Magnetic OB[A] Stars with TESS: probing their Evolutionary and Rotational properties (MOBSTER) – I. First-light observations of known magnetic B and A stars

David-Uraz, Alexandre; Neiner, C.; Sikora, J.; Bowman, D. M.; Petit, Véronique; Chowdhury, S.; Handler, G.; Pergeorelis, Michael; Cantiello, Matteo; Cohen, David H.; Erba, C.; Keszthelyi, Z.; Khalack, V.; Kobzar, Oleh; Kochukhov, Oleg; Labadie-Bartz, Jonathan; Lovekin, Catherine; Macinnis, R.; Owocki, S. P.; Pablo, H.; Shultz, Matthew; ud‐Doula, Asif; Wade, G. A.

doi:10.1093/mnras/stz1181

Cited by 51 publications

(24 citation statements)

References 137 publications

(189 reference statements)

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“…No rotation period is reported in the literature for this star with Mathys et al (2020b) classifying the star as a super slowly rotating Ap (ssrAp) star, although the longitudinal field measurements reported in the catalogue by Bagnulo et al (2015) do show some indication of variability on the time scale of a few years. No sign of rotation variability was found in any of the published analyses of the TESS data (Cunha et al 2019;David-Uraz et al 2019;Mathys et al 2020b).…”

Section: Tic 139191168mentioning

confidence: 87%

TESS cycle 1 observations of roAp stars with 2-min cadence data

Holdsworth

Cunha

Kurtz

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present the results of a systematic search for new rapidly oscillating Ap (roAp) stars using the 2-min cadence data collected by the Transiting Exoplanet Survey Satellite (TESS) during its Cycle 1 observations. We identify 12 new roAp stars. Amongst these stars we discover the roAp star with the longest pulsation period, another with the shortest rotation period, and six with multiperiodic variability. In addition to these new roAp stars, we present an analysis of 44 known roAp stars observed by TESS during Cycle 1, providing the first high-precision and homogeneous sample of a significant fraction of the known roAp stars. The TESS observations have shown that almost 60 per cent (33) of our sample of stars are multiperiodic, providing excellent cases to test models of roAp pulsations, and from which the most rewarding asteroseismic results can be gleaned. We report four cases of the occurrence of rotationally split frequency multiplets that imply different mode geometries for the same degree modes in the same star. This provides a conundrum in applying the oblique pulsator model to the roAp stars. Finally, we report the discovery of non-linear mode interactions in α Cir (TIC 402546736, HD 128898) around the harmonic of the principal mode – this is only the second case of such a phenomenon.

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Section: Tic 139191168mentioning

confidence: 87%

TESS cycle 1 observations of roAp stars with 2-min cadence data

Holdsworth

Cunha

Kurtz

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…This would be a new important step into the recent domain of magneto-asteroseismology, but such observational detections have not been made yet. The new TESS samples of pulsating OB stars are promising in this respect (David-Uraz et al 2019;Neiner et al, in prep.). To progress even further on magneto-seismic diagnostics, a non-perturbative treatment of the magnetic field would be needed to be able to consider (i) a magnetic field that is not confined inside the star, and (ii) stronger fields such as those of Ap stars.…”

Section: Discussionmentioning

confidence: 99%

Period spacings of gravity modes in rapidly rotating magnetic stars

Prat

Mathis

Neiner

et al. 2020

A&A

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Context. Stellar internal magnetic fields have recently been shown to leave a detectable signature on period spacing patterns of gravity modes. Aims. We investigate the effect of the obliquity of a mixed (poloidal and toroidal) dipolar internal fossil magnetic field with respect to the rotation axis on the frequency of gravity modes in rapidly rotating stars. Methods. We use the traditional approximation of rotation to compute non-magnetic modes, and a perturbative treatment of the magnetic field to compute the corresponding frequency shifts. We apply the new formalism to HD 43317, a magnetic, rapidly rotating, slowly pulsating B-type star, whose field has an obliquity angle of about 80 • . Results. We find that frequency shifts induced by the magnetic field on high-radial-order gravity modes are larger with increasing obliquity angle, when the magnetic axis is closer to the equatorial region, where these modes are trapped. The maximum value is reached for an obliquity angle of 90 • . This trend is observed for all mode geometries. Conclusions. Our results predict that the signature of an internal oblique dipolar magnetic field is detectable using asteroseismology of gravity modes.

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“…Their light curves (detrended following the procedure described by Bowman et al 2018), which show similarities with those of known magnetic stars (e.g. David-Uraz et al 2019), and the associated Lomb-Scargle periodograms are shown in Fig. 1.…”

Section: Target Selectionmentioning

confidence: 95%

MOBSTER – IV. Detection of a new magnetic B-type star from follow-up spectropolarimetric observations of photometrically selected candidates★

David-Uraz

Shultz

Petit

et al. 2021

Monthly Notices of the Royal Astronomical Society

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In this paper, we present results from the spectropolarimetric follow-up of photometrically selected candidate magnetic B stars from the MOBSTER project. Out of four observed targets, one (HD 38170) is found to host a detectable surface magnetic field, with a maximum longitudinal field measurement of 105±14 G. This star is chemically peculiar and classified as an α2 CVn variable. Its detection validates the use of TESS to perform a photometric selection of magnetic candidates. Furthermore, upper limits on the strength of a putative dipolar magnetic field are derived for the remaining three stars, and we report the discovery of a previously unknown spectroscopic binary system, HD 25709. Finally, we use our non-detections as case studies to further inform the criteria to be used for the selection of a larger sample of stars to be followed up using high-resolution spectropolarimetry.

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Magnetic OB[A] Stars with TESS: probing their Evolutionary and Rotational properties (MOBSTER) – I. First-light observations of known magnetic B and A stars

Cited by 51 publications

References 137 publications

TESS cycle 1 observations of roAp stars with 2-min cadence data

TESS cycle 1 observations of roAp stars with 2-min cadence data

Period spacings of gravity modes in rapidly rotating magnetic stars

MOBSTER – IV. Detection of a new magnetic B-type star from follow-up spectropolarimetric observations of photometrically selected candidates★

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