Variable star GD 99 investigated by researchers

Utilizing the 1-m Ritchey–Chrétien–Coudé telescope of the Konkoly Observatory in Budapest, Hungary and NASA’s Transiting Exoplanet Survey Satellite tv for pc (TESS), Hungarian astronomers have noticed a variable star referred to as GD 99. Outcomes of the examine, printed November 21 on the arXiv pre-print server, shed extra mild on the properties of this variable.

Detecting and finding out variable stars may provide necessary hints into elements of stellar construction and evolution. Investigation of variables may very well be additionally useful for a greater understanding of the space scale of the universe.

ZZ Ceti stars (also referred to as DAV stars), are variables with modest luminosity variations and intervals between 30 and 1,200 seconds. They’re pulsating white dwarfs of kind DA, which have a pure hydrogen outer layer composition.

GD 99 is without doubt one of the brightest ZZ Ceti stars identified so far. Nonetheless, though GD 99 was recognized as a variable white dwarf virtually half a century in the past, its pulsating conduct and asteroseismology haven’t been comprehensively studied but. In an effort to change this, a crew of astronomers from the Konkoly Observatory, led by Zsófia Bognár, has carried out long-term, single-site observations of GD 99 with the principle purpose of performing a seismic evaluation of this star.

“We chosen GD 99 for a long-time ground-based follow-up measurement, which resulted in 30 nights of observations, spanning greater than 119 observing hours…. We carried out observations between 2002 and 2022 with the 1-m Ritchey–Chrétien–Coudé telescope on the Piszkésteto mountain station of Konkoly Observatory, Hungary…. TESS noticed GD 99 for 27.4 days in sector 21 with the 120-second short-cadence mode between January 21, and February 18, 2020,” the researchers wrote within the paper.

The observations allowed the crew to determine 11 eigenmodes for seismology. It was discovered that GD 99 generally is wealthy in pulsation modes within the 200–1,100 s interval vary, provided that the astronomers detected seven new intervals.

Based mostly on the outcomes, the astronomers have been in a position to decide basic parameters of GD 99. The mass of the star was calculated to be about 0.8 solar masses and its effective temperature was estimated to be at a degree of 13,500 Okay. It turned out that the star is positioned some 110 light years away and its rotation interval is roughly 13.17 hours.

By evaluating the outcomes with earlier research, GD 99 is hotter, extra large and positioned nearer than beforehand thought. The authors of the paper assume that the star could also be on the blue fringe of the empirical ZZ Ceti instability strip—a area of the Hertzsprung–Russell diagram largely occupied by a number of associated lessons of pulsating variables.

All in all, the researchers underlined that GD 99 joins the at present small group of identified white dwarf pulsators wealthy in oscillation modes.

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