Beta Trianguli

Beta Trianguli (Beta Tri, β Trianguli, β Tri) is the Bayer designation for a binary star[11] system in the constellation Triangulum, located about 127 light years from Earth.[1] Although the apparent magnitude is only 3.0,[2] it is the brightest star in the constellation Triangulum.[12]

Not to be confused with Beta Trianguli Australis.

β Trianguli

Location of β Trianguli (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Triangulum
Right ascension	02^h 09^m 32.62712^s[1]
Declination	+34° 59′ 14.2694″[1]
Apparent magnitude (V)	+3.00[2]
Characteristics
Spectral type	A5IV[3]
U−B color index	+0.11[2]
B−V color index	+0.14[2]
Astrometry
Radial velocity (Rv)	+9.9[4] km/s
Proper motion (μ)	RA: 149.16[1] mas/yr Dec.: –39.10[1] mas/yr
Parallax (π)	25.71 ± 0.34[1] mas
Distance	127 ± 2 ly (38.9 ± 0.5 pc)
Absolute magnitude (MV)	+0.05[5]
Orbit[6]
Period (P)	31.3884 d
Eccentricity (e)	0.53
Periastron epoch (T)	2432004.255 JD
Argument of periastron (ω) (secondary)	318.4°
Semi-amplitude (K1) (primary)	33.3 km/s
Semi-amplitude (K2) (secondary)	69.2 km/s
Details
Mass	3.5[7] M☉
Luminosity	74 (combined)[7] L☉
Surface gravity (log g)	3.70[3] cgs
Temperature	8,186[3] K
Rotational velocity (v sin i)	70[8] km/s
Age	0.73[9] Gyr
Other designations
β Trianguli, β Tri, Beta Tri, 4 Trianguli, HR 622, HD 13161, BD+34°381, FK5 75, HIP 10064, SAO 55306.[10]
Database references
SIMBAD	data

This is a double-lined spectroscopic binary star system with an orbital period of 31.39 days and an eccentricity of 0.53.[6] The members are separated by a distance of less than 5 AU.[13] The primary component has a stellar classification of A5IV, indicating that it has evolved away from the main sequence and is now a subgiant star. However, the classification is uncertain and not consistent with the mass derived from the orbit.[7] It is among the least variable of the stars that were observed by the Hipparcos spacecraft, with a magnitude varying by only 0.0005.[14]

Based on observations using the Spitzer Space Telescope, as reported in 2005, this system is emitting an excess of infrared radiation. This emission can be explained by a circumbinary ring of dust. The dust is emitting infrared radiation at a blackbody temperature of 100 K.[13] It is thought to extend from 50 to 400 AU away from the stars.[7]

Naming

• In combination with Alpha Trianguli, these stars were called Al Mīzān, which is Arabic for "The Scale Beam".[12]
• In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of β Trianguli, γ Andromedae, φ Persei, 51 Andromedae, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, γ Trianguli and δ Trianguli. Consequently, the Chinese name for β Trianguli itself is 天大將軍九 (Tiān Dà Jiāng Jūn jiǔ, English: the Ninth Star of Heaven's Great General.).[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. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
3. Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365.
4. Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Washington, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W
5. 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.
6. Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
7. Kennedy, G. M.; Wyatt, M. C.; Sibthorpe, B.; Phillips, N. M.; Matthews, B.; Greaves, J. S. (2012). "Coplanar Circumbinary Debris Disks". Monthly Notices of the Royal Astronomical Society. 426 (3): 2115–28. arXiv:1208.1759. Bibcode:2012MNRAS.426.2115K. doi:10.1111/j.1365-2966.2012.21865.x.
8. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943
9. Booth, M.; Kennedy, G.; Sibthorpe, B.; Matthews, B. C.; Wyatt, M. C.; Duchene, G.; Kavelaars, J. J.; Rodriguez, D.; Greaves, J. S.; Koning, A.; Vican, L.; Rieke, G. H.; Su, K. Y. L.; Moro-Martin, A.; Kalas, P. (2012). "Resolved debris discs around a stars in the Herschel DEBRIS survey". Monthly Notices of the Royal Astronomical Society. 428 (2): 1263. arXiv:1210.0547. Bibcode:2013MNRAS.428.1263B. doi:10.1093/mnras/sts117.
10. "bet Tri -- Spectroscopic binary", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-12
11. 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
12. Garfinkle, Robert A. (1997), Star-Hopping: Your Visa to Viewing the Universe, Cambridge University Press, p. 238, ISBN 0-521-59889-3
13. Stansberry, J. A.; et al. (2005). "A Spitzer Survey for Debris Disks in Binary Star Systems". Protostars and Planets V, Proceedings of the Conference held October 24-28, 2005, in Hilton Waikoloa Village, Hawai'i. Protostars and Planets V. p. 8613. Bibcode:2005prpl.conf.8613S.
14. Adelman, S. J. (February 2001), "Research Note Hipparcos photometry: The least variable stars", Astronomy and Astrophysics, 367: 297–298, Bibcode:2001A&A...367..297A, doi:10.1051/0004-6361:20000567
15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日