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Upsilon² Hydrae

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Upsilon² Hydrae
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	10^h05^m 07.46888^s^[1]
Declination	−13° 03′ 52.6561″^[1]
Apparent magnitude (V)	4.59^[2]
Characteristics
Spectral type	B9 III-IV^[3]
U−B color index	−0.27^[2]
B−V color index	−0.08^[2]
Astrometry

Radial velocity (R_v)	+24.3±2.6^[4] km/s
Proper motion (μ)	RA: −39.39^[1] mas/yr Dec.: +19.65^[1] mas/yr
Parallax (π)	10.40 ± 0.23 mas^[1]
Distance	314 ± 7 ly (96 ± 2 pc)
Absolute magnitude (M_V)	−0.31^[5]

Details

Mass	3.29±0.03^[6] `M`_☉
Radius	3.2^[7] `R`_☉
Luminosity	182^[6] `L`_☉
Surface gravity (log g)	3.87^[8] cgs
Temperature	11758±400^[8] K
Rotational velocity (v sin i)	58^[8] km/s
Age	97^[8] Myr

Other designations
υ² Hya, 40 Hydrae, BD−12°3073, FK5 1261, HD 87504, HIP 49402, HR 3970, SAO 155713^[9]
Database references
SIMBAD	data

Upsilon² Hydrae, Latinised from υ² Hydrae, is a solitary^[10] star in the equatorial constellationofHydra. 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[edit]

^ ^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^ ^a ^b ^c ^d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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.

Constellation of Hydra

Stars

Bayer	α (Alphard) β γ δ ε (Ashlesha) ζ η θ ι (Ukdah) κ λ μ ν ξ ο π ρ σ (Minchir) τ¹ τ² υ¹ (Zhang) υ² φ¹ φ² φ³ χ¹ χ² ψ ω
Flamsteed	1 2 3 6 (a) 9 10 12 (D) 14 15 17 19 20 21 23 24 25 26 27 (P) 28 29 33 (A) 34 37 44 47 48 50 51 (k) 52 (l) 54 (m) 55 56 57 58 (E) 59 60 3 Crt (b¹) 5 Crt (b²) 6 Crt (b³) 10 Crt 17 Crt (N) 20 Crt 14 Lib 30 Mon (C) 31 Mon (F) 2 Sex
Variable	R U V W TW EX HS KU LQ V419 V421 V478
HR	3378 3538 3749 (G) 3750 3858 (I) 3862 3919 3923 (Felis) 4162 4328 4339 4445 5265
HD	72659 74156 82943 86226 86264 90156
Gliese	328 357 433 453 3517 3634
Other	HE 1256-2738 HE 1327-2326 LHS 2065 LHS 3003 LTT 3780 2MASS 1114−2618 WASP-25 WASP-36 WASP-84 WISE 0855−0714 SSSPM J0829-1309