8.9 hr Rotation in the Partly Burnt Runaway Stellar Remnant LP 40-365 (GD 492)

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8.9 hr Rotation in the Partly Burnt Runaway Stellar Remnant LP 40-365 (GD 492)

Hermes, JJ; Putterman, O; Hollands, MA; Wilson, DJ; Swan, A; Raddi, R; Shen, KJ; (2021) 8.9 hr Rotation in the Partly Burnt Runaway Stellar Remnant LP 40-365 (GD 492). Astrophysical Journal Letters , 914 (1) 10.3847/2041-8213/ac00a8. Green open access

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Abstract

We report the detection of 8.914 hr variability in both optical and ultraviolet light curves of LP 40−365 (also known as GD 492), the prototype for a class of partly burnt runaway stars that have been ejected from a binary due to a thermonuclear supernova event. We first detected this 1.0% amplitude variation in optical photometry collected by the Transiting Exoplanet Survey Satellite (TESS). Reanalysis of observations from the Hubble Space Telescope at the TESS period and ephemeris reveal a 5.8% variation in the ultraviolet of this 9800 K stellar remnant. We propose that this 8.914 hr photometric variation reveals the current surface rotation rate of LP 40−365, and is caused by some kind of surface inhomogeneity rotating in and out of view, though a lack of observed Zeeman splitting puts an upper limit on the magnetic field of <20 kG. We explore ways in which the present rotation period can constrain progenitor scenarios if angular momentum was mostly conserved, which suggests that the survivor LP 40−365 was not the donor star but was most likely the bound remnant of a mostly disrupted white dwarf that underwent advanced burning from an underluminous (Type Iax) supernova.

Type:	Article
Title:	8.9 hr Rotation in the Partly Burnt Runaway Stellar Remnant LP 40-365 (GD 492)
Open access status:	An open access version is available from UCL Discovery
DOI:	10.3847/2041-8213/ac00a8
Publisher version:	https://doi.org/10.3847/2041-8213/ac00a8
Language:	English
Additional information:	This version is the version of record. For information on re-use, please refer to the publisher's terms and conditions.
UCL classification:	UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI:	https://discovery.ucl.ac.uk/id/eprint/10130131