Six new rapidly oscillating Ap stars in the Kepler long-cadence data using super-Nyquist asteroseismology

Hey, Daniel R.; Holdsworth, Daniel Luke; Bedding, Timothy R.; Murphy, Simon J.; Cunha, M. S.; Kurtz, D. W.; Huber, Daniel; Fulton, Benjamin J.; Howard, Andrew W.

doi:10.1093/mnras/stz1633

Cited by 26 publications

(36 citation statements)

References 83 publications

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“…Although these stars pulsate above the Nyquist frequency, as does KIC 7582608, Hey et al (2019) was able to apply the oblique pulsator model to four of the six stars and found significant frequency variability in three of them. However, it seems that all six stars show a degree of frequency variability, as evidenced in the right column of Figure 3.…”

Section: Long Cadence Observationsmentioning

confidence: 90%

“…The first, KIC 7582608, was identified in SuperWASP photometry, with the Kepler data subsequently analyzed by Holdsworth et al (2014b). The other 6 stars were identified as roAp stars by Hey et al (2019) via a search of the 4-yr data set in the super-Nyquist regime.…”

Section: Long Cadence Observationsmentioning

confidence: 99%

“…The other six roAp stars observed with Kepler in LC mode were KIC 6631188, KIC 7018170, KIC 10685175, KIC 11031749, KIC 11296437, and KIC 11409673 (Figure 3). These stars were identified in a novel way by Hey et al (2019). By selecting all stars in the Kepler data set with T eff > 6, 000 K, they identified variable stars by calculating the skewness of high-pass filtered light curves, and searching for non-aliased peaks.…”

Section: Long Cadence Observationsmentioning

confidence: 99%

“…Again, the source of the frequency variability is unclear in these stars, but for KIC 11031749 the change seems to be cyclic, but on the order of the length of the Kepler data set, making conclusions uncertain. Given the stellar parameters derived by Hey et al (2019), two of the roAp stars show pulsations above the theoretical cut-off limit, an upper frequency limit where pulsations are not driven in models of non-magnetic stars of the same fundamental parameters (e.g., Shibahashi and Saio, 1985b;Gautschy et al, 1998;Sousa and Cunha, 2011), thus providing more examples to challenge the theoretical models of these stars.…”

Section: Long Cadence Observationsmentioning

confidence: 99%

“…The rapid oscillations in Ap stars were first discovered through the targeted observations of these stars by Kurtz (1978), with the seminal paper following a few years later (Kurtz, 1982). Since their discovery, over 75 roAp stars have been identified through ground-and space-based observations (e.g., Martinez and Kurtz, 1994a;Kochukhov et al, 2013;Holdsworth et al, 2014a;Joshi et al, 2016;Cunha et al, 2019;Hey et al, 2019). They show pulsational variability in the range 5-24 min and pulsate in low degree (ℓ ≤ 3), high-overtone (n > 15) modes that are thought to be driven by the κ-mechanism acting on the H I ionization zone (e.g., Balmforth et al, 2001;Saio, 2005).…”

Section: Introductionmentioning

confidence: 99%

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The roAp Stars Observed by the Kepler Space Telescope

Holdsworth

2021

Front. Astron. Space Sci.

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Before the launch of the Kepler Space Telescope, most studies of the rapidly oscillating Ap (roAp) stars were conducted with ground-based photometric B observations, supplemented with high-resolution time-resolved spectroscopy and some space observations with the WIRE, MOST, and BRITE satellites. These modes of observation often only provided information on a single star at a time, however, Kepler provided the opportunity to observe hundreds of thousands of stars simultaneously. Over the duration of the primary 4 year Kepler mission, and its 4 year reconfigured K2 mission, the telescope observed at least 14 new and known roAp stars. This paper provides a summary the results of these observations, including a first look at the entire data sets, and provides a look forward to NASA's TESS mission.

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Section: Long Cadence Observationsmentioning

confidence: 90%

Section: Long Cadence Observationsmentioning

confidence: 99%

Section: Long Cadence Observationsmentioning

confidence: 99%

Section: Long Cadence Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The roAp Stars Observed by the Kepler Space Telescope

Holdsworth

2021

Front. Astron. Space Sci.

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Oblique Pulsation: New, Challenging Observations with TESS Data

Kurtz

Holdsworth

2020

Astrophysics and Space Science Proceedings

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Long-period Ap stars discovered with TESS data: The northern ecliptic hemisphere

Mathys

Kurtz

Holdsworth

2022

A&A

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The rotation periods of the magnetic Ap stars span five to six orders of magnitude. While it is well established that period differentiation must have taken place at the pre-main sequence stage, the physical processes that lead to it remain elusive. The existence of Ap stars that have rotation periods of tens to hundreds of years is particularly intriguing, and their study represents a promising avenue to gain additional insight into the origin and evolution of rotation in Ap stars. Historically, almost all the longest period Ap stars known have been found to be strongly magnetic; very few weakly magnetic Ap stars with very long periods have been identified and studied. To remedy that, we showed how a systematic search based on the analysis of TESS photometric data could be performed to identify super-slowly rotating Ap (ssrAp) stars independently of the strengths of their magnetic fields, with the intention to characterise the distribution of the longest Ap star rotation periods in an unbiased manner. We successfully applied this method to the analysis of the TESS 2-min cadence observations of Ap stars of the southern ecliptic hemisphere. For our present study, we applied the same approach to the analysis of the TESS 2-min cadence observations of Ap stars of the northern ecliptic hemisphere. We confirm that the technique leads to the reliable identification of ssrAp star candidates in an unbiased manner. We find 67 Ap stars with no rotational variability in the northern ecliptic hemisphere TESS data. Among them, 46 are newly identified ssrAp star candidates, which is double the number found in the southern ecliptic hemisphere. We confirm that super-slow rotation tends to occur less frequently in weakly magnetic Ap stars than in strongly magnetic stars. We present new evidence of the existence of a gap between ∼2 kG and ∼3 kG in the distribution of the magnetic field strengths of long period Ap stars. We also confirm that the incidence of roAp stars is higher than average in slowly rotating Ap stars. We report the unexpected discovery of nine definite and five candidate δ Sct stars, and of two eclipsing binaries. This work paves the way for a systematic, unbiased study of the longest period Ap stars, with a view to characterise the correlations between their rotational, magnetic, and pulsational properties.

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Six new rapidly oscillating Ap stars in the Kepler long-cadence data using super-Nyquist asteroseismology

Cited by 26 publications

References 83 publications

The roAp Stars Observed by the Kepler Space Telescope

The roAp Stars Observed by the Kepler Space Telescope

Oblique Pulsation: New, Challenging Observations with TESS Data

Long-period Ap stars discovered with TESS data: The northern ecliptic hemisphere

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