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Eta Horologii 
Summary
Eta Horologii (η Horologii, η Hor) is a binary star system[3] in the southern constellation of Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 5.31.[2] Based upon an annual parallax shift of 21.95 mas as seen from Earth,[1] it is located around 149 light years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Horologium |
| Right ascension | 02h 37m 24.37297s[1] |
| Declination | −52° 32′ 35.0855″[1] |
| Apparent magnitude (V) | 5.31[2] |
| Characteristics | |
| Spectral type | A6 V + F0 V[3] |
| B−V color index | +0.27[2] |
| Astrometry | |
| Radial velocity (Rv) | −3.0±7.4[4] km/s |
| Proper motion (μ) | RA: +112.70[1] mas/yr Dec.: +3.73[1] mas/yr |
| Parallax (π) | 21.95 ± 1.10 mas[1] |
| Distance | 149 ± 7 ly (46 ± 2 pc) |
| Absolute magnitude (MV) | 2.13[5] |
| Orbit[6] | |
| Period (P) | 3.01±0.18 yr |
| Semi-major axis (a) | 0.0231±0.0014″ |
| Eccentricity (e) | 0.16±0.14 |
| Details | |
| η Hor A | |
| Mass | 1.75[7] M☉ |
| Luminosity | 12.6[8] L☉ |
| Surface gravity (log g) | 4.21[9] cgs |
| Temperature | 7,552±257[9] K |
| Rotational velocity (v sin i) | 6.6±2.2[5] km/s |
| Age | 474[9] Myr |
| η Hor B | |
| Mass | 1.65[7] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The orbit for this pair is not yet well constrained. They appear to have an orbital period of three years and an eccentricity of roughly 0.16.[6] As of 2012, the pair have an angular separation of 78.7 mas, which corresponds to a projected separation of 3.6 AU.[3] The primary member, component A, is an A-type main sequence star with a stellar classification of A6 V. The secondary, component B, has an inferred class of F0 V, which would indicate it is an F-type main sequence star.[3]
References edit
- ^ 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 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
- ^ a b c d Marion, L.; et al. (October 2014), "Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey", Astronomy & Astrophysics, 570: 12, arXiv:1409.6105, Bibcode:2014A&A...570A.127M, doi:10.1051/0004-6361/201424780, S2CID 8756486, A127.
- ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
- ^ a b Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
- ^ a b Malkov, O. Yu.; et al. (2012), "Dynamical Masses of a Selected Sample of Orbital Binaries", Astronomy & Astrophysics, 546: 5, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774, A69.
- ^ a b Asensio-Torres, R.; Janson, M.; Bonavita, M.; Desidera, S.; Thalmann, C.; Kuzuhara, M.; Henning, Th.; Marzari, F.; Meyer, M. R.; Calissendorff, P.; Uyama, T. (2018). "SPOTS: The Search for Planets Orbiting Two Stars. III. Complete sample and statistical analysis". Astronomy & Astrophysics. 619: A43. arXiv:1807.08687. Bibcode:2018A&A...619A..43A. doi:10.1051/0004-6361/201833349. S2CID 118953455.
- ^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352
- ^ a b c David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
- ^ "eta Hor -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-04-25.