Astronomy:Tau9 Eridani

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Short description: Binary star in the constellation Eridanus


τ9 Eridani
Tau09EriLightCurve.png
A light curve for Tau9 Eridani plotted from TESS data[1]
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Eridanus
Right ascension  03h 59m 55.48381s[2]
Declination −24° 00′ 58.3798″[2]
Apparent magnitude (V) 4.63[3]
Characteristics
Spectral type B9.5V Si[4]
U−B color index −0.40[3]
B−V color index −0.13[3]
Variable type α2 CVn[5]
Astrometry
Radial velocity (Rv)25.5±0.5[6] km/s
Proper motion (μ) RA: +12.12[2] mas/yr
Dec.: +16.48[2] mas/yr
Parallax (π)9.96 ± 0.22[2] mas
Distance327 ± 7 ly
(100 ± 2 pc)
Absolute magnitude (MV)−0.44[5]
Orbit[7]
Period (P)5.95382 days
Eccentricity (e)0.129
Periastron epoch (T)246991.65 JD
Argument of periastron (ω)
(secondary)		183.2°
Semi-amplitude (K1)
(primary)		40.0 km/s
Semi-amplitude (K2)
(secondary)		89.9 km/s
Details
τ9 Eri A
Mass3.6[7] M☉
Radius3.06[7] R☉
Luminosity209[7] L☉
Surface gravity (log g)4.11±0.11[8] cgs
Temperature12,580[7] K
Rotational velocity (v sin i)26.8[7] km/s
Age140[7] Myr
τ9 Eri B
Mass1.6[7] M☉
Radius1.5[7] R☉
Luminosity6.3[7] L☉
Temperature7530[7] K
Rotational velocity (v sin i)15[7] km/s
Other designations
τ9 Eridani, τ9 Eri, 36 Eridani, CD−24° 2022, FK5 2287, HD 25267, HIP 18673, HR 1240, SAO 169017.[9]
Database references
SIMBADdata

Tau9 Eridani (τ9 Eri) is a binary star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 4.63.[3] The distance to this system can be estimated using the parallax method, which yields a value of roughly 327 light years.[3]

This is a double-lined spectroscopic binary system with an orbital period of 5.95382 days and an eccentricity of 0.12.[7] The primary component, τ9 Eri A, is a magnetic chemically peculiar star[10] with a stellar classification of B9.5V Si,[4] indicating that it is a B-type main sequence star that shows abundance anomalies in its silicon absorption lines.[4] It is an Alpha² Canum Venaticorum variable[5] with a rotational periodicity of 5.954 days.[11] The averaged strength of the stellar effective magnetic field is 240.6±91.0 G.[4]

The primary component Tau9 Eridani A has an estimated 326%[10] the mass of the Sun and 3.1 times the Sun's radius.[8] It shines with 166[12] times the solar luminosity from an outer atmosphere at an effective temperature of 10,866 K.[12] The star is spinning with a projected rotational velocity of 30 km/s.[13] The secondary star, designated Tau9 Eridani B, is a late A-type or early F-type star with a mass of 1.6 solar masses and an effective temperature of 7530 K.[7]

References

  1. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 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. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M. 
  4. ↑ 4.0 4.1 4.2 4.3 Bychkov, V. D. et al. (April 2009), "Catalogue of averaged stellar effective magnetic fields - II. Re-discussion of chemically peculiar A and B stars", Monthly Notices of the Royal Astronomical Society 394 (3): 1338–1350, doi:10.1111/j.1365-2966.2008.14227.x, Bibcode: 2009MNRAS.394.1338B. 
  5. ↑ 5.0 5.1 5.2 Dubath, P. et al. (2011), "Random forest automated supervised classification of Hipparcos periodic variable stars", Monthly Notices of the Royal Astronomical Society 414 (3): 2602–2617, doi:10.1111/j.1365-2966.2011.18575.x, Bibcode: 2011MNRAS.414.2602D. 
  6. ↑ De Bruijne, J. H. J.; Eilers, A.-C. (2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: A61, doi:10.1051/0004-6361/201219219, Bibcode: 2012A&A...546A..61D. 
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 7.13 Woodcock, K. (2021), "τ9 Eri: a bright pulsating magnetic Bp star in a 5.95-d double-lined spectroscopic binary", Monthly Notices of the Royal Astronomical Society 502 (4): 5200–5209, doi:10.1093/mnras/stab338, Bibcode: 2021MNRAS.502.5200W 
  8. ↑ 8.0 8.1 North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics 334: 181–187, Bibcode: 1998A&A...334..181N. 
  9. ↑ "tau09 Eri". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau09+Eri. 
  10. ↑ 10.0 10.1 Shulyak, D. et al. (September 2014), "Interferometry of chemically peculiar stars: theoretical predictions versus modern observing facilities", Monthly Notices of the Royal Astronomical Society 443 (2): 1629–1642, doi:10.1093/mnras/stu1259, Bibcode: 2014MNRAS.443.1629S. 
  11. ↑ Bychkov, V. D. et al. (February 2005), "A catalog of stellar magnetic rotational phase curves", Astronomy and Astrophysics 430 (3): 1143–1154, doi:10.1051/0004-6361:20034563, Bibcode: 2005A&A...430.1143B. 
  12. ↑ 12.0 12.1 McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M. 
  13. ↑ Abt, Helmut A. et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A. 



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