EQ Virginis

EQ Virginis is a single^[10] variable star in the equatorial constellation of Virgo. It has a baseline visual apparent magnitude of 9.36,^[3] but is a flare star that undergoes sporadic bursts of brightening. The star is located at a distance of 67 light-years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −23 km/s.^[2] It is a member of the IC 2391 moving group^[11] of stars, which is between 30 and 50 million years old.^[8]

EQ Virginis

A light curve for EQ Virginis, plotted from Kepler data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Virgo
Right ascension	13h 34m 43.2063s[2]
Declination	−08° 20′ 31.3353″[2]
Apparent magnitude (V)	9.36[3]
Characteristics
Spectral type	K5Ve[3]
Variable type	UV Cet + BY Dra[4]
Astrometry
Radial velocity (Rv)	−23.16±0.16[2] km/s
Proper motion (μ)	RA: −286.577±0.110 mas/yr[2] Dec.: −91.866±0.083 mas/yr[2]
Parallax (π)	48.7322±0.0587 mas[2]
Distance	66.93 ± 0.08 ly (20.52 ± 0.02 pc)
Absolute magnitude (MV)	10.51
Details
Mass	0.68[5] M☉
Radius	0.62+0.02 −0.04[2] R☉
Luminosity	0.136±0.001[2] L☉
Surface gravity (log g)	4.49[6] cgs
Temperature	4,224±80[6] K
Metallicity [Fe/H]	−0.144[7] dex
Rotation	3.9±0.1[7] days
Rotational velocity (v sin i)	2.06[7] km/s
Age	30-50[8] Myr
Other designations
EQ Vir, BD−07°3646, GJ 517, HD 118100, HIP 66252, SAO 139419, LTT 5253, PLX 3101, Ross 478[9]
Database references
SIMBAD	data
ARICNS	data

This is an orange-hued K-type main-sequence star with a stellar classification of K5Ve,^[3] where the 'e' suffix indicates emission lines in the spectrum. It is a young, rapidly rotating star with a mean magnetic field strength of 2,500±300 G.^[12] In 1971, Sylvio Ferraz-Mello and Carlos Alberto Pinto Coelho de Oliveira Torres discovered that the star, then called HD 118100, is a variable star.^[13] It was given its variable star designation, EQ Virginis, in 1972.^[14] The star is classified as an eruptive variable of the UV Ceti type and a BY Draconis variable.^[4] It shows strong chromospheric activity with extensive star spots that, on average, cover ~24% of the surface.^[7] The star displays a strong X-ray emission.^[12]