56 Andromedae

56 Andromedae, abbreviated 56 And, is a probable binary star[8] system in the northern constellation of Andromeda. 56 Andromedae is the Flamsteed designation. It has a combined apparent visual magnitude of 5.69,[2] which is just bright enough to be dimly visible to the naked eye under good seeing conditions. The distance to this system can be ascertained from its annual parallax shift, measured at 9.9 mas[1] with the Gaia space observatory, which yields a separation of 330 light years. It is moving further from the Earth with a heliocentric radial velocity of +62 km/s[5] and is traversing the celestial sphere at a relatively high rate of 0.183″ per year.[9] This pair is positioned near the line of sight to the open cluster NGC 752, located 1,490 light-years away.[10]

56 Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  01h 56m 09.36412s[1]
Declination +37° 15′ 06.5973″[1]
Apparent magnitude (V) 5.69[2]
Characteristics
Evolutionary stage giant[3]
Spectral type K0 III[4]
B−V color index +1.060[2]
Astrometry
Radial velocity (Rv)+61.77±0.13[5] km/s
Proper motion (μ) RA: +183.659[1] mas/yr
Dec.: +11.670[1] mas/yr
Parallax (π)9.8863 ± 0.1292[1] mas
Distance330 ± 4 ly
(101 ± 1 pc)
Absolute magnitude (MV)+0.76[2]
Details
Mass1.34±0.37[6] M☉
Radius11[5] R☉
Luminosity56.2[5] L☉
Surface gravity (log g)2.58±0.18[3] cgs
Temperature4,765±35[3] K
Metallicity [Fe/H]−0.15±0.07[3] dex
Rotational velocity (v sin i)0.0[5] km/s
Age3.16+1.11
−0.82[6] Gyr
Other designations
56 And, BD+36° 355, HD 11749, HIP 9021, HR 557, SAO 55107, WDS J01562+3715A, NLTT 6465[7]
Database references
SIMBADdata

The brighter primary is an aging giant star[3] with a stellar classification of K0 III,[4] having exhausted the hydrogen at its core and evolved off the main sequence. It is a red clump giant, having undergone "helium flash" and is presently generating energy at its core through helium fusion.[11] The star is about 3.1[6] billion years old with a negligible observable rotation rate, so the rotation axis of the star is likely pointing towards us.[5] It has 1.3[6] times the mass of the Sun and has expanded to 11[5] times the Sun's radius The star is radiating 56[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,765 K.[3]

The faint secondary component is a magnitude 11.93 star located at an angular separation of 18.50″ along a position angle (PA) of 77°, as of 2001. This has changed little since 1903 when it was at a separation of 18.4″ along a PA of 80°.[12]

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.
  3. Da Silva, Ronald; 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.
  4. Cottrell, P. L.; Sneden, C. (June 1986), "A detailed kinematic and abundance analysis of old disk giants", Astronomy and Astrophysics, 161: 314−326, Bibcode:1986A&A...161..314C.
  5. Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  6. Feuillet, Diane K.; et al. (2016), "Determining Ages of APOGEE Giants with Known Distances", The Astrophysical Journal, 817: 40, arXiv:1511.04088, Bibcode:2016ApJ...817...40F, doi:10.3847/0004-637X/817/1/40.
  7. "56 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 2, 2018.
  8. Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  9. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854.
  10. Kharchenko, N. V.; et al. (2005), "Astrophysical parameters of Galactic open clusters", Astronomy and Astrophysics, 438 (3): 1163, arXiv:astro-ph/0501674, Bibcode:2005A&A...438.1163K, doi:10.1051/0004-6361:20042523.
  11. Mishenina, T. V.; et al. (September 2006), "Elemental abundances in the atmosphere of clump giants", Astronomy and Astrophysics, 456 (3): 1109–1120, arXiv:astro-ph/0605615, Bibcode:2006A&A...456.1109M, doi:10.1051/0004-6361:20065141.
  12. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
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