Gliese 223.2

Coordinates: 05^h 55^m 09.53^s, −04° 10′ 07.1″

Gliese 223.2

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Orion
Right ascension	05h 55m 09.53s[1]
Declination	−04° 10′ 07.1″[1]
Apparent magnitude (V)	14.488[2]
Characteristics
Spectral type	DZ11.8[2]
Apparent magnitude (B)	15.49[1]
Apparent magnitude (V)	14.488[2]
Apparent magnitude (RKC)	13.99[3]
Apparent magnitude (IKC)	13.51[3]
Apparent magnitude (J)	13.05 ± 0.03[3]
Apparent magnitude (H)	12.86 ± 0.03[3]
Apparent magnitude (KS)	12.78 ± 0.03[3]
B−V color index	1.0[1][2]
Astrometry
Proper motion (μ)	RA: 551[3] mas/yr Dec.: −2311[3] mas/yr
Parallax (π)	156.13 ± 0.84[3] mas
Distance	20.9 ± 0.1 ly (6.4 ± 0.03 pc)
Absolute magnitude (MV)	15.44 ± 0.03[3]
Details
Mass	0.45 ± 0.01[2], or 0.80 ± 0.01[3] M☉
Radius	0.014[2][note 1], or 0.010[3] R☉
Surface gravity (log g)	7.80 ± 0.02[2], or 8.35 ± 0.01[3]
Temperature	4270 ± 70[2], or 5180 ± 70[3] K
Age	6.42[4], or 6.82 ± 0.02[3][note 2] Gyr
Other designations
GJ 223.2, GJ 9193, HL 4, LHS 32, LP 658-2, NLTT 15811, G 099-044[5] , G 99-44, G 106-12, WD 0552–041, EGGR 45.[1]
Database references
SIMBAD	data

Gliese 223.2 (GJ 9193) is a degenerate (white dwarf) star in the constellation of Orion,^[1] the single known object in its system. It has an apparent visual magnitude of approximately 14.488.^[2]

Distance

According to a 2009 paper, it is the eighth closest known white dwarf to the Sun (after Sirius B, Procyon B, van Maanen's star, Gliese 440, 40 Eridani B, Stein 2051 B and GJ 1221).^[6] Its trigonometric parallax from the CTIOPI (Cerro Tololo Inter-American Observatory (CTIO) Parallax Investigation) 0.9 m telescope program, published in 2009, is 0.15613 ± 0.00084 arcsec,^[3] corresponding to a distance 6.40 ± 0.03 pc, or 20.89 ± 0.11 ly. Also, previous less precise parallax measurements of Gliese 223.2 present in YPC (Yale Parallax Catalog) and among results of CTIOPI 1.5 m telescope program:

Gliese 223.2 parallax measurements

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
YPC	van Altena et al., 1995	155.0 ± 2.1	6.45 ± 0.09	21.04 ± 0.29	[5]
CTIOPI 1.5 m	TSN-14 (Costa et al., 2005)	156.93 ± 2.67	6.37 ± 0.11	20.78 ± 0.35	[7]
CTIOPI 0.9 m	TSN-21 (Subasavage et al., 2009)	156.13 ± 0.84	6.40 ± 0.03	20.89 ± 0.11	[3]

Physical parameters

There are two sets of published physical parameters of Gliese 223.2, significantly differing from each other: from Holberg et al. 2008, April^[2] / Sion et al. 2009, December^[4] articles, and from Subasavage et al. 2009, June^[3] article:

Holberg et al. 2008 / Sion et al. 2009 version

• Mass: 0.45 ± 0.01 Solar masses
• Surface gravity: 10^{7.80 ± 0.02} (6.31 · 10⁷) cm·s^-2, or approximately 64 000 of Earth's
• Radius: 9771 km, or 153 % of Earth's^{[note 1]}
• Temperature: 4270 ± 70 K
• Age: 6.42 Gyr^{[4][note 2]}

Subasavage et al. 2009 version

• Mass: 0.80 ± 0.01 Solar masses
• Surface gravity: 10^{8.35 ± 0.01} (2.24 · 10⁸) cm·s^-2, or approximately 228 000 of Earth's
• Radius: 6916 km, or 109 % of Earth's^{[note 1]}
• Temperature: 5180 ± 70 K
• Age: 6.82 ± 0.02 Gyr^{[note 2]}

Color

Despite it is classified as "white dwarf", it should appear orange, not white, due low temperature, comparable with that of late (according Holberg et al. 2008 / Sion et al. 2009 version), or early (according Subasavage et al. 2009 version) K-type main sequence stars.

Notes

1. ^ ^{a b c} From surface gravity and mass.
2. ^ ^{a b c} White dwarf cooling age, i. e. age as degenerate star (not including lifetime as main sequence star and as giant star)

References

1. ^ ^{a b c d e f} NAME HL 4 -- White Dwarf, database entry, SIMBAD. Accessed on line January 17, 2011.
2. ^ ^{a b c d e f g h i j} Holberg, J. B.; Sion; Oswalt; McCook; Foran; Subasavage (2008). "A NEW LOOK AT THE LOCAL WHITE DWARF POPULATION". The Astronomical Journal 135: 1225–1238. Bibcode 2008AJ....135.1225H. doi:10.1088/0004-6256/135/4/1225. 
3. ^ ^{a b c d e f g h i j k l m n o p q} Subasavage, John P.; Jao; Henry; Bergeron; Dufour; Ianna; Costa; Mendez (2009). "THE SOLAR NEIGHBORHOOD. XXI. PARALLAX RESULTS FROM THE CTIOPI 0.9 m PROGRAM: 20 NEW MEMBERS OF THE 25 PARSEC WHITE DWARF SAMPLE". The Astronomical Journal 137: 4547–4560. Bibcode 2009AJ....134.4547S. doi:10.1088/0004-6256/137/6/4547. 
4. ^ ^{a b c} Sion, Edward M.; Holberg; Oswalt; McCook; Wasatonic (2009). "THE WHITE DWARFS WITHIN 20 PARSECS OF THE SUN: KINEMATICS AND STATISTICS". The Astronomical Journal 138: 1681–1689. Bibcode 2009AJ....138.1681S. doi:10.1088/0004-6256/138/6/1681. 
5. ^ ^{a b} Yale Trigonometric Parallaxes, Fourth Edition (van Altena+ 1995)
6. ^ Table 1, "The White Dwarfs Within 20 Parsecs of the Sun: Kinematics and Statistics", Edward M. Sion et al., The Astronomical Journal 138, #6 (December 2009), pp. 1681-1689, doi:10.1088/0004-6256/138/6/1681, Bibcode: 2009AJ....138.1681S.
7. ^ Costa, Edgardo; Mendez; Jao; Henry; Subasavage; Brown; Ianna; Bartlett (2005). "THE SOLAR NEIGHBORHOOD. XIV. PARALLAXES FROM THE CERRO TOLOLO INTER-AMERICAN OBSERVATORY PARALLAX INVESTIGATION—FIRST RESULTS FROM THE 1.5 m TELESCOPE PROGRAM". The Astronomical Journal 130: 337–349. Bibcode 2005AJ....130..337C. doi:10.1086/430473.