6 Andromedae

6 Andromedae is an astrometric binary star[7] system in the northern constellation of Andromeda. The designation comes from the star catalogue of John Flamsteed, first published in 1712. Its apparent visual magnitude is 5.91,[2] which is just bright enough to be visible to the naked eye under good seeing conditions. Based upon an annual parallax shift of 34.1 mas as seen from Earth,[1] it is around 96 light years from the Sun. It is moving closer to the Sun with a radial velocity of −32.4 km/s.[2] The system has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.272 arc seconds per annum.[8]

6 Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 10m 27.23746s[1]
Declination +43° 32′ 38.4336″[1]
Apparent magnitude (V) 5.91[2]
Characteristics
Spectral type F5 V[3]
U−B color index −0.05[3]
B−V color index +0.450±0.004[2]
Astrometry
Radial velocity (Rv)−32.4±0.7[2] km/s
Proper motion (μ) RA: +209.057[1] mas/yr
Dec.: +138.052[1] mas/yr
Parallax (π)34.1008 ± 0.1650[1] mas
Distance95.6 ± 0.5 ly
(29.3 ± 0.1 pc)
Absolute magnitude (MV)3.71[2]
Orbit[3]
Period (P)3,373±6 d
Periastron epoch (T)53116 ± 16 MJD
Argument of periastron (ω)
(secondary)		165.2±2.0°
Semi-amplitude (K1)
(primary)		8.75±0.09 km/s
Details
Mass1.30[4] M☉
Radius1.50+0.03
−0.06[1] R☉
Luminosity3.090+0.018
−0.017[1] L☉
Surface gravity (log g)4.09±0.14[4] cgs
Temperature6,425±218[4] K
Metallicity [Fe/H]−0.19±0.03[2] dex
Rotational velocity (v sin i)18[5] km/s
Age2.91[4] Gyr
Other designations
6 And, BD+42° 4592, FK5 3857, HD 218804, HIP 114430, HR 8825, SAO 52761[6]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 9.2 years and an eccentricity of 0.3.[3] Some early observations of the star gave it a subgiant luminosity class and it was published in the Bright Star Catalogue as spectral class F5 IV. More modern measurements identify the visible component as an F-type main-sequence star with a stellar classification of F5 V.[3][9] The star is an estimated 2.9[4] billion years old with 1.3[4] times the mass of the Sun and 1.5[1] times the Sun's radius. It is radiating 3.1[1] times the Sun's luminosity from its photosphere at an effective temperature of around 6,425 K.[4] 6 Andromedae displays an infrared excess at a wavelength of 22 μm, which may indicate a circumstellar disk of warm dusty debris.[5]

The mass of the secondary component is roughly at or above that of the Sun. If it were a single, ordinary star, it should be readily visible as it would be just one magnitude fainter than the primary. The lack of conspicuous ultraviolet emission appears to rule out a white dwarf companion, so it may instead itself be a binary system consisting of two smaller stars having an orbital period between a week and a year.[3]

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. 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. Griffin, R. F. (April 2012), "Spectroscopic binary orbits from photoelectric radial velocities - Paper 223: HR 396, HR 7477, HR 7636, and 6 Andromedae", The Observatory, 132 (2): 76−97, Bibcode:2012Obs...132...76G.
  4. 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.
  5. Mizusawa, Trisha F.; et al. (November 2012), "Exploring the Effects of Stellar Rotation and Wind Clearing: Debris Disks around F Stars", The Astronomical Journal, 144 (5): 16, arXiv:1208.6248, Bibcode:2012AJ....144..135M, doi:10.1088/0004-6256/144/5/135, 135.
  6. "6 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-01.
  7. Frankowski, A.; et al. (March 2007), "Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data", Astronomy and Astrophysics, 464 (1): 377–392, arXiv:astro-ph/0612449, Bibcode:2007A&A...464..377F, doi:10.1051/0004-6361:20065526.
  8. 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.
  9. Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/mk. Originally Published in: Lowell Observatory (October 2014). 1. Bibcode:2014yCat....1.2023S.
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