26 Hydrae

26 Hydrae
Observation data; Epoch J2000 Equinox J2000
Constellation	Hydra
Right ascension	09h 19m 46.38309s
Declination	−11° 58′ 29.4577″
Apparent magnitude (V)	4.770 + 12.4
Characteristics
Spectral type	G7III or G8II
U−B color index	+0.67
B−V color index	+0.927±0.017
Astrometry
Radial velocity (Rv)	−1.18±0.09 km/s
Proper motion (μ)	RA: −29.269 mas/yr ; Dec.: +11.613 mas/yr
Parallax (π)	9.7770 ± 0.1610 mas
Distance	334 ± 5 ly ; (102 ± 2 pc)
Absolute magnitude (MV)	−0.29
Details
26 Hya A
Mass	2.72 M☉
Radius	15.14+0.81; −2.47 R☉
Luminosity	138.5±2.7 L☉
Surface gravity (log g)	2.48±0.07 cgs
Temperature	5,003±82 K
Metallicity [Fe/H]	−0.13±0.06 dex
Rotational velocity (v sin i)	2.7 km/s
Age	0.51 Gyr
Other designations
	26 Hya, BD−11°2609, FK5 2741, HD 80499, HIP 45751, HR 3706, SAO 155096, WDS J09198-1158AB
Database references
SIMBAD	data

26 Hydrae is a binary star^[3] system located 334 light years away from the Sun in the equatorial constellation of Hydra. It is visible to the naked eye as a faint, yellow-hued point of light with a combined apparent visual magnitude of 4.77,^[2] just a few degrees away from Alphard. The system is moving closer to the Earth with a leisurely radial velocity of -1 km/s.^[8]

Keenan and McNeil (1989) gave the brighter component a stellar classification of G7 III,^[4] matching an aging giant star. Houk and Swift (1999) have it classed as a G8II^[5] bright giant. This is a red clump giant,^[12] which indicates it is on the horizontal branch and is generating energy through helium fusion at its core. It has a high lithium abundance and displays a far infrared emission excess.^[13] The star is an estimated 510^[9] million years old with 2.72^[9] times the mass of the Sun and has expanded to 15^[1] times the Sun's radius. It is radiating 139^[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 5,003 K.^[9]

The secondary component is a magnitude 12.4 star at an angular separation of 3.2″, as of 2008.^[3]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ 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.
^ ^a ^b Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 – L30. Bibcode:2000A&A...355L..27H.
^ ^a ^b ^c 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.
^ ^a ^b Keenan, P.; McNeil, R. (October 1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245–266. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. S2CID 123149047.
^ ^a ^b Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
^ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
^ ^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, S2CID 119257644.
^ ^a ^b ^c Massarotti, Alessandro; et al. (2008). "Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity". The Astronomical Journal. 135 (1): 209–231. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
^ ^a ^b ^c ^d ^e ^f 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. S2CID 118505114.
^ ^a ^b Wu, Yue; et al. (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014. S2CID 53480665.
^ "26 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-12.
^ Alves, David R. (August 2000). "K-Band Calibration of the Red Clump Luminosity". The Astrophysical Journal. 539 (2): 732–741. arXiv:astro-ph/0003329. Bibcode:2000ApJ...539..732A. doi:10.1086/309278. S2CID 16673121.
^ Jasniewicz, G.; et al. (2000). da silva, L.; de Medeiros, R.; Spite, M (eds.). Search for Lithium-Rich Stars Among G-K Giants with IR-excess. The Light Elements and their Evolution, Proceedings of IAU Symposium 198, held 22-26 Nov 1999, Natal, Brazil. p. 325. Bibcode:2000IAUS..198..325J.

[GaiaDR2-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ 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.

[TYC2-2] Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 – L30. Bibcode:2000A&A...355L..27H.

[Eggleton2008-3] 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. S2CID 14878976.

[Keenan1989-4] Keenan, P.; McNeil, R. (October 1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245–266. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. S2CID 123149047.

[HD-5] Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.

[EgUBV-6] Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.

[Anderson2012-7] 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.

[Massarotti-8] Massarotti, Alessandro; et al. (2008). "Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity". The Astronomical Journal. 135 (1): 209–231. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.

[Luck-9] ^ ^a ^b ^c ^d ^e ^f 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. S2CID 118505114.

[Wu-10] Wu, Yue; et al. (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014. S2CID 53480665.

[SIMBAD-11] "26 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-12.

[Alves2000-12] Alves, David R. (August 2000). "K-Band Calibration of the Red Clump Luminosity". The Astrophysical Journal. 539 (2): 732–741. arXiv:astro-ph/0003329. Bibcode:2000ApJ...539..732A. doi:10.1086/309278. S2CID 16673121.

[Jasniewiczw2000-13] Jasniewicz, G.; et al. (2000). da silva, L.; de Medeiros, R.; Spite, M (eds.). Search for Lithium-Rich Stars Among G-K Giants with IR-excess. The Light Elements and their Evolution, Proceedings of IAU Symposium 198, held 22-26 Nov 1999, Natal, Brazil. p. 325. Bibcode:2000IAUS..198..325J.

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26 Hydrae

References

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