  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 10h 05m 07.46888s1 |
| Declination | −13° 03′ 52.6561″1 |
| Apparent magnitude (V) | 4.592 |
| Characteristics | |
| Evolutionary stage | main sequence3 |
| Spectral type | B9 III-IV4 |
| U−B color index | −0.272 |
| B−V color index | −0.082 |
| Astrometry | |
| Radial velocity (Rv) | +24.3±2.65 km/s |
| Proper motion (μ) | RA: −39.391 mas/yr Dec.: +19.651 mas/yr |
| Parallax (π) | 10.40±0.23 mas1 |
| Distance | 314 ± 7 ly (96 ± 2 pc) |
| Absolute magnitude (MV) | −0.316 |
| Details | |
| Mass | 2.927 M☉ |
| Radius | 3.527 R☉ |
| Luminosity | 1727 L☉ |
| Surface gravity (log g) | 3.817 cgs |
| Temperature | 11,1437 K |
| Rotational velocity (v sin i) | 588 km/s |
| Age | 978 Myr |
| Other designations | |
| υ2 Hya, 40 Hydrae, BD−12°3073, FK5 1261, HD 87504, HIP 49402, HR 3970, SAO 1557139 | |
| Database references | |
| SIMBAD | data |
Upsilon2 Hydrae, Latinised from υ2 Hydrae, is a solitary10 star in the equatorial constellation of Hydra. Visible to the naked eye, it is photometrically stable11 with an apparent visual magnitude of 4.59.2 Based upon an annual parallax shift of 10.40 mas as seen from Earth,1 it is located about 314 light-years from the Sun.
This is a B-type star with a stellar classification of B9 III-IV,4 showing partial traits of a subgiant and giant star in its spectrum. However, Zorec and Royer (2012) estimate the star still only 79% of the way through its life span on the main sequence.3 With an age of around 97 million years,8 it is spinning with a projected rotational velocity of 58 km/s.8 The star has an estimated 2.9 times the mass of the Sun and around 3.5 times the Sun's radius. It is radiating 172 times the solar luminosity from its photosphere at an effective temperature of about 11,143 K.7
References
References
- 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.
- Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
- 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.
- Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
- 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.
- 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.
- Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.
- 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.
- "* ups02 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-21.
{{cite web}}: CS1 maint: postscript (link) - 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.
- Adelman, S. J.; et al. (October 2000), "On the Variability of Late B III-V Stars", Information Bulletin on Variable Stars, 4968 (4968): 1, Bibcode:2000IBVS.4968....1A.