HD 156846

HD 156846 is a binary star[5] system in the equatorial constellation of Ophiuchus, positioned a degree SSE of Messier 9.[8] It has a yellow hue and is just barely bright enough to be visible to the naked eye with an apparent visual magnitude of 6.5.[2] The system is located at a distance of 156 light years from the Sun based on parallax.[1] It is drifting closer with a radial velocity of −68.5 km/s, and is predicted to come to within 85.0 light-years in about 476,000 years.[6]

HD 156846
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 17h 20m 34.31093s[1]
Declination −19° 20′ 01.4944″[1]
Apparent magnitude (V) 6.506[2] + 14.10[3]
Characteristics
Spectral type G1V[4] + M4V[5]
B−V color index 0.557[2]
Astrometry
Radial velocity (Rv)−68.50±0.22[6] km/s
Proper motion (μ) RA: −137.102±0.097[1] mas/yr
Dec.: −143.204±0.074[1] mas/yr
Parallax (π)20.9210 ± 0.0508 mas[1]
Distance155.9 ± 0.4 ly
(47.8 ± 0.1 pc)
Absolute magnitude (MV)3.055[2]
Details[2]
A
Mass1.35±0.045 M☉
Radius2.12±0.12 R☉
Luminosity5.07[6] L☉
Surface gravity (log g)3.92±0.08 cgs
Temperature5,969±44 K
Metallicity [Fe/H]+0.17±0.04 dex
Rotational velocity (v sin i)5.05±0.50 km/s
Age2.8+0.1
−0.2[6] Gyr
B
Mass0.59[5] M☉
Other designations
BD−19°4605, GC 23420, HD 156846, HIP 84856, HR 6441, SAO 160474[7]
Database references
SIMBADdata

The primary, component A, is a G-type star with a stellar classification of G1V.[4] The absolute visual magnitude of this star is 1.13 magnitudes above the main sequence, indicating it has evolved slightly off the main sequence.[2] It has 1.35 times the mass of the Sun and 2.12 times the Sun's radius.[2] The star is an estimated 2.8[6] billion years old and is spinning with a projected rotational velocity of 5 km/s.[2] It is radiating five[6] times the luminosity of the Sun from its photosphere at an effective temperature of 5,969 K.[2]

The magnitude 14.4 secondary companion, component B, was discovered by the American astronomer R. G. Aitken in 1910.[3] It lies at an angular separation of 5.1″ from the primary, corresponding to a projected separation of 250 AU. This is a red dwarf with a class of M4V and has an estimated 59% of the Sun's mass.[5]

Planetary system

On 26 October 2007, a planet HD 156846 b was found orbiting the primary star by Tamuz, using the radial velocity method.[9] It has an orbital period of 0.98 years and a large eccentricity of 0.85. The estimated mass of this object is, at a minimum, 10.6 times the mass of Jupiter. If it were following the same orbit within the Solar System, it would have a perihelion within the orbit of Mercury and an aphelion outside the orbit of Mars.[2]

The HD 156846 planetary system[2]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥10.57±0.29 MJ 1.096±0.021 359.5546±0.0071 0.84785±0.00050 — —

See also

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. Kane, Stephen R.; et al. (May 2011). "Improved Orbital Parameters and Transit Monitoring for HD 156846b". The Astrophysical Journal. 733 (1): 7. arXiv:1103.4127. Bibcode:2011ApJ...733...28K. doi:10.1088/0004-637X/733/1/28. S2CID 13001033. 28.
  3. Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  4. Houk, N.; Smith-Moore, M. (1988). Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Vol. 4. Bibcode:1988mcts.book.....H.
  5. Fontanive, C.; et al. (June 2019). "A high binary fraction for the most massive close-in giant planets and brown dwarf desert members". Monthly Notices of the Royal Astronomical Society. 485 (4): 4967–4996. arXiv:1903.02332. Bibcode:2019MNRAS.485.4967F. doi:10.1093/mnras/stz671. S2CID 84180618.
  6. 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.
  7. "HD 156846". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-13.
  8. Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 3. Sky Publishing Corporation and the European Space Agency. ISBN 0-933346-84-0.
  9. Tamuz, O.; et al. (2008). "The CORALIE survey for southern extra-solar planets XV. Discovery of two eccentric planets orbiting HD 4113 and HD 156846". Astronomy and Astrophysics. 480 (3): L33–L36. arXiv:0710.5028. Bibcode:2008A&A...480L..33T. doi:10.1051/0004-6361:20078737. S2CID 11350536.
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