Ross 458, also referred to as DT Virginis, is a binary star system in the constellation of Virgo. It has an apparent visual magnitude of 9.79 and is located at a distance of 37.6 light-years from the Sun. Both of the stars are low-mass red dwarfs with at least one of them being a flare star. This binary system has a circumbinary sub-stellar companion.
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Description
This star was mentioned as a suspected variable by M. Petit in 1957. In 1960, O. J. Eggen classified it as a member of the Hyades moving group based on the system's space motion; it is now considered a likely member of the Carina Near Moving Group. Two flares were reported from this star in 1969 by N. I. Shakhovskaya, confirming it as a flare star. It was identified as an astrometric binary in 1994 by W. D. Heintz, who found a period of 14.5 years. The pair were resolved using adaptive optics in 1999. Early mass estimates placed the companion near the substellar limit, and it was initially proposed as a brown dwarf but is now considered late-type red dwarf.
The primary member, component A, is an M-type main-sequence star with a stellar classification of M0.5. It is young, magnetically very active star with a high rate of rotation and strong Hα emission. The star experiences star spots that cover 10–15% of the surface It is smaller and less massive than the Sun. The star is radiating just 4.4% of the luminosity of the Sun from its photosphere at an effective temperature of 3,484 K.
Substellar companion
A distant sub-stellar companion to the binary star system was discovered in 2010 as part of a deep infrared sky survey. This is most likely a T8 spectral type brown dwarf with an estimated rotation period of 6.75±1.58 h. The object varies slightly in brightness, which may be due to patchy clouds. The companion lacks detectable oxygen in the atmosphere, implying its formation from sequestrated source or peculiar atmospheric chemistry. Analysis of its chemical composition show it to be similar to that of Ross 458 A, indicating that the object formed in a stellar-like manner.