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Delta Horologii 
Summary
Delta Horologii (δ Horologii) is a binary star[3] system in the constellation Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 4.93.[2] As of 2014, the pair had an angular separation of 0.20 arc seconds along a position angle of 24°.[9] Based upon an annual parallax shift of 18.24 mas as seen from Earth,[1] it is located 179 ± 4 light years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Horologium |
| Right ascension | 04h 10m 50.58927s[1] |
| Declination | −41° 59′ 36.8537″[1] |
| Apparent magnitude (V) | 4.93[2] (5.15 + 7.29)[3] |
| Characteristics | |
| Spectral type | A9 V[3] |
| U−B color index | +0.084[2] |
| B−V color index | +0.338[2] |
| Astrometry | |
| Radial velocity (Rv) | +38.3±2.6[4] km/s |
| Proper motion (μ) | RA: +199.08[1] mas/yr Dec.: +70.18[1] mas/yr |
| Parallax (π) | 18.24 ± 0.41 mas[1] |
| Distance | 179 ± 4 ly (55 ± 1 pc) |
| Absolute magnitude (MV) | 1.50[5] |
| Details | |
| δ Hor A | |
| Mass | 1.41[6] M☉ |
| Surface gravity (log g) | 3.71±0.14[6] cgs |
| Temperature | 7,033±239[6] K |
| Metallicity [Fe/H] | −0.32[7] dex |
| Rotational velocity (v sin i) | 220.1±11.0[5] km/s |
| Age | 768[6] Myr |
| δ Hor B | |
| Rotational velocity (v sin i) | 51.7±2.6[5] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary, component A, is a magnitude 5.15 A-type main sequence star with a stellar classification of A9 V.[3] At the estimated age of 768 million years,[6] it is spinning rapidly with a projected rotational velocity of 220 km/s,[5] giving the star an oblate shape with an equatorial bulge that is 15% larger than the polar radius.[10] The star has 1.4[6] times the mass of the Sun.
The secondary has an apparent magnitude of 7.29.[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 d Cousins, A. W. J. (1983), "UBV photometry of E region standard stars of intermediate brightness", South African Astronomical Observatory Circular, 7 (7): 36–46, Bibcode:1983SAAOC...7...36C.
- ^ a b c d e Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
- ^ 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 c d 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 c d e f 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.
- ^ Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016.
- ^ "del Hor -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-04-25.
- ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
- ^ Belle, G. T. (2012). "Interferometric observations of rapidly rotating stars". The Astronomy and Astrophysics Review. 20 (1): 51. arXiv:1204.2572. Bibcode:2012A&ARv..20...51V. doi:10.1007/s00159-012-0051-2. S2CID 119273474.