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WD 2359−434

Coordinates: Sky map 00h 02m 10.766s, −43° 09′ 56.02″
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Gliese 915

Size of Gliese 915 in comparison with Earth. On the left is Earth, on the right is Gliese 915.
Observation data
Epoch J2000[1]      Equinox J2000[1]
Constellation Template:Constel
Right ascension 00h 02m 10.766s[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 mas[4]
Distance26.7 ± 0.2 ly
(8.18 ± 0.08 pc)
Absolute magnitude (MV)13.20[2][4][note 1]
Details
Mass0.85 ± 0.01[4] M☉
Radius0.0097[4][note 2] R☉
Surface gravity (log g)8.39 ± 0.01[4] cgs
Temperature8570 ± 50[2] K
Age1.82 ± 0.06[4][note 3] Gyr
Other designations
WD 2359-434,[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
SIMBADdata

Gliese 915 (WD 2359-434, 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 Template:Constel, the nearest star in this constellation.

Distance

Gliese 915, 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 Gliese 915 is trigonometric parallax from CTIOPI (Cerro Tololo Inter-American Observatory Parallax Investigation) 0.9 m telescope program, published in 2009 in the 21th 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.

Gliese 915 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

Gliese 915's mass is 0.85 ± 0.01 Solar masses,[4] its surface gravity is 108.39 ± 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.

Gliese 915 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, Gliese 915 is composed of very dense degenegate matter, its mean density is 1,300,000 g·cm−3,[4][note 4] i.e. mass of one cubic millimetre of Gliese 915 matter is 1.3 kg.

Main sequence progenitor properties

As all degenerate stars, Gliese 915 previously existed initially as main-sequence star and then as giant star, until all the thermonuclear fuel was exhausted, after which Gliese 915 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 Gliese 915'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 · (MMS/M☉)2.5 (Gyr),[11] was found Gliese 915 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] Gliese 915'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).

References

  1. ^ a b c d e f g h i j "GJ 915 -- White Dwarf". Centre de Données astronomiques de Strasbourg. Retrieved 2011-11-03.
  2. ^ a b c d e f g h Holberg, J. B. (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. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ a b c Sion, Edward M. (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. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ a b c d e f g h i j k l m n o p q r s t Subasavage, John P. (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. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ Pauli, E.-M. (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. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) (see Table 8)
  6. ^ a b 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. ^ a b 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.
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