Eta Andromedae

{{short description|Spectroscopic binary star in the constellation Andromeda}}

{{Starbox begin

| name = η Andromedae

}}

{{Starbox image

| image=

{{Location mark

|image=Andromeda constellation map.svg|alt=|float=center|width=260

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=η Andromedae

|x=512|y=904

}}

|caption=Location of η Andromedae (circled)

}}

{{Starbox observe

| epoch = J2000.0

| equinox = J2000.0 (ICRS)

| constell = Andromeda

| pronounce =

| ra = {{RA|00|57|12.400}}{{Cite Gaia EDR3|2803727064255015424}}

| dec = {{DEC|+23|25|03.54}}

| appmag_v = 4.403

}}

{{Starbox character

| class = {{nowrap|G8III-IV + G8III-IV}}

| r-i = +0.48

| b-v = +0.94

| u-b = +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.

}}

{{Starbox astrometry

| component1 = η And A

| radial_v = −10.30{{±|0.29}}{{cite journal | title=Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution | display-authors=1 | last1=Karataș | first1=Yüksel | last2=Bilir | first2=Selçuk | last3=Eker | first3=Zeki | last4=Demircan | first4=Osman | last5=Liebert | first5=James | last6=Hawley | first6=Suzanne L. | last7=Fraser | first7=Oliver J. | last8=Covey | first8=Kevin R. | last9=Lowrance | first9=Patrick | last10=Kirkpatrick | first10=J. Davy | last11=Burgasser | first11=Adam J. | journal=Monthly Notices of the Royal Astronomical Society | volume=349 | issue=3 | pages=1069–1092 | year=2004 | bibcode=2004MNRAS.349.1069K | arxiv=astro-ph/0404219 | doi=10.1111/j.1365-2966.2004.07588.x | doi-access=free | s2cid=15290475 }}

| prop_mo_ra = −43.008

| prop_mo_dec = −45.254

| pm_footnote =

| parallax = 12.5624

| p_error = 0.2525

| parallax_footnote =

| absmag_v = 0.52{{±|0.06}}

| component2 = η And B

| absmag_v2 = 1.07{{±|0.07}}

}}

{{Starbox orbit

| reference =

| period_unitless = {{val|115.72|0.01|u=d}}

| axis_unitless = {{val|10.37|0.03|u=mas}}

| eccentricity = 0.006{{±|0.002}}

| inclination = 30.5{{±|0.4}}

| node = 69.4{{±|0.5}}

| periastron = {{val|48013|1|ul=MJD}}

| periarg = 215{{±|4}}

}}

{{Starbox detail

| component1 = η And A

| mass = 2.6{{±|0.35}}{{cite journal | title=Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses | last=Pourbaix | first=D. | journal=Astronomy and Astrophysics Supplement | volume=145 | date=August 2000 | issue=2 | pages=215–222 | doi=10.1051/aas:2000237 | bibcode=2000A&AS..145..215P }} See table 2.

| radius = 10.7{{cite journal | title=Models for 60 double-lined binaries containing giants | last1=Eggleton | first1=Peter P. | last2=Yakut | first2=Kadri | journal=Monthly Notices of the Royal Astronomical Society | volume=468 | issue=3 | pages=3533–3556 | date=July 2017 | doi=10.1093/mnras/stx598 | doi-access=free | arxiv=1611.05041 | bibcode=2017MNRAS.468.3533E }}

| luminosity_bolometric = 65{{±|3}}

| gravity = 2.8

| temperature = 4,900

| age_myr = 800{{CN|date=March 2025}}

| component2 = η And B

| mass2 = 2.3{{±|0.31}}

| radius2 = 8.6

| luminosity_bolometric2 = 39{{±|3}}

| gravity2 = 3.0

| temperature2 = 4,900

}}

{{Starbox catalog

| names={{odlist | name=Kui | B=η Andromedae, η And, Eta And | F=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 }}{{cite simbad|title=* eta And|access-date=August 23, 2008}}Entry 00572+2325, discoverer code MKT 2, components Aa,

[http://ad.usno.navy.mil/wds/wdsnewframe1.html The Washington Double Star Catalog] {{webarchive |url=https://web.archive.org/web/20080412091309/http://ad.usno.navy.mil/wds/wdsnewframe1.html |date=April 12, 2008 }},

United States Naval Observatory. Accessed on line August 27, 2008.

}}

{{Starbox reference

| Simbad =eta+and

}}

{{Starbox end}}

Eta Andromedae, also named Kui, is a spectroscopic binary star system in the northern constellation of Andromeda. It consists of two G-type evolved stars orbiting each other with a period of 115.7 days and has an overall apparent visual magnitude of approximately 4.403.{{cite journal

| title=The spectroscopic binary eta Andromedae: Determination of the orbit by optical interferometry

| display-authors=1 | last1=Hummel | first1=C. A.

| last2=Armstrong | first2=J. T. | last3=Quirrenbach | first3=A.

| last4=Buscher | first4=D. F. | last5=Mozurkewich | first5=D.

| last6=Simon | first6=R. S. | last7=Johnston | first7=K. J.

| journal=Astronomical Journal

| volume=106 | issue=6 | date=December 1993 | pages=2486–2492

| bibcode=1993AJ....106.2486H | doi=10.1086/116816 }} Based on parallax measurements, this system is located at a distance of approximately 260 light years from the Sun. But it is drawing closer with a heliocentric radial velocity of −10.30 km/s.

Image:Eta And AB Orbit.jpg in background]]

This star was discovered to be a double-lined spectroscopic binary in a series of spectra taken in 1899 and 1900.{{cite journal

| title=A list of nine stars whose velocities in the line of sight are variable

| first1=W. W. | last1=Campbell | first2=W. H. | last2=Wright

| journal=Astrophysical Journal

| volume=12 | date=November 1900 | pages=254–257

| bibcode=1900ApJ....12..254C | doi=10.1086/140765

}} Its orbit was computed in 1946 from spectroscopic observations.{{cite journal

| title=The Spectroscopic Binary η Andromedae

| first=Katherine C. | last=Gordon

| journal=Astrophysical Journal

| volume=103 | date=January 1946 | pages=13–15

| doi=10.1086/144783 | 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.

The primary component has 2.6 times the mass of the Sun and 10.7 times the Sun's radius. It is radiating 65 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,900 K. The fainter secondary member has 2.3 times the mass and 8.6 times the radius of the Sun. It radiates 39 times the luminosity of the Sun at a temperature of 4,900 K.

Eta Andromedae has a visual companion star of apparent visual magnitude 11.5, BD+22°153B, visible 129.2 arcseconds away.Entry 00572+2325, discoverer code FOX 116, components AB,

[http://ad.usno.navy.mil/wds/wdsnewframe1.html The Washington Double Star Catalog] {{webarchive |url=https://web.archive.org/web/20080412091309/http://ad.usno.navy.mil/wds/wdsnewframe1.html |date=April 12, 2008 }},

United States Naval Observatory. Accessed on line August 23, 2008.