WD 2359-434

Coordinates: 00^h 02^m 10.766^s, −43° 09′ 56.02″

WD 2359-434

Size of WD 2359-434 in comparison with Earth. On the left is Earth, on the right is WD 2359-434.
Observation data Epoch J2000[1]      Equinox J2000[1]
Constellation	Phoenix
Right ascension	00^h 02^m 10.766^s[1]
Declination	−43° 09′ 56.02″[1]
Apparent magnitude (V)	12.76[2]
Characteristics
Spectral type	DAP5.8[3]
Apparent magnitude (B)	13.12[1]
Apparent magnitude (V)	12.76[2]
Apparent magnitude (RKC)	12.82[4]
Apparent magnitude (IKC)	12.66[4]
Apparent magnitude (J)	12.60 ± 0.03[4]
Apparent magnitude (H)	12.43 ± 0.02[4]
Apparent magnitude (KS)	12.45 ± 0.02[4]
Astrometry
Radial velocity (Rv)	-58.8 ± 10.8[5] km/s
Proper motion (μ)	RA: 589[4] mas/yr Dec.: -664[4] mas/yr
Parallax (π)	122.27 ± 1.13[4] mas
Distance	26.7 ± 0.2 ly (8.18 ± 0.08 pc)
Absolute magnitude (MV)	13.20[2][4][note 1]
Details
Mass	0.85 ± 0.01[4] M☉
Radius	0.0097[4][note 2] R☉
Surface gravity (log g)	8.39 ± 0.01[4] cgs
Temperature	8570 ± 50[2] K
Age	1.82 ± 0.06[4][note 3] Gyr
Other designations
Gliese 915,[2][3] LHS 1005,[2] LFT 1849,[1] LTT 9857,[1] LP 988-88,[1] L 362-81,[6] EGGR 165,[1] 2MASS J00021076-4309560[1]
Database references
SIMBAD	data

WD 2359-434 (Gliese 915, LHS 1005, L 362-81) is a nearby degenerate star (white dwarf) of spectral class DAP5.8,^[3] the single known component of the system, located in the constellation Phoenix, the nearest star in this constellation.

Distance

WD 2359-434, probably, is the 11th closest white dwarf, or, possibly, 9th, 10th, or 12th (see Gliese 293, GJ 1087 and Gliese 518). Currently, the most accurate distance estimate of WD 2359-434 is trigonometric parallax from CTIOPI (Cerro Tololo Inter-American Observatory Parallax Investigation) 0.9 m telescope program, published in 2009 in the 21st paper of RECONS's The Solar Neighborhood (TSN) series^[7] Subasavage et al. 2009:^[4] 122.27 ± 1.13 mas, corresponding to a distance 8.18 ± 0.08 pc, or 26.68 ± 0.25 ly.

WD 2359-434 distance estimates

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
Woolley	Woolley et al. 1970	122 ± 8	8.2 ± 0.6	26.7 ± 1.9	[8]
GJ, 3rd version	Gliese, Jahreiss 1991	128.2 ± 6.4	7.80 ± 0.41	25.44 ± 1.37	[9]
YPC, 4th edition	van Altena et al. 1995	127.4 ± 6.8	7.85 ± 0.44	25.60 ± 1.44	[6]
CTIOPI 0.9 m	TSN 21 (Subasavage et al. 2009)	122.27 ± 1.13	8.18 ± 0.08	26.68 ± 0.25	[4]

The most accurate estimate is marked in bold.

Physical parameters

WD 2359-434's mass is 0.85 ± 0.01 Solar masses,^[4] its surface gravity is 10^{8.39 ± 0.01} (2.45 · 10⁸) cm·s⁻²,^[4] or approximately 250,000 of Earth's, corresponding to a radius 6780 km, or 1.06 of Earth's.

WD 2359-434 is relatively hot and young white dwarf, its temperature is 8570 ± 50 K;^[2] its cooling age, i. e. age as degenerate star (not including lifetime as main sequence star and as giant star) is 1.82 ± 0.06 Gyr.^[4] Gliese 518 should appear bluish-white, due temperature, comparable with that of A-type main sequence stars.

As all white dwarfs, WD 2359-434 is composed of very dense degenerate matter, its mean density is 1,300,000 g·cm⁻³,^{[4][note 4]} i.e. mass of one cubic millimetre of WD 2359-434 matter is 1.3 kg.

Main sequence progenitor properties

As all degenerate stars, WD 2359-434 previously existed initially as main-sequence star and then as giant star, until all the thermonuclear fuel was exhausted, after which WD 2359-434 lost most of its mass. According 2010 thesis for the degree of Doctor of Science,^[10] using Wood model D^[11] initial–final mass relation and WD 2359-434's white dwarf mass value 0.97 ± 0.03 M_☉ from Holberg et al. 2008,^[2] its main sequence progenitor mass was 7.09 M_☉. Using expression for pre-white dwarf lifetime 10 · (M_MS/M_☉)^2.5 (Gyr),^[11] was found WD 2359-434 main sequence age 0.07 Gyr.

White dwarf mass value 0.85 ± 0.01 M_☉ from Subasavage et al. 2009,^[4] in Wood model D yields MS (main sequence) mass 6.03 M_☉, and MS lifetime 0.11 Gyr, corresponding to B-type main sequence star.

According initial-final mass relation from Weidemann 2000 paper,^[12] WD 2359-434's main sequence progenitor should have mass about 4.6 M_☉ and lifespan 0.22 Gyr, and, again, should be of B spectral type. There are also other models.

Notes

1. From apparent magnitude and parallax.
2. From surface gravity and mass.
3. White dwarf cooling age, i. e. age as degenerate star (not including lifetime as main sequence star and as giant star).
4. From mass and surface gravity (assuming spherical shape).

See also

• List of star systems within 25–30 light-years

References

1. "GJ 915 -- White Dwarf". Centre de Données astronomiques de Strasbourg. Retrieved 2011-11-03.
2. 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. 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. arXiv:0910.1288. Bibcode:2009AJ....138.1681S. doi:10.1088/0004-6256/138/6/1681.
4. 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.
5. Pauli, E.-M.; Napiwotzki; Heber; Altmann & Odenkirchen (2006). "3D kinematics of white dwarfs from the SPY project. II". Astronomy and Astrophysics. 447: 173–184. arXiv:astro-ph/0510494. Bibcode:2006A&A...447..173P. doi:10.1051/0004-6361:20052730. (see Table 8)
6. Yale Trigonometric Parallaxes, Fourth Edition (van Altena+ 1995)
7. The Solar Neighborhood (TSN) Series in The Astronomical Journal
8. Stars within 25 pc of the Sun (Woolley+ 1970)
9. Nearby Stars, Preliminary 3rd Version (Gliese+ 1991)
10. Matías Cristóbal Radiszcz Sotomayor, BINARIEDAD ESTELAR Y SUB-ESTELAR EN ENANAS BLANCAS CERCANAS
11. Wood, M. A. (1992). "Constraints on the age and evolution of the Galaxy from the white dwarf luminosity function". The Astrophysical Journal. 386: 539–561. Bibcode:1992ApJ...386..539W. doi:10.1086/171038.
12. Weidemann, V. (2000). "Revision of the initial-to-final mass relation". Astronomy and Astrophysics. 363: 647–656. Bibcode:2000A&A...363..647W.