An investigation of the rotational properties of magnetic chemically peculiar stars

Netopil, M.; Paunzen, E.; Hümmerich, Stefan; Bernhard, Klaus

doi:10.1093/mnras/stx674

Cited by 73 publications

(83 citation statements)

References 73 publications

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“…The rotational period distribution is in very good agreement with the literature (e.g. Renson & Manfroid 2009;Netopil et al 2017) and shows the typical peak distribution in the 0.0 < log(P[d]) < 0.5 bin. We note that because of the time span and characteristics of the here employed photometric time-series data, we will have missed very slowly rotating ACV variables with periods of several years or more (Mathys 2017).…”

Section: Colour-magnitude Diagramsupporting

confidence: 88%

New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

Bernhard

Hümmerich

Paunzen

2020

Monthly Notices of the Royal Astronomical Society

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Magnetic chemically peculiar (mCP) stars allow the investigation of such diverse phenomena as atomic diffusion, magnetic fields and stellar rotation. The aim of the present investigation is to enhance our knowledge of the rotational properties of mCP stars by increasing the sample of objects with accurately determined rotational periods. To this end, archival photometric time-series data from the ASAS-3, KELT and MASCARA surveys were employed to improve existing rotational period information and derive rotational periods for mCP stars hitherto not known to be photometric variables. Our final sample consists of 294 mCP stars, a considerable amount of which (more than 40%) are presented here as photometric variables for the first time. In addition, we identified 24 mCP star candidates that show light variability in agreement with rotational modulation but lack spectroscopic confirmation. The rotational period distribution of our sample agrees well with the literature. Most stars are between 100 Myr and 1 Gyr old, with an apparent lack of very young stars. No objects were found on the zero age main sequence; several stars seem to have evolved to the subgiant stage, albeit well before the first dredge-up. We identified four eclipsing binaries (HD 244391, HD 247441, HD 248784 and HD 252519), which potentially host an mCP star. This is of great interest because mCP stars are very rarely found in close binary systems, particularly eclipsing ones. Using archival spectra, we find strong evidence that the HD 252519 system indeed harbours an mCP star component.

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Section: Colour-magnitude Diagramsupporting

confidence: 88%

New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

Bernhard

Hümmerich

Paunzen

2020

Monthly Notices of the Royal Astronomical Society

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“…We found that one, TIC 410451777 (HD 66295) is classified as B8/9p Si by Hartoog (1976). The rotation period is known to be 2.45 d (Netopil et al 2017) which is significantly different from what we find for TIC 410451752. The other stars in the region have no rotation period reported in the literature.…”

Section: Contamination and Multiplicitycontrasting

confidence: 85%

Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2

Cunha

Antoci

Holdsworth

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with periods around 4.7 min, making it the shortest period roAp star known to date. Four out of the five new roAp stars are multiperiodic. Three of these, and the singly-periodic one show the presence of rotational mode splitting. Individual frequencies are provided in all cases. In addition, seven previously known roAp stars are analysed. Additional modes of oscillation are found in some stars, while in others we are able to distinguish the true pulsations from possible aliases present in the ground-based data. We find that the pulsation amplitude in the TESS filter is typically a factor 6 smaller than that in the B filter which is usually used for ground-based observations. For four roAp stars we set constraints on the inclination angle and magnetic obliquity, through the application of the oblique pulsator model. We also confirm the absence of roAp-type pulsations down to amplitude limits of 6 and 13 µmag, respectively, in two of the best characterised non-oscillating Ap (noAp) stars. We announce 27 new rotational variables along with their rotation periods, and provide different rotation periods for seven other stars. Finally, we discuss how these results challenge state-of-the-art pulsation models for roAp stars.

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“…randomly distributed inclination angles (Netopil et al 2017), rotationally induced variability should be readily detectable with the employed data in this study. However, we were not able to detect variability with a statistically significant amplitude for any of our sample stars.…”

Section: Discussionmentioning

confidence: 82%

Search for stellar spots in field blue horizontal-branch stars

Paunzen

Bernhard

Hümmerich

et al. 2019

A&A

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Context. Blue horizontal-branch stars are Population II objects which are burning helium in their core and possess a hydrogen-burning shell and radiative envelope. Because of their low rotational velocities, diffusion has been predicted to work in their atmospheres. In many respects, blue horizontal-branch stars closely resemble the magnetic chemically peculiar stars of the upper main sequence, which show photometric variability caused by abundance spots on their surfaces. These spots are thought to be caused by diffusion and the presence of a stable magnetic field. However, the latter does not seem to be axiomatic. Aims. We searched for rotationally induced variability in 30 well-established bright field blue horizontal-branch stars in the solar neighbourhood and searched the literature for magnetic fields measurements of our targets. Methods. We employed archival photometric time series data from the All Sky Automated Survey (ASAS), All-Sky Automated Survey for Supernovae (ASAS-SN), and Wide Angle Search for Planets (SuperWASP) surveys. The data were carefully reduced and processed, and a time series analysis was applied using several different techniques. We also synthesized existing photometric and spectroscopic data of magnetic chemically peculiar stars in order to study possible different surface characteristics producing lower amplitudes. Results. In the accuracy limit of the employed data, no significant variability signals were found in our sample stars. The resulting upper limits for variability are given. Conclusions. We conclude that either no stellar surface spots are present in field blue horizontal-branch stars, or their characteristics (contrast, total area, and involved elements) are not sufficient to produce amplitudes larger than a few millimagnitudes in the optical wavelength region. New detailed models taking into account the elemental abundance pattern of blue horizontal-branch stars are needed to synthesize light curves for a comparison with our results.

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An investigation of the rotational properties of magnetic chemically peculiar stars

Cited by 73 publications

References 73 publications

New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data

Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2

Search for stellar spots in field blue horizontal-branch stars

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