44 Boötis

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44 Boötis
44 Bootis System.png
A brown dwarf orbiting 44 Bootis B-C.
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 15h 03m 47.304s
Declination +47° 39′ 14.616″
Apparent magnitude (V) 4.75
Spectral type G0Vnv
U−B color index 0.11
B−V color index 0.65
Variable type W UMa variable
Radial velocity (Rv) -30.8 km/s
Proper motion (μ) RA: -436.26 mas/yr
Dec.: 18.93 mas/yr
Parallax (π) 78.39 ± 1.03 mas
Distance 41.6 ± 0.5 ly
(12.8 ± 0.2 pc)
Absolute magnitude (MV) 5.41
Mass 1.1/1+0.79 M
Radius 1.1/0.89+0.66 R
Luminosity 1.2/1 L
Temperature 5900/5500+5000 K
Rotation <= 16 km/s
0,0095423 Year
Age (1.4–1.5) × 109[1] years
Companion 44 Boötis B
Period (P) 225 yr
Semi-major axis (a) 3.772"
Eccentricity (e) 0.43
Inclination (i) 83.9°
Longitude of the node (Ω) 57.8°
Periastron epoch (T) 2021
Other designations
i Boötis, HR 5618, HD 133640, Gl 575, BD+48°2259, HIP 73695, SAO 45357, GC 20281, ADS 9494, CCDM 15038+4739.
Database references
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

44 Boötis or i Boötis is a triple star system in the constellation Boötes. It is approximately 41.6 light years from Earth.

The primary component, 44 Boötis A, is a yellow-white G-type main sequence dwarf with a mean apparent magnitude of +4.83. The companion component, 44 Boötis B, is a W Ursae Majoris variable spectroscopic binary. The brightness of the binary varies from magnitude +5.8 to +6.40 with a period of 6.43 hours. The components of the eclipsing binary are separated by 0.008 Astronomical Units, roughly 3 times the distance of the Moon from Earth.

A substellar companion?[edit]

Recent analysis in timing variations for 44 Bootis B would suggest the presence of a third body orbiting the W Ursae Majoris-type eclipsing binary with likely substellar mass.[2] Its minimum mass is estimated at 48 times that of Jupiter and the orbital separation at 10.73 AUs (a bit farther away than Saturn in the Solar System). So far unconfirmed, such an object seems unstable considering the system's architecture, with 44 Bootis B-C getting as close as 26.6 AUs to 44 Bootis A,[3] unless it is locked in some kind of peculiar configuration and inclination.

The 44 Boötis system[2]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (unconfirmed) ≥47.5 MJ 10.73 ≈35  ?


  1. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785. 
  2. ^ a b Byrd-Fisher et al. (2008). "Patterns in the Long Term Behavior of Eclipsing Binary Star System 44i-Bootis". American Physical Society, 10th Annual Meeting of the Northwest Section of APS, May 15–17, 2008. Bibcode:2008APS..NWS.C1013B. 
  3. ^ Heintz (1997). "Orbits of 40 Visual Binaries". Astrophysical Journal Supplement 111: 1–4. Bibcode:1997ApJS..111..335H. doi:10.1086/313011. 

External links[edit]