Ground-based observation of ZZ Ceti stars and the discovery of four new variables (original) (raw)
2019, Monthly Notices of the Royal Astronomical Society
We perform ground-based photometric observations of 22 DA white dwarf stars, 10 already known ZZ Cetis and 12 candidates with atmospheric parameters inside the classical instability strip. We report on the discovery of four new variable DA white dwarf stars. Two objects are near the middle of the instability strip, SDSS J082804.63+094956.6 and SDSS J094929.09+101918.8, and two red edge pulsators, GD 195 and L495−82. In addition, we classified four objects as possible variables, since evidence of variability was detected in the light curve, but the signal-to-noise ratio was not sufficient to establish a definite detection. Follow-up observations were performed for 10 known ZZ Ceti stars to verify period stability and search for new periodicities. For each confirmed variable, we perform a detailed asteroseismological fit and compare the structural parameters obtained from the best-fitting models with those obtained from spectroscopy and photometry from Gaia. Finally we present a study...
Related papers
Astrophysical Journal, 2004
We report the discovery of two new ZZ Ceti pulsators, LP 133-144 and HE 1258+0123, selected on the basis of model atmosphere fits to optical spectroscopic data. The atmospheric parameters for LP 133-144, Teff = 11,800 +/- 200 K and log g = 7.87 +/- 0.05, and for HE 1258+0123, Teff = 11,410 +/- 200 K and log g = 8.04 +/- 0.05, place them within the empirical boundaries of the ZZ Ceti instability strip. This brings the number of known ZZ Ceti stars to a total of 36, a quarter of which have now been discovered using the spectroscopic approach for estimating their atmospheric parameters. This method has had a 100% success rate so far in predicting the variability of candidate ZZ Ceti stars. We have also analyzed additional spectra of known nonvariable white dwarfs in the vicinity of the ZZ Ceti instability strip. Our study further strengthens the idea that ZZ Ceti stars occupy a pure region in the log g-Teff plane, a region where no nonvariable stars are found. This result supports the thesis that ZZ Ceti pulsators represent a phase through which all DA stars must evolve.
We present a large bank of chemical profiles and pulsation periods suited for asteroseismological studies of ZZ Ceti (or DAV) variable stars. Our background equilibrium DA white dwarf models are the result of fully evolutionary computations that take into account the complete history of the progenitor stars from the ZAMS. The models are characterized by self-consistent chemical structures from the centre to the surface, and cover a wide range of stellar masses, effective temperatures, and H envelope thicknesses. We present dipole and quadrupole pulsation ggg-mode periods comfortably covering the interval of periods observed in ZZ Ceti stars. Complete tabulations of chemical profiles and pulsation periods to be used in asteroseismological period fits, as well as other quantities of interest, can be freely downloaded from our website (\url{http://www.fcaglp.unlp.edu.ar/evolgroup}
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.