Nu Hydri

ν Hydri, Latinized as Nu Hydri, is a single[10] star in the southern circumpolar constellation of Hydrus. It is orange-hued and faintly visible to the naked eye with an apparent visual magnitude of 4.76.[2] This object is located approximately 331 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +3 km/s.[1] It is a member of the Ursa Major Moving Group of stars that share a common motion through space.[11]

Nu Hydri
Location of ν Hydri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hydrus
Right ascension  02h 50m 28.45915s[1]
Declination −75° 04′ 00.9969″[1]
Apparent magnitude (V) 4.76[2]
Characteristics
Spectral type K3III[3]
U−B color index +1.56[4]
B−V color index +1.33[4]
Astrometry
Radial velocity (Rv)+3.09±0.16[1] km/s
Proper motion (μ) RA: −33.392[1] mas/yr
Dec.: −27.286[1] mas/yr
Parallax (π)9.8538 ± 0.1433[1] mas
Distance331 ± 5 ly
(101 ± 1 pc)
Absolute magnitude (MV)−0.33[2]
Details
Mass3.5[5] or 1.79[6] M☉
Radius21.23+3.23
−4.50[1] R☉
Luminosity183.8±3.2[1] L☉
Surface gravity (log g)3.30[7] cgs
Temperature4,612+584
−315[1] K
Metallicity [Fe/H]−1.52[7] dex
Rotation50 d[5]
Rotational velocity (v sin i)1.3[8] km/s
Age2.38[6] Gyr
Other designations
ν Hyi, CPD−75°204, FK5 2199, GC 3463, HD 18293, HIP 13244, HR 872, SAO 255929[9]
Database references
SIMBADdata

This is an aging giant star with a stellar classification of K3III.[3] With the supply of hydrogen at its core exhausted, the star has expanded and cooled. At present it has 21[1] times the girth of the Sun. It is 2.4[6] billion years old with estimates of its mass ranging from 1.8[6] to 3.5[5] times the mass of the Sun. The star is radiating 184[1] times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,612 K.[1]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. 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. Vizier catalog entry
  3. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H
  4. Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42: 443. Bibcode:2014JAVSO..42..443M.Vizier catalog entry
  5. Gondoin, P. (December 2005), "The relation between X-ray activity and rotation in intermediate-mass G giants", Astronomy and Astrophysics, 444 (2): 531–538, Bibcode:2005A&A...444..531G, doi:10.1051/0004-6361:20053567.
  6. Luck, R. Earle (2015). "Abundances in the Local Region. I. G and K Giants". The Astronomical Journal. 150 (3): 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88.
  7. Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497.
  8. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (2014). "A catalog of rotational and radial velocities for evolved stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. Vizier catalog entry
  9. "nu Hyi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-30.
  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.
  11. Chupina, N. V.; et al. (June 2006), "Kinematic structure of the corona of the Ursa Major flow found using proper motions and radial velocities of single stars", Astronomy and Astrophysics, 451 (3): 909–916, Bibcode:2006A&A...451..909C, doi:10.1051/0004-6361:20054009.
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