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Tidally Tilted Pulsations in HD 265435, a Subdwarf B Star with a Close White Dwarf Companion

Jayaraman, Rahul and Handler, Gerald and Rappaport, Saul A. and Fuller, Jim and Kurtz, Donald W. and Charpinet, Stéphane and Ricker, George R. (2022) Tidally Tilted Pulsations in HD 265435, a Subdwarf B Star with a Close White Dwarf Companion. Astrophysical Journal Letters, 928 (2). Art. No. L14. ISSN 2041-8205. doi:10.3847/2041-8213/ac5c59.

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Tidally tilted pulsators (TTPs) are an intriguing new class of oscillating stars in binary systems; in such stars, the pulsation axis coincides with the line of apsides, or tidal axis, of the binary. All three TTPs discovered so far have been δ Scuti stars. In this Letter, we report the first conclusive discovery of tidally tilted pulsations in a subdwarf B (sdB) star. HD 265435 is an sdB–white dwarf binary with a 1.65 hr period that has been identified and characterized as the nearest potential Type Ia supernova progenitor. Using TESS 20 s cadence data from Sectors 44 and 45, we show that the pulsation axis of the sdB star has been tidally tilted into the orbital plane and aligned with the tidal axis of the binary. We identify 31 independent pulsation frequencies, 27 of which have between 1 and 7 sidebands separated by the orbital frequency (ν_(orb)) or multiples thereof. Using the observed amplitude and phase variability due to tidal tilting, we assign ℓ and m values to most of the observed oscillation modes and use these mode identifications to generate preliminary asteroseismic constraints. Our work significantly expands our understanding of TTPs, as we now know that (i) they can be found in stars other than δ Scuti pulsators, especially highly evolved stars that have lost their H-rich envelopes, and (ii) tidally tilted pulsations can be used to probe the interiors of stars in very tight binaries.

Item Type:Article
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URLURL TypeDescription Paper ItemCode
Jayaraman, Rahul0000-0002-7778-3117
Handler, Gerald0000-0001-7756-1568
Rappaport, Saul A.0000-0003-3182-5569
Fuller, Jim0000-0002-4544-0750
Kurtz, Donald W.0000-0002-1015-3268
Charpinet, Stéphane0000-0002-6018-6180
Ricker, George R.0000-0003-2058-6662
Additional Information:© 2022. 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. Received 2022 February 9; revised 2022 March 9; accepted 2022 March 9; published 2022 March 30. G.H. acknowledges support by the Polish NCN grant 2015/18/A/ST9/00578. S.C. acknowledges support from the Agence Nationale de la Recherche (ANR, France) under grant No. ANR-17-CE31-0018, funding the INSIDE project, and financial support from the Centre National d'Études Spatiales (CNES, France). This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Science Mission Directorate. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center to produce the SPOC data products. Code and inlists used for our MESA analysis are available on Zenodo, at Facility: TESS. - Software: SPOC (Jenkins et al. 2016), astropy (Astropy Collaboration et al. 2013, 2018), numpy (Harris et al. 2020), matplotlib (Hunter 2007), scipy (Virtanen et al. 2020), pandas (McKinney 2010; Pandas development team 2020), Period04 (Lenz & Breger 2005), MESA (Paxton et al. 2011, 2013, 2015, 2018, 2019), GYRE (Townsend & Teitler 2013; Goldstein & Townsend 2020).
Group:TAPIR, Walter Burke Institute for Theoretical Physics, Astronomy Department
Funding AgencyGrant Number
National Science Centre (Poland)2015/18/A/ST9/00578
Agence Nationale pour la Recherche (ANR)ANR-17-CE31-0018
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:Asteroseismology; B subdwarf stars; Pulsation modes; Tidal distortion
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Asteroseismology (73); B subdwarf stars (129); Pulsation modes (1309); Tidal distortion (1697)
Record Number:CaltechAUTHORS:20220427-51143900
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Official Citation:Rahul Jayaraman et al 2022 ApJL 928 L14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114502
Deposited By: Tony Diaz
Deposited On:27 Apr 2022 23:27
Last Modified:27 Apr 2022 23:27

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