New triple-mode high-amplitude Delta Scuti variables

Khruslov, A. V.

doi:10.1515/astro-2022-0020

Cited by 5 publications

(3 citation statements)

References 17 publications

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“…The smaller Galactic Scuti amplitudes, caused by smaller temperature fluctuations lead to a flatter PC relation at maximum light. Hence, we have good support for the HIF stellar photosphere theory as described in Simon et al 1993;Das et al 2020, and references therein. We also note that there is some controversy over the pulsation mode of Scuti stars and in fact whether they may be pulsating in a number of modes and/or have a non-radial component (Netzel et al 2022;Lv et al 2022;Khruslov 2022;Netzel & Smolec 2022). When we cross-checked our sample with the triple mode stars as listed in Netzel et al (2022), we found 32 such stars in our sample.…”

Section: A Possible Theoretical Explanationmentioning

confidence: 90%

Period–colour and amplitude–colour relations for OGLE-δ Scuti stars in the Galactic bulge and LMC

Deka

Deb

Das

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We present an analysis on the behaviour of the Galactic bulge and the Large Magellanic Cloud (LMC) δ Scuti stars in terms of period-colour and amplitude-colour (PCAC) relations at maximum, mean and minimum light. The publicly available Optical Gravitational Lensing Experiment-IV (OGLE-IV) light curves for Galactic bulge and OGLE-III light curves for LMC δ Scuti stars are exploited for the analysis. It has been found that the Galactic bulge δ Scuti stars obey flat PC relations at maximum/mean/minimum light while the LMC δ Scutis have sloped/sloped/flat PC relations at maximum/mean/minimum light. Both the Galactic bulge and the LMC δ Scutis have sloped/flat/sloped AC relations at maximum/mean/minimum. These relations also show that Galactic δ Scutis are hotter as compared to their LMC counterparts. The period-amplitude (PA) relations for δ Scutis exhibit different behaviour in the Galactic bulge and the LMC. The LMC variables are found to have higher amplitudes at a given period. The amplitude of the Galactic bulge δ Scuti shows a bimodal distribution which can be modelled using a two-component Gaussian Mixture Model: one component with a lower amplitude and another with a higher amplitude. The observed behaviour of the δ Scuti PCAC relations can be explained using the theory of the interaction of hydrogen ionization front (HIF) and stellar photosphere as well as the PA diagram. We use MESA-RSP to calculate theoretical non-linear hydrodynamical pulsation models for δ Scuti stars with input metallicities of Z = 0.02 and Z = 0.008 appropriate for the Galactic bulge and LMC, respectively. The observed PCAC relations and theoretical calculations support the HIF-photosphere interaction theory.

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Section: A Possible Theoretical Explanationmentioning

confidence: 90%

Period–colour and amplitude–colour relations for OGLE-δ Scuti stars in the Galactic bulge and LMC

Deka

Deb

Das

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…High-amplitude δ Scuti stars (hereafter HADS) are a subclass of δ Scuti stars, who always have larger amplitudes and slower rotations. Most of the HADS show single or double radial pulsation modes (Niu et al 2013(Niu et al , 2017Xue et al 2018;Alton 2019;Bowman et al 2021;Daszyńska-Daszkiewicz et al 2022;Alton 2022a,b,c), and some of them have three radial pulsation modes (Handler et al 1998;Wils et al 2008;Mow et al 2016;Yang et al 2021;Kazarovets et al 2020;Khruslov 2014Khruslov , 2022Poleski et al 2010; or even some non-radial pulsation modes (Poretti et al 2011). SX Phoenicis (SX Phe) stars, a subgroup of HADS, are old Population II stars, which are characterized by high amplitudes of pulsation, low metallicity, and large spatial motion.…”

Section: Introductionmentioning

confidence: 99%

Uncorrelated Amplitude and Frequency Variations of the Harmonics in SX Phoenicis Star XX Cygni

