WD 0806−661

WD 0806−661 (L 97-3, GJ 3483), formally named Maru,[9] is a DQ white dwarf with an extremely cold Y-type substellar companion (designated "B"), located in the constellation Volans at 62.7 light-years (19.2 parsecs) from Earth. The companion was discovered in 2011, and is the only known Y-type companion to a star or stellar remnant. At the time of its discovery WD 0806-661 B had the largest actual (2500 AU) and apparent separation (more than 2 arcminutes) of any known planetary-mass object, as well as being the coldest directly imaged substellar object then known.

WD 0806−661 / Maru

The right side shows an image taken by ESO's VLT HAWK-I in near-infrared. The white dwarf is marked with an arrow. The left side shows an image taken by the NASA/ESA HST WFC3 also in near-infrared wavelengths. The sub-brown dwarf appears as green pixels (2014) and purple pixels (2015) in an insert.
Observation data
Epoch J2000[1]      Equinox J2000[1]
Constellation Volans
Right ascension 08h 06m 53.75366s[2]
Declination −66° 18′ 16.7011″[2]
Characteristics
Spectral type DQ4.2[3][4] + Y1[5]
Apparent magnitude (B) 13.74[6] / -
Apparent magnitude (V) 13.71[6] / -
Apparent magnitude (R) 13.64[6] / -
Apparent magnitude (I) 13.60[6] / -
Apparent magnitude (J) 13.704 ± 0.023[1] / ~25.42[7]
Apparent magnitude (H) 13.739 ± 0.025[1] / ~25.29[7]
Apparent magnitude (K) 13.781 ± 0.043[1] / -
Astrometry
Proper motion (μ) RA: 335.519(16) mas/yr[2]
Dec.: −288.994(17) mas/yr[2]
Parallax (π)51.9970 ± 0.0141 mas[2]
Distance62.73 ± 0.02 ly
(19.232 ± 0.005 pc)
Absolute magnitude (MV)12.30[6] / -
Details
Component A
Mass0.58 ± 0.03[6] M☉
Surface gravity (log g)8.00 ± 0.05[6] cgs
Temperature10205 ± 390[6] K
Age1.5–2.7[7] Gyr
Component B
Mass7–9[7] MJup
Surface gravity (log g)4.2–4.3[7] cgs
Temperature325–350[7] K
Metallicity<0[7]
Position (relative to A)
ComponentB
Angular distance130.2 ± 0.2″ [8]
Position angle104.2 ± 0.2° [8]
Observed separation
(projected)		2500 AU [8]
Other designations
Maru, GJ 3483, BPM 4834, L 97-3, LAWD 27, LTT 3059, NLTT 19008, WD 0806-661, WD 0806−66, GSC 08936−01284, 2MASS J08065373−6618167, GEN# +6.00204834, uvby98 986097003, WG 12[1]
Database references
SIMBADdata
Extrasolar Planets
Encyclopaedia		data

WD 0806-661 B
Main article: WD 0806-661 b

Component WD 0806-661 B was discovered in 2011 with the Spitzer Space Telescope. Its discovery paper is Luhman et al., 2011. The secondary has a mass between 7 and 9 MJ and a temperature between 325–350 Kelvin (52-77 °C; 125-170 °F).[7] At the time of its discovery, WD 0806−661 B was the coldest "brown dwarf" that has ever been found.[8] The object is too faint to acquire a spectrum even with the Hubble Space Telescope, however the spectral type of this object was estimated to be Y1 based on its detection in Hubble images at near-infrared wavelengths.[5] The photometric colors of this object suggest that it is metal-poor. The metal-poor composition of the companion could explain the DQ spectral type of the primary white dwarf.[7] Hydrogen-deficient AGB stars might evolve into DB white dwarfs and then into DQ white dwarfs as they cool down.[10]

In August 2022, WD 0806-661 and its planetary-mass companion were included among 20 systems to be named by the third NameExoWorlds project.[11] The approved names, proposed by a team from South Korea, were announced in June 2023. WD 0806-661 is named Maru and its companion is named Ahra, after Korean words meaning "sky" and "ocean".[9]

See also

References
  1. "GJ 3483 -- White Dwarf". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-19.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. Holberg, J. B.; Sion, E. M.; Oswalt, T.; McCook, G. P.; Foran, S.; Subasavage, John P. (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. S2CID 122855486.
  4. Sion, Edward M.; Holberg, J. B.; Oswalt, Terry D.; McCook, George P.; Wasatonic, Richard (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. S2CID 119284418.
  5. Leggett, S. K.; Morley, Caroline V.; Marley, M. S.; Saumon, D. (January 2015). "Near-infrared Photometry of Y Dwarfs: Low Ammonia Abundance and the Onset of Water Clouds". The Astrophysical Journal. 799 (1): 37. arXiv:1411.2020. Bibcode:2015ApJ...799...37L. doi:10.1088/0004-637X/799/1/37. ISSN 0004-637X. S2CID 118530454.
  6. Giammichele, N.; Bergeron, P.; Dufour, P. (2012). "Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs". The Astrophysical Journal Supplement. 199 (2): 29. arXiv:1202.5581. Bibcode:2012ApJS..199...29G. doi:10.1088/0067-0049/199/2/29. S2CID 118304737.
  7. Leggett, S. K.; Tremblin, P.; Esplin, T. L.; Luhman, K. L.; Morley, Caroline V. (June 2017). "The Y-type Brown Dwarfs: Estimates of Mass and Age from New Astrometry, Homogenized Photometry, and Near-infrared Spectroscopy". The Astrophysical Journal. 842 (2): 118. arXiv:1704.03573. Bibcode:2017ApJ...842..118L. doi:10.3847/1538-4357/aa6fb5. ISSN 0004-637X. S2CID 119249195.
  8. Luhman, K. L.; Burgasser, Adam J.; Bochanski, J. J. (2011). "Discovery of a Candidate for the Coolest Known Brown Dwarf". The Astrophysical Journal Letters. 730 (1): L9. arXiv:1102.5411. Bibcode:2011ApJ...730L...9L. doi:10.1088/2041-8205/730/1/L9. S2CID 54666396.
  9. "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
  10. Althaus, L. G.; Serenelli, A. M.; Panei, J. A.; Córsico, A. H.; García-Berro, E.; Scóccola, C. G. (May 2005). "The formation and evolution of hydrogen-deficient post-AGB white dwarfs: The emerging chemical profile and the expectations for the PG 1159-DB-DQ evolutionary connection". Astronomy and Astrophysics. 435 (2): 631–648. arXiv:astro-ph/0502005. Bibcode:2005A&A...435..631A. doi:10.1051/0004-6361:20041965. ISSN 0004-6361.
  11. "List of ExoWorlds 2022". nameexoworlds.iau.org. IAU. 8 August 2022. Retrieved 27 August 2022.
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