GD 165

GD 165 is a binary white dwarf and brown dwarf system located in the Boötes constellation, roughly 109 light-years from Earth.

GD 165

The white dwarf GD 165 A is seen in the center of the image as a bright star. The brown dwarf GD 165 B is below the white dwarf, seen as a red spot.
Observation data Epoch J2000      Equinox J2000
Constellation	Boötes
Right ascension	14^h 24^m 39.144^s
Declination	09° 17′ 13.98″
Characteristics
Evolutionary stage	white dwarf + brown dwarf
Spectral type	DA4+L4
Astrometry
Radial velocity (Rv)	−26.8 ± 4.3 km/s
Proper motion (μ)	RA: −213.353 ± 0.084 mas/yr Dec.: −149.648 ± 0.074 mas/yr
Parallax (π)	29.9335±0.0559 mas
Distance	109.0 ± 0.2 ly (33.41 ± 0.06 pc)
Details
GD 165 A
Mass	0.64 ± 0.02 M☉
Radius	0.0124 ± 0.0003 R☉
Luminosity	0.0030 ± 0.0006 L☉
Surface gravity (log g)	8.052 ± 0.035 cgs
Temperature	12,130 ± 450 K
Rotation	57.29 ± 0.34 hours
Age	1.2–5.5 Gyr
GD 165 B
Mass	62.58 ± 15.57 MJup
Radius	1.00 ± 0.08 RJup
Surface gravity (log g)	5.19 ± 0.21 cgs
Temperature	1755 ± 102 K
Age	1.2–5.5 Gyr
Other designations
CX Boo, LSPM J1424+0917, 2MASS J14243914+0917139, WDS J14247+0917A, WD 1422+095
Database references
SIMBAD	GD 165 A
	GD 165 B

Nomenclature and observation

The system GD 165 is named after Henry L. Giclas, an American Astronomer who lived throughout the 20th century.

In 1990, GD 165 A was discovered to be a variable star by Pierre Bergeron and John Thomas McGraw. It was given its variable star designation, CX Boötis, in 1993.

GD 165 B was discovered in 1988 by Eric Becklin and Benjamin Zuckerman at the University of California, Los Angeles. GD 165 B was the first brown dwarf discovered to be cooler than M-Type stars and was initially assigned the spectral type ≥M10. It would not be regarded as a brown dwarf until 1999, when new spectral types L-Type and T-Type for objects cooler than M-type stars were established, reclassifying GD 165 B as L4.

Physical properties

GD 165 A is a pulsating white dwarf with a temperature of about 12,100 K, a mass of 0.64 M_☉, and a radius of 0.0124 R_☉.

GD 165 B is an L-Type brown dwarf with a temperature of about 1,750 K, a mass of about 63 M_J, and a radius of 1.00 R_J. GD 165B is separated by 123±12 astronomical units from its host white dwarf. It is the second closest spacially resolved brown dwarf after PHL 5038, which has a separation of around 69 AU.

See also

Other cooler than M brown dwarfs, discovered before 1998:

• Gliese 229 B – T6.5
• 2MASP J0345432+254023 – L0 (first isolated L-dwarf)
• DENIS-P J020529.0-115925 – L7
• DENIS-P J1058.7-1548 – L3
• DENIS-P J1228.2-1547 – L5
• Kelu-1 – L2