Eta Andromedae

Starbox 2
name = η Andromedae


caption = Eta Andromeda A/B.
epoch = J2000.0
equinox = J2000.0 (ICRS)
constell = Andromeda
ra_system = RA|00|57|12.4000SIMBAD link|eta+and|HD 5516 -- Spectroscopic binary, database entry, SIMBAD. Accessed on line August 23, 2008.]
dec_system = DEC|+23|25|03.533
appmag_v_system=4.403
u-b_system = +0.69 [http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/50/catalog&recno=271 HR 271] , database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID [http://vizier.u-strasbg.fr/viz-bin/Cat?V/50 V/50] . Accessed on line August 23, 2008.]
b-v_system = +0.94
r-i_system = +0.48
class_a = G8III-IV
class_b=G8III-IV
radial_v_system = −10.3 ± 0.9
prop_mo_ra_system = −43.72
prop_mo_dec_system = −46.06
parallax = 13.44
p_error = 0.75
parallax_footnote =
mass_a = 2.6 ± 0.35Table 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.]
mass_b = 2.3 ± 0.31
gravity_a = 2.8
gravity_b = 3.0
absmag_v_a = 0.52 ± 0.06
absmag_v_b = 1.07 ± 0.07
temperature_a = 4900
temperature_b = 4900
luminosity_bolometric_a = 65 ± 3
luminosity_bolometric_b = 39 ± 3
age_system=8×10⁸
orbit_footnote= [Entry 00572+2325, [http://ad.usno.navy.mil/wds/orb6/orb6orbits.txt Sixth Catalog of Orbits of Visual Binary Stars] ,
United States Naval Observatory. Accessed on line August 27, 2008.]
period_unitless=115.72 ± 0.01 d
axis_unitless=10.37 ± 0.03 mas
periastron=48013 ± 1 MJD
inclination=30.5 ± 0.4
node=69.4 ± 0.5
eccentricity=0.006 ± 0.002
periarg=215 ± 4
names=η And, Eta Andromedae, 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.Entry 00572+2325, discoverer code MKT 2, components Aa, [http://ad.usno.navy.mil/wds/wdsnewframe1.html The Washington Double Star Catalog] ,
United States Naval Observatory. Accessed on line August 27, 2008.]
simbad_system=eta+and

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.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.]

History

Eta Andromedae was discovered to be a double-lined spectroscopic binary in a series of spectra taken in 1899 and 1900. [A list of nine stars whose velocities in the line of sight are variable, W. W. Campbell and W. H. Wright, "Astrophysical Journal" 12 (November 1900), pp. 254–257, bibcode|1900ApJ....12..254C, doi|10.1086/140765.] Its orbit was computed in 1946 from spectroscopic observations. [The Spectroscopic Binary η Andromedae, Katherine C. Gordon, "Astrophysical Journal" 103 (January 1946), pp. 13–15, bibcode|1946ApJ...103...13G.] Because spectroscopy only reveals the radial velocity of a star towards or away from the viewer, such a computation does not determine all orbital elements. In observations made from 1990 to 1992, Eta Andromedae was resolved interferometrically by the Mark III Stellar Interferometer at Mount Wilson Observatory, California, United States. This allowed a more complete orbit to be computed and, in 1993, published.

Location

This star's location in the constellation Andromeda can be seen in the following diagram:

Visual companion

Starbox observe
constell = Andromeda
epoch = J2000.0 (ICRS)
ra = RA|00|57|04.9SIMBAD link|BD%2B22+153B|BD+22 153B -- Star in double system, database entry, SIMBAD. Accessed on line August 22, 2008.]
dec = DEC|+23|23|43
appmag_v = 11.5Starbox relpos
epoch = 1997
primary=η And
posang= 232
posangref = Entry 00572+2325, discoverer code FOX 116, components AB, [http://ad.usno.navy.mil/wds/wdsnewframe1.html The Washington Double Star Catalog] ,
United States Naval Observatory. Accessed on line August 23, 2008.]
angdistsec= 129.2
angdistref = Starbox reference
Simbad=BD%2B22+153B

The star has a visual companion star of apparent visual magnitude 11.5, BD+22°153B, visible 129.2 arcseconds away.

References

External links

* [http://www.alcyone.de/cgi-bin/search.pl?object=HR0271 η Andromedae] at Alycone Software's Star Data Pages
* [http://aladin.u-strasbg.fr/AladinPreview?-c=HD+++5516&ident=HD+++5516&submit=Aladin+previewer Image η Andromedae]