HD 212771

Last updated
HD 212771 / Lionrock
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Aquarius
Right ascension 22h 27m 03.072s [1]
Declination −17° 15 49.164 [1]
Apparent magnitude  (V)7.6±0.01 [2]
Characteristics
Spectral type G8 IV [3]
U−B color index +0.54 [4]
B−V color index +0.88 [2]
Astrometry
Radial velocity (Rv)14.9±0.03 [5]  km/s
Proper motion (μ)RA: −85.892  mas/yr [1]
Dec.: −104.042  mas/yr [1]
Parallax (π)8.9648 ± 0.0314  mas [1]
Distance 364 ± 1  ly
(111.5 ± 0.4  pc)
Absolute magnitude  (MV)2.04 [6]
Details
Mass 1.56 [7]   M
Radius 5.27 [7]   R
Luminosity 11.55±0.08 [8]   L
Surface gravity (log g)3.31 [7]   cgs
Temperature 5,003 [7]   K
Metallicity [Fe/H]−0.09±0.01 [9]   dex
Age 1.676±0.287 [9]   Gyr
Other designations
BD−17°6526, HD  212771, HIP  110813, SAO  165086
Database references
SIMBAD data
Exoplanet Archive data
Extrasolar Planets
Encyclopaedia
data

HD 212771, also named Lionrock, is a solitary star in the southern zodiac constellation Aquarius. It has an apparent magnitude of 7.60, [2] making it readily visible with binoculars but not the naked eye. Parallax measurements place the object at a distance of 364 light years, [1] and is currently receding with a radial velocity of 15  km/s . [5]

HD 212771 has a stellar classification of G8 IV, [3] indicating that it is a subgiant evolving towards the red giant branch after being an F-type main-sequence star for 1.7 billion years. [9] It has 156% the mass of the Sun and 5 times its radius. [7] It radiates at 11  solar luminosities [8] from its slightly enlarged photosphere at an effective temperature of 5,003 K, [7] giving it a yellow-hue. Unlike most planetary hosts, HD 212771 is slightly metal deficient, and spins with a projected rotational velocity of about 2  km/s . [9]

Planetary system

In 2010, a group of astronomers at the Keck Observatory surveyed several subgiant stars for extrasolar planets via Doppler spectroscopy They happened to find a massive Jupiter-like planet orbiting HD 212771. [10]

HD 212771 is named Lionrock. The name was selected in the NameExoWorlds campaign by Hong Kong, during the 100th anniversary of the IAU. It is named after the Lion Rock. The planet is named Victoriapeak, after the Victoria Peak. [11] [12]

The HD 212771 planetary system [7]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b / Victoriapeak ≥2.39±0.27  MJ 1.19±0.13381±10.076±0.051

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References

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