Summary
Omicron Hydrae (ο Hya) is the Bayer designation for a solitary[8] star in the equatorial constellation Hydra. At one time it bore the Flamsteed designation 25 Crateris, but this is no longer used by astronomers so as to avoid confusion.[9] With an apparent visual magnitude of 4.70,[2] this star is visible to the naked eye. Based upon an annual parallax shift of 7.27 mas,[1] it is located around 449 light years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 11h 40m 12.78970s[1] |
| Declination | −34° 44′ 40.7733″[1] |
| Apparent magnitude (V) | 4.70[2] |
| Characteristics | |
| Spectral type | B9 V[3] |
| U−B color index | −0.20[2] |
| B−V color index | −0.08[2] |
| Astrometry | |
| Radial velocity (Rv) | +5.9[4] km/s |
| Proper motion (μ) | RA: −43.24[1] mas/yr Dec.: −1.61[1] mas/yr |
| Parallax (π) | 7.27 ± 0.16 mas[1] |
| Distance | 449 ± 10 ly (138 ± 3 pc) |
| Absolute magnitude (MV) | −0.99[5] |
| Details[6] | |
| Mass | 3.56±0.04 M☉ |
| Luminosity | 309 L☉ |
| Temperature | 10,495 K |
| Rotational velocity (v sin i) | 160 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a B-type main sequence star with a stellar classification of B9 V.[3] It has completed an estimated 98.4%±1.1% of its lifetime on the main sequence. With 3.56[6] times the mass of the Sun, it radiates 309 times the Sun's luminosity from its outer atmosphere at an effective temperature of 10,495 K.[6] The rate of spin is relatively high, with a projected rotational velocity of 160 km/s.[6]
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- ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
- ^ a b Houk, N. (1982), Michigan Catalogue of Two-dimensional Spectral Types for the HD stars, vol. 3, Ann Arbor, MI: Department of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H.
- ^ Wielen, R.; et al. (2000), "Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions", Veröffentlichungen Astronomisches Rechen-Institut Heidelberg, vol. 37, no. 37, Karlsruhe: Verlag G. Braun, pp. 1–308, Bibcode:2000VeARI..37....1W, ISBN 3-7650-0536-3.
- ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ a b c d Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
- ^ "* omi Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-06.
- ^ 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.
- ^ Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18 (3): 216, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305, S2CID 118445625.