Eta Andromedae

η Andromedae
Location of η Andromedae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 00h 57m 12.4000s[1]
Declination +23° 25′ 03.533″[1]
Apparent magnitude (V) 4.403[1]
Characteristics
Spectral type G8III-IV + G8III-IV[2]
U−B color index +0.69[3]
B−V color index +0.94[3]
R−I color index +0.48[3]
Astrometry
η And A
Radial velocity (Rv)−10.3 ± 0.9[1] km/s
Proper motion (μ) RA: −43.72[1] mas/yr
Dec.: −46.06[1] mas/yr
Parallax (π)13.44 ± 0.75 mas[1]
Distance240 ± 10 ly
(74 ± 4 pc)
Absolute magnitude (MV)0.52 ± 0.06[2]
η And B
Absolute magnitude (MV)1.07 ± 0.07[2]
Orbit[2]
Period (P)115.72 ± 0.01 d
Semi-major axis (a)10.37 ± 0.03 mas
Eccentricity (e)0.006 ± 0.002
Inclination (i)30.5 ± 0.4°
Longitude of the node (Ω)69.4 ± 0.5°
Periastron epoch (T)48013 ± 1 MJD
Argument of periastron (ω)
(secondary)		215 ± 4°
Details
η And A
Mass2.6 ± 0.35[4] M☉
Luminosity (bolometric)65 ± 3[2] L☉
Surface gravity (log g)2.8[2] cgs
Temperature4900[2] K
Age800 Million years
η And B
Mass2.3 ± 0.31[4] M☉
Luminosity (bolometric)39 ± 3[2] L☉
Surface gravity (log g)3.0[2] cgs
Temperature4900[2] K
Other designations
η Andromedae, η And, Eta And, 38 Andromedae, 38 And, MKT 2, FOX 116A, BD+22°153, CCDM J00572+2325A, FK5 2060, GC 1136, HD 5516, HIP 4463, HR 271, IDS 00519+2253 A, PPM 90327, SAO 74388, WDS 00572+2325A/Aa.[1][5][6]
Database references
SIMBADdata

Eta Andromedae (Eta And, η Andromedae, η And) is a spectroscopic binary star in the constellation of Andromeda. It consists of two G-type subgiant or giant stars orbiting each other with a period of 115.7 days and has an overall apparent visual magnitude of approximately 4.403.[1][2]

  1. ^ a b c d e f g h i "* eta And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 23, 2008.
  2. ^ a b c d e f g h i j k The spectroscopic binary eta Andromedae: Determination of the orbit by optical interferometry, C. A. Hummel et al., Astronomical Journal 106, #6 (December 1993), pp. 2486–2492, Bibcode:1993AJ....106.2486H, doi:10.1086/116816.
  3. ^ a b c HR 271, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line August 23, 2008.
  4. ^ a b Table 2, Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses, D. Pourbaix, Astronomy and Astrophysics Supplement 145 (August 2000), pp. 215–222, Bibcode:2000A&AS..145..215P.
  5. ^ Entry 00572+2325, discoverer code MKT 2, components Aa, The Washington Double Star Catalog Archived April 12, 2008, at the Wayback Machine, United States Naval Observatory. Accessed on line August 27, 2008.
  6. ^ Cite error: The named reference wds was invoked but never defined (see the help page).