High-amplitude γ Doradus variables

Paunzen, E.; Bernhard, Klaus; Hümmerich, Stefan; Hambsch, Franz-Josef; Lloyd, C.; Otero, S.

doi:10.1093/mnras/staa2905

Cited by 10 publications

(3 citation statements)

References 50 publications

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“…We also did not distinguish between DSCT and SX Phe stars and do not divide DSCT into LADS and HADS classes (Frolov & Irkaev 1984;Petersen & Christensen-Dalsgaard 1996). Similarly, we do not distinguish between lowand high-amplitude GDOR stars (Paunzen et al 2020).…”

Section: Classification Scheme and Notationcontrasting

confidence: 69%

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

Skarka

Žák

Fedurco

et al. 2022

A&A

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Context. In the time of large space surveys that provide tremendous amounts of precise data, it is highly desirable to have a commonly accepted methodology and system for the classification of variable stars. This is especially important for A-F stars, which can show intrinsic brightness variations due to both rotation and pulsations. Aims. The goal of our study is to provide a reliable classification of the variability of A-F stars brighter than 11 mag located in the northern TESS continuous viewing zone. We also aim to provide a thorough discussion about issues in the classification related to data characteristics and the issues arising from the similar light-curve shape generated by different physical mechanisms. Methods. We used TESS long-and short-cadence photometric data and corresponding Fourier transform to classify the variability type of the stars. We also used spectroscopic observations to determine the projected rotational velocity of a few stars. Results. We present a clear and concise classification system that is demonstrated on many examples. We find clear signs of variability in 3025 of 5923 studied stars (51 %). For 1813 of these 3025 stars, we provide a classification; the rest cannot be unambiguously classified. Of the classified stars, 64.5 % are pulsating stars of g-mode γ Doradus (GDOR) and p-mode δ Scuti types and their hybrids. We realised that the long-and short-cadence pre-search data conditioning simple aperture photometry data can differ significantly not only in amplitude but also in the content of instrumental and data-reduction artefacts, making the long-cadence data less reliable. We identified a new group of stars that show stable light curves and characteristic frequency spectrum patterns (8.5 % of the classified stars). According to the position in the Hertzsprung-Russell diagram, these stars are likely GDOR stars but are on average about 200 K cooler than GDORs and have smaller amplitudes and longer periods. With the help of spectroscopic measurements of v sin i, we show that the variability of stars with unresolved groups of peaks located close to the positions of the harmonics in their frequency spectra (16 % of the classified stars) can be caused by rotation rather than by pulsations. We show that without spectroscopic observations it can be impossible to unambiguously distinguish between ellipsoidal variability and rotational variability. We also applied our methodology to three previous studies and find significant discrepancies in the classification. Conclusions. We demonstrate how difficult the classification of variable A-F stars can be when using only photometric data, how the residual artefacts can produce false positives, and that some types cannot actually be distinguished without spectroscopic observations. Our analysis provides collections that can be used as training samples for automatic classification.

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Section: Classification Scheme and Notationcontrasting

confidence: 69%

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

Skarka

Žák

Fedurco

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…We also did not distinguish between DSCT and SX Phe stars and do not divide DSCT to LADS and HADS classes (Frolov & Irkaev 1984;Petersen & Christensen-Dalsgaard 1996). Similarly, we do not distinguish between lowand high-amplitude GDOR stars (Paunzen et al 2020).…”

Section: Classification Scheme and Notationcontrasting

confidence: 69%

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

Skarka¹,

Žák²,

Fedurco³

et al. 2022

Preprint

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Context. In the time of large space surveys that provide tremendous amount of precise data, it is highly desirable to have a commonly accepted methodology and system for the classification of the variable stars. This is important especially for A-F stars that can show intrinsic brightness variations due to both rotation and pulsations. Aims. The goal of our study is to provide a reliable classification of variability of A-F stars brighter than 11 mag located in the northern TESS continuous viewing zone. We also aim at thorough discussion about issues in the classification related to the data characteristics and the issues arising from the similar light curve shape generated by different physical mechanisms. Methods. We used TESS long-and short-cadence photometric data and corresponding Fourier transform to classify the variability type of the stars. We also used spectroscopic observations to get projected rotational velocity of a few stars. Results. We present a clear and concise classification system that is demonstrated on many examples. We found clear signs of variability in 3025 of 5923 studied stars (51 %). For 1813 of these 3025 stars, we provide a classification, the rest cannot be unambiguously classified. From the classified stars, 64.5 % are pulsating stars of GDOR and DSCT types and their hybrids. We realised that the longand short-cadence PDCSAP data can differ significantly not only in amplitudes but also in the content of instrumental/data reduction artifacts making the long-cadence data less reliable. We identified a new group of stars showing stable light curves and characteristic frequency spectra pattern (8.5 % of the classified stars). According to the position in the Hertzsprung-Russell diagram, these stars are likely GDOR stars but are about 200 K cooler than GDORs on average and have smaller amplitudes and longer periods in average. With the help of spectroscopic measurements of v sin i, we show that variability of stars having unresolved groups of peaks located close to the positions of the harmonics in their frequency spectra (16 % of the classified stars) can rather be caused by rotation than by pulsations. We show that without spectroscopic observations, it can be impossible to unambiguously distinguish between ellipsoidal variability and rotational variability. We also apply our methodology to three previous studies and found significant discrepancies in the classification. Conclusions. We demonstrate how difficult the classification of variable A-F stars can be when using only photometric data, how the residual artifacts can produce false positives and that some types cannot be actually distinguished without spectroscopic observations. Our analysis provides collections that can be used as training samples for automatic classification.

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“…TIC 30531417 shows a very regular light curve. The principal component of the power spectrum belongs to the g-mode frequency range (0.3 < ν < 3 d −1 ) but presents an unusually high amplitude for its pulsation variability (0.33 peak-to-peak mag) for a γ Dor star (typically of 0.1 mag Paunzen et al, 2020). For this reason, it was baptized by Antoci et al (2019) as a highamplitude γ Dor (HAGD) star.…”

Section: Tic 30531417mentioning

confidence: 99%

Asteroseismic inferences from the study of non-linearities in δ Sct stars

Lares-Martiz

2022

Front. Astron. Space Sci.

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Many pulsating star light curves must be interpreted strictly within the framework of a non-linear theory. The detection of non-linear interactions between pulsation modes has increased due to the ultra-precise photometric data provided by space missions. For this reason, it is now possible and essential to continue the effort of building data-driven non-linear pulsation models. The analysis of non-linear stellar light curves has become a fundamental challenge in asteroseismology in the era of space missions. In this article, a diagnostic method is presented. It is based on an observational characterization of the non-linear behavior of high-amplitude delta Scuti (HADS) stars. It diagnoses the nature of non-linear pulsations in δ Sct stars of lower amplitudes. It potentially provides an extra hint for identifying a radial mode and determine its radial order n. Additionally, it could show signatures of moderate to rapid rotation in these stars. Overall, this article shows the capabilities for making asteroseismic inferences from studying combination frequencies in δ Sct stars.

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High-amplitude γ Doradus variables

Cited by 10 publications

References 50 publications

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone

Asteroseismic inferences from the study of non-linearities in δ Sct stars

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