HD 119921

This article is about z Centauri and is not to be confused with the supernovae SN 1895B associated with a variable star given Bayer designation of "Z Centauri".

HD 119921 is a single,^[4] white-hued star in the southern constellation of Centaurus. it has the Bayer designation z Centauri. This is faintly visible to the naked eye, having an apparent visual magnitude of 5.15.^[1] It forms a wide double star with a faint, magnitude 12.50 visual companion, which is located at an angular separation of 27.20″ as of 2010.^[11] HD 119921 is moving closer to us with a heliocentric radial velocity of around −10 km/s,^[6] and is currently located some 420±10 light year from the Sun. At that distance, the visual magnitude of this star is diminished by 0.15 from extinction due to interstellar dust.^[9]

HD 119921

Observation data Epoch J2000      Equinox J2000
Constellation	Centaurus[1]
Right ascension	13h 46m 56.35149s[2]
Declination	−36° 15′ 06.9563″[2]
Apparent magnitude (V)	5.15[1]
Characteristics
Spectral type	A0 V[3][4] or B9.5 III-n[5]
Astrometry
Radial velocity (Rv)	−9.8±2.8[6] km/s
Proper motion (μ)	RA: −13.293[2] mas/yr Dec.: −11.115[2] mas/yr
Parallax (π)	7.7881±0.2382 mas[2]
Distance	420 ± 10 ly (128 ± 4 pc)
Absolute magnitude (MV)	−0.48[1]
Details
Mass	2.6[7] M☉
Radius	4.1[7] R☉
Luminosity	160[7] L☉
Surface gravity (log g)	3.62[7] cgs
Temperature	10,102[7] K
Rotational velocity (v sin i)	220[8] km/s
Age	337[9] Myr
Other designations
z Cen, CD−35°8995, FK5 3091, HD 119921, HIP 67244, HR 5174, SAO 204835, WDS J13469-3615A[10]
Database references
SIMBAD	data

This is an A-type main-sequence star with a stellar classification of A0 V, per Houk (1979).^[3] However, Gray & Garrison (1987) have it classed as B9.5 III-n, suggesting it is a more evolved giant star.^[5] HD 119921 is spinning rapidly with a projected rotational velocity of 220 km/s.^[8] The star is radiating around 160 times the Sun's luminosity from its photosphere at an effective temperature of 10,102 K.^[7]

In 1983, Molaro et al. reported the presence of super-ionized elements (triple-ionized carbon and silicon) in the far ultraviolet spectrum of HD 119921. These anomalous features are not normally detected from a star in this temperature range.^[12] Instead, these blue-shifted absorption features may originate in the local interstellar medium.^[8]