BD-19 5044L: discovery of a short-period SB2 system with a magnetic Bp primary in the open cluster IC 4725

Landstreet, J. D.; Kochukhov, Oleg; Alécian, E.; Bailey, J. D.; Mathis, S.; Neiner, C.; Wade, G. A.

doi:10.1051/0004-6361/201630233

Cited by 18 publications

(17 citation statements)

References 48 publications

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“…The spectroscopic binary fraction of Ap stars is of the order 45 per cent (Carrier et al 2002;Mathys 2017). However, the short period (P < 20 d) spectroscopic binary fraction amongst the Ap stars is very low, with only about 10 known (Landstreet et al 2017). Although some roAp stars have been observed to be in visual binary systems (Schöller et al 2012), there is only one known to be a spectroscopic binary: HD 42659.…”

Section: Parametermentioning

confidence: 99%

HD 42659: the only known roAp star in a spectroscopic binary observed with B photometry, TESS, and SALT

Holdsworth

Saio

Kurtz

2019

Monthly Notices of the Royal Astronomical Society

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We present a multi-instrument analysis of the rapidly oscillating Ap (roAp) star HD 42659. We have obtained B photometric data for this star and use these data, in conjunction with TESS observations, to analyse the high-frequency pulsation in detail. We find a triplet which is split by the rotation frequency of the star (ν rot = 0.3756 d −1 ; P rot = 2.66 d) and present both distorted dipole and distorted quadrupole mode models. We show that the pulsation frequency, 150.9898 d −1 (P puls = 9.54 min) is greater than the acoustic cutoff frequency. We utilise 27 high-resolution (R ≃ 65 000), high signal-to-noise (∼ 120) spectra to provide new orbital parameters for this, the only known roAp star to be in a short period binary (P orb = 93.266 d). We find the system to be more eccentric than previously thought, with e = 0.317, and suggest the companion is a mid-F to early-K star. We find no significant trend in the average pulsation mode amplitude with time, as measured by TESS, implying that the companion does not have an affect on the pulsation in this roAp star. We suggest further photometric observations of this star, and further studies to find more roAp stars in close binaries to characterise how binarity may affect the detection of roAp pulsations.

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Section: Parametermentioning

confidence: 99%

HD 42659: the only known roAp star in a spectroscopic binary observed with B photometry, TESS, and SALT

Holdsworth

Saio

Kurtz

2019

Monthly Notices of the Royal Astronomical Society

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“…They also found a dearth of ApBp stars in close binary systems, yet a binary fraction for wide binary systems that is typical of normal A and B stars. Later works by Gerbaldi et al (1985), North et al (1998), Carrier et al (2002, Mathys (2017), and Landstreet et al (2017) have confirmed the dearth of ApBp stars in close-binary systems, which are typically defined as orbital periods less than 3 d. The only known exception being HD 200405, which has a binary orbital period of 1.635 d (Carrier et al 2002).…”

Section: Introductionmentioning

confidence: 96%

K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B stars

Bowman

Buysschaert

Neiner

et al. 2018

A&A

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Context. The physics of magnetic hot stars and how a large-scale magnetic field affects their interior properties is largely unknown. Few studies have combined high-quality observations and modelling of magnetic pulsating stars, known as magneto-asteroseismology, primarily because of the dearth of detected pulsations in stars with a confirmed and well-characterised large-scale magnetic field. Aims. We aim to characterise observational signatures of rotation and pulsation in chemically peculiar candidate magnetic stars using photometry from the K2 space mission. Thus, we identify the best candidate targets for ground-based, optical spectropolarimetric follow-up observations to confirm the presence of a large-scale magnetic field. Methods. We employed customised reduction and detrending tools to process the K2 photometry into optimised light curves for a variability analysis. We searched for the periodic photometric signatures of rotational modulation caused by surface abundance inhomogeneities in 56 chemically peculiar A and B stars. Furthermore, we searched for intrinsic variability caused by pulsations (coherent or otherwise) in the amplitude spectra of these stars. Results. The rotation periods of 38 chemically peculiar stars are determined, 16 of which are the first determination of the rotation period in the literature. We confirm the discovery of high-overtone roAp pulsation modes in HD 177765 and find an additional 3 Ap and Bp stars that show evidence of high-overtone pressure modes found in roAp stars in the form of possible Nyquist alias frequencies in their amplitude spectra. Furthermore, we find 6 chemically peculiar stars that show evidence of intrinsic variability caused by gravity or pressure pulsation modes. Conclusions. The discovery of pulsations in a non-negligible fraction of chemically peculiar stars make these stars high-priority targets for spectropolarimetric campaigns to confirm the presence of their expected large-scale magnetic field. The ultimate goal is to perform magneto-asteroseismology and probe the interior physics of magnetic pulsating stars.

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“…Both telescopes have a 42 mm aperture, a 26 • x 26 • field of view, and a pixel scale of 23 ′′ . The KELT survey is designed to detect giant exoplanets transiting stars with apparent magnitudes between 8 V 11, and is well-suited for detecting periodic signals in stellar light curves down to amplitudes of a few mmag (Labadie-Bartz et al 2019). The single passband of the KELT telescopes is roughly equivalent to a broadband V + R + I filter.…”

Section: Keltmentioning

confidence: 99%

“…Since only a handful of magnetic close binaries are known (a list is provided by Landstreet et al 2017), there is value in both increasing the sample of such stars, as well as closely studying the known systems. Recently, examination of the Kilodegree Extremely Little Telescope (KELT; Pepper et al 2007) light curve of the little-studied star HD 62658 revealed the presence of eclipses as well as outof-eclipse brightness modulations.…”

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confidence: 99%

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

Shultz

Johnston

Labadie-Bartz

et al. 2019

Monthly Notices of the Royal Astronomical Society

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HD 62658 (B9p V) is a little-studied chemically peculiar star. Light curves obtained by the Kilodegree Extremely Little Telescope (KELT) and Transiting Exoplanet Survey Satellite (TESS) show clear eclipses with a period of about 4.75 d, as well as out-of-eclipse brightness modulation with the same 4.75 d period, consistent with synchronized rotational modulation of surface chemical spots. High-resolution ESPaDOnS circular spectropolarimetry shows a clear Zeeman signature in the line profile of the primary; there is no indication of a magnetic field in the secondary. PHOEBE modelling of the light curve and radial velocities indicates that the two components have almost identical masses of about 3 M ⊙ . The primary's longitudinal magnetic field B z varies between about +100 and −250 G, suggesting a surface magnetic dipole strength B d = 850 G. Bayesian analysis of the Stokes V profiles indicates B d = 650 G for the primary and B d < 110 G for the secondary. The primary's line profiles are highly variable, consistent with the hypothesis that the out-of-eclipse brightness modulation is a consequence of rotational modulation of that star's chemical spots. We also detect a residual signal in the light curve after removal of the orbital and rotational modulations, which might be pulsational in origin; this could be consistent with the weak line profile variability of the secondary. This system represents an excellent opportunity to examine the consequences of magnetic fields for stellar structure via comparison of two stars that are essentially identical with the exception that one is magnetic. The existence of such a system furthermore suggests that purely environmental explanations for the origin of fossil magnetic fields are incomplete.

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BD-19 5044L: discovery of a short-period SB2 system with a magnetic Bp primary in the open cluster IC 4725

Cited by 18 publications

References 48 publications

HD 42659: the only known roAp star in a spectroscopic binary observed with B photometry, TESS, and SALT

HD 42659: the only known roAp star in a spectroscopic binary observed with B photometry, TESS, and SALT

K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B stars

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

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