Theta Circini
Star in the constellation Circinus From Wikipedia, the free encyclopedia
Theta Circini (θ Cir), is a binary star located in the southern constellation of Circinus, to the northwest of Alpha Circini.[6] It is faintly visible to the naked eye with an apparent visual magnitude of 5.110.[3] Based upon an annual parallax shift of 11.82 mas,[2] it is located at a distance of about 276 light years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Circinus |
| Right ascension | 14h 56m 43.987s[2] |
| Declination | −62° 46′ 51.66″[2] |
| Apparent magnitude (V) | 5.110[3] (5.90 + 5.90)[4] |
| Characteristics | |
| Spectral type | B3 Ve[5] (B2 + B2)[4] |
| B−V color index | +0.00[3] |
| Variable type | GCAS[6] |
| Astrometry | |
| Proper motion (μ) | RA: +102.65[2] mas/yr Dec.: +9.35[2] mas/yr |
| Parallax (π) | 11.82±0.30 mas[2] |
| Distance | 276 ± 7 ly (85 ± 2 pc) |
| Absolute magnitude (MV) | −2.43/−2.43[4] |
| Orbit[5] | |
| Period (P) | 39.62±0.78 yr |
| Semi-major axis (a) | 0.08564±0.00056″ |
| Eccentricity (e) | 0.3014±0.0081 |
| Inclination (i) | 153.3±2.0° |
| Longitude of the node (Ω) | 228.0±5.2° |
| Periastron epoch (T) | 1993.81±0.12 |
| Argument of periastron (ω) (secondary) | 68.6±6.5° |
| Details | |
| θ Cir A | |
| Mass | 9.3±0.6[7] M☉ |
| Surface gravity (log g) | 3.38[3] cgs |
| Temperature | 19,099[3] K |
| Rotational velocity (v sin i) | 195±13[8] km/s |
| Age | 27.1±6.1[7] Myr |
| Other designations | |
| θ Cir, CD−62°891, HD 131492, HIP 73129, HR 5551, SAO 252965.[9] | |
| Database references | |
| SIMBAD | data |
This is an astrometric binary[10] star system with an orbital period of about 39.6 years, an eccentricity of 0.3, and a semimajor axis of 85.64 mas.[5] The pair show a combined stellar classification of B3 Ve,[5] which matches a B-type main sequence star.[5] The 'e' suffix on the class indicates this is a Be star. Alternate classifications include B4 Vnp[7] and B4npe,[5] with the 'n' indicating broad ("nebulous") absorption lines due to rotation and the 'p' meaning a chemically peculiar star. The two components appear to have similar visual magnitude, mass, and classification.[5] The system behaves as a Gamma Cassiopeiae variable[6] showing occasional outbursts of up to 0.27 in magnitude.[11]
References
External links
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