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, Bibcode2007A&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), Bibcode1986EgUBV........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, Bibcode2009MNRAS.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, Bibcode2011MNRAS.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, Bibcode2012A&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, Bibcode2021MNRAS.502.5200W 
  8. 8.0 8.1 North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics 334: 181–187, Bibcode1998A&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, Bibcode2014MNRAS.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, Bibcode2005A&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, Bibcode2012MNRAS.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, Bibcode2002ApJ...573..359A.