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Omicron Hydrae - Wikipedia

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Omicron Hydrae
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Hydra^[1]
Right ascension	11^h 40^m 12.78970^s^[2]
Declination	−34° 44′ 40.7733″^[2]
Apparent magnitude (V)	4.70^[3]
Characteristics
Spectral type	B9 V^[4]
U−B color index	−0.20^[3]
B−V color index	−0.08^[3]
Astrometry

Radial velocity (R_v)	+5.9^[5] km/s
Proper motion (μ)	RA: −43.24^[2] mas/yr Dec.: −1.61^[2] mas/yr
Parallax (π)	7.27±0.16 mas^[2]
Distance	449 ± 10 ly (138 ± 3 pc)
Absolute magnitude (M_V)	−0.99^[1]

Details

Mass	3.56±0.04^[6] `M`_☉
Radius	5.5^[7] `R`_☉
Luminosity	309^[6] `L`_☉
Surface gravity (log g)	2.87^[8] cgs
Temperature	10,495^[6] K
Rotation	27.2 days^[8]
Rotational velocity (v sin i)	160^[6] km/s
Age	252^[9] Myr

Other designations
ο Hya, CD−34°7610, FK5 439, HD 101431, HIP 56922, HR 4494, SAO 202695^[10]
Database references
SIMBAD	data

Omicron Hydrae (ο Hya) is the Bayer designation for a solitary^[11] star in the equatorial constellation Hydra. At one time it bore the Flamsteed designation 25 Crateris, but this is no longer used by astronomers so as to avoid confusion.^[12] With an apparent visual magnitude of 4.70,^[3] this star is visible to the naked eye. Based upon an annual parallax shift of 7.27 mas,^[2] it is located around 449 light years from the Sun.

This is a B-type main sequence star with a stellar classification of B9 V.^[4] It has completed an estimated 98.4%±1.1% of its lifetime on the main sequence. With 3.56^[6] times the mass of the Sun, it radiates 309 times the Sun's luminosity from its outer atmosphere at an effective temperature of 10,495 K.^[6] The rate of spin is relatively high, with a projected rotational velocity of 160 km/s.^[6]

References

^ ^a ^b 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. XHIP record for this object at VizieR.
^ ^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^ ^a ^b ^c ^d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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, N. (1982), Michigan Catalogue of Two-dimensional Spectral Types for the HD stars, vol. 3, Ann Arbor, MI: Department of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H.
^ Wielen, R.; et al. (2000), "Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions", Veröffentlichungen Astronomisches Rechen-Institut Heidelberg, vol. 37, no. 37, Karlsruhe: Verlag G. Braun, pp. 1–308, Bibcode:2000VeARI..37....1W, ISBN 3-7650-0536-3.
^ ^a ^b ^c ^d ^e ^f ^g 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.
^ Stassun, Keivan G.; et al. (2019), "The Revised TESS Input Catalog and Candidate Target List", The Astronomical Journal, 158 (4): 138, arXiv:1905.10694, Bibcode:2019AJ....158..138S, doi:10.3847/1538-3881/ab3467.
^ ^a ^b Oelkers, Ryan J.; Rodriguez, Joseph E.; Stassun, Keivan G.; Pepper, Joshua; Somers, Garrett; Kafka, Stella; Stevens, Daniel J.; Beatty, Thomas G.; Siverd, Robert J.; Lund, Michael B.; Kuhn, Rudolf B.; James, David; Gaudi, B. Scott (2018), "Variability Properties of Four Million Sources in the TESS Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey", The Astronomical Journal, 155 (1): 39, arXiv:1711.03608, Bibcode:2018AJ....155...39O, doi:10.3847/1538-3881/aa9bf4.
^ Gontcharov, G. A. (2012), "Dependence of kinematics on the age of stars in the solar neighborhood", Astronomy Letters, 38 (12): 771, arXiv:1606.08814, Bibcode:2012AstL...38..771G, doi:10.1134/S1063773712120031.
^ "* omi Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-06.
^ 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.
^ Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18 (3): 216, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305, S2CID 118445625.

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, Solitaire) 59 60 10 Crt 17 Crt (N) 20 Crt 30 Mon (C) 31 Mon (F) 2 Sex
Variable	R U V W TW EX HS KU LQ V419 V421 V434 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
Other	Gliese 328 Gliese 357 Gliese 433 Gliese 453 GJ 3517 GJ 3634 HE 1256−2738 HE 1327−2326 LHS 2065 LHS 3003 LTT 3780 2MASS 1114−2618 WASP-25 WASP-36 WASP-84 WISE 0855−0714

Star clusters	Messier 48 Messier 68 NGC 5694

Nebulae	Abell 33 Abell 35 NGC 3242

Galaxies

Messier	83
NGC	2617 2697 2708 2835 2865 2890 2936 2937 2962 2992 3054 3081 3109 3124 3285 3305 3307 3308 3309 3311 3312 3313 3314 3315 3316 3336 3369 3393 3402 3464 3585 3621 3673 3717 3923 4980 4993 5042 5078 5085 5101 5135 5260 5264 5495
Other	3C 196.1 AM 1316-241 Arp 7 ESO 510-G13 GAMA202627 IC 535 MRC 1138-262 Peekaboo Galaxy RX J0911.4+0551 TN J0924-2201 Tololo 1247-232

Galaxy clusters	Abell 754 Abell 3411 Abell 3412 Hickson 40

Astronomical events	GW170817