WD 0806−661

WD 0806−661 (L 97-3, GJ 3483) is a DQ white dwarf with an extremely cold Y-type substellar companion (designated "B"), located in constellation Volans at 63 light-years 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

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	08^h 06^m 53.736^s[1]
Declination	−66° 18′ 16.74″[1]
Characteristics
Spectral type	DQ4.2[2][3] + Y1[4]
Apparent magnitude (B)	13.74[5] / -
Apparent magnitude (V)	13.71[5] / -
Apparent magnitude (R)	13.64[5] / -
Apparent magnitude (I)	13.60[5] / -
Apparent magnitude (J)	13.704 ± 0.023[1] / ~25.42[6]
Apparent magnitude (H)	13.739 ± 0.025[1] / ~25.29[6]
Apparent magnitude (K)	13.781 ± 0.043[1] / -
Astrometry
Proper motion (μ)	RA: 335.547 ± 0.044[7] mas/yr Dec.: -288.888 ± 0.041[7] mas/yr
Parallax (π)	51.9342 ± 0.0195[7] mas
Distance	62.80 ± 0.02 ly (19.255 ± 0.007 pc)
Absolute magnitude (MV)	12.30[5] / -
Details
Component A
Mass	0.58 ± 0.03[5] M☉
Surface gravity (log g)	8.00 ± 0.05[5] cgs
Temperature	10205 ± 390[5] K
Age	1.5–2.7[6] Gyr
Component B
Mass	7–9[6] MJup
Surface gravity (log g)	4.2–4.3[6] cgs
Temperature	325–350[6] K
Metallicity	<0[6]
Position (relative to A)
Component	B
Angular distance	130.2 ± 0.2″ [8]
Position angle	104.2 ± 0.2° [8]
Observed separation (projected)	2500 AU [8]
Other designations
Component A: BPM 4834, LAWD 27, L 97-3, LTT 3059, NLTT 19008, WD 0806-661, WD 0806−66, GJ 3483, 2MASS J08065373−6618167, GSC 08936−01284, GEN# +6.00204834, uvby98 986097003, WG 12 Component B: WD 0806-661 B,[8][9] WD 0806−661B,[10] GJ 3483B[11]
Database references
SIMBAD	data
Extrasolar Planets Encyclopaedia	data

WD 0806-661 B

Component B was discovered in 2011 with Spitzer Space Telescope. Its discovery paper is Luhman et al., 2011. The secondary has a mass between 7 and 9 M_J and a temperature between 325–350 Kelvin (52-77 °C; 125-170 °F).[6] 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 its detection in Hubble images at near-infrared wavelengths.[4] 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.[6] Hydrogen-deficient AGB stars might evolve into DB white dwarfs and then into DQ white dwarfs as they cool down.[12]

See also

• 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

References

1. "GJ 3483 -- White Dwarf". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-19.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. Gaia Collaboration (2018-08-01). "Gaia Data Release 2 - Summary of the contents and survey properties". Astronomy & Astrophysics. 616: A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. ISSN 0004-6361. S2CID 49211658.
8. Luhman, K. L.; Burgasser, A. 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. Luhman, K. L.; Burgasser, A. J.; Labbé, I.; Saumon, D.; Marley, M. S.; Bochanski, J. J.; Monson, A. J.; Persson, S. E. (2012). "Confirmation of One of the Coldest Known Brown Dwarfs". The Astrophysical Journal. 744 (2): 135. arXiv:1110.4353. Bibcode:2012ApJ...744..135L. doi:10.1088/0004-637X/744/2/135. S2CID 119293823.
10. "WD 0806-661B -- Brown Dwarf (M<0.08solMass)". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-06-19.
11. Rodriguez, David R.; Zuckerman, B.; Melis, Carl; Song, Inseok (2011). "The Ultra Cool Brown Dwarf Companion of WD 0806-661B: Age, Mass, and Formation Mechanism". The Astrophysical Journal Letters. 732 (2): L29. arXiv:1103.3544. Bibcode:2011ApJ...732L..29R. doi:10.1088/2041-8205/732/2/L29. S2CID 118382542.
12. 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.

External links

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