LP 658-2

LP 658-2 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]

LP 658-2
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
Distance20.9 ± 0.1 ly
(6.40 ± 0.03 pc)
Absolute magnitude (MV)15.44 ± 0.03[3]
Details
Mass0.45 ± 0.01,[2] or 0.80 ± 0.01[3] M☉
Radius0.014,[2][note 1] or 0.010[3] R☉
Surface gravity (log g)7.80 ± 0.02,[2] or 8.35 ± 0.01[3] cgs
Temperature4270 ± 70,[2] or 5180 ± 70[3] K
Age6.42,[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
SIMBADdata

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 LP 658-2 present in YPC (Yale Parallax Catalog) and among results of CTIOPI 1.5 m telescope program:

LP 658-2 parallax measurements

SourcePaperParallax, masDistance, pcDistance, lyRef.
YPCvan Altena et al., 1995155.0 ± 2.16.45 ± 0.0921.04 ± 0.29[5]
CTIOPI 1.5 mTSN-14 (Costa et al., 2005)156.93 ± 2.676.37 ± 0.1120.78 ± 0.35[7]
CTIOPI 0.9 mTSN-21 (Subasavage et al., 2009)156.13 ± 0.846.40 ± 0.0320.89 ± 0.11[3]

Physical parameters

There are two sets of published physical parameters of LP 658-2, significantly differing from each other: one from Holberg et al. 2008 and Sion et al. 2009, the other from Subasavage et al. 2009.

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

Subasavage et al. 2009 version

Color

Despite it being classified as a "white" dwarf, it appears orange rather than white, due to its relatively cool 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. From surface gravity and mass.
  2. White dwarf cooling age, i. e. age as degenerate star (not including lifetime as main sequence star and as giant star)

References
  1. "GJ 223.2". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-01-17.
  2. Holberg, J. B.; Sion, E. M.; Oswalt, T.; McCook, G. P.; Foran, S.; Subasavage, John P. (1 April 2008). "A new look at the local white dwarf population". The Astronomical Journal. 135 (4): 1225–1238. Bibcode:2008AJ....135.1225H. doi:10.1088/0004-6256/135/4/1225.
  3. Subasavage, John P.; Jao, Wei-Chun; Henry, Todd J.; Bergeron, P.; Dufour, P.; Ianna, Philip A.; Costa, Edgardo; Méndez, René A. (1 June 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 (6): 4547–4560. arXiv:0902.0627. Bibcode:2009AJ....137.4547S. doi:10.1088/0004-6256/137/6/4547.
  4. Sion, Edward M.; Holberg, J. B.; Oswalt, Terry D.; McCook, George P.; Wasatonic, Richard (1 December 2009). "The white dwarfs within 20 parsecs of the Sun: kinematics and statistics". The Astronomical Journal. 138 (6): 1681–1689. arXiv:0910.1288. Bibcode:2009AJ....138.1681S. doi:10.1088/0004-6256/138/6/1681.
  5. van Altena, W. F.; Lee, J. T.; Hoffleit, E. D. (1995). The General Catalogue of Trigonometric [Stellar] Parallaxes (4th ed.). New Haven, CT: Yale University Observatory. Bibcode:1995gcts.book.....V. VizieR entry.
  6. Table 1 in Sion et al. 2009
  7. Costa, Edgardo; Méndez, René A.; Jao, W.-C.; Henry, Todd J.; Subasavage, John P.; Brown, Misty A.; Ianna, Philip A.; Bartlett, Jennifer (July 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 (1): 337–349. Bibcode:2005AJ....130..337C. doi:10.1086/430473.
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