Astronomy:Tau1 Hydrae

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Short description: Triple star system in the constellation Hydra


For other stars with this Bayer designation, see τ Hydrae.
Tau1 Hydrae
Observation data
Equinox J2000.0]] (ICRS)
Constellation Hydra
Right ascension  09h 29m 08.89655s[1]
Declination −02° 46′ 08.2649″[1]
Apparent magnitude (V) +4.59 (4.60 + 7.15)[2]
Characteristics
Spectral type F6 V + ? + K0[3]
B−V color index +0.411±0.015[2]
Astrometry
Radial velocity (Rv)+10.85±0.28[4] km/s
Absolute magnitude (MV)+3.28[5]
τ1 Hydrae A
Proper motion (μ) RA: +107.115[6] mas/yr
Dec.: −29.652[6] mas/yr
Parallax (π)56.2938 ± 0.5309[6] mas
Distance57.9 ± 0.5 ly
(17.8 ± 0.2 pc)
τ1 Hydrae B
Proper motion (μ) RA: +138.487[7] mas/yr
Dec.: −17.371[7] mas/yr
Parallax (π)55.3675 ± 0.0638[7] mas
Distance58.91 ± 0.07 ly
(18.06 ± 0.02 pc)
Orbit[8]
Period (P)2,807±23 d
Eccentricity (e)0.33±0.12
Periastron epoch (T)2445260 ± 150 JD
Semi-amplitude (K1)
(primary)		2.98±0.39 km/s
Details
τ1 Hydrae A
Mass1.20[9] M☉
Radius1.4[10] R☉
Luminosity (bolometric)3.369[2] L☉
Surface gravity (log g)4.12±0.14[9] cgs
Temperature6,473±220[9] K
Metallicity [Fe/H]−0.01[2] dex
Rotational velocity (v sin i)30.4±1.5[5] km/s
Age3.61[2] Gyr
τ1 Hydrae B
Mass0.86[11] M☉
Radius0.81[10] R☉
Luminosity0.435[7] L☉
Temperature5,197[7] K
Other designations
τ1 Hya, 31 Hydrae, BD−02°2901, GJ 348, HD 81997, HIP 46509, HR 3759, SAO 136895, WDS J09291-0246[12]
Database references
SIMBADτ1 Hya AB
τ1 Hya A
τ1 Hya B

Tau1 Hydrae is a triple star[3] system in the equatorial constellation of Hydra. Based upon the annual parallax shift of the two visible components as seen from Earth,[1] they are located about 18 parsecs (59 ly) from the Sun. The system has a combined apparent visual magnitude of +4.59,[2] which is bright enough to be visible to the naked eye at night.

The inner pair of stars form a single-lined spectroscopic binary with an orbital period of about 2,807 days and an eccentricity of 0.33.[8] The visible member of the pair, component A, is a visual magnitude 4.60[2] F-type main sequence star with a stellar classification of F6 V.[3] During the 1990s, it was thought to be a Gamma Doradus variable, but this was later discounted as it shows no short-term photometric variability. The star does show some long-term variability, possibly as a result of a magnetic activity cycle similar to the solar cycle.[13]

The tertiary member, component B, is a visual magnitude 7.15[2] K-type star with a class of K0.[3] It lies at a separation of 1,120 AU from the primary.[14] As of 2012, it was positioned at an angular separation of 67.5 arc seconds along a position angle of 4°.[15]

References

  1. ↑ 1.0 1.1 1.2 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Montesinos, B. et al. (September 2016), "Incidence of debris discs around FGK stars in the solar neighbourhood", Astronomy & Astrophysics 593: 31, doi:10.1051/0004-6361/201628329, A51, Bibcode: 2016A&A...593A..51M. 
  3. ↑ 3.0 3.1 3.2 3.3 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  5. ↑ 5.0 5.1 Reiners, Ansgar (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics 446 (1): 267–277, doi:10.1051/0004-6361:20053911, Bibcode: 2006A&A...446..267R 
  6. ↑ 6.0 6.1 6.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  8. ↑ 8.0 8.1 Pourbaix, D. et al. (September 2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics 424: 727–732, doi:10.1051/0004-6361:20041213, Bibcode: 2004A&A...424..727P. 
  9. ↑ 9.0 9.1 9.2 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  10. ↑ 10.0 10.1 Pasinetti Fracassini, L. E. et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics 367: 521–524, doi:10.1051/0004-6361:20000451, Bibcode: 2001A&A...367..521P. 
  11. ↑ Tokovinin, Andrei (2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal 147 (4): 14, doi:10.1088/0004-6256/147/4/87, 87, Bibcode: 2014AJ....147...87T. 
  12. ↑ "tau01 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau01+Hya. 
  13. ↑ Henry, G. W. et al. (March 1999), "tau1 Hydrae: NOT A gamma DORADUS VARIABLE", Information Bulletin on Variable Stars 4688 (4688): 1, Bibcode: 1999IBVS.4688....1H. 
  14. ↑ Allen, Peter R. et al. (August 2012), "Low-mass Tertiary Companions to Spectroscopic Binaries. I. Common Proper Motion Survey for Wide Companions Using 2MASS", The Astronomical Journal 144 (2): 12, doi:10.1088/0004-6256/144/2/62, 62, Bibcode: 2012AJ....144...62A. 
  15. ↑ Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M. 



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