Niu¹,

Xue²

2023

Preprint

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Harmonics are quite common in pulsating stars, and they are always considered to mimic the behaviors of their independent parent pulsation modes and not taken as the key information for asteroseismology. Here, we report an SX Phoenicis star XX Cygni, whose periodogram is dominated by the fundamental frequency f 0 = 7.41481 ± 0.00004 c d −1 and its 19 harmonics. According to the analysis of the archival data from TESS , we find that both the amplitudes and frequencies of the fundamental mode and the harmonics vary within TESS Sectors 14-17 and 54-57, which might be caused by the contamination by neighbouring stars. What is more interesting is that, the harmonics show significantly uncorrelated amplitude and frequency variations over time. Some possible origins and interesting issues are proposed to scheme the further research of this hidden corner in current asteroseismology.

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“…High-amplitude δ-Scuti stars (hereafter HADS) are a subclass of δ-Scuti stars, which always have larger amplitudes and slower rotations. Most of the HADS show single or double radial-pulsation modes (Niu et al 2013(Niu et al , 2017Xue et al 2018;Alton 2019, Bowman et al 2021Alton 2022aAlton , 2022bDaszyńska-Daszkiewicz et al 2022), and some of them have three radial-pulsation modes (Handler et al 1998;Wils et al 2008;Mow et al 2016;Yang et al 2021, Poleski et al 2010Khruslov 2014;Kazarovets et al 2020;Khruslov 2022;, or even some nonradial pulsation modes (Poretti et al 2011) , V = 11.86 mag) is an Population II SX Phe star pulsating with a single radial mode (Ceraski 1904;Nijland 1923;McNamara & Feltz 1980;Szeidl & Mahdy 1981;Joner 1982;Hintz & Joner 1997;Kiss & Derekas 2000;Zhou et al 2002;Blake et al 2003), which shows a continuous linearperiod variation rate of (1/P 0 )( dP 0 / dt) = 1.19(13) × 10 −8 yr −1 (Yang et al 2012). Although XX Cyg has a clean periodogram (which consists of the fundamental frequency f 0 = 7.4148 c day −1 and its harmonics), the residuals in the O − C diagram have deviations of about 0.001-0.005 day, which is an order of magnitude larger than the uncertainties of the times of maximum light (TML; about 0.0001 day).…”

Section: Introductionmentioning

confidence: 99%

Uncorrelated Amplitude and Frequency Variations of the Harmonics in SX Phoenicis Star XX Cygni

Niu

Liu

Xue

2023

View full text Add to dashboard Cite

Harmonics are quite common in pulsating stars. They are always considered to mimic the behaviors of their independent parent pulsation modes, and are not taken for key information in asteroseismology. Here, we report an SX Phoenicis star XX Cygni, whose periodogram is dominated by the fundamental frequency f 0 = 7.41481 ± 0.00004 c day−1 and its 19 harmonics. According to the analysis of the archival data from the Transiting Exoplanet Survey Satellite (TESS), we find that both the amplitudes and frequencies of the fundamental mode and the harmonics vary within TESS Sectors 14–17 and 54–57, which might be caused by the contamination of neighboring stars. What is more interesting is that the harmonics show significantly uncorrelated amplitude and frequency variations over time. Some possible origins and interesting issues are proposed to scheme further research of this hidden corner in current asteroseismology.

show abstract

New triple-mode high-amplitude Delta Scuti variables

Cited by 5 publications

References 17 publications

Period–colour and amplitude–colour relations for OGLE-δ Scuti stars in the Galactic bulge and LMC

Period–colour and amplitude–colour relations for OGLE-δ Scuti stars in the Galactic bulge and LMC

Uncorrelated Amplitude and Frequency Variations of the Harmonics in SX Phoenicis Star XX Cygni

Uncorrelated Amplitude and Frequency Variations of the Harmonics in SX Phoenicis Star XX Cygni

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