Lambda Andromedae
{{Short description|Binary star system in the constellation of Andromeda}}
{{Starbox begin}}
{{Starbox image
| image =
{{Location mark
|image=Andromeda constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=λ And
|x=890|y=220
}}
|caption=Location of λ Andromedae (circled)
}}
{{Starbox observe
| epoch = J2000
| constell = Andromeda
| dec = {{DEC|+46|27|29.3447}}
}}
{{Starbox character
| type = subgiant
| variable = RS CVn
}}
{{Starbox astrometry
| prop_mo_ra = {{val|159.606|(101)}}
| prop_mo_dec = {{val|−421.822|(97)}}
| parallax = 38.5736
| p_error = 0.1179
}}
{{Starbox orbit
| primary = A
| name = B
| period_unitless = {{val|20.520394|(41)}} days
| axis_unitless = {{val|p=≥|1.8536|0.0021|e=6|u=km}}
| k1 = {{val|6.5815|0.0076}}
| eccentricity = {{Val|0.0607|0.0012}}
| periastron = {{Val|2459696.372|0.056|u=BJD}}
| periarg_primary = {{Val|336.8|1.0}}
}}
{{Starbox detail
| component1 = A
| radius = {{val|7.787|0.053}}
| temperature = {{val|4633|fmt=commas}}
| rotation = {{Val|54.41|0.30}} days
| age_myr =
| component2 = B
| mass2 = {{Val|0.086|-|0.115}}
}}
{{Starbox catalog
| names = {{odlist | name=Udkadua | B=λ And | F=16 Andromedae | BD=+45°4283 | FK5=890 | GJ=9832 | HD=222107 | HIP=116584 | HR=8961 | LTT=16964 | NLTT=57442 | SAO=53204 | PPM=64456 }}
}}
{{Starbox reference
| Simbad = lam+And
}}
{{Starbox end}}
Lambda Andromedae, Latinized from λ Andromedae, also named Udkadua, is a binary star system in the northern constellation of Andromeda. At an estimated distance of approximately {{convert|84.6|ly|pc|abbr=off|lk=on}} from Earth, it has an apparent visual magnitude of around +3.8. This is bright enough to be seen with the naked eye. The system is drifting further away from the Sun with a radial velocity of +6.8 km/s.
Naming
This star represented the heel of the ancient Sumerian constellation Udkadua, "the storm demon with the gaping mouth". The IAU Working Group on Star Names approved the name Udkadua for this star on 8 May 2025 and it is now so entered in the IAU Catalog of Star Names.
In traditional Arabic astronomy, the stars ι Andromedae, κ Andromedae, and λ Andromedae were known as Kaff al-Musalsala, the hand of the chained woman (i.e. Andromeda), and as Ra’s al-Nāqa, the head of the she-camel.
In Chinese, {{lang|zh|螣蛇}} ({{lang|zh-Latn|Téng Shé}}), meaning Flying Serpent, refers to an asterism consisting of λ Andromedae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for λ Andromedae itself is {{lang|zh|螣蛇十九}} ({{lang|zh-Latn|Téng Shé shíjiǔ}}, {{langx|en|the Nineteenth Star of Flying Serpent}}).
Properties
File:LambdaAndLightCurve.png for Lambda Andromedae, plotted from Hipparcos data]]
Lambda Andromedae is a single-lined spectroscopic binary with an orbital period of 20.52 days. The spectrum of the primary matches a stellar classification of G8 IV, meaning that it is an evolved star that is in the subgiant stage. The mass of this star is about 50% larger than that of the Sun, but it has expanded to around seven times the Sun's radius. It is radiating over 28 times the luminosity of the Sun from its outer envelope at an effective temperature of 4,800 K, giving it the characteristic yellow hue of a G-type star.
