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 | |
| 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
edit- ^ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
- ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
- ^ a b c d e Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
- ^ a b c Cvetkovic, Z.; Ninkovic, S. (June 2010), "On the Component Masses of Visual Binaries", Serbian Astronomical Journal, 180 (180): 71–80, Bibcode:2010SerAJ.180...71C, doi:10.2298/SAJ1080071C.
- ^ a b c d e f g Mason, Brian D.; et al. (September 2010), "Binary Star Orbits. IV. Orbits of 18 Southern Interferometric Pairs", The Astronomical Journal, 140 (3): 735–743, Bibcode:2010AJ....140..735M, doi:10.1088/0004-6256/140/3/735.
- ^ a b c Arnold, H. J. P.; et al. (1999), The Photographic Atlas of the Stars, CRC Press, p. 176, ISBN 0750306548.
- ^ a b c Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
- ^ Frémat, Y.; et al. (September 2005), "Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars", Astronomy and Astrophysics, 440 (1): 305–320, arXiv:astro-ph/0503381, Bibcode:2005A&A...440..305F, doi:10.1051/0004-6361:20042229, S2CID 19016751.
- ^ "tet Cir -- Be Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-01-18.
- ^ Mason, Brian D.; et al. (July 1997), "A Speckle Survey of Southern Be Stars", Be Star Newsletter, 32: 9–10, Bibcode:1997BeSN...32....9M.
- ^ Adelman, S. J.; et al. (December 2000), "On the Variability of O4-B5 Luminosity Class III-V Stars", Information Bulletin on Variable Stars, 5008 (5008): 1, Bibcode:2000IBVS.5008....1A.
External links
edit- http://server3.wikisky.org/starview?object_type=1&object_id=2046
- http://varsao.com.ar/Curva_theta_Cir.htm Archived 2009-10-27 at the Wayback Machine (light curve)