cancri will turn around within 2100 ± 800 yr from now. We present Hubble Space Telescope ultra-violet spectra which display Lyman-α absorption, indicative of the presence of hydrogen accreted from the donor star. We use these pieces of information to explore a grid of permitted donor and accretor masses with the Modules for Experiments in Stellar Astrophysics suite, finding models in good accordance with many of the observed properties for a cool and initially hydrogen-rich extremely low mass white dwarf (≈0.17 M⊙) coupled with a high-accretor mass white dwarf (≈1.0 M⊙). Our measurements and models affirm that HM Cancri is still one of the brightest verification binaries for the Laser Interferometer Space Antenna spacecraft.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 The Authors. This is an author-produced version of a paper subsequently published in Monthly Notices of the Royal Astronomical Society. This version is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0). |
Keywords: | gravitational waves; binaries: close; individual: RX J0806.3+1527; HM Cancri; stars: white dwarfs |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Funding Information: | Funder Grant number European Research Council 340040 SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/V000853/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 01 Feb 2023 11:57 |
Last Modified: | 17 Mar 2023 17:50 |
Status: | Published |
Publisher: | Oxford University Press (OUP) |
Refereed: | Yes |
Identification Number: | 10.1093/mnras/stac3385 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:195922 |
Available Versions of this Item
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Two decades of optical timing of the shortest-period binary star system HM Cancri. (deposited 25 Nov 2022 11:41)
- Two decades of optical timing of the shortest-period binary star system HM Cancri. (deposited 01 Feb 2023 11:57) [Currently Displayed]