Chi¹ Hydrae

Chi¹ Hydrae (χ¹ Hydrae) is a binary star[3] in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 9 Crateris before being placed in the Hydra constellation.[10] Based upon an annual parallax shift of 22.8 mas as seen from Earth, it is located about 143 light years from the Sun. It is visible to the naked with a combined apparent visual magnitude of 4.94.[2]

For other stars with this Bayer designation, see χ Hydrae

Chi¹ Hydrae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	11^h 05^m 19.90766^s[1]
Declination	−27° 17′ 36.9957″[1]
Apparent magnitude (V)	4.94[2]
Characteristics
Spectral type	F4 V + F7 V[3]
U−B color index	+0.04[2]
B−V color index	+0.36[2]
Astrometry
Radial velocity (Rv)	+19.1±1.6[4] km/s
Proper motion (μ)	RA: −190.728[5] mas/yr Dec.: −6.273[5] mas/yr
Parallax (π)	22.8323 ± 0.1828[5] mas
Distance	143 ± 1 ly (43.8 ± 0.4 pc)
Absolute magnitude (MV)	1.74[6]
Orbit[7]
Period (P)	7.5535±0.0064 yr
Semi-major axis (a)	0.1388±0.0016″
Eccentricity (e)	0.349±0.015
Inclination (i)	96.50±0.84°
Longitude of the node (Ω)	224.00±0.59°
Periastron epoch (T)	1983.455 ± 0.084
Argument of periastron (ω) (secondary)	343.0±4.3°
Details
χ^1 Hya A
Mass	1.93[8] M☉
Radius	3.19[5] R☉
Luminosity	17.798[5] L☉
Temperature	6,637[5] K
Metallicity [Fe/H]	−0.10[6] dex
Age	1.3[6] Gyr
χ^1 Hya B
Mass	1.93[8] M☉
Other designations
χ^1 Hya, CD−26°8338, FK5 419, GJ 3642, HD 96202, HIP 54204, HR 4314, SAO 179514[9]
Database references
SIMBAD	data

The two components of this system appear to have equal masses of 1.93 times the mass of the Sun.[7] The pair circle each other with an orbital period of 7.55 years with an eccentricity of 0.35.[7]

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. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
3. 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.
4. 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.
5. 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.
6. Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959.
7. Mason, Brian D.; et al. (February 1999), "Binary Star Orbits from Speckle Interferometry. I. Improved Orbital Elements of 22 Visual Systems", The Astronomical Journal, 117 (2): 1023–1036, Bibcode:1999AJ....117.1023M, doi:10.1086/300748.
8. Jaime, Luisa G.; et al. (December 2012), "Regions of dynamical stability for discs and planets in binary stars of the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 427 (4): 2723–2733, arXiv:1208.2051, Bibcode:2012MNRAS.427.2723J, doi:10.1111/j.1365-2966.2012.21839.x.
9. "chi01 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-17.
10. Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18: 216, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305.