This is an RS Canum Venaticorum variable and its brightness varies by 0.225 magnitudes, reaching a maximum of 3.70, with a period of 53.952 days. Such variability is theorized to occur because of tidal friction, which results in chromospheric activity. However, the orbit of this system is nearly circular, so the cause of this system's variability remains uncertain. The X-ray luminosity of this star, as measured by the ROSAT satellite, is {{val|2.95|e=30|u=erg/s}}. A magnetic field with an average strength of {{val|21|ul=G}} has been detected on this star, which is stronger than the field on the Sun. Starspots on the star's surface have been resolved with Doppler imaging.
The secondary has a very low mass of about {{solar mass|0.1}}. It is most likely an L-type brown dwarf.
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Evolution
Many different spectral classes have been published for λ Andromedae, ranging from G6 to K1. Most sources give a luminosity class of III (giant) or IV (subgiant). Analysis of the physical properties of the star, including its temperature, luminosity, magnetic field, and stellar wind, show that it has recently experienced the first dredge-up and has begun to ascend the red giant branch although it still has a hot corona and is classified as a subgiant by some definitions.
References
{{reflist|refs=
{{Cite Gaia DR3|1939115478598580352}}
| url=https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats
| website=Centre de Données astronomiques de Strasbourg | title=/ftp/cats/more/HIP/cdroms/cats
| publisher=Strasbourg astronomical Data Center |access-date=15 October 2022}}
{{citation | last=Wilson | first=Ralph Elmer | year=1953 | title=General catalogue of stellar radial velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution of Washington | location=Washington | bibcode=1953GCRV..C......0W | postscript=. }}
{{citation | display-authors=1 | last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W. | last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey | title=Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity | journal=The Astronomical Journal | volume=135 | issue=1 | pages=209–231 |date=January 2008 | doi=10.1088/0004-6256/135/1/209 | bibcode=2008AJ....135..209M | s2cid=121883397 | postscript=. | doi-access=free }}
{{citation | last1=Jennens | first1=P. A. | last2=Helfer | first2=H. L. | title=A new photometric metal abundance and luminosity calibration for field G and K giants. | journal=Monthly Notices of the Royal Astronomical Society | volume=172 | pages=667–679 |date=September 1975 | issue=3 | bibcode=1975MNRAS.172..667J | postscript=. | doi=10.1093/mnras/172.3.667| doi-access=free }}
{{cite simbad | title=lam And | access-date=2012-06-21 | mode=cs2 | postscript=. }}
| last1=Ó Fionnagáin | first1=D. | last2=Vidotto | first2=A. A.
| last3=Petit | first3=P. | last4=Neiner | first4=C.
| last5=Manchester IV | first5=W. | last6=Folsom | first6=C. P.
| last7=Hallinan | first7=G.
| title=λ And: a post-main-sequence wind from a solar-mass star
| journal=Monthly Notices of the Royal Astronomical Society
| volume=500 | issue=3 | pages=3438–3453 | date=January 2021
| doi=10.1093/mnras/staa3468 | doi-access=free | arxiv=2011.02406
| bibcode=2021MNRAS.500.3438O | postscript=. }}
{{cite web |title=Kaffalmusalsala (كفّ المسلسة) |url=https://xing.fmi.uni-jena.de/mediawiki/index.php/Kaffalmusalsala |website=All Skies Encyclopaedia |publisher=IAU Working Group on Star Names |access-date=8 May 2025}}
{{cite web |title=al-Nāqa (الناقة) |url=https://xing.fmi.uni-jena.de/mediawiki/index.php/Al-Naqa |website=All Skies Encyclopaedia |publisher=IAU Working Group on Star Names |access-date=8 May 2025}}
}}
External links
- http://www.alcyone-software.com/cgi-bin/search.pl?object=HR8961 {{Webarchive|url=https://web.archive.org/web/20110707104141/http://www.alcyone-software.com/cgi-bin/search.pl?object=HR8961 |date=2011-07-07 }}
- [http://aladin.u-strasbg.fr/AladinPreview?-c=23+37+33.8425%2B46+27+29.347&ident=V*+lam+And&submit=Aladin+previewer Image Lambda Andromedae]
{{Stars of Andromeda}}
{{DEFAULTSORT:Lambda Andromedae}}
Category:RS Canum Venaticorum variables
Category:Spectroscopic binaries