HD 16760

HD 16760

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Perseus
Right ascension	02^h 42^m 21^s
Declination	+38° 37′ 07″
Apparent magnitude (V)	8.74
Characteristics
Spectral type	G5V[1]
B−V color index	0.715[1]
Astrometry
Proper motion (μ)	RA: 82.84 mas/yr Dec.: -110.65 mas/yr
Parallax (π)	22.00 ± 2.35[1][2] mas
Distance	approx. 150 ly (approx. 45 pc)
Absolute magnitude (MV)	5.41[1]
Details
Mass	0.78 ± 0.05[1] M☉
Radius	0.81 ± 0.27[1] R☉
Luminosity (bolometric)	0.72 ± 0.43[1] L☉
Surface gravity (log g)	4.47 ± 0.06[1] cgs
Temperature	5629 ± 44[1] K
Metallicity	[Fe/H] = +0.067 ± 0.05[1]
Rotational velocity (v sin i)	0.5 ± 0.5[1] km/s
Other designations
2MASS J02422130+3837073, BD +37°604, GSC 02845-02243, HIP 12638, SAO 55798, TYC 2845-2243-1
Database references
SIMBAD	data
Exoplanet Archive	data
Extrasolar Planets Encyclopaedia	data

HD 16760 is a binary star system approximately 150 light-years away in the constellation Perseus. The primary star HD 16760 (HIP 12638) is a G-type main sequence star similar to our 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 substellar object orbiting it. Whether or not this object is a brown dwarf or an extrasolar planet is currently not understood.^[1][3]

Substellar companion

The companion object was discovered independently by the SOPHIE extrasolar planets program^[3] and the N2K Consortium.^[1] 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.^[4] However its orbit is nearly circular, indicating that it may have formed in the same way as planets do, from a circumstellar disc.^[3] The formation of massive planets up to 20–25 Jupiter masses has been predicted in some models of the core accretion process.^[5] The identity of this object as a brown dwarf or a massive planet was thus unclear.

However, recently data analysed from direct imaging, using ground based telescopes fitted with adaptive optics, on the companion object 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 our sun, or nearly 300 Jupiter masses, it easily qualifies as a stellar object, probably a red dwarf.^[6]

The HD 16760 planetary system^{[1][note 1]}

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥13.13 ± 0.56 MJ	1.084 ± 0.023	466.47 ± 0.35	0.084 ± 0.003	—	—

Notes

1. Both groups quote slightly different parameters for the object, the primary difference being the stellar mass which is given in the SOPHIE paper as 0.88 stellar masses, which leads to a companion mass at least 14.3 times that of Jupiter. The values quoted here are from the N2K consortium, whose modelling of the stellar properties incorporated the distance from most recent reduction of the Hipparcos catalogue.

References

1. 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.
2. F. van Leeuwen (2007). "HIP 12638". Hipparcos, the New Reduction.
3. Bouchy, F., Hébrard, G., Udry, S., Delfosse, X., Boisse, I., Desort, M., Bonfils, X., Eggenberger, A., Ehrenreich, D., Forveille, T., Le Coroller, H., Lagrange, A.M., Lovis, C., Moutou, C., Pepe, F., Perrier, C., Pont, F., Queloz, D., Santos, N.C., Ségransan, D., and Vidal-Madjar, A. (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.
4. "Definition of a "Planet"". Working Group on Extrasolar Planets (WGESP) of the International Astronomical Union.
5. Christoph Mordasini, Yann Alibert, Willy Benz, Dominique Naef (2007). "Giant Planet Formation by Core Accretion". arXiv:0710.5667 [astro-ph].
6. 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.

Coordinates: 2^h 42^m 21^s, +38° 37′ 7″