Metallicism and pulsation: the discovery of δ Scuti variability in a classical Am star, HD 1097

Kurtz, D. W.

doi:10.1093/mnras/238.4.1077

Cited by 49 publications

(38 citation statements)

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“…The observational exclusion of pulsation in classical Am stars remained, despite several counterexamples that were all dismissed by Kurtz et al (1976), until 1989 when the classical Am star HD 1097 was shown to be a δ Sct star (Kurtz, 1989).…”

Section: Pulsating Am Starsmentioning

confidence: 99%

Investigating the A-Type Stars Using Kepler Data

Murphy

2015

Springer Theses

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Rotation is a key physical process operating in the A stars. We present a method by which rotation periods might be measured with Fourier transforms of Kepler data, potentially removing the requirement of spectroscopic observations to acquire similar information. Angular rotational velocities reach their maximum at about A5, but slowly rotating A stars are also seen and these tend to be chemically peculiar. For Ap stars, rotational braking is understood, but too few progenitors are observed. A review of a rare class of stars, the 'sn' stars, leads us to suggest these may contribute to the 'missing' Ap progenitors. For Am stars, we find the tidal braking mechanisms proposed in the literature induce mixing that is incompatible with observed abundance anomalies. At the other end of the scale are the λ Boo stars, whose rotation velocities are above average. The two main theories for the origin of their metal underabundances are discussed and it is suggested that both of them imply the λ Boo stars contain a high fraction of pulsators -a suggestion that is backed up by observations in the literature. Many λ Boo stars also have circumstellar material, suggesting they are potential planet hosts. This, and the use of asteroseismology to study their interiors, are two excellent reasons to adopt them as prime targets for detailed investigation with Kepler.Pulsation is a common phenomenon in A stars. The δ Sct stars receive wide attention but the fraction of stars that pulsate at the 50 µmag level is shown to be only 56 per cent. The non-δ Sct stars in the δ Sct instability strip receive far less attention. Some of these stars, without appreciable granulation or stellar winds, ii are probably the least variable objects on the HR diagram. It is shown that they have the potential to be among the most peculiar Am stars. Their investigation has led to two important conclusions: (1) the presence of γ Dor pulsation in non-δ Sct stars in the δ Sct instability strip may inhibit the development of the expected Am peculiarities; and (2) chemically normal, non-δ Sct stars in the δ Sct instability strip do exist at the µmag level.Fourier transforms are invaluable tools in the field of stellar pulsation. TheKepler Space Telescope is providing data of exquisite precision, and thus more detail is seen in the Fourier transform than ever before. Truly understanding the properties of the data is fundamental to their successful utilisation. Through statistical analysis of noise levels in over 20 000 stars, granulation is concluded to be visible in Fourier transforms of stars cooler than 7500 K. Another property investigated is the Nyquist frequency. We found that periodically modulated sampling on board Kepler allows distinction between real pulsation frequencies and Nyquist aliases, even when those real frequencies exceed the Nyquist frequency of the data. This discovery opens up study of many hundreds of stars previously thought to have insurmountable Nyquist ambiguities in their data.iii ContentsAbstract ii In Don Kurtz, I have h...

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Section: Pulsating Am Starsmentioning

confidence: 99%

Investigating the A-Type Stars Using Kepler Data

Murphy

2015

Springer Theses

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“…However, there are some important exceptions. Classical Am stars that have been proven to be low-amplitude δ Scuti stars do exist, such as HD 1097 (Kurtz 1989), HD 13038 (Martinez et al 1999a), and HD 13079 (Martinez et al 1999b). Recently, more Ap and Am stars showing pulsation were reported by Joshi et al (2006).…”

Section: Comparison With Single δ Scuti Starsmentioning

confidence: 99%

Abundance analysis of seven δ Scuti stars

Fossati

Kolenberg

Reegen

et al. 2008

A&A

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Context. The current knowledge of the abundance pattern in δ Scuti stars is based on the analysis of just a few field stars. Aims. We aim to determine the general chemical properties of the atmospheres of δ Scuti stars based on a statistically relevant sample of stars and will investigate whether the abundance pattern is close to solar, an assumption generally made for pulsation models. Methods. We have analysed high-resolution, high signal-to-noise ratio spectra of seven field δ Scuti stars. We derived the fundamental parameters and the photospheric abundances and compared them to a similar sample of cluster δ Scuti stars. Results. With the use of a t-test we demonstrated that there is no difference between the two samples, which allows us to merge them, resulting in a sample of fifteen δ Scuti stars. We did not find any substantial difference between the abundance pattern of our sample of δ Scuti stars and a sample of normal early A-and late F-type stars. One field star in our sample, HD 124953, is most likely a pulsating Am star.

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“…5). It might be a star similar to HD 1097: an Am-type star which is pulsating with low amplitudes and was discovered by Kurtz (1989Kurtz ( , 2000. Unfortunately ∆a photometry was not made for this star.…”

Section: Star #508mentioning

confidence: 99%

Rotation of stars in NGC 6134

Rasmussen¹,

Bruntt²,

Frandsen³

et al. 2002

A&A

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Abstract. We present results of spectroscopic observations of selected stars in the southern open cluster NGC 6134. We have determined the rotational velocities of the six known δ Scuti stars in NGC 6134 as well as several other non-variable stars with similar colour temperature in order to investigate if v sin i and variability is somehow connected: we find no such correlation. We also compare the distribution of v sin i of δ Scuti stars and non-variable stars with four other well-studied open clusters to look for any systematic behaviour, but we find no conclusive evidence for v sin i and variability to be connected. We have also used the spectra to carry out an abundance analysis of the δ Scuti stars in NGC 6134 to confirm the high metal content of the cluster. We find [Fe/H] = +0.38 ± 0.05 which is in agreement with the result obtained from Strömgren photometry. We also present ∆a photometry of the cluster, but we find no chemical peculiar stars based on this index.

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Metallicism and pulsation: the discovery of δ Scuti variability in a classical Am star, HD 1097

Cited by 49 publications

References 0 publications

Investigating the A-Type Stars Using Kepler Data

Investigating the A-Type Stars Using Kepler Data

Abundance analysis of seven δ Scuti stars

Rotation of stars in NGC 6134

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