Astronomy:Phi2 Hydrae
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 10h 36m 16.65960s[1] |
| Declination | −16° 20′ 39.5778″[1] |
| Apparent magnitude (V) | 6.0943[2] |
| Characteristics | |
| Spectral type | M1 III[3] |
| U−B color index | +1.95[4] |
| B−V color index | +1.64[4] |
| Variable type | SR[5] |
| Astrometry | |
| Radial velocity (Rv) | +15.7±2.9[2] km/s |
| Proper motion (μ) | RA: −29.14[1] mas/yr Dec.: +2.31[1] mas/yr |
| Parallax (π) | 4.31 ± 0.33[1] mas |
| Distance | 760 ± 60 ly (230 ± 20 pc) |
| Absolute magnitude (MV) | −0.80[6] |
| Details | |
| Luminosity | 703[7] L☉ |
| Temperature | 3,791[7] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Phi2 Hydrae, Latinized from φ2 Hydrae, is a star in the constellation Hydra. It originally received the Flamsteed designation of 1 Crateris before being placed in the Hydra constellation.[9] Based upon an annual parallax shift of 4.31 mas as seen from Earth, it is located roughly 760 light years from the Sun. The star is faintly visible to the naked with an apparent visual magnitude of 6.09.[2] It forms a triangle with the fainter φ1 Hydrae and the brighter φ3 Hydrae, between μ Hydrae and ν Hydrae.
| Period (days) |
Amplitude (magnitude) |
|---|---|
| 11.0 | 0.008 |
| 110.3 | 0.012 |
| 153.6 | 0.015 |
This is an evolved red giant star with a stellar classification of M1 III.[10] It is currently on the asymptotic giant branch,[10] and is a semiregular variable that undergoes changes in luminosity according to three pulsation periods.[5] The star is radiating an estimated 703[7] times the Sun's luminosity from its photosphere at an effective temperature of 3,791 K.[7]
Phi2 Hydrae has a faint visual companion: a magnitude 12.20 star at an angular separation of 3.50 arc seconds along a position angle of 280°, as of 1959.[11]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V.
- ↑ 2.0 2.1 2.2 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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D.
- ↑ Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode: 1988mcts.book.....H.
- ↑ 4.0 4.1 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M.
- ↑ 5.0 5.1 5.2 Tabur, V. et al. (2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society 400 (4): 1945–61, doi:10.1111/j.1365-2966.2009.15588.x, Bibcode: 2009MNRAS.400.1945T.
- ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 7.0 7.1 7.2 7.3 McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M.
- ↑ "* phi02 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+phi02+Hya.
- ↑ Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy 18 (3): 216, doi:10.1177/002182868701800305, Bibcode: 1987JHA....18..209W.
- ↑ 10.0 10.1 Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal 104 (1): 275–313, doi:10.1086/116239, Bibcode: 1992AJ....104..275E.
- ↑ Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M.
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