The search for roAp stars: null results and new candidates from Strömgren-Crawford photometry

Paunzen, E.; Handler, G.; Hoňková, K.; Jurýšek, Jakub; Mašek, M.; Dróżdż, M.; Janík, Ján; Ogłoza, W.; Hermansson, L.; Johansson, Mats I.; Jelínek, M.; Skarka, Marek; Zejda, Miloslav

doi:10.1088/1674-4527/18/11/135

Cited by 7 publications

(3 citation statements)

References 68 publications

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“…Unfortunately, most of our sample stars are also too faint to be observed by the TESS satellite (Sikora et al 2019). Therefore, new ground-based observations are needed to search for this type of variability in our sample stars (Paunzen et al 2015b(Paunzen et al , 2018.…”

Section: Rectified Intensitymentioning

confidence: 99%

A case study of ACV variables discovered in the Zwicky Transient Facility survey

Faltová

Kallova

Prišegen

et al. 2021

A&A

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Context. Magnetic chemically peculiar (mCP) stars exhibit complex atmospheres that allow the investigation of the interplay of atomic diffusion, magnetic fields, and stellar rotation. A non-uniform surface distribution of chemical elements and the non-alignment of the rotational and magnetic axes result in the variability of several observables. Photometrically variable mCP stars are referred to as α 2 Canum Venaticorum (ACV) variables. Aims. The present work presents a case study of known variables from the Zwicky Transient Facility (ZTF) survey, with the aim of investigating the survey's suitability for the detection and study of new ACV variables. Methods. Using suitable selection criteria based on the known characteristics of ACV variables, candidate ACV stars were selected from the ZTF Catalog of Periodic Variable Stars. All light curves were inspected in detail to select the most promising candidates. Where available, low-resolution spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) were employed to classify the stars on the MK system and confirm their status as mCP stars. Results. We have identified 86 new promising ACV star candidates. Fifteen of these stars have LAMOST spectra available that, in all cases, confirm them as classical mCP stars, which highlights the viability of our approach. We present astrophysical parameters for all sample stars that can be sorted into four subgroups characterized by distinct light curve shapes. Anti-phase variations in different photometric passbands, in particular, is a unique characteristic of a subset of ACV stars readily usable for their identification. The availability of data in three different passbands (g, r, and i) is a major advantage of the ZTF survey. Conclusions. On the basis of our experience with other photometric surveys and the analysis of light curves, we conclude that the ZTF is well suited to the search for, and the analysis of, ACV variables that are not considered in the available ZTF variable star catalogs. Further work will focus on the development and refinement of a search algorithm to correctly identify these stars in ZTF data and, subsequently, in massive photometric time series databases in general.

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Section: Rectified Intensitymentioning

confidence: 99%

A case study of ACV variables discovered in the Zwicky Transient Facility survey

Faltová

Kallova

Prišegen

et al. 2021

A&A

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“…There are currently 61 known roAp stars. There have been a number of photometric surveys yielding negative results (e.g., Joshi et al, 2016;Paunzen et al, 2018) and it is unlikely that ground-based observations will lead to a significant increase in the number of roAp stars.…”

Section: The Roap Starsmentioning

confidence: 99%

Pulsation in Intermediate-Mass Stars

Balona

2018

Front. Astron. Space Sci.

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A new perspective of pulsation in stars within the δ Scuti instability strip has recently emerged as a result of Kepler observations. The majority of stars within the instability strip do not pulsate and practically all δ Scuti stars contain low frequencies. Because γ Doradus stars co-exist with δ Sct stars in the same region of the instability strip, it follows that γ Dor stars are driven by the same mechanism as δ Sct stars. The difference must be due to different mode selection processes. The search for an unknown damping factor which is missing from the models will be essential for further progress. Maia variables and hot γ Dor stars are briefly discussed. Luminosities of roAp stars obtained from Gaia DR2 parallaxes and spectroscopic effective temperatures show that the roAp stars are slightly evolved with temperatures in the range 6,300-8,300 K, considerably cooler than predicted by the models. The roAp stars and stars with solar-like oscillations share the same mass-temperature-luminosity relation, but with frequencies which are about 50 percent higher. This suggests that roAp frequencies are determined by the critical acoustic frequency, but this frequency is larger than in standard models, perhaps as a result of a temperature inversion in the atmosphere.

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“…Since their discovery (Kurtz 1978(Kurtz , 1982 there have been several attempts to enlarge, and study, the sample of roAp stars. These have included targeted and survey ground-based photometry (e.g., Martinez et al 1991;Nelson & Kreidl 1993;Paunzen et al 2012;Holdsworth et al 2014a;Joshi et al 2016;Paunzen et al 2018), time-resolved high resolution spectroscopic observations (e.g., Elkin et al 2008;Freyhammer et al 2008a;Kochukhov et al 2013) and most recently space photometry (e.g., Bruntt et al 2009;Gruberbauer et al 2011;Kurtz et al 2011;Balona et al 2011;…”

Section: Introductionmentioning

confidence: 99%

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

Holdsworth,

Cunha,

Kurtz

et al. 2021

Preprint

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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 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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The search for roAp stars: null results and new candidates from Strömgren-Crawford photometry

Cited by 7 publications

References 68 publications

A case study of ACV variables discovered in the Zwicky Transient Facility survey

A case study of ACV variables discovered in the Zwicky Transient Facility survey

Pulsation in Intermediate-Mass Stars

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

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