MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’

Shultz, Matt; Johnston, C.; Labadie-Bartz, Jonathan; Petit, Véronique; David-Uraz, Alexandre; Kochukhov, O.; Wade, G. A.; Pepper, Joshua; Stassun, Keivan G.; Rodriguez, Joseph E.; Lund, Michael B.; James, D. J.

doi:10.1093/mnras/stz2846

Cited by 24 publications

(19 citation statements)

References 70 publications

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“…The light curve of HD 102797 shows eclipses, which may either originate from a contaminating star or from the Ap star itself. If the latter, this would be only the fourth Ap star known in an eclipsing binary (Kochukhov et al 2018;Skarka et al 2019;Shultz et al 2019). Finally, HD 94660 and HD 116458 both show variability of the type observed in cool stars.…”

Section: Discussionmentioning

confidence: 84%

Long-period Ap stars discovered with TESS data

Mathys

Kurtz

Holdsworth

2020

A&A

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The TESS space mission’s primary goal is to search for exoplanets around bright, nearby stars. Because of the high-precision photometry required for the main mission, it is also producing superb data for asteroseismology, eclipsing binary stars, gyrochronology, indeed any field of stellar astronomy where the data are variable light curves. In this work we show that the TESS data are excellent for astrophysical inference from peculiar stars that show no variability. Ap stars have the strongest magnetic fields of any main-sequence star. Some Ap stars have also been shown to have rotation periods of months, years, decades, and even centuries. The astrophysical cause of their slow rotation – the braking mechanism – is not known with certainty. These stars are rare: there are currently about three dozen with known periods. Magnetic Ap stars have long-lived spots that allow precise determination of their rotation periods. We argue and show that most Ap stars with TESS data that show no low-frequency variability must have rotation periods longer than, at least, a TESS sector of 27 d. From this we find 60 Ap stars in the southern ecliptic hemisphere TESS data with no rotational variability, of which at most a few can be pole-on, and six likely have nearly aligned magnetic and rotation axes. Of the other 54, 31 were previously known to have long rotation periods or very low projected equatorial velocities, which proves our technique; 23 are new discoveries. These are now prime targets for long-term magnetic studies. We also find that 12 of the 54 (22%) long-period Ap stars are roAp stars, versus only 3% (29 out of 960) of the other Ap stars studied with TESS in Sectors 1–13, showing that the roAp phenomenon is correlated with rotation, although this correlation is not necessarily causal. In addition to probing rotation in Ap stars, these constant stars are also excellent targets to characterise the instrumental behaviour of the TESS cameras, as well as for the CHEOPS and PLATO missions. This work demonstrates astrophysical inference from nonvariable stars – we can get “something for nothing”.

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Section: Discussionmentioning

confidence: 84%

Long-period Ap stars discovered with TESS data

Mathys

Kurtz

Holdsworth

2020

A&A

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“…Magnetic Ap (or late Bp) stars in eclipsing binaries are rare. To the best of our knowledge, only five have been reported in the literature: HD 123335 (Bp He wk Sr; Hensberge et al 2007), HD 66051 (A0p Si; Kochukhov et al 2018), HD 99458 (Skarka et al 2019), HD 62658 (B9p Si;Shultz et al 2019a), and HD 102797 (B9p Si; Paper I). The spectral types are from Renson & Manfroid (2009), except for HD 99458, whose peculiarity was noted by Skarka et al (2019).…”

Section: Eclipsing Binariesmentioning

confidence: 97%

Long-period Ap stars discovered with TESS data: The northern ecliptic hemisphere

Mathys,

Kurtz,

Holdsworth

2022

Preprint

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The rotation periods of the magnetic Ap stars span five to six orders of magnitude. While it is well established that period differentiation must have taken place at the pre-main sequence stage, the physical processes that lead to it remain elusive. The existence of Ap stars that have rotation periods of tens to hundreds of years is particularly intriguing, and their study represents a promising avenue to gain additional insight into the origin and evolution of rotation in Ap stars. Historically, almost all the longest period Ap stars known have been found to be strongly magnetic; very few weakly magnetic Ap stars with very long periods have been identified and studied. To remedy that, we showed how a systematic search based on the analysis of TESS photometric data could be performed to identify super-slowly rotating Ap (ssrAp) stars independently of the strengths of their magnetic fields, with the intention to characterise the distribution of the longest Ap star rotation periods in an unbiased manner. We successfully applied this method to the analysis of the TESS 2-min cadence observations of Ap stars of the southern ecliptic hemisphere.For our present study, we applied the same approach to the analysis of the TESS 2-min cadence observations of Ap stars of the northern ecliptic hemisphere. We confirm that the technique leads to the reliable identification of ssrAp star candidates in an unbiased manner. We find 67 Ap stars with no rotational variability in the northern ecliptic hemisphere TESS data. Among them, 46 are newly identified ssrAp star candidates, which is double the number found in the southern ecliptic hemisphere. We confirm that super-slow rotation tends to occur less frequently in weakly magnetic Ap stars than in strongly magnetic stars. We present new evidence of the existence of a gap between ∼2 kG and ∼3 kG in the distribution of the magnetic field strengths of long period Ap stars. We also confirm that the incidence of roAp stars is higher than average in slowly rotating Ap stars. We report the unexpected discovery of nine definite and five candidate δ Sct stars, and of two eclipsing binaries. This work paves the way for a systematic, unbiased study of the longest period Ap stars, with a view to characterise the correlations between their rotational, magnetic, and pulsational properties.

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“…Formally, none of the studied objects has a field detected, however, one of the stars has a longitudinal field of the order of 2-4 kG. Shultz et al (2019a) describe the results of the study of the magnetic Bp star HD 62658, an eclipsing binary with two identical non-magnetic components. The light curves of the system were obtained from the KELT and TESS satellites.…”

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confidence: 97%

Magnetic Fields of Chemically Peculiar and Related Stars. VII. Main Results of 2020 and Near-Future Prospects

Romanyuk

2021

Astrophys. Bull.

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We present a review of the papers written in the field of stellar magnetism studies in 2020. More than 70 original papers related to different areas of the specified scientific topics have been analyzed. Instruments, methods of analysis, and software are considered, as well as: chemically peculiar stars and their identification; magnetic fields, chemical abundance, and photometry of chemically peculiar stars; magnetic white dwarfs, active cool stars and other objects. In the field of stellar magnetism research, 6–7 scientific groups continue to work actively using the world’s largest telescopes, which fact indicates the relevance and importance of the problem under study.

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MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’

Cited by 24 publications

References 70 publications

Long-period Ap stars discovered with TESS data

Long-period Ap stars discovered with TESS data

Long-period Ap stars discovered with TESS data: The northern ecliptic hemisphere

Magnetic Fields of Chemically Peculiar and Related Stars. VII. Main Results of 2020 and Near-Future Prospects

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