Araunah

Mathys, Hans-Peter

doi:10.1515/ebr.araunah

Cited by 11 publications

(33 citation statements)

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“…This is likely to be incorrect because of the spots on the surface of roAp stars. Mathys (1985) showed, with his spotted pulsator model, that the spots on the surface of the Ap stars contribute to pulsations, albeit in a small way (as shown by Kurtz 1990).…”

Section: Discussion S a N D C O N C L U S I O N Smentioning

confidence: 95%

Determining temperature amplitude as a function of depth in the atmospheres of rapidly oscillating Ap stars

Medupe

Kurtz

1998

Monthly Notices of the Royal Astronomical Society

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We present numerical models based on realistic treatment of the intensity spectrum (from model atmospheres), and demonstrate that they are consistent with Kurtz and Medupe's recent formula in showing that limb darkening is too small an effect to explain the observed sharp decline of pulsation light amplitude with wavelength in rapidly oscillating Ap stars. Kurtz and Medupe's formula is shown to be a special form of Watson's earlier general formula for non‐radial light variations of a star pulsating in any mode (lm). Using a technique suggested by Kurtz and Medupe we derive temperature semi‐amplitude as a function of depth in the atmospheres of α Cir and HR 3831, assuming that we can neglect non‐adiabatic effects.

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Section: Discussion S a N D C O N C L U S I O N Smentioning

confidence: 95%

Determining temperature amplitude as a function of depth in the atmospheres of rapidly oscillating Ap stars

Medupe

Kurtz

1998

Monthly Notices of the Royal Astronomical Society

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“…This star is part of the Scorpio-Centaurus association and has a strong magnetic field with a mean magnetic field modulus of < B > 16 kG (Thompson et al 1987;Mathys 1995;Bailey & Landstreet 2013;Mathys 2017). HD 147010 has a rotation period of P rot = 3.9209 ± 0.0048 d (Wraight et al 2012).…”

Section: Epic 204964091 -Hd 147010mentioning

confidence: 99%

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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“…The only alternative to the oblique pulsator model is the spotted pulsator model proposed by Mathys (1985). In this model the axis of pulsation is the rotational axis (actually any axis) and the amplitude modulation is not an aspect effect but an effect on the pulsational light amplitude created by the inhomogeneous abundance and temperature distribution in the photosphere.…”

Section: T H E M O D E S O F P U L S At I O Nmentioning

confidence: 99%

Radial velocity study of the roAp star HR 3831

Balona

2002

Monthly Notices of the Royal Astronomical Society

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We present results of 566 high‐dispersion echelle spectra of the roAp star HR 3831. We obtain radial velocities of different ions by cross‐correlation with suitable templates. The inhomogeneous abundance distribution results in different rotational velocity curves for different ions. We confirm the large pulsational amplitude in doubly ionized rare‐earth ions. In addition we show that, whereas Hα has a large pulsational velocity amplitude, the pulsational velocity amplitudes in Hβ and Hγ are below the detection limit. This supports the idea that the pulsational amplitude is a function of height and that there is a layer enriched with rare earths in the upper atmosphere. We present a list of lines where the pulsational velocity is the largest. In the radial velocities of the Nd iii line we are able to resolve the two frequencies of highest amplitude seen in the light variations. Co‐added spectra indicate that one of these frequencies is an axisymmetric mode [possibly (ℓ, m) = (2, 0)] and the other a non‐axisymmetric mode [possibly (2, −2)]. This confirms recent observations of non‐axisymmetric modes in roAp stars. We suggest that the presence of non‐axisymmetric modes is simply a consequence of the departure of the eigenfunction from a pure spherical harmonic inclined to the rotational axis and is not related to the Coriolis force. Hence the frequency splitting is precisely equal to the rotational frequency, as observed. Whereas the light variations show strong harmonics, these are not present in the radial velocities.

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Araunah

Cited by 11 publications

References 0 publications

Determining temperature amplitude as a function of depth in the atmospheres of rapidly oscillating Ap stars

Determining temperature amplitude as a function of depth in the atmospheres of rapidly oscillating Ap stars

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

Radial velocity study of the roAp star HR 3831

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