Triple star system in the constellation Hydra
27 Hydrae
Observation dataEpoch J2000 Equinox J2000
Constellation
Hydra
Right ascension
09h 20m 29.01857s [ 1]
Declination
−09° 33′ 20.5054″[ 1]
Apparent magnitude (V)
4.818[ 2] (4.91 + 7.03 + 10.99) [ 3]
Characteristics
Spectral type
K0III[ 4] + F4V + K2V [ 5]
Astrometry Radial velocity (Rv ) +25.60± 0.13[ 6] km/sProper motion (μ) RA: −12.48[ 1] mas /yr Dec.: −27.37[ 1] mas /yr Parallax (π)14.66 ± 0.31 mas [ 1] Distance 222 ± 5 ly (68 ± 1 pc )
Details A Mass 2.17[ 2] M ☉ Radius 11[ 6] R ☉ Luminosity 57.5[ 2] L ☉ Surface gravity (log g )2.9[ 6] cgs Temperature 4,965± 26[ 2] K Metallicity [Fe/H]−0.07[ 6] dex Rotational velocity (v sin i )3.3[ 6] km/s Age 1.91[ 2] Gyr
B Radius 1.82[ 7] R ☉ Luminosity 5.885[ 7] L ☉ Temperature 6,664[ 7] K C Radius 0.72[ 8] R ☉ Luminosity 0.227[ 8] L ☉ Temperature 4,685[ 8] K
Other designations A : 27 Hya , BD −08°2643 , HD 80586, HIP 45811, HR 3709, SAO 136768B : BD −09°2801 , HD 80550, HIP 45802, SAO 136767C : TYC 5463-1518-1
Database references SIMBAD data B C
27 Hydrae is a triple star system [ 5] system in the equatorial constellation of Hydra ,[ 9] located 222 light years away from the Sun.[ 1] It is visible to the naked eye as a faint, orange-hued star with a combined apparent visual magnitude of 4.82.[ 2] The system is moving further from the Earth with a heliocentric radial velocity of +25.6 km/s.[ 6]
The magnitude 4.91[ 5] primary, component A, is an aging giant star with a stellar classification of K0 III.[ 4] It is a red clump giant,[ 10] which indicates it is on the horizontal branch and is generating energy through helium fusion at its core . The star is 1.9[ 2] billion years old with 2.17[ 2] times the mass of the Sun . It has swelled to 11[ 6] times the Sun's radius and is radiating 57.5[ 2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,965 K.[ 2] The star is suspected to host a low-mass companion.[ 11]
The stellar companions to this star, designated components B and C, lie at an angular separation of 229.10″ from the primary, and form a binary pair with a separation of 9.20″ as of 2015.[ 3] The brighter member of the pair, component B, is a seventh magnitude F-type main-sequence star with a class of F4 V, while its companion is an eleventh magnitude K-type main-sequence star with a class of K2 V.[ 5]
Substellar companion
The Okayama Planet Search team published a paper in late 2008 reporting investigations into radial velocity variations observed for a set of evolved stars, showing hints of a substellar companion orbiting the primary member of the wide binary system 27 Hydrae.[ 11] Its orbital period is estimated at 9.3 years, but no planet has been confirmed yet.
References
^ 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 e f g h i j Luck, R. Earle (2015). "Abundances in the Local Region. I. G and K Giants". Astronomical Journal . 150 (3). 88. arXiv :1507.01466 . Bibcode :2015AJ....150...88L . doi :10.1088/0004-6256/150/3/88 . S2CID 118505114 .
^ a b Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog" , The Astronomical Journal , 122 (6): 3466, Bibcode :2001AJ....122.3466M , doi :10.1086/323920 , retrieved 2015-07-22
^ 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 .
^ a b c d 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 c d e f g Massarotti, Alessandro; et al. (January 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 . S2CID 121883397 .
^ a b c 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 c 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 "27 Hya" . SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved May 3, 2019 .
^ 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
^ a b Toyota, Eri; et al. (2008). "Radial Velocity Search for Extrasolar Planets in Visual Binary Systems" . Publications of the Astronomical Society of Japan . 61 (1): 19–28. Bibcode :2009PASJ...61...19T . doi :10.1093/pasj/61.1.19 . hdl :20.500.14094/90001422 .