26 Hydrae
{{Short description|Binary star system in the constellation Hydra}}
{{Starbox begin}}
{{Starbox observe
| epoch = J2000
| constell = Hydra
| dec = {{DEC|-11|58|29.4577}}
| appmag_v = 4.770 + 12.4
}}
{{Starbox character
| type = red clump
| class = G7III or G8II
| variable =
}}
{{Starbox astrometry
| radial_v = {{Val|-1.18|0.09}}
| parallax = 9.7770
| p_error = 0.1610
}}
{{Starbox detail
| component1 = 26 Hya A
| radius = {{Val|15.14|0.81|2.47}}
| temperature = {{Val|5003|82|fmt=commas}}
| luminosity = {{Val|138.5|2.7}}
| metal_fe = {{Val|-0.13|0.06}}
}}
{{Starbox catalog
| names={{odlist | F=26 Hya | BD=-11°2609 | FK5=2741 | HD=80499 | HIP=45751 | HR=3706 | SAO=155096 | WDS=J09198-1158AB }}
}}
{{Starbox reference
| Simbad=26+Hya
}}
{{Starbox end}}
26 Hydrae is a binary star 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, just a few degrees away from Alphard. The system is moving closer to the Earth with a leisurely radial velocity of -1 km/s.
Keenan and McNeil (1989) gave the brighter component a stellar classification of G7 III, matching an aging giant star. Houk and Swift (1999) have it classed as a G8II bright giant. This is a red clump giant, 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. The star is an estimated 510 million years old with 2.72 times the mass of the Sun and has expanded to 15 times the Sun's radius. It is radiating 139 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 5,003 K.
The secondary component is a magnitude 12.4 star at an angular separation of {{Val|3.2|ul=arcsecond}}, as of 2008.
References
{{reflist|refs=
{{Cite Gaia DR2|5738958360595725312}}
{{cite simbad | title=26 Hya | access-date=2019-06-12 }}
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}
| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.
| title=A catalogue of multiplicity among bright stellar systems
| journal=Monthly Notices of the Royal Astronomical Society
| volume=389 | issue=2 | pages=869–879 | date=September 2008
| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E
| arxiv=0806.2878 | s2cid=14878976 }}
| last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W.
| last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey
| title=Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity
| display-authors=1 | journal=The Astronomical Journal
| volume=135 | issue=1 | pages=209–231 | year=2008
| bibcode=2008AJ....135..209M | doi=10.1088/0004-6256/135/1/209 | doi-access=free }}
| last1=Luck | first1=R. Earle
| title=Abundances in the Local Region. I. G and K Giants
| journal=The Astronomical Journal
| volume=150 | issue=3 | pages=88 | year=2015
| bibcode=2015AJ....150...88L | arxiv=1507.01466
| doi=10.1088/0004-6256/150/3/88 | s2cid=118505114
}}
| display-authors=1 | last1=Wu | first1=Yue
| last2=Singh | first2=H. P. | last3=Prugniel | first3=P.
| last4=Gupta | first4=R. | last5=Koleva | first5=M.
| title=Coudé-feed stellar spectral library – atmospheric parameters
| journal=Astronomy & Astrophysics
| volume=525 | pages=A71 | year=2010
| bibcode=2011A&A...525A..71W | arxiv=1009.1491
| doi=10.1051/0004-6361/201015014 | s2cid=53480665 }}
| title=Michigan catalogue of two-dimensional spectral types for the HD Stars
| journal=Michigan Spectral Survey
| last1=Houk | first1=N.
| last2=Swift | first2=C.
| volume=5 | year=1999
| bibcode=1999MSS...C05....0H }}
| last1=Mermilliod | first1=J.-C.
| title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)
| journal=Catalogue of Eggen's UBV Data
| date=1986 | bibcode= 1986EgUBV........0M }}
| title=The Tycho-2 catalogue of the 2.5 million brightest stars
| last1=Høg | first1=E. | display-authors=etal
| journal=Astronomy and Astrophysics
| date=2000 | volume=355 | pages=L27–L30
| bibcode=2000A&A...355L..27H }}
| first1=P. | last1=Keenan | first2=R. | last2=McNeil
| title = The Perkins catalog of revised MK types for the cooler stars
| journal=Astrophysical Journal Supplement Series
| volume=71 | pages=245–266 | date=October 1989
| bibcode=1989ApJS...71..245K | doi=10.1086/191373 | s2cid=123149047 }}
| title=Search for Lithium-Rich Stars Among G-K Giants with IR-excess
| last1=Jasniewicz | first1=G. | last2=Parthasarathy | first2=M.
| last3=de Laverny | first3=P. | last4=Thévenin | first4=F.
| last5=Mauron | first5=N. | last6=Chadid | first6=M.
| conference=The Light Elements and their Evolution, Proceedings of IAU Symposium 198, held 22-26 Nov 1999, Natal, Brazil
| editor1-first=L. | editor1-last=da silva
| editor2-first=R. | editor2-last=de Medeiros
| editor3-first=M | editor3-last=Spite
| display-authors=1 | page=325 | year=2000
| bibcode=2000IAUS..198..325J }}
| last1=Alves | first1=David R.
| title=K-Band Calibration of the Red Clump Luminosity
| journal=The Astrophysical Journal
| volume=539 | issue=2 | pages=732–741 | date=August 2000
| doi=10.1086/309278 | arxiv=astro-ph/0003329
| bibcode=2000ApJ...539..732A | s2cid=16673121
}}
}}
{{Stars of Hydra}}
{{DEFAULTSORT:26 Hydrae}}
Category:Horizontal-branch stars
Category:Hydra (constellation)