HD 16760

HD 16760 is a binary star system approximately 227 light-years away in the constellation Perseus. The primary star HD 16760 (HIP 12638) is a G-type main sequence star similar to the Sun. The secondary, HIP 12635 is 1.521 magnitudes fainter and located at a separation of 14.6 arcseconds from the primary, corresponding to a physical separation of at least 660 AU. Announced in July 2009, HD 16760 has been confirmed to have a red dwarf orbiting it, formerly thought to be a brown dwarf or exoplanet.[2][6][4]

HD 16760
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Perseus
Right ascension 02h 42m 21.3071s[1]
Declination +38° 37′ 07.1392″[1]
Apparent magnitude (V) 8.74
Characteristics
Spectral type G5V[2]
B−V color index 0.715[2]
Astrometry
Proper motion (μ) RA: 78.493±0.760[1] mas/yr
Dec.: −100.691±0.717[1] mas/yr
Parallax (π)14.3851 ± 0.4554 mas[1]
Distance227 ± 7 ly
(70 ± 2 pc)
Absolute magnitude (MV)5.41[2]
Orbit[3]
CompanionHD 16760 b
Period (P)466.048±0.057 d
Semi-major axis (a)1.161±0.097 AU
Eccentricity (e)0.0812±0.0018
Inclination (i)3.164+0.810
−0.762[4]°
Periastron epoch (T)24513802.6±1.9
Argument of periastron (ω)
(secondary)		241.9±1.4°
Semi-amplitude (K1)
(primary)		407.16±0.71 km/s
Details
HD 16760 A
Mass0.78 ± 0.05[2] M☉
Radius0.81 ± 0.27[2] R☉
Luminosity (bolometric)0.72 ± 0.43[2] L☉
Surface gravity (log g)4.47 ± 0.06[2] cgs
Temperature5629 ± 44[2] K
Metallicity [Fe/H]+0.067 ± 0.05[2] dex
Rotational velocity (v sin i)0.5 ± 0.5[2] km/s
Age1.3 ± 0.9[5] Gyr
HD 16760 b
Mass291.9+120.7
−69.4[4] MJup
Other designations
2MASS J02422130+3837073, BD+37°604, GSC 02845-02243, HIP 12638, SAO 55798, TYC 2845-2243-1
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

Stellar companion

The companion object was discovered independently by the SOPHIE extrasolar planets program[6] and the N2K Consortium.[2] It has a mass exceeding the lower limit required for fusion of deuterium in its interior. This criterion is sometimes used to distinguish between brown dwarfs, which lie above the limit, and planets which lie below the limit.[7] However its orbit is nearly circular, indicating that it may have formed in the same way as planets do, from a circumstellar disc.[6] The formation of massive planets up to 20–25 Jupiter masses has been predicted in some models of the core accretion process.[8] The identity of this object as a brown dwarf or a massive planet was thus unclear.

However, data analysed from direct imaging of the companion object using ground-based telescopes fitted with adaptive optics has revealed that it is aligned in a much more face-on orbit than previously realised. Consequently, its mass has been revised upwards. It is now no longer believed to be a large gas giant or even a brown dwarf but with a new mass calculated at around one quarter that of the Sun, or nearly 300 Jupiter masses, it easily qualifies as a stellar object, probably a red dwarf.[9] This was confirmed by Gaia astrometry in 2020.[4]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "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. Gaia DR2 record for this source at VizieR.
  2. Bunei Sato; Debra A. Fischer; Shigeru Ida; Hiroki Harakawa; Masashi Omiya; John A. Johnson; Geoffrey W. Marcy; Eri Toyota; Yasunori Hori; Howard Isaacson; Andrew W. Howard; Kathryn M.G. Peek (2009). "A Substellar Companion in a 1.3 yr Nearly-circular Orbit of HD 16760". The Astrophysical Journal. 703 (1): 671–674. arXiv:0907.5080. Bibcode:2009ApJ...703..671S. doi:10.1088/0004-637X/703/1/671. S2CID 5435270.
  3. Ment, Kristo; et al. (2018). "Radial Velocities from the N2K Project: Six New Cold Gas Giant Planets Orbiting HD 55696, HD 98736, HD 148164, HD 203473, and HD 211810". The Astronomical Journal. 156 (5). 213. arXiv:1809.01228. Bibcode:2018AJ....156..213M. doi:10.3847/1538-3881/aae1f5. S2CID 119243619.
  4. Kiefer, Flavien; Hébrard, Guillaume; Lecavelier, Alain; Martioli, Eder; Dalal, Shweta; Vidal-Madjar, Alfred (2021). "Determining the true mass of radial-velocity exoplanets with Gaia 9 planet candidates in the brown-dwarf/stellar regime and 27 confirmed planets". Astronomy & Astrophysics. A7: 645. arXiv:2009.14164. doi:10.1051/0004-6361/202039168. S2CID 221995447.
  5. Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. S2CID 54555839.
  6. Bouchy, François; Hébrard, Guillaume; Udry, Stéphane; Delfosse, Xavier; Boisse, Isabelle; Desort, Morgan; Bonfils, Xavier; Eggenberger, Anne; Ehrenreich, David; Forveille, Thierry; Le Coroller, Hervé; Lagrange, Anne-Marie; Lovis, Christophe; Moutou, Claire; Pepe, Francesco; Perrier, Christian; Pont, Frédéric; Queloz, Didier; Santos, Nuno C.; Ségransan, Damien; Vidal-Madjar, Alfred (2009). "The SOPHIE northern extrasolar planets. I. A companion close to the planet/brown-dwarf transition around HD16760". Astronomy and Astrophysics. 505 (2): 853–858. Bibcode:2009A&A...505..853B. doi:10.1051/0004-6361/200912427.
  7. "Definition of a "Planet"". Working Group on Extrasolar Planets (WGESP) of the International Astronomical Union.
  8. Christoph Mordasini; Yann Alibert; Willy Benz; Dominique Naef (2007). "Giant Planet Formation by Core Accretion". arXiv:0710.5667 [astro-ph].
  9. Evans T.M.; Ireland M.J.; Kraus A.L.; Martinache F.; Stewart P.; Tuthill P.G.; Lacour S.; Carpenter, J.M.; Hillenbrand L.A. (2011). "Mapping The Shores Of The Brown Dwarf Desert III: Young Moving Groups". The Astrophysical Journal. 744 (2): 120. arXiv:1109.5900. Bibcode:2012ApJ...744..120E. doi:10.1088/0004-637X/744/2/120. S2CID 118650120.
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