Utilizing the Southern African Giant Telescope (SALT), a global group of astronomers has found eight new very popular white dwarf and pre-white dwarf stars with efficient temperatures over 100,000 Okay. The discovering is reported in a paper printed within the Month-to-month Notices of the Royal Astronomical Society.
White dwarfs (WDs) are stellar cores left behind after a star has exhausted its nuclear gas. On account of their excessive gravity, they’re identified to have atmospheres of both pure hydrogen or pure helium. Nonetheless, a small fraction of WDs reveals traces of heavier parts.
Though WDs have a comparatively small measurement, corresponding to that of the Earth, they’re few million occasions extra huge than our planet. Pre-white dwarfs (PWDs) are few occasions bigger and slated to shrink in measurement, finally turning into WDs inside about a number of thousand years.
Now, a bunch of astronomers led by Simon Jeffery of the Armagh Observatory and Planetarium, U.Okay., reviews the detection of recent WDs and PWDs with extreme temperatures. The new stars had been found utilizing SALT’s Robert Stobie Spectrograph (RSS) through the seek for helium-rich sizzling subdwarfs.
“Serendipitously, the SALT survey for helium-rich subdwarfs has led to the invention of eight sizzling white dwarfs and pre-white dwarfs with efficient temperatures exceeding 100,000 Okay,” the researchers wrote within the paper.
In line with the research, two newfound PWDs turned out to be PG 1159 stars—precursors of the DO white dwarfs or DA white dwarfs, retaining some hydrogen of their envelope, named after their prototype. The pattern additionally consists of one DO white dwarf, three O(He) and two O(H) stars.
It was discovered that one of many two O(H) stars is the central star of a newly-discovered planetary nebula (PN), whereas the opposite is the most popular O(H) star and not using a PN. The PG 1159 star designated SALT J213742.6−382901 (or J2137 for brief) seems to be the most popular one out of the newly detected eight—its efficient temperature was estimated to be about 180,000 Okay. Furthermore, the DO white dwarf, with an effective temperature of 130,000 Okay, is the most popular DO WD thus far detected.
J2137, along with the opposite PG 1159 star designated SALT J172411.7−632147 (or J1724) had been discovered to be variable, with a couple of interval detected within the vary of 600–1,200 seconds. The astronomers labeled these two stars as GW Vir variables, which makes SALT J213742.6−382901 the most popular GW Vir variable identified so far.
Summing up the outcomes, the authors of the paper underlined that additional research of J2137 and J1724 may very well be essential for testing theoretical fashions of stability in GW Vir stars. They suggest extra prolonged observations, almost definitely utilizing space observatories, that may assist to unveil their asteroseismic properties intimately.
Extra info:
C S Jeffery et al, Sizzling white dwarfs and pre-white dwarfs found with SALT, Month-to-month Notices of the Royal Astronomical Society (2023). DOI: 10.1093/mnras/stac3531. On arXiv: DOI: 10.48550/arxiv.2301.03550
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SALT discovers new sizzling white dwarf and pre-white dwarf stars (2023, January 17)
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