epsilon Aquarii

{{Starbox image

| image=

{{Location mark

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

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=ε Aquarii

|x=906|y=480

}}

|caption=Location of ε Aquarii (circled)

}}

{{Starbox observe

| epoch = J2000

| ra = {{RA|20|47|40.54957}}

| dec = {{DEC|−09|29|44.79693}}

| appmag_v = 3.77

| constell = Aquarius

}}

{{Starbox character

| type = Main sequence or subgiant

| class = A1 V + KV

| b-v = –0.001

| u-b = +0.029

| variable = Constant

}}

{{Starbox astrometry

| radial_v = {{Val|−19.82|0.58}}

| prop_mo_ra = +33.923

| prop_mo_dec = -34.926

| pm_footnote =

| parallax = 13.3619

| p_error = 0.3737

| parallax_footnote =

| absmag_v = −0.46

}}

{{Starbox orbit

| reference =

| primary = A

| name = B

| axis_unitless = {{val|25.9|ul=mas}}
{{val|1.7|ul=AU}}

| period_unitless = 1.2 years

}}

{{Starbox detail

| component1 = A

| mass = {{Val|2.98|0.03}}

| radius = 4.2

| luminosity = {{Val|161|9}}

| temperature = {{Val|9622|327|fmt=commas}}

| gravity = {{Val|3.66|0.14}}

| metal_fe = {{Val|−0.08|0.35}}

| rotational_velocity = {{Val|118.0|5.9}}

| age_myr = 388

| component2 = B

| radius2 = 0.57

| mass2 = 0.61

| temperature2 = 4,070

}}

{{Starbox catalog

| names = {{odlist | name=Albali | B=ε Aqr | F=2 Aquarii | BD=–10°5506 | FK5=781 | HD=198001 | HIP=102618 | HR=7950 | SAO=144810 }}

}}

{{Starbox reference

| Simbad = eps+Aqr

}}

Epsilon Aquarii is a binary star system in the equatorial zodiac constellation of Aquarius, located near the western constellation border with Capricornus. Its identifier is a Bayer designation that is Latinized from ε Aquarii, and abbreviated Eps Aqr or ε Aqr, respectively. It has the proper name Albali {{IPAc-en|æ|l|ˈ|b|eɪ|l|i}}, now formally recognized by the IAU. This system is visible to the naked eye as a point of light with an apparent visual magnitude of 3.77, and has an absolute magnitude of −0.46. Based upon parallax measurements taken by the Gaia spacecraft, it is located at a distance of approximately {{Convert|244|ly|pc}} from Earth. The star is drifting closer with a radial velocity of −20 km/s.

Properties

The primary member has a stellar classification of A1 V, indicating it is an A-type main-sequence star. However, isochrone fitting suggests this star has recently evolved away from the main sequence and is now a subgiant star. It is estimated to be 388 million years old with a high rate of spin, showing a projected rotational velocity of around 118 km/s. The elemental abundances in the stellar atmosphere are close to solar, with pronounced underabundances of aluminium and strontium. The star has three times the mass of the Sun and about 4.2 times the Sun's radius. It is radiating 161 times the luminosity of the Sun from its photosphere at an effective temperature of 9,622 K.

The binary nature of this system was discovered in 2023 based on observations from the European Southern Observatory. The secondary component is a K-type main-sequence star with 0.6 times the mass and 0.57 times the radius of the Sun. Located at a projected separation of 26 milliarcseconds from the primary, this translates to a physical separation of 1.7 astronomical units. Albali A and B complete an orbit around their center of mass each 1.2 years.

Nomenclature

ε Aquarii (Latinised to Epsilon Aquarii) is the star's Bayer designation.

It bore the traditional name, Albali, from the Arabic البالع (albāli‘), meaning "the swallower". (See also Albulaan.) Along with Mu Aquarii (Albulaan) and Nu Aquarii (also Albulaan), they were al Bulaʽ (البلع), meaning "the Swallower". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Albali for this star on 12 September 2016, and it is now so included in the List of IAU-approved Star Names.

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, it was designated Nir Saad Bula (نير سعد ألبلع nayyir sa'd al bulaʽ), which was translated into Latin as Lucida Fortunæ Dissipantis, meaning "the brightest of luck of the swallower".

