Lambda Hydrae

λ Hydrae, Latinised as Lambda Hydrae, is a spectroscopic binary[12] star in the constellation Hydra. Its apparent magnitude is 3.61 Located around 33.3 parsecs (109 ly) distant. The spiral galaxy NGC 3145 is only 7.8′ away to the southwest.

λ Hydrae
Location of λ Hydrae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension  10h 10m 35.27667s[1]
Declination −12° 21′ 14.6938″[1]
Apparent magnitude (V) 3.61[2]
Characteristics
Spectral type K0IIIbCN0.5[3]
U−B color index 0.92[4]
B−V color index 1.00[4]
Astrometry
Radial velocity (Rv)19.4[5] km/s
Proper motion (μ) RA: -201.27[1] mas/yr
Dec.: -99.63[1] mas/yr
Parallax (π)30.0232 ± 0.6973[6] mas
Distance109 ± 3 ly
(33.3 ± 0.8 pc)
Absolute magnitude (MV)+0.92[7]
Orbit[8]
Period (P)1585.8 days
Semi-major axis (a)16.79 mas
Eccentricity (e)0.138
Inclination (i)79.49°
Longitude of the node (Ω)249.62°
Periastron epoch (T)2448664.3906
Argument of periastron (ω)
(secondary)		238.9°
Details
λ Hya A
Mass1-2[9] M☉
Radius9.7[9] R☉
Luminosity39.8[9] L☉
Surface gravity (log g)2.64[9] cgs
Temperature4,656[9] K
Metallicity [Fe/H]+0.25[10] dex
Rotational velocity (v sin i)1.9[11] km/s
Other designations
λ Hya, 41 Hydrae, BD-11°2820, HD 88284, HIP 49841, SAO 155785, HR 3994, GC 13982, TYC 5485-1310-1
Database references
SIMBADdata

The primary is an orange giant of spectral type K0IIICN+1,[13] a star that has used up its core hydrogen, left the main sequence, and expanded into a giant. It is considered to be a red clump giant, a cool horizontal branch star that is burning helium in its core.[14]

λ Hydrae has two visual companions, components B and C, 11th and 13th magnitude stars respectively 71″ and 111″ away.[15]

References
  1. van Leeuwen, F. (November 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. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  3. Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. Jennens, P. A. (1975). "A new photometric metal abundance and luminosity calibration for field G and K giants". Monthly Notices of the Royal Astronomical Society. 172 (3): 667–679. Bibcode:1975MNRAS.172..667J. doi:10.1093/mnras/172.3.667.
  5. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.c. Publication: 0. Bibcode:1953GCRV..C......0W.
  6. 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.
  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.
  8. ESA (1997). "The Hipparcos and Tycho Catalogues". VizieR On-line Data Catalog. Bibcode:1997yCat.1239....0E.
  9. Cruzalèbes, P.; Rabbia, Y.; Jorissen, A.; Spang, A.; Sacuto, S.; Pasquato, E.; Chiavassa, A.; Chesneau, O.; Fréville, P. (2013). "SPIDAST: A new modular software to process spectrointerferometric measurements". Monthly Notices of the Royal Astronomical Society. 432 (2): 1658. Bibcode:2013MNRAS.432.1658C. doi:10.1093/mnras/stt593.
  10. Hinkel, Natalie R.; Timmes, F. X.; Young, Patrick A.; Pagano, Michael D.; Turnbull, Margaret C. (2014). "Stellar Abundances in the Solar Neighborhood: The Hypatia Catalog". The Astronomical Journal. 148 (3): 54. arXiv:1405.6719. Bibcode:2014AJ....148...54H. doi:10.1088/0004-6256/148/3/54.
  11. De Medeiros, J. R.; Da Silva, J. R. P.; Maia, M. R. G. (2002). "The Rotation of Binary Systems with Evolved Components". The Astrophysical Journal. 578 (2): 943. Bibcode:2002ApJ...578..943D. doi:10.1086/342613.
  12. 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.
  13. Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637.
  14. Alves, David R. (2000). "K-Band Calibration of the Red Clump Luminosity". The Astrophysical Journal. 539 (2): 732. Bibcode:2000ApJ...539..732A. doi:10.1086/309278.
  15. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
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