A1 Refereed original research article in a scientific journal
A TESS search for donor-star pulsations in high-mass X-ray binaries
Authors: Ramsay Gavin, Hakala Pasi, Charles Philip A.
Publisher: OXFORD UNIV PRESS
Publication year: 2022
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 516
Issue: 1
First page : 1219
Last page: 1236
Number of pages: 18
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stac2223
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/176525505
Ground-based optical photometry of the counterparts of high-mass X-ray binaries (HMXBs) has revealed the presence of periodic modulations on time-scales of similar to 0.3-0.5 d. More recent space-based observations (CoRoT and TESS) of OB and Be stars have shown that pulsations caused by p and g modes are common in early-type stars. We have therefore undertaken a systematic search for variability in the optical counterparts of 23 HMXBs (mostly neutron star systems, but including one black hole, Cyg X-1) using TESS data primarily in 2 min cadence mode. After removing the orbital period modulation in four systems, we find that all 23 sources show evidence for quasi-periodic variability on periods shorter than similar to 1 d. We compare their power spectra with those from observations of other OB- and Be-type stars. In two systems, V725 Tau and HD 249179 (which may not be an HMXB), we find evidence for an outburst, the former being simultaneous with an X-ray flare. We search for changes in the power spectra over the outburst duration and compare them with outbursts seen in other Be systems.
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