Tau2 Hydrae

For other stars with this Bayer designation, see τ Hydrae.

Tau^2 Hydrae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	09^h 31^m 58.92729^s[1]
Declination	−01° 11′ 04.7899″[1]
Apparent magnitude (V)	+4.56[2]
Characteristics
Spectral type	A3 V[3]
U−B color index	+0.06[2]
B−V color index	+0.11[2]
Variable type	Suspected[4]
Astrometry
Radial velocity (Rv)	+3.9±0.4[5] km/s
Proper motion (μ)	RA: −12.60[1] mas/yr Dec.: −3.99[1] mas/yr
Parallax (π)	6.30 ± 0.72 mas[1]
Distance	approx. 520 ly (approx. 160 pc)
Absolute magnitude (MV)	−1.43[6]
Details
Radius	4.5[7] R☉
Luminosity	285[8] L☉
Temperature	7,918[8] K
Rotational velocity (v sin i)	54.0±0.6[3] km/s
Other designations
Ukdah, τ^2 Hya, 32 Hydrae, BD−00°2211, HD 82446, HIP 46776, HR 3787, SAO 136932.[9]
Database references
SIMBAD	data

Tau² Hydrae is a probable astrometric binary^[10] star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 6.30 mas as seen from Earth, it is located around 520 light years from the Sun. The brighter component is visible to the naked eye with an apparent visual magnitude of +4.56.^[2]

The primary member, component A, is an A-type main sequence star with a stellar classification of A3 V.^[3] It is a suspected variable of unknown type, with an amplitude of 0.06 in visual magnitude.^[4] The star has around 4.5^[7] times the radius of the Sun and is radiating about 285 times the solar luminosity from its photosphere at an effective temperature of 7,918 K.^[8]

References

1. 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.
2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
3. Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, arXiv:1012.4858, Bibcode:2011A&A...531A.143D, doi:10.1051/0004-6361/201016386, S2CID 119286673.
4. Adelman, S. J. (October 2000), "On the Variability of A3-F0 Luminosity Class III-V Stars", Information Bulletin on Variable Stars, 4969 (4969): 1, Bibcode:2000IBVS.4969....1A.
5. 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.
6. 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.
7. Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics, 367 (3rd ed.): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
8. 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.
9. "* tau02 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-22.
10. 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.