Upsilon2 Hydrae
Star in the constellation Hydra
Upsilon2 Hydrae , Latinised from υ2 Hydrae , is a solitary[ 10] star in the equatorial constellation of Hydra . Visible to the naked eye, it is photometrically stable[ 11] 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,[ 3] 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 .[ 6] 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 3.29[ 6] times the mass of the Sun and around 3.2[ 7] times the Sun's radius . It is radiating 182[ 6] times the solar luminosity from its photosphere at an effective temperature of about 11,758 K .[ 8]
References
^ 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^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data , SIMBAD , Bibcode :1986EgUBV........0M .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, 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 .
^ a b c d e 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 .
^ a b 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 .
^ a b c d e f g 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 .