WD 0806−661

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 inset.
Observation data Epoch J2000[1]      Equinox J2000[1]
Constellation	Volans
Right ascension	08^h 06^m 53.75366^s[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]
Distance	62.73 ± 0.02 ly (19.232 ± 0.005 pc)
Absolute magnitude (MV)	12.30[6] / -
Details
Component A
Mass	0.562±0.005[8] M☉
Radius	0.0129[8][a] R☉
Luminosity	0.015[8] L☉
Surface gravity (log g)	7.969±0.006[8] cgs
Temperature	10029±41[8] K
Age	1.5–2.7[7] Gyr
Component B
Mass	7–9[7] MJup
Surface gravity (log g)	4.2–4.3[7] cgs
Temperature	325–350[7] K
Metallicity	<0[7]
Position (relative to A)
Component	B
Angular distance	130.2 ± 0.2″ [9]
Position angle	104.2 ± 0.2° [9]
Projected separation	2500 AU [9]
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
SIMBAD	data

WD 0806−661 (L 97-3, GJ 3483), formally named Maru,^[10] 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 B

Main article: WD 0806−661 B

Component WD 0806-661 B was discovered in 2011 with the Spitzer Space Telescope. Its discovery was announced in the paper Luhman et al., 2011. The secondary has a mass between 7 and 9 M_J and a temperature between 325 and 350 kelvins (52 and 77 °C; 125 and 170 °F).^[7] At the time of its discovery, WD 0806−661 B was the coldest "brown dwarf" that has ever been found.^[9] 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.^[11]

In August 2022, WD 0806-661 and its planetary-mass companion were included among 20 systems to be named by the third NameExoWorlds project.^[12] The approved names, proposed by a team from South Korea, were announced in June 2023. WD 0806-661 and its companion are named after the Korean words Maru (마루) and Ahra (아라).^[10]

See also

• List of exoplanets and planetary debris around white dwarfs
• WISE 0146+4234 – a Y0 companion to a T9 brown dwarf
• WISE 1217+1626 B – another Y0 companion to a T9 brown dwarf
• DT Virginis
• HD 106906 b
• GU Piscium b

Notes

1. Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:$${\displaystyle {\sqrt {{\biggl (}{\frac {5,772}{10,029}}{\biggr )}^{4}\cdot 10^{-2.8207}}}=0.0129\ R_{\odot }.}$$

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. Vincent, O.; Barstow, M. A.; Jordan, S.; Mander, C.; Bergeron, P.; Dufour, P. (2024-01-26). "Classification and parameterization of a large Gaia sample of white dwarfs using XP spectra". Astronomy & Astrophysics. 682: A5. Bibcode:2024A&A...682A...5V. doi:10.1051/0004-6361/202347694. ISSN 0004-6361.
9. 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.
10. "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
11. 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.
12. "List of ExoWorlds 2022". nameexoworlds.iau.org. IAU. 8 August 2022. Retrieved 27 August 2022.

External links

• Simbad — component b
• WD 0806-661 on Solstation.com