In Chinese, {{lang|zh|女宿}} ({{lang|zh-Latn|Nǚ Sù}}), meaning Girl (asterism), refers to an asterism consisting of Epsilon Aquarii, Mu Aquarii, 4 Aquarii, 5 Aquarii and 3 Aquarii.{{in lang|zh}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}. Consequently, the Chinese name for Epsilon Aquarii itself is {{lang|zh|女宿一}} ({{lang|zh-Latn|Nǚ Sù yī}}, {{langx|en|the First Star of Girl}}).{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive |url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=October 25, 2008 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.

References

{{reflist|refs=

{{citation | postscript=.

| title=Hidden Companions to Intermediate-mass Stars. VIII. Discovery of a 0.6 M ⊙, 1.7 au Companion to Albali = ϵ Aquarii

| display-authors=1 | last1=Waisberg |first1=Idel

| last2=Klein | first2=Ygal | last3=Katz | first3=Boaz

| journal=Research Notes of the American Astronomical Society

| volume=7 | issue=8 | pages=163 | date=August 1, 2023

| doi=10.3847/2515-5172/acebe1 | doi-access=free

| bibcode=2023RNAAS...7..163W | issn=2515-5172}}

{{citation | postscript=.

| title=Simultaneous Six-way Observations from the Navy Precision Optical Interferometer

| last1=Baines |first1=Ellyn K. | last2=Blomquist | first2=Solvay

| last3=Clark III | first3=James H. | last4=Gorney | first4=Jim

| last5=Maier | first5=Erin | last6=Sanborn | first6=Jason

| last7=Schmitt | first7=Henrique R. | last8=Stone | first8=Jordan M.

| last9=van Belle | first9=Gerard T. | last10=Braun | first10=Kaspar von

| display-authors=1 | journal=The Astronomical Journal

| doi=10.3847/1538-3881/aca277 | doi-access=free

| bibcode=2023AJ....165...41B | issn=0004-6256}}

{{citation

| last1=Kunitzsch | first1=Paul | last2=Smart | first2=Tim

| date=2006 | edition=2nd rev.

| title=A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations

| publisher=Sky Pub | location=Cambridge, Massachusetts

| isbn=978-1-931559-44-7 | postscript=. }}

{{citation

| url=https://www.iau.org/public/themes/naming_stars/

| title=Naming Stars | publisher=IAU.org

| access-date=16 December 2017 | postscript=. }}

{{citation

| last1=Ammler-von Eiff | first1=Matthias | last2=Reiners | first2=Ansgar

| title=New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?

| journal=Astronomy & Astrophysics | arxiv=1204.2459

| volume=542 | page=A116 | date=June 2012 | postscript=.

| doi=10.1051/0004-6361/201118724 | bibcode=2012A&A...542A.116A | s2cid=53666672 }}

{{citation

| url=https://www.iau.org/science/scientific_bodies/working_groups/280/

| title=IAU Working Group on Star Names (WGSN)

| publisher=International Astronomical Union

| access-date=22 May 2016 | postscript=. }}

{{citation

| last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A.

| title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets

| journal=The Astrophysical Journal

| volume=804 | issue=2 | pages=146 | year=2015

| bibcode=2015ApJ...804..146D | postscript=.

| doi=10.1088/0004-637X/804/2/146 | arxiv=1501.03154 | s2cid=33401607 }}

{{citation

| last1=Zorec | first1=J. | last2=Royer | first2=F.

| title=Rotational velocities of A-type stars. IV. Evolution of rotational velocities

| journal=Astronomy & Astrophysics

| volume=537 | pages=A120 | year=2012

| bibcode=2012A&A...537A.120Z | arxiv=1201.2052

| doi=10.1051/0004-6361/201117691 | s2cid=55586789 | postscript=. }}

{{citation

| title=Elemental abundance analyses with DAO spectrograms. XXVII. The superficially normal stars theta And (A2 IV), epsilon Del (B6 III), epsilon Aqr (A1.5 V), and iota And (B9 V)

| display-authors=1 | last1=Kocer | first1=D.

| last2=Adelman | first2=S. J. | last3=Caliskan | first3=H.

| last4=Gulliver | first4=A. F. | last5=Gokmen Tektunali | first5=H.

| journal=Astronomy and Astrophysics | postscript=.

| volume=406 | pages=975–980 | date=August 2003

| issue=3 | doi=10.1051/0004-6361:20030620 | bibcode=2003A&A...406..975K | doi-access=free }}

{{citation

| last=Levato | first=O. H.

| title=Rotational Velocities and Spectral Types of Some A-Type Stars

| journal=Publications of the Astronomical Society of the Pacific

| volume=84 | issue=500 | page=584 |date=August 1972

| doi=10.1086/129336 | doi-access=free