HD 118889

HD 118889 is a binary star system in the northern constellation of Boötes. It is faintly visible to the naked eye as a point of light with an apparent visual magnitude of 5.57.[2] The system is located at a distance of approximately 196 light years from the Sun based on stellar parallax,[1] but is drifting closer with a radial velocity of −26 km/s.[8]

HD 118889
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 13h 39m 34.61613s[1]
Declination +10° 44′ 46.5827″[1]
Apparent magnitude (V) 5.57[2] (6.35 + 6.47)[3]
Characteristics
Evolutionary stage Main sequence[4][5]
Spectral type F0V[6]
U−B color index +0.045[7]
B−V color index +0.33[7]
Astrometry
Radial velocity (Rv)−25.9±1.9[8] km/s
Proper motion (μ) RA: −114.96[1] mas/yr
Dec.: −11.74[1] mas/yr
Parallax (π)16.67 ± 0.58 mas[1]
Distance196 ± 7 ly
(60 ± 2 pc)
Absolute magnitude (MV)+2.40[9]
Orbit[10]
Period (P)22.460±0.019 yr
Semi-major axis (a)0.19983±0.00055″
Eccentricity (e)0.5450±0.0022
Inclination (i)43.50±0.40°
Longitude of the node (Ω)34.58±0.52°
Periastron epoch (T)B 1929.850±0.024
Argument of periastron (ω)
(secondary)		359.93±0.79°
Details
A
Mass1.89±0.03 M☉[5]
1.41[11] M☉
Luminosity18.5[5] L☉
Surface gravity (log g)3.97[11] cgs
Temperature7,080±241[11] K
Rotational velocity (v sin i)144[5] km/s
Age718[11] Myr
Other designations
BD+11° 2589, HD 118889, HIP 66640, HR 5138, SAO 100654, ADS 8987, WDS 13396+1045, BU 612
Database references
SIMBADdata

The binary components of this system were first measured by S. W. Burnham in 1878 and it was given the discovery code BU 612.[12] The pair are orbiting each other with a period of 22.46 years with an eccentricity (ovalness) of 0.545. The primary component is a magnitude 6.35[3] star with a stellar classification of F0V,[6] matching an F-type main-sequence star. It is an estimated 718[11] million years old and is spinning rapidly with a projected rotational velocity of 144[5] km/s. The star has 1.4–1.9 times the mass of the Sun. The secondary is slightly fainter at magnitude 6.47.[3]

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  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. Malkov, O. Yu.; et al. (2012), "Dynamical Masses of a Selected Sample of Orbital Binaries", Astronomy & Astrophysics, 546: 5, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774, A69
  4. Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377
  5. Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789
  6. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298
  7. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M
  8. Holmberg, J.; et al. (2007), "The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk", Astronomy & Astrophysics, 475 (2): 519–537, arXiv:0707.1891, Bibcode:2007A&A...475..519H, doi:10.1051/0004-6361:20077221, S2CID 119054949
  9. Reiners, Ansgar (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics, 446 (1): 267–277, arXiv:astro-ph/0509399, Bibcode:2006A&A...446..267R, doi:10.1051/0004-6361:20053911, S2CID 8642707
  10. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 2021-04-01.
  11. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607
  12. Mason, Brian D.; et al. (February 1999). "Binary Star Orbits from Speckle Interferometry. I. Improved Orbital Elements of 22 Visual Systems". The Astronomical Journal. 117 (2): 1023–1036. Bibcode:1999AJ....117.1023M. doi:10.1086/300748. S2CID 122382211.
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