WD J2356−209

WD J2356−209 (also known as WD 2354−211)[4] is a white dwarf star located 65 pc (212 ly) away from the Earth.[5] It is a very faint white dwarf, with an apparent visual magnitude of 21.03.[6] Its visible spectrum is dominated by a broad absorption feature[2] that has been attributed to pressure-broadened sodium D lines.[7] The presence of this sodium absorption feature and the detection of spectral lines from other heavy elements (calcium, iron and magnesium) indicate that the photosphere of WD J2356−209 has been polluted by a recent rocky debris accretion episode. A detailed analysis of the spectrum of WD J2356−209 shows that the accreted planetesimal was abnormally sodium-rich, containing up to ten times more sodium than calcium.[3] With an effective temperature of 4040 K, WD J2356−209 is the coolest metal-polluted white dwarf observed to date (and also the oldest, with a white dwarf cooling age of about 8 Gyr).[3]

WD J2356−209
Observation data
Epoch J2000.0 (ICRS)      Equinox J2000.0 (ICRS)
Constellation Vela
Right ascension 23h 56m 45.576s[1]
Declination −20° 54′ 45.01″[1]
Characteristics
Spectral type DC[2] or DZ[3]
Astrometry
Distance211.3 ± 8.2 ly (64.8 ± 2.5 pc)[3] ly
Details
Surface gravity (log g)8.26±0.15[3] cgs
Temperature4,310±190[3] K
Age8.0±0.8[3] Gyr
Database references
SIMBADdata

References
  1. Lasker, Barry M.; et al. (August 2008). "The Second-Generation Guide Star Catalog: Description and Properties". The Astronomical Journal. 136 (2): 735–766. arXiv:0807.2522. Bibcode:2008AJ....136..735L. doi:10.1088/0004-6256/136/2/735.
  2. Oppenheimer, B. R.; et al. (22 March 2001). "Direct Detection of Galactic Halo Dark Matter". Science. 292 (5517): 698–702. arXiv:astro-ph/0104293. doi:10.1126/science.1059954. PMID 11264524.
  3. Blouin, S.; Dufour, P.; Allard, N. F.; Salim, S.; Rich, R. M.; Koopmans, L. V. E. (February 2019). "A New Generation of Cool White Dwarf Atmosphere Models. III. WD J2356-209: Accretion of a Planetesimal with an Unusual Composition". The Astrophysical Journal. 872 (2): 188. arXiv:1902.03219. Bibcode:2019ApJ...872..188B. doi:10.3847/1538-4357/ab0081.
  4. "WD 2354-211". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-01-16.
  5. Gaia Collaboration (2016). "The Gaia mission". Astronomy and Astrophysics. 595: A1. arXiv:1609.04153. doi:10.1051/0004-6361/201629272.
  6. Bergeron, P.; et al. (June 2005). "On the Interpretation of High‐Velocity White Dwarfs as Members of the Galactic Halo". The Astrophysical Journal. 625 (2): 838–848. arXiv:astro-ph/0502350. Bibcode:2005ApJ...625..838B. doi:10.1086/429715.
  7. Salim, Samir; Rich, R. Michael; Hansen, Brad M.; Koopmans, L. V. E.; Oppenheimer, Ben R.; Blandford, Roger D. (February 2004). "Cool White Dwarfs Revisited: New Spectroscopy and Photometry". The Astrophysical Journal. 601 (2): 1075–1087. arXiv:astro-ph/0308126. Bibcode:2004ApJ...601.1075S. doi:10.1086/380581.


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