Gamma Leonis

Coordinates: Sky map 10h 19m 58.3s, +19° 50′ 30″
Source: Wikipedia, the free encyclopedia.
γ Leonis
Location of γ Leonis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Leo
Right ascension 10h 19m 58.35056s[1]
Declination +19° 50′ 29.3468″[1]
Apparent magnitude (V) 2.08 (2.37/3.64)[2]
Characteristics
Evolutionary stage Red clump (both stars)[3]
Spectral type K0III + G7III[3]
U−B color index 1.00
B−V color index 1.14
Variable type RS CVn[4]
Distance
130 ± 3 ly
(39.9 ± 0.8 pc)[1]
Absolute magnitude (MV)−0.27/+0.98[6]
Periastron epoch (T)
1671.3[7]
Details
Gyr
HR 4058, SAO
 81299
Position (relative to A)[2]
ComponentB
″
Database references
Exoplanet Archive
data

Gamma Leonis (γ Leonis, abbreviated Gamma Leo, γ Leo), also named Algieba /ælˈdʒiːbə/,[8][9] is a binary star system in the constellation of Leo, made up of two red giants. In 2009, a planetary companion around the primary was announced.

Nomenclature

γ Leonis (Latinised to Gamma Leonis) is the star's Bayer designation. The A and B components of the binary are often referred to as γ1 Leonis and γ2 Leonis, respectively.

It also bore the traditional name Algieba or Al Gieba, which originated from the

Working Group on Star Names (WGSN)[10] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[11]
included a table of the first two batches of names approved by the WGSN, which included Algieba for this star.

The star's traditional Latin name was Juba. It is known as 軒轅十二 (the Twelfth Star of Xuanyuan) in Chinese (Xuanyuan is the name of the Yellow Emperor).[citation needed]

Algieba, along with Zeta Leonis, Regulus, Mu Leonis, Epsilon Leonis and Eta Leonis, have collectively been called the Sickle, which is an asterism that marks the head of Leo.[12]

Stellar system

Double star γ Leonis as seen by a telescope

The bright binary system in Leo with orange-red and yellow or greenish-yellow components is visible through a modest telescope under good atmospheric conditions. To the naked eye, the Algieba system shines at mid-second magnitude, but a telescope easily splits the pair. The double nature of Gamma Leonis was discovered by William Herschel in 1992.[7]

The brighter component (named Gamma1 Leonis) has an

G star has a temperature of 4,970 K, is 63 times more luminous and 10 times larger than the Sun. Both are more likely red clump giants after helium ignition. They are estimated to be 2 billion years old and have subsolar metallicites.[3]

The orbital parameters of Gamma Leonis are still uncertain due to the very long orbit. The

Kepler's third law, it would imply that the combined mass is of 6.3 M☉. Another data set show parameters that imply a combined mass of 18.6 M☉, even more contradictory with the observed combined mass (3.21 M☉).[3]

Variability

γ Leonis was a suspected variable star, with a

eclipsing binary due to a typographical error when referring to Y Leonis.[15]

The flare star AD Leonis lies just 5' from γ Leonis.[14] It is unrelated to the pair,[16] and much closer to Earth at a distance of 4.97 parsecs (16.2 ly).[17]

Planetary system

On November 6, 2009, the discovery of a planetary companion around primary star γ1 Leonis (γ Leonis A) was announced.[7] The radial velocity measurements suggest two additional periodicities of 8.5 and 1,340 days. The former is likely due to stellar pulsation, whereas the latter could be indicative of the presence of an additional planetary companion with 2.14 Jupiter masses, moderate eccentricity (e=0.13) and located at 2.6 AU away from the giant star. Nevertheless, the nature of such a signal is still unclear and further investigations are needed to confirm or rule out an additional substellar companion.

A new study revised the minimum mass for Gamma1 Leonis b to about 10.7 MJ (increased by 20%),[a] based on a larger mass for the host star (1.66 M☉ intsead of 1.23 M☉).[3]

The γ1 Leonis planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥10.7 MJ 1.19 429 0.14 — —
c (unconfirmed) ≥2.14 MJ 2.6 1,340 0.13 — —

Notes

  1. ^ The previous mass estimate was 8.78 MJ.
  1. ^ The orbital parameters are still subject to uncertainites and should be viewed with caution.

References

  1. ^
    S2CID 18759600
    .
  2. ^
    ISSN 0004-6256. Gamma Leonis' database entry at VizieR
    .
  3. ^
    ISSN 0004-640X
    .
  4. ^
    AAVSO
    . Retrieved 2024-06-14.
  5. S2CID 17804304
  6. doi:10.1086/191527
  7. ^
    S2CID 118962986
    .
  8. ISBN 978-1-931559-44-7
    .
  9. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  10. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  11. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  12. ^ Proctor, Mary (July 1896), "Evenings with the Stars", Popular Astronomy, 4: 565
  13. Bibcode:2009yCat....102025S
    .
  14. ^
    Bibcode:1995yCat.5050....0H.{{cite journal}}: CS1 maint: multiple names: authors list (link) Gamma Leonis' database entry at VizieR
    .
  15. doi:10.1086/107936
    .
  16. ^ Cite error: The named reference wds was invoked but never defined (see the help page).
  17. S2CID 244398875
    . Gaia DR3 record for this source at VizieR.

External links


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