Light curves from segments 46 (120s–cadence) and 63 (20s–cadence) for the new ZZ Cetis – TIC 0902514572 are shown in the top and middle panels, respectively. The bottom panel gives the Fourier transform of the binned data. The horizontal red line corresponds to the false alarm probability FAP=1/1,000 detection limit. Credit: Romero et al., 2024.
Using NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers have discovered 32 new bright pulsating DA white dwarfs of the ZZ Ceti subclass. This discovery is a Research paper Published on the preprint server on July 9 arXiv.
White dwarfs (WDs) are the stellar cores left behind after a star has exhausted its nuclear fuel. Because of their high gravity, they are known to have atmospheres of pure hydrogen or pure helium. However, a small fraction of WDs show traces of heavier elements.
In pulsating WDs, the luminosity varies due to non-radial gravitational wave pulsations within these objects. A subtype of pulsating WDs is known as DAVs or ZZ Ceti stars – these are WDs of spectral type DA, with only hydrogen absorption lines in their spectra.
Now, Alejandra D. of the Federal University of Rio Grande do Sul in Porto Alegre, Brazil. A team of astronomers led by Romero reports finding 32 new ZZ Cetis. The discovery was made by analyzing the light curves of WDs and WD candidates obtained by TESS.
„In this work, we present the discovery of 32 new pulsating DA white dwarf stars based on observations from the TESS mission from Segment 40 to Segment 69,” the researchers write in the paper.
The new sample of ZZ Cetis has an average stellar mass of approximately 0.6 solar masses, which is generally consistent with the average stellar mass of the 351 known objects of this type (0.64 solar masses). New pulsating DA white dwarfs are found to have effective temperatures in the range 8,477–13,910 K.
Also, the astronomers found a component of rotation division for nine objects reported in the study, with rotation periods ranging from four hours to one day. The average for the cycle period of these objects was calculated to be approximately 13.6 hours. This is typical of WDs, as they are typically slow rotators, with rotation periods ranging from a few hours to several days.
Analyzing a newly discovered sample of pulsating DA white dwarfs, the paper’s authors found a modest correlation to both photometric or spectroscopic and seismic efficiency temperatures. However, they did not find a strong dependence on stellar mass.
Summarizing the results, the researchers noted that their discovery increases the number of pulsating DA white dwarfs identified by TESS to 103, underscoring how important this telescope is for such discoveries.
„In its first five years, TESS has already proven to be a powerful tool for discovering new pulsating white dwarfs,” the scientists conclude.
More information:
Alejandra D. Romero et al, Thirty-two new bright ZZ Ceti stars from TESS: adding cycles 4 and 5, arXiv (2024) DOI: 10.48550/arxiv.2407.07260
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Quotation: Astronomers discover dozens of new pulsating white dwarfs (2024, July 17) Retrieved 17 July 2024 from https://phys.org/news/2024-07-astronomers-dozens-pulsating-white-dwarfs.html.
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