Sigma Boötis

σ Boötis

Observation data Epoch J2000      Equinox J2000
Constellation	Boötes
Right ascension	14^h 34^m 40.8171^s
Declination	+29° 44′ 42.468″
Apparent magnitude (V)	4.46
Characteristics
Spectral type	F2V
U−B color index	-0.08
B−V color index	0.36
R−I color index	0.19
Variable type	Variable star
Astrometry
Radial velocity (Rv)	0.2 km/s
Proper motion (μ)	RA: 188.32 mas/yr Dec.: 132.72 mas/yr
Parallax (π)	64.66 ± 0.72 mas
Distance	50.4 ± 0.6 ly (15.5 ± 0.2 pc)
Absolute magnitude (MV)	4.82
Details
Radius	1.431 ± 0.023[1] R☉
Luminosity	3.461 ± 0.042[1] L☉
Temperature	6,594 ± 55[1] K
Age	1.7[2] Gyr
Other designations
28 Boötis, HR 5447, HD 128167, Gl 557, BD+30°2536, FK5 1380, HIP 71284, SAO 83416, GC 19659, CCDM 14347+2945.
Database references
SIMBAD	data
Data sources:
Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.)
Database references
SIMBAD	data

Sigma Boötis (σ Boo, σ Boötis) is a star in the constellation Boötes.

Sigma Boötis is a yellow-white F-type main sequence dwarf with an apparent magnitude of +4.47. It is approximately 50.4 light years from Earth.

In Chinese, 梗河 (Gěng Hé), meaning Celestial Lance, refers to an asterism consisting of σ Boötis, ε Boötis and ρ Boötis.^[3] Consequently, σ Boötis itself is known as 梗河二 (Gěng Hé èr, English: the Second Star of Celestial Lance.)^[4]

Located to the southeast of Rho Boötis, the fusing dwarf Sigma may at first appear as a naked-eye double, but the angular proximity with Rho is merely line-of-sight. Like many of its spectral class, Sigma is apparently a variable of the Delta Scuti variety, which vary subtly with multiple periods of hours.

References

1. Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101. See Table 10.
2. Decin, G.; et al. (November 2003), "Age Dependence of the Vega Phenomenon: Observations", The Astrophysical Journal 598 (1): 636–644, arXiv:astro-ph/0308294, Bibcode:2003ApJ...598..636D, doi:10.1086/378800
3. (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
4. (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 29 日

External links

• HR 5447
• CCDM J14347+2945
• Image Sigma Boötis