The roAp Stars Observed by the Kepler Space Telescope

Abstract

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.

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

“…Since the frequency variability is only seen in one mode, it is likely to be intrinsic to the star, rather than caused by binary motion, for example. This type of frequency variability seems common in the roAp stars studied with high-precision data (Holdsworth 2021), with a possible explanation of stochastic perturbations of classical pulsators (Avelino et al 2020;Cunha et al 2020), although this is currently untested.…”

“…★ e-mail:dlholdsworth@uclan.ac.uk Weiss et al 2016;Hey et al 2019;Balona et al 2019;Cunha et al 2019;Holdsworth 2021). To date, including the results presented here, there are 88 roAp stars known in the literature.…”

Highlights of Discoveries for $δ$ Scuti Variable Stars From the Kepler Era

“…In Ap stars,"chemical spots" form at the magnetic poles that cause brightness contrasts that show up as light curve variations as the star rotates; these variables are also called α 2 CVn variables. Misalignment of the dipole magnetic field axis and rotation axis is the preferred explanation for properties of high-frequency p modes of the rapidly-oscillating Ap (roAp) stars (see Kurtz [1982] and review by Holdsworth [2021], this collection).…”

“…The A-F main-sequence stars occupy a small region in the center of the H-R diagram, but have been differentiated into not only δ Sct and γ Doradus (abbreviated as γ Dor) variables [Pollard, 2009;Balona et al, 2011a], but also metallic-line A (Am), [Smalley et al, 2017], peculiar abundance A (Ap) [Mathys et al, 2020], rapidly-oscillating Ap (roAp) [Holdsworth, 2021] stars, α 2 CVn variables [Sikora et al, 2019], λ Boo stars [Murphy and Paunzen, 2017], the High Amplitude δ Sct (HADS) [McNamara, 2000] and SX Phe [Nemec et al, 2017] stars, blue stragglers [Rain et al, 2021], and the maybe 'mythical' 1 Maia variables [Balona, 2018;White et al, 2017;Daszyńska-Daszkiewicz et al, 2017;Breger, 1980;Cox, 1983]. Kepler observations have revealed overlap and commonalities among these types, pointing the way to a more fundamental understanding of the origins of the diverse phenomena seen in these stars.…”

Highlights of Discoveries for δ Scuti Variable Stars From the Kepler Era

“…The A-F main-sequence stars occupy a small region in the center of the H-R diagram, but have been differentiated into not only δ Sct and γ Doradus (abbreviated as γ Dor) variables (Pollard, 2009;Balona et al, 2011a), but also metallic-line A (Am) (Smalley et al, 2017), peculiar abundance A (Ap) (Mathys et al, 2020), rapidly-oscillating Ap (roAp) (Holdsworth, 2021) stars, α 2 CVn variables (Sikora et al, 2019), λ Boo stars (Murphy and Paunzen, 2017), the High Amplitude δ Sct (HADS) (McNamara, 2000) and SX Phe (Nemec et al, 2017) stars, blue stragglers (Rain et al, 2021), and the maybe "mythical" 1 Maia variables (Breger, 1980;Cox, 1983;Daszyńska-Daszkiewicz et al, 2017;White et al, 2017;Balona, 2018). Kepler observations have revealed overlap and commonalities among these types, pointing the way to a more fundamental understanding of the origins of the diverse phenomena seen in these stars.…”