Wandering near the red edge: photometric observations of three cool ZZ Ceti stars

Bognár, Zs.; Paparó, M.; Sódor, Á.; Jenei, D. I.; Kalup, Cs.; Bertone, E.; Chavez-Dagostino, Miguel; Montgomery, M. H.; Győrffy, Á.; Molnár, L.; Ollé, H.; Pápics, P. I.; Plachy, E.; Verebélyi, Erika

doi:10.1093/mnras/sty2884

Cited by 8 publications

(10 citation statements)

References 19 publications

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“…Cool ZZ Cetis, near the red edge of the instability strip, show long pulsation periods, and those observed -i.e., with significant amplitude-in general change with time. Bognár et al (2018b) detected 14 frequencies for HS 0733+4119, of which 8 are independent modes; for GD 154, 17 frequencies, with 4 independent modes, and for R808, the 28 frequencies discussed in Thompson et al (2009) and 2 new ones.…”

Section: Recent Observational Achievementsmentioning

confidence: 96%

Pulsating white dwarfs: new insights

Córsico

Althaus

Bertolami

et al. 2019

Astron Astrophys Rev

204

224

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Stars are extremely important astronomical objects that constitute the pillars on which the Universe is built, and as such, their study has gained increasing interest over the years. White dwarf stars are not the exception. Indeed, these stars constitute the final evolutionary stage for more than 95 per cent of all stars. The Galactic population of white dwarfs conveys a wealth of information about several fundamental issues and are of vital importance to study the structure, evolution and chemical enrichment of our Galaxy and its components -including the star formation history of the Milky Way. Several important studies have emphasized the advantage of using white dwarfs as reliable clocks to date a variety of stellar populations in the solar neighborhood and in the nearest stellar clusters, including the thin and thick disks, the Galactic spheroid and the system of globular and open clusters. In addition, white dwarfs are tracers of the evolution of planetary systems along several phases of stellar evolution. Not less relevant than these applications, the study of matter at high densities has benefited from our detailed knowledge about evolutionary and observational properties of white dwarfs. In this sense, white dwarfs are used as laboratories for astro-particle physics, being their interest focused on physics beyond the standard model, that is, neutrino physics, axion physics and also radiation from "extra dimensions", and even crystallization.The last decade has witnessed a great progress in the study of white dwarfs. In particular, a wealth of information of these stars from different surveys has

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Section: Recent Observational Achievementsmentioning

confidence: 96%

Pulsating white dwarfs: new insights

Córsico

Althaus

Bertolami

et al. 2019

Astron Astrophys Rev

204

224

View full text Add to dashboard Cite

show abstract

“…It is definitely a great advantage for the present generation that they do not have to fight for the acceptance of the observed data. Comparative analyses of the observation of the subsequent years for GD 154 revealed that the star not only varied its pulsational behavior between a "simple" multi-periodic and a quasi mono-periodic phase with harmonic and subharmonic peaks, but there were differences between the visibility of the near-subharmonics in the latter phase (Bognár et al, 2019). GD 154 will be a target of TESS (private communication by Zs.…”

Section: Results Between 1970-1980mentioning

confidence: 99%

An Observer's View on the Future of Asteroseismology

Paparó

2019

Front. Astron. Space Sci.

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Scientific research is a continuous process, and the speed of future progress can be estimated by the pace of finding explanations for previous research questions. In this observers based view of stellar pulsation and asteroseismology, we start with the earliest observations of variable stars and the techniques used to observe them. The earliest variable stars were large amplitude, radial pulsators but were followed by other classes of pulsating stars. As the field matured, we outline some cornerstones of research into pulsating star research with an emphasis on changes in observational techniques. Improvements from photographs, to photometry, CCDs, and space telescopes allowed researchers to separate out pulsating stars from other stars with light variations, recognize radial and nonradial pulsation courtesy of increased measurement precision, and then use nonradial pulsations to look inside the stars, which cannot be done any other way. We follow several highlighted problems to show that even with excellent space data, there still may not be quick theoretical explanations. As the result of technical changes, the structure of international organizations devoted to pulsating stars has changed, and an increasing number of conferences specialized to space missions or themes are held. Although there are still many unsolved problems, such as mode identification in non-asymptotic pulsating stars, the large amount of data with unprecedented precision provided by space missions (MOST, CoRoT, Kepler) and upcoming missions allow us to use asteroseismology to its full potential. However, the enormous flow of data will require new techniques to extract the science before the next missions. The future of asteroseismology will be successful if we learn from the past and improve with improved techniques, space missions, and a properly educated new generation.

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“…We accepted a frequency peak as significant if its amplitude reached the five signal-to-noise ratio (S/N), where the noise level was calculated by the average Fourier amplitude in a ∼1700 µHz radius vicinity (150 d −1 ) of the peak in question (see e.g. Bognár et al 2019b). That is, we used a higher significance level than the usual four S/N; we accepted the highest amplitude peaks as possible pulsational frequencies during the pre-whitening process of these targets showing complex pulsational behaviour, with several closely spaced peaks in their Fourier transforms (FTs).…”

Section: Light Curve Analysismentioning

confidence: 99%

“…With this publication on PM J22299+3024 and LP 119-10, we continue our efforts to introduce the results of our long-term ground-based observations on pulsating white dwarf stars in a series of papers (see e.g. Bognár et al 2009Bognár et al , 2014Bognár et al , 2016Bognár et al , 2019bPaparó et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Exploring the pulsational properties of two ZZ Ceti stars

Bognár

Kalup

Sódor

2021

A&A

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Context. We continued our ground-based observing project with the season-long observations of ZZ Ceti stars at the Konkoly Observatory. Our present targets are the newly discovered PM J22299+3024 and the already known LP 119–10 variables. LP 119–10 was also observed by the TESS space telescope in 120-second cadence mode. Aims. Our main aims are to characterise the pulsation properties of the targets and extract pulsation modes from the data for asteroseismic investigations. Methods. We performed a standard Fourier analysis of the daily, weekly, and entire data sets, together with test data of different combinations of weekly observations. We then performed asteroseismic fits utilising the observed and the calculated pulsation periods. For the calculations of model grids necessary for the fits, we applied the 2018 version of the White Dwarf Evolution Code. Results. We derived six possible pulsation modes for PM J22299+3024 and five plus two TESS pulsation frequencies for LP 119–10. We note that further pulsation frequencies may be present in the data sets, but we found their detection ambiguous, so we omitted them from the final frequency list. Our asteroseismic fits of PM J22299+3024 give 11 400 K and 0.46 M⊙ for the effective temperature and the stellar mass, respectively. The temperature is ≈800 K higher, while the mass of the model star is exactly the same as was earlier derived by spectroscopy. Our model fits of LP 119–10 put the effective temperature in the range of 11 800−11 900 K, which is again higher than the spectroscopic 11 290 K value. Moreover, our best model solutions give M* = 0.70 M⊙ mass for this target, which is near to the spectroscopic value of 0.65 M⊙ and likewise in the case of PM J22299+3024. The seismic distances of our best-fit model stars agree with the Gaia astrometric distances of PM J22299+3024 and LP 119–10 within the errors, validating our model results.

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Wandering near the red edge: photometric observations of three cool ZZ Ceti stars

Cited by 8 publications

References 19 publications

Pulsating white dwarfs: new insights

Pulsating white dwarfs: new insights

An Observer's View on the Future of Asteroseismology

Exploring the pulsational properties of two ZZ Ceti stars

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