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SDSS J134441.83+204408.3: A Highly Asynchronous Short-period Magnetic Cataclysmic Variable with a 56 MG Field Strength

Littlefield, Colin; Mason, Paul A.; Garnavich, Peter; Szkody, Paula; Thorstensen, John; Scaringi, Simone; Iłkiewicz, Krystian; Kennedy, Mark R.; Wells, Natalie

SDSS J134441.83+204408.3: A Highly Asynchronous Short-period Magnetic Cataclysmic Variable with a 56 MG Field Strength Thumbnail


Authors

Colin Littlefield

Paul A. Mason

Peter Garnavich

Paula Szkody

John Thorstensen

Krystian Iłkiewicz

Mark R. Kennedy

Natalie Wells



Abstract

When the accreting white dwarf in a magnetic cataclysmic variable star (mCV) has a field strength in excess of 10 MG, it is expected to synchronize its rotational frequency to the binary orbit frequency, particularly at small binary separations, due to the steep radial dependence of the magnetic field. We report the discovery of an mCV (SDSS J134441.83+204408.3, hereafter J1344) that defies this expectation by displaying asynchronous rotation (Pspin/Porb = 0.893) in spite of a high surface field strength (B = 56 MG) and a short orbital period (114 minutes). Previously misidentified as a synchronously rotating mCV, J1344 was observed by Transiting Exoplanet Survey Satellite during sector 50, and the resulting power spectrum shows distinct spin and orbital frequencies, along with various sidebands and harmonics. Although there are several other asynchronous mCVs at short orbital periods, the presence of cyclotron humps in J1344's Sloan Digital Sky Survey spectrum makes it possible to directly measure the field strength in the cyclotron-emitting region, and while a previously study estimated 65 MG based on its identification of two cyclotron humps, we revise this to 56 ± 2 MG based on the detection of a third hump and on our modeling of the cyclotron spectrum. Short-period mCVs with field strengths above 10 MG are normally expected to be synchronous, so the highly asynchronous rotation in J1344 presents an interesting challenge for theoretical studies of spin-period evolution.

Citation

Littlefield, C., Mason, P. A., Garnavich, P., Szkody, P., Thorstensen, J., Scaringi, S., …Wells, N. (2023). SDSS J134441.83+204408.3: A Highly Asynchronous Short-period Magnetic Cataclysmic Variable with a 56 MG Field Strength. Astrophysical Journal Letters, 943(2), Article L24. https://doi.org/10.3847/2041-8213/acaf04

Journal Article Type Article
Acceptance Date Dec 22, 2022
Online Publication Date Feb 1, 2023
Publication Date Feb 1, 2023
Deposit Date Oct 12, 2023
Publicly Available Date Oct 12, 2023
Journal The Astrophysical Journal Letters
Print ISSN 2041-8205
Electronic ISSN 2041-8213
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 943
Issue 2
Article Number L24
DOI https://doi.org/10.3847/2041-8213/acaf04
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL https://durham-repository.worktribe.com/output/1790919

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