GD 165

GD 165 is a binary white dwarf and brown dwarf system located in the Boötes constellation, roughly 109 light-years from Earth.^[7] Neither of the stars have any known exoplanets.

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[1]      Equinox J2000[1]
Constellation	Boötes
Right ascension	14h 24m 39.144s[1]
Declination	09° 17′ 13.98″[1]
Characteristics
Evolutionary stage	white dwarf + brown dwarf
Spectral type	DA4[2]+L4[3]
Astrometry
Radial velocity (Rv)	−26.8 ± 4.3[4] km/s
Proper motion (μ)	RA: −213.353 ± 0.084[5] mas/yr Dec.: −149.648 ± 0.074[5] mas/yr
Parallax (π)	29.9335±0.0559 mas[5]
Distance	109.0 ± 0.2 ly (33.41 ± 0.06 pc)
Details
GD 165 A
Mass	0.64 ± 0.02[6] M☉
Radius	0.0124 ± 0.0003[6] R☉
Luminosity	0.0030 ± 0.0006[6] L☉
Surface gravity (log g)	8.052 ± 0.035[6] cgs
Temperature	12,130 ± 450[6] K
Rotation	57.29 ± 0.34 hours[6]
Age	1.2–5.5[7] Gyr
GD 165 B
Mass	62.58 ± 15.57[8] MJup
Radius	1.00 ± 0.08[8] RJup
Surface gravity (log g)	5.19 ± 0.21[8] cgs
Temperature	1755 ± 102[8] K
Age	1.2–5.5[7] 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.^[9]

In 1990, GD 165 A was discovered to be a variable star by Pierre Bergeron and John Thomas McGraw.^[10] It was given its variable star designation, CX Boötes, in 1993.^[11]

GD 165 B was discovered in 1988 by Eric Becklin and Benjamin Zuckerman at the University of California, Los Angeles.^[12] GD 165 B was the first brown dwarf discovered to be cooler than M-Type stars^[13] 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.^[3]

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_☉.^[6] GD 165 A has an extremely dim luminosity of 0.0030L_☉,^[6] making it completely invisible to the naked eye.

A broad band optical light curve for GD 165, adapted from Giammichele et al. (2015)^[6]

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.^[8] 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.^[14] It produces almost no light and is completely invisible to the naked eye.

See also

Other cooler than M brown dwarfs, discovered before 1998:

• Gliese 229 B – T6.5^[15][16]
• 2MASP J0345432+254023 – L0 (first isolated L-dwarf)^[3]
• DENIS-P J020529.0-115925 – L7^[3][17]
• DENIS-P J1058.7-1548 – L3^{[3] [17]}
• DENIS-P J1228.2-1547 – L5^[3][17]
• Kelu-1 – L2^[3][18]