Nu Centauri

Nu Centauri
Location of ν Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 49m 30.27644s[1]
Declination −41° 41′ 15.7521″[1]
Apparent magnitude (V) +3.41[2]
Characteristics
Spectral type B2 IV[3]
U−B color index −0.891[4]
B−V color index −0.234[4]
Variable type Ellipsoidal + β Cep[5]
Astrometry
Radial velocity (Rv)+9.0[6] km/s
Proper motion (μ) RA: −26.77[1] mas/yr
Dec.: −20.18[1] mas/yr
Parallax (π)7.47 ± 0.17 mas[1]
Distance437 ± 10 ly
(134 ± 3 pc)
Absolute magnitude (MV)−2.4[2]
Orbit[7]
Period (P)2.622±0.018 d
Eccentricity (e)0
Periastron epoch (T)2,450,894.32±0.01
Semi-amplitude (K1)
(primary)		22.4±0.4 km/s
Details
Mass8.5±0.3[3] M☉
Radius6.4[8] R☉
Luminosity5,000[2] L☉
Surface gravity (log g)4.02[2] cgs
Temperature22,400[2] K
Rotational velocity (v sin i)90[9] km/s
Age18.2±3.2[3] Myr
Other designations
CD−41°8171, GC 18665, HD 120307, HIP 67464, HR 5190, SAO 224469[10]
Database references
SIMBADdata

Nu Centauri, Latinized from ν Centauri, is a binary star system in the southern constellation of Centaurus. The combined apparent visual magnitude of the pair is +3.41,[2] making this one of the brightest members of the constellation. Based upon parallax measurements made during the Hipparcos mission, this star system is located at a distance of roughly 437 light-years (134 parsecs) from Earth. The margin of error for this distance is about 2%, which is enough to give an error in distance of ±10 light years.[1]

This is a single-lined spectroscopic binary system, which means that the two stellar components have not been individually resolved with a telescope.[7] Instead, their orbital motion can be tracked through periodic shifts in the spectrum of the primary. The gravitational perturbation of the hidden secondary component upon the primary is causing the latter to first move toward and then away from the Earth, creating Doppler shift changes in the spectrum. From these subtle shifts, the orbital elements of the pair can be extracted. The pair are orbiting their common center of mass in a circular orbit with a period of only 2.622 days, indicating that they are in a relatively tight orbit.[7]

A red-light light curve for Nu Centauri, adapted from Jerzykiewicz et al. (2021)[11]

The interaction between the two components of this system appears to be creating emission lines in the spectrum, turning the primary into a Be star.[7] It has a stellar classification of B2 IV,[3] which matches a massive B-type subgiant star. The primary has 8.5[3] times the mass of the Sun and 6.4[8] times the Sun's radius. It is a Beta Cephei type variable star with a brightness that periodically varies from magnitude +3.38 to +3.41 over an interval of 0.17 days.[7] The tidal interaction with the secondary component has turned it into a rotating ellipsoidal variable.

This star system is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such association of co-moving massive stars to the Sun.[2]

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  11. ^ Cite error: The named reference Jerzykiewicz was invoked but never defined (see the help page).