Most Rotational Variables Dominated by a Single Bright Feature are $α^2$ CVn Stars
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arXiv
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| Natura: | Preprint |
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2023
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| _version_ | 1866909077009858560 |
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| author | Heinze, A. N. Flewelling, Heather Huber, Mark E. |
| author_facet | Heinze, A. N. Flewelling, Heather Huber, Mark E. |
| contents | We previously reported a rare class of variable star light curves isolated from a sample of 4.7 million candidate variables from the ATLAS survey. Dubbed `UCBH' light curves, they have broad minima and narrow, symmetrical maxima, with typical periods of 1-10 days and amplitudes of 0.05--0.20 mag. They maintain constant amplitude, shape, and phase coherence over multiple years, but do not match any known class of pulsating variables. A localized bright spot near the equator of a rotating star will produce a UCBH-type light curve for most viewing geometries. Most stars that exhibit rotational variability caused primarily by a single bright feature should therefore appear as UCBH stars, although a rotating bright spot is not the only thing that could produce a UCBH-type lightcurve. We have spectroscopically investigated fourteen UCBH stars and found ten of them to be Ap/Bp stars: A-type or B-type stars with greatly enhanced photospheric abundances of specific heavy elements. Rotationally variable Ap/Bp stars are referred to as $α^2$ CVn variables. Most ATLAS UCBH stars are therefore $α^2$ CVn stars, although only a minority of $α^2$ CVn stars in the literature have UCBH light curves. The fact that $α^2$ CVn stars dominate the UCBH class suggests that lone bright spots with sufficient size and contrast develop more readily on Ap/Bp stars than on any other type. The $α^2$ CVn UCBH stars may be characterized by a specific magnetic field topology, making them intriguing targets for future Zeeman-Doppler imaging. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2309_04905 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Most Rotational Variables Dominated by a Single Bright Feature are $α^2$ CVn Stars Heinze, A. N. Flewelling, Heather Huber, Mark E. Solar and Stellar Astrophysics We previously reported a rare class of variable star light curves isolated from a sample of 4.7 million candidate variables from the ATLAS survey. Dubbed `UCBH' light curves, they have broad minima and narrow, symmetrical maxima, with typical periods of 1-10 days and amplitudes of 0.05--0.20 mag. They maintain constant amplitude, shape, and phase coherence over multiple years, but do not match any known class of pulsating variables. A localized bright spot near the equator of a rotating star will produce a UCBH-type light curve for most viewing geometries. Most stars that exhibit rotational variability caused primarily by a single bright feature should therefore appear as UCBH stars, although a rotating bright spot is not the only thing that could produce a UCBH-type lightcurve. We have spectroscopically investigated fourteen UCBH stars and found ten of them to be Ap/Bp stars: A-type or B-type stars with greatly enhanced photospheric abundances of specific heavy elements. Rotationally variable Ap/Bp stars are referred to as $α^2$ CVn variables. Most ATLAS UCBH stars are therefore $α^2$ CVn stars, although only a minority of $α^2$ CVn stars in the literature have UCBH light curves. The fact that $α^2$ CVn stars dominate the UCBH class suggests that lone bright spots with sufficient size and contrast develop more readily on Ap/Bp stars than on any other type. The $α^2$ CVn UCBH stars may be characterized by a specific magnetic field topology, making them intriguing targets for future Zeeman-Doppler imaging. |
| title | Most Rotational Variables Dominated by a Single Bright Feature are $α^2$ CVn Stars |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2309.04905 |