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Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
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Constellation | Eridanus |
Right ascension | 03h59m 55.48381s[2] |
Declination | −24° 00′ 58.3798″[2] |
Apparent magnitude (V) | 4.63[3] |
Characteristics | |
Spectral type | B9.5V Si[4] |
U−B color index | −0.40[3] |
B−V color index | −0.13[3] |
Variable type | α2 CVn[5] |
Astrometry | |
Radial velocity (Rv) | 25.5±0.5[6] km/s |
Proper motion (μ) | RA: +12.12[2] mas/yr Dec.: +16.48[2] mas/yr |
Parallax (π) | 9.96 ± 0.22 mas[2] |
Distance | 327 ± 7 ly (100 ± 2 pc) |
Absolute magnitude (MV) | −0.44[5] |
Orbit[7] | |
Period (P) | 5.95382 days |
Eccentricity (e) | 0.129 |
Periastron epoch (T) | 246991.65 JD |
Argument of periastron (ω) (secondary) | 183.2° |
Semi-amplitude (K1) (primary) | 40.0 km/s |
Semi-amplitude (K2) (secondary) | 89.9 km/s |
Details | |
τ9 Eri A | |
Mass | 3.6[7] M☉ |
Radius | 3.06[7] R☉ |
Luminosity | 209[7] L☉ |
Surface gravity (log g) | 4.11±0.11[8] cgs |
Temperature | 12,580[7] K |
Rotational velocity (v sin i) | 26.8[7] km/s |
Age | 140[7] Myr |
τ9 Eri B | |
Mass | 1.6[7] M☉ |
Radius | 1.5[7] R☉ |
Luminosity | 6.3[7] L☉ |
Temperature | 7530[7] K |
Rotational velocity (v sin i) | 15[7] km/s |
Other designations | |
τ9 Eridani, τ9 Eri, 36 Eridani, CD−24° 2022, FK5 2287, HD 25267, HIP 18673, HR 1240, SAO 169017.[9] | |
Database references | |
SIMBAD | data |
Tau9 Eridani (τ9 Eri) is a binary star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 4.63.[3] The distance to this system can be estimated using the parallax method, which yields a value of roughly 327 light years.[3]
This is a double-lined spectroscopic binary system with an orbital period of 5.95382 days and an eccentricity of 0.12.[7] The primary component, τ9 Eri A, is a magnetic chemically peculiar star[10] with a stellar classificationofB9.5V Si,[4] indicating that it is a B-type main sequence star that shows abundance anomalies in its silicon absorption lines.[4] It is an Alpha² Canum Venaticorum variable[5] with a rotational periodicity of 5.954 days.[11] The averaged strength of the stellar effective magnetic fieldis240.6±91.0 G.[4]
The primary component Tau9 Eridani A has an estimated 326%[10] the mass of the Sun and 3.1 times the Sun's radius.[8] It shines with 166[12] times the solar luminosity from an outer atmosphere at an effective temperature of 10,866 K.[12] The star is spinning with a projected rotational velocity of 30 km/s.[13] The secondary star, designated Tau9 Eridani B, is a late A-type or early F-type star with a mass of 1.6 solar masses and an effective temperature of 7530 K.[7]
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