Astronomy:Tau4 Eridani

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Short description: Binary star system in the constellation Eridanus
For other star systems with this Bayer designation, see Tau Eridani.
τ4 Eridani
Location of τ4 Eridani (circled)
Observation data
{{#ifeq:J2000.0 (ICRS)|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| [[History:Epoch|Epoch J2000.0 (ICRS)]]      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0 (ICRS)}}
Constellation Eridanus
τ4 Eridani A
Right ascension  03h 19m 31.0006s [1]
Declination −21° 45′ 28.315″ [1]
Apparent magnitude (V) 3.57−3.72[2]
τ4 Eridani B
Right ascension  03h 19m 30.6092s[3]
Declination −21° 45′ 26.348″[3]
Apparent magnitude (V) 9.5[4]
Characteristics
τ4 Eridani A
Evolutionary stage asymptotic giant branch[5]
Spectral type M3/4 III[6]
U−B color index +1.79[7]
B−V color index +1.61[7]
Variable type Lb[2]
Astrometry
τ4 Eridani A
Radial velocity (Rv)+41.7±0.7[8] km/s
Proper motion (μ) RA: +52.774[1] mas/yr
Dec.: +32.718[1] mas/yr
Parallax (π)10.6153 ± 0.3213[1] mas
Distance307 ± 9 ly
(94 ± 3 pc)
Absolute magnitude (MV)−0.79[9]
τ4 Eridani B
Proper motion (μ) RA: +52.919 mas/yr
Dec.: +34.104 mas/yr
Parallax (π)10.6682 ± 0.1066[3] mas
Distance306 ± 3 ly
(93.7 ± 0.9 pc)
Position (relative to A)
ComponentB
Angular distance5.7[4]″
Position angle291[4]°
Observed separation
(projected)		5,800[10] AU {{{projsepref}}}
Details
τ4 Eridani A
Mass1.73±0.3[11] M☉
Radius103[12] R☉
Luminosity1,537[13] L☉
Surface gravity (log g)0.91[14] cgs
Temperature3,652[12] K
τ4 Eridani B
Mass0.9[10] M☉
Other designations
τ4 Eridani, τ4 Eri, 16 Eridani, BD−22°584, HD 20720, HIP 15474, HR 1003, SAO 168460[15]
Database references
τ4 Eridani A
SIMBADdata
τ4 Eridani B
SIMBADdata

Tau4 Eridani (τ4 Eridani, τ4 Eri) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude that varies from 3.57 to 3.72.[2] The distance to this star can be estimated using the parallax method, which yields a value of roughly 300 light years.[1]

A visual band light curve for Tau4 Eridani, plotted from data published by Tabur et al. (2009)[16]

The primary components ia an evolved red giant star currently on the asymptotic giant branch[5] with a stellar classification of M3/4 III.[6] It is a slow irregular variable star of type Lb, undergoing changes in magnitude over the range 3.57−3.72[2] with a periodicity of 23.8 d.[16] This star has 1.73 times the mass of the Sun[11] and 103 times the radius of the Sun.[12] It shines with 1,537 times the luminosity of the Sun from its photosphere[13] at an effective temperature of 3,650 K.[12]

The secondary is a magnitude 9.5 star at an angular separation of 5.7″ along a position angle of 291°, as of 2013.[4] This angular separation implies a projected separation of 5,800 astronomical units.[10]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Ruban, E. V. et al. (September 2006), "Spectrophotometric observations of variable stars", Astronomy Letters 32 (9): 604–607, doi:10.1134/S1063773706090052, Bibcode: 2006AstL...32..604R. 
  3. ↑ 3.0 3.1 3.2 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 4.2 4.3 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, http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/wds, retrieved 2015-07-22 
  5. ↑ 5.0 5.1 Lebzelter, T.; Hron, J. (January 2008), "BRITE stars on the AGB", Communications in Asteroseismology 152: 178–181, doi:10.1553/cia152s178, Bibcode: 2008CoAst.152..178L, https://hw.oeaw.ac.at/0xc1aa5576_0x0019d7d9.pdf. 
  6. ↑ 6.0 6.1 Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, 4, Bibcode: 1988mcts.book.....H. 
  7. ↑ 7.0 7.1 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M. 
  8. ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  9. ↑ Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics 430: 303–311, doi:10.1051/0004-6361:20041440, Bibcode: 2005A&A...430..303C. 
  10. ↑ 10.0 10.1 10.2 Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (January 2022). "Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs" (in en). Astronomy and Astrophysics 657: A7. doi:10.1051/0004-6361/202142146. ISSN 0004-6361. Bibcode: 2022A&A...657A...7K. 
  11. ↑ 11.0 11.1 Halabi, Ghina M.; Eid, Mounib El (2015). "Exploring masses and CNO surface abundances of red giant stars". Monthly Notices of the Royal Astronomical Society 451 (3): 2957. doi:10.1093/mnras/stv1141. Bibcode: 2015MNRAS.451.2957H. 
  12. ↑ 12.0 12.1 12.2 12.3 Wood, Brian E.; Müller, Hans-Reinhard; Harper, Graham M. (2016-09-23), "Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars" (in en), The Astrophysical Journal 829 (2): 74, doi:10.3847/0004-637X/829/2/74, ISSN 0004-637X, Bibcode: 2016ApJ...829...74W 
  13. ↑ 13.0 13.1 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. 
  14. ↑ Ayres, Thomas (2023-05-01), "In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022", The Astrophysical Journal Supplement Series 266 (1): 6, doi:10.3847/1538-4365/acb535, ISSN 0067-0049, Bibcode: 2023ApJS..266....6A  Tau4 Eridani database entry at VizieR.
  15. ↑ "tau04 Eri". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau04+Eri. 
  16. ↑ 16.0 16.1 Tabur, V. et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society 400 (4): 1945–1961, doi:10.1111/j.1365-2966.2009.15588.x, Bibcode: 2009MNRAS.400.1945T. 



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