WD 2359−434
White dwarf
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WD 2359-434 (Gliese 915, LHS 1005, L 362-81) is a nearby degenerate star (white dwarf) of spectral class DAP5.8,[4] the single known component of the system, located in the constellation Phoenix, the nearest star in this constellation.
| Observation data Epoch J2000[1] Equinox J2000[1] | |
|---|---|
| Constellation | Phoenix |
| Right ascension | 00h 02m 10.72420s[2] |
| Declination | −43° 09′ 55.3906″[2] |
| Apparent magnitude (V) | 12.76[3] |
| Characteristics | |
| Spectral type | DAP5.8[4] |
| Apparent magnitude (B) | 13.12[1] |
| Apparent magnitude (V) | 12.76[3] |
| Apparent magnitude (RKC) | 12.82[5] |
| Apparent magnitude (IKC) | 12.66[5] |
| Apparent magnitude (J) | 12.60 ± 0.03[5] |
| Apparent magnitude (H) | 12.43 ± 0.02[5] |
| Apparent magnitude (KS) | 12.45 ± 0.02[5] |
| Astrometry | |
| Radial velocity (Rv) | -58.8 ± 10.8[6] km/s |
| Proper motion (μ) | RA: 613.785 mas/yr[2] Dec.: -686.989 mas/yr[2] |
| Parallax (π) | 120.0143±0.0215 mas[2] |
| Distance | 27.176 ± 0.005 ly (8.332 ± 0.001 pc) |
| Absolute magnitude (MV) | 13.39±0.03 |
| Details[7] | |
| Mass | 0.83±0.02 M☉ |
| Radius | 0.0097±0.0001[8] R☉ |
| Luminosity | 4.37+0.42 −0.38×10−4 L☉ |
| Surface gravity (log g) | 8.37±0.02 cgs |
| Temperature | 8,506±122[8] K |
| Age | 1.83±0.18[note 1] Gyr |
| Other designations | |
| GJ 915, EGGR 165, L 362-81, LAWD 96, LFT 1849, LHS 1005, LP 988-88, LTT 9857, WD 2359-434, 2MASS J00021076-4309560[1] | |
| Database references | |
| SIMBAD | data |
  WD 2359−434 Location of WD 2359−434 in the constellation Phoenix | |
Distance
Physical parameters
WD 2359−434's mass is 0.85 ± 0.01 Solar masses,[5] its surface gravity is 108.39 ± 0.01 (2.45 · 108) cm·s−2,[5] 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;[3] 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.[5] 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,[5][note 2] i.e. mass of one cubic millimetre of WD 2359−434 matter is 1.3 kg.
Unusually for a white dwarf star, WD 2359-434 has a weak, non-dipole magnetic field of 50,000 - 100,000 Gauss.[10]
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 to the 2010 thesis for the degree of Doctor of Science,[11] using Wood model D[12] initial–final mass relation and WD 2359−434's white dwarf mass value 0.97 ± 0.03 M☉ from Holberg et al. 2008,[3] its main sequence progenitor mass was 7.09 M☉. Using expression for pre-white dwarf lifetime 10 · (MMS/M☉)2.5 (Gyr),[12] 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,[5] 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 to initial-final mass relation from Weidemann 2000 paper,[13] 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.