15 Sagittae

From Wikipedia, the free encyclopedia
Jump to: navigation, search
15 Sagittae
Diagram showing star positions and boundaries of the constellation of Sagitta and its surroundings
Cercle rouge 100%.svg
A star chart of the constellation of Sagitta showing the position of 15 Sagittae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagitta
Right ascension 20h 04m 06.22s
Declination 17° 04′ 12.6″
Apparent magnitude (V) 5.8
Spectral type G0V[1]
Radial velocity (Rv) 5.39 km/s
Parallax (π) 56.28 mas
Distance 57.7 ly
(17.69 pc)
Mass 1.08 ± 0.04[1] M
Radius 1.115 ± 0.021[1] R
Luminosity 1.338 ± 0.032[1] L
Surface gravity (log g) 4.42 ± 0.06[1] cgs
Temperature 5883 ± 59[1] K
Metallicity [Fe/H] 0.05 ± 0.07[1] dex
Rotation 17.5 ± 2.3[1]
Rotational velocity (v sin i) 4.42 ± 0.06[1] km/s
Age 2.5 ± 1.8[1] Gyr
Other designations
HR 7672, Gl 779, HIP 98819, HD 190406, BD+16 4121, SAO 105635, LHS 3515, LTT 15872, LFT 1517, Wolf 866
Database references

15 Sagittae (15 Sge) is a 6th magnitude star in the constellation Sagitta. Considered a solar analog, it was the target of the first radial velocity survey from Lick Observatory, which found a drift due to a companion;[2] In 2002, the cause of this was found to be brown dwarf companion B via direct imaging.

15 Sagittae B[edit]

15 Sagittae B is a high-mass substellar L dwarf of spectral class L4 ± 1.5, only a few Jupiter masses below the limit for stars, in a long-period orbit around the primary star. Imaged by the Keck telescope, was the first brown dwarf candidate orbiting a sun-like star detected via imaging and is currently the only known companion brown dwarf which both has a significant radial velocity trend on the primary that has also been imaged.

The brown dwarf was originally thought to have a semi-major axis of 14 AU and a circular orbit viewed from pole-on,[3] but ten more years of observations found that the brown dwarf's orbit is viewed from nearly edge-on, is significantly eccentric and appeared to be moving in a circular orbit when first discovered, but is now approaching the primary as viewed from Earth.[1]

Companion Mass


B 68.7+2.4
1.0 ± 0.4 0.000075
± 0.000016
1510-1850 73.3+2.2
± 0.01
97.3 +0.4

External links[edit]


  1. ^ a b c d e f g h i j k Crepp, Justin R.; et al. (2012). "The Dynamical Mass and Three-Dimensional Orbit of HR7672B: A Benchmark Brown Dwarf with High Eccentricity". arXiv:1112.1725Freely accessible. Bibcode:2012ApJ...751...97C. doi:10.1088/0004-637X/751/2/97. 
  2. ^ Cumming, Andrew; Geoffrey W. Marcy; R. Paul Butler (1999). "The Lick Planet Search: Detectability and Mass Thresholds". arXiv:astro-ph/9906466Freely accessible. Bibcode:1999ApJ...526..890C. doi:10.1086/308020. 
  3. ^ Liu, Michael C.; et al. (2002). "Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672". arXiv:astro-ph/0112407Freely accessible. Bibcode:2002ApJ...571..519L. doi:10.1086/339845.