HD 29587

HD 29587 is a Sun-like[6] star with a candidate brown dwarf companion[7] in the northern constellation of Perseus. It has an apparent visual magnitude of 7.29,[2] which means it is too faint to be viewed with the naked eye. Based upon an annual parallax shift of 36.3 mas,[1] it is located 89.8 light years away. The star is moving away from the Earth with a heliocentric radial velocity of +113 km/s,[1] having come to within 55.8 ly some 148,000 years ago.[2] It is a hyper-velocity halo[6] star moving at a rate of 170 km/s relative to the local standard of rest.[8]

HD 29587

An artist's concept of brown dwarf HD 29587 b.
Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	04^h 41^m 36.31645^s[1]
Declination	+42° 07′ 06.4209″[1]
Apparent magnitude (V)	7.29[2]
Characteristics
Spectral type	G2 V[3]
B−V color index	0.633[3]
Astrometry
Radial velocity (Rv)	+112.67±0.20[1] km/s
Proper motion (μ)	RA: +534.004[1] mas/yr Dec.: −414.768[1] mas/yr
Parallax (π)	36.3130 ± 0.0697[1] mas
Distance	89.8 ± 0.2 ly (27.54 ± 0.05 pc)
Absolute magnitude (MV)	5.08[3]
Orbit[4]
Period (P)	1,474.9±10.2 d
Eccentricity (e)	0.356±0.095
Periastron epoch (T)	JD 2,447,763.5±45.8
Argument of periastron (ω) (secondary)	80.2±13.3°
Semi-amplitude (K1) (primary)	1.02±0.16 km/s
Details[3]
Mass	0.78±0.03 M☉
Luminosity	0.798+0.040 −0.038 L☉
Surface gravity (log g)	4.54±0.22 cgs
Temperature	5,709±35 K
Metallicity [Fe/H]	−0.51±0.05 dex
Age	14.7+3.8 −2.7 Gyr
Other designations
BD+41° 931, FK5 4419, HD 29587, HIP 21832, SAO 39690, TYC 2901-00064-1, 2MASS J04413631+4207065[5]
Database references
SIMBAD	data
Exoplanet Archive	data
Extrasolar Planets Encyclopaedia	data

This ancient star has a stellar classification of G2 V,[3] matching a G-type main-sequence star. It has 78% of the mass of the Sun and is radiating 80% of the Sun's luminosity from its photosphere at an effective temperature of 5,709 K.[3]

Formerly an IAU radial velocity standard, this star was found to have a variable radial velocity due to a suspected orbiting companion.[7] The a sin i value for the unseen object is 0.0957 ± 0.0108 AU (14.31 ± 1.62 Gm),[4] where a is the semimajor axis and i is the orbital inclination – providing a lower bound for the semimajor axis. The secondary object most likely has a mass in the range 41.0–97.8 M_J, making it a probable brown dwarf.[9]

The HD 29587 planetary system[9]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥0.78±0.03 MJ	≥0.0957±0.0108	1,474.9±10.2	0.356±0.095	—	—

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.
2. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
3. Da Silva, Ronaldo; et al. (2015). "Homogeneous abundance analysis of FGK dwarf, subgiant, and giant stars with and without giant planets". Astronomy & Astrophysics. 580: A24. arXiv:1505.01726. Bibcode:2015A&A...580A..24D. doi:10.1051/0004-6361/201525770. S2CID 119216425.
4. Halbwachs, J. L.; et al. (March 2000). "Exploring the brown dwarf desert with Hipparcos". Astronomy and Astrophysics. 355: 581–594. Bibcode:2000A&A...355..581H.
5. "HD 29587". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-08-02.
6. Fossati, L.; et al. (2017). "The effect of ISM absorption on stellar activity measurements and its relevance for exoplanet studies". Astronomy & Astrophysics. 601: 17. arXiv:1702.02883. Bibcode:2017A&A...601A.104F. doi:10.1051/0004-6361/201630339. S2CID 17549819. A104.
7. Mazeh; Latham, David W.; Stefanik, Robert P. (1996). "Spectroscopic Orbits for Three Binaries with Low-Mass Companions and the Distribution of Secondary Masses near the Substellar Limit". Astrophysical Journal. 466: 415–427. Bibcode:1996ApJ...466..415M. CiteSeerX 10.1.1.30.5905. doi:10.1086/177521.
8. Hobbs, L. M.; Duncan, Douglas K. (June 15, 1987). "The lithium abundance in halo stars". Astrophysical Journal, Part 1. 317: 796–809. Bibcode:1987ApJ...317..796H. doi:10.1086/165328.
9. Reffert, S.; Quirrenbach, A. (March 2011). "Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: nine confirmed planets and two confirmed brown dwarfs". Astronomy & Astrophysics. 527: 22. arXiv:1101.2227. Bibcode:2011A&A...527A.140R. doi:10.1051/0004-6361/201015861. S2CID 54986291. A140.