CU Virginis information

CU Virginis
	; A light curve for CU Virginis, plotted from Hipparcos data
Observation data; Epoch J2000 Equinox J2000
Constellation	Virgo
Right ascension	14h 12m 15.80569s
Declination	+02° 24′ 33.9342″
Apparent magnitude (V)	4.99 (4.92–5.07)
Characteristics
Spectral type	ApSi or B8.5 Vp Si
B−V color index	−0.118±0.006
Variable type	α2 CVn
Astrometry
Radial velocity (Rv)	−2.0±7.4 km/s
Proper motion (μ)	RA: −43.049 mas/yr ; Dec.: +26.081 mas/yr
Parallax (π)	13.9366 ± 0.2601 mas
Distance	234 ± 4 ly ; (72 ± 1 pc)
Absolute magnitude (MV)	0.50
Details
Mass	3.06±0.06 M☉
Radius	2.06±0.14 R☉
Luminosity	100±11 L☉
Surface gravity (log g)	4.30±0.06 cgs
Temperature	12,750±250 K
Rotation	0.5207137±0.0000010 d
Rotational velocity (v sin i)	145±3 km/s
Other designations
	CU Vir, BD+03°2867, FK5 3127, HD 124224, HIP 69389, HR 5313, SAO 120339, ADS 9152 A, WDS J14123+0225A
Database references
SIMBAD	data

CU Virginis is a single^[11] star in the equatorial constellation of Virgo.^[12] It has an apparent visual magnitude of 4.99,^[3] which is bright enough to be faintly visible to the naked eye. The distance to this star can be estimated from its annual parallax shift of 13.9 mas,^[2] yielding a separation of 234 light years.

This is one of the best studied Ap stars.^[13] It has a stellar classification of Ap Si^[5] with strong lines of silicon and weak helium lines. The star is a fast rotator with a period of 0.52 days and an axis that is inclined by 46.5°±4.1° to the line of sight from the Earth.^[8] Both the spectrum and luminosity of the star vary with the rotation,^[13] and it is classified as a α² Canum Venaticorum variable with the designation CU Virginis (CU Vir).^[4] There is some evidence that the rotation period may vary slightly over a timescale measured in decades.^[14] Such changes have been observed to occur in glitches, rather than varying constantly.^[13]

CU Virginis has three times the mass of the Sun and double the Sun's radius. It is radiating 100 times the Sun's luminosity from its photosphere at an effective temperature of 12,750 K.^[8] The star has a strong magnetic field, placing it in the class of magnetic chemically peculiar stars. The polar magnetic field has a strength of about 3 kG.^[13] The magnetic pole may be displaced by 87° from the axis of rotation, and the effective magnetic field is seen to vary over the course of a rotation.^[13] The mean surface magnetic field varies over the range 1.2–3.2 kG.^[15]

This star is a radio emitter, with the emission being modulated by the rotational phase. This emission is believed to be gyrosynchrotron radiation emitted by mildly relativistic (Lorentz factor of γ ≤ 2) electrons trapped in the magnetosphere". Two pulses of 100% circularly polarized radio energy are detected each rotation, which may be produced via an electron cyclotron maser process. These polarized beams are then refracted as they pass through cold plasma in the star's magnetosphere.^[13]

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Observation data Epoch J2000 Equinox J2000
A light curve for CU Virginis, plotted from Hipparcos data^[1]
Constellation	Virgo
Right ascension	14^h 12^m 15.80569^s^[2]
Declination	+02° 24′ 33.9342″^[2]
Apparent magnitude (V)	4.99^[3] (4.92–5.07)^[4]
Characteristics
Spectral type	ApSi^[5] or B8.5 Vp Si^[6]
B−V color index	−0.118±0.006^[3]
Variable type	α² CVn^[4]
Astrometry

Radial velocity (R_v)	−2.0±7.4^[7] km/s
Proper motion (μ)	RA: −43.049^[2] mas/yr Dec.: +26.081^[2] mas/yr
Parallax (π)	13.9366 ± 0.2601 mas^[2]
Distance	234 ± 4 ly (72 ± 1 pc)
Absolute magnitude (M_V)	0.50^[3]

Details^[8]

Mass	3.06±0.06 `M`_☉
Radius	2.06±0.14 `R`_☉
Luminosity	100±11 `L`_☉
Surface gravity (log g)	4.30±0.06 cgs
Temperature	12,750±250 K
Rotation	0.5207137±0.0000010 d^[9]
Rotational velocity (v sin i)	145±3 km/s

Other designations
CU Vir, BD+03°2867, FK5 3127, HD 124224, HIP 69389, HR 5313, SAO 120339, ADS 9152 A, WDS J14123+0225A^[10]
Database references
SIMBAD	data

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