Tau2 Hydrae

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]

For other stars with this Bayer designation, see τ Hydrae.
Tau2 Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension  09h 31m 58.92729s[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[1] mas
Distanceapprox. 520 ly
(approx. 160 pc)
Absolute magnitude (MV)−1.43[6]
Details
Radius4.5[7] R☉
Luminosity285[8] L☉
Temperature7,918[8] K
Rotational velocity (v sin i)54.0±0.6[3] km/s
Other designations
Ukdah, τ2 Hya, 32 Hydrae, BD−00°2211, HD 82446, HIP 46776, HR 3787, SAO 136932.[9]
Database references
SIMBADdata

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.
  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 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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.
  4. Adelman, S. J. (October 2000), "On the Variability of A3-F0 Luminosity Class III-V Stars", Information Bulletin on Variable Stars (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, 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.
  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 (3rd ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  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.
  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.
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