Authors:

Jesus Perez

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About Paper:

Stellar rotation provides a critical diagnostic of stellar angular momentum evolution. While spin-down models are well studied for single solar-type stars, less is known about the rotational evolution of stars that have experienced binary interactions such as mergers and mass transfer. We analyzed a sample of 250 candidate post-mass-transfer main sequence-white dwarf (MS-WD) binary systems identified from Gaia DR3 astrometry, each with far-UV (FUV) and near-UV (NUV) photometry from GALEX. We cross-matched Gaia DR3 with TESS light curves, extracting photometry using the eleanor and lightkurve software packages and measuring rotation periods with Lomb-Scargle periodograms. Of the 250 MS-WD binaries, 127 systems exhibited periodic brightness variations suitable for rotation analysis. We recovered rotation periods spanning 0.5-10 days, with clear variability signatures consistent with starspots moving in and out of view. To test whether stellar rotation traces the time since mass transfer, we derived gyrochronology ages from rotation periods and Gaia colors, and inferred white dwarf cooling ages using ultraviolet photometry and theoretical cooling models. We find that rapid rotators are preferentially found among systems with hotter white dwarf companions, as indicated by FUV-NUV color. We further find that gyrochronology ages broadly follow the expected white dwarf cooling trend. This correlation is consistent with angular momentum transfer scenarios in which mass accretion accelerates stellar rotation, with subsequent spin-down occurring on timescales comparable to standard gyrochronology models of the same stellar type.

Source:

Illinois Institute of Technology

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Co-authors:

Jesus Perez