HD 233731

HD 233731 is a G-type main-sequence star about 267 light-years away. It has a suspected stellar companions and hosts one known planet, HAT-P-22b.

HD 233731
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension  10h 22m 43.5924s[1]
Declination +50° 07′ 42.0635″[1]
Apparent magnitude (V) 9.76[1]
Characteristics
Spectral type G5V
Astrometry
Radial velocity (Rv)12.63 km/s
Proper motion (μ) RA: -26.182 mas/yr
Dec.: 83.727 mas/yr
Parallax (π)12.2014 ± 0.0371[1] mas
Distance267.3 ± 0.8 ly
(82.0 ± 0.2 pc)
Details[2]
Mass0.936+0.028
−0.033 M☉
Radius1.062+0.046
−0.013 R☉
Surface gravity (log g)4.357+0.039
−0.005 cgs
Temperature5314±50 K
Metallicity0.30±0.09
Rotation28.7±0.4d
Rotational velocity (v sin i)1.65±0.26 km/s
Age9.0+1.4
−2.2 Gyr
Other designations
HAT-P-22,Gaia DR2 846946629987527168, TYC 3441-925-1, GSC 03441-00925, 2MASS J10224361+5007420[1]
Database references
SIMBAD233731 data

Characteristics

HD 233731 is a main sequence G-type star. Its age is estimated at 9.0 billion years (twice older than the Sun). Its metallicity is twice that of the the Sun, unusual for its advanced age. The HD 233731 have a low stellar activity[2]. One wide-orbit red dwarf stellar companion with the temperature 4000+250
−400 K and mass 0.63+0.07
−0.17M☉ is suspected, but was not directly imaged as in 2015.[3]

Planetary system

In 2010 a transiting hot Jupiter like planet was detected.[4] It has an equilibrium temperature of 1463±19 K, and planetary atmosphere is cloudy.[5] The measurement of Rossiter-McLaughlin effect in 2018 has allowed to detect what the planetary orbit is well aligned with the equatorial plane of the star, misalignment angle equal to 25±18°.[2]

Size comparison of HAT-P-22 b and Jupiter
The HAT-P-22 planetary system[4][2]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 2.192+0.073
−0.013 MJ		 0.04171+0.00042
−0.00050		 3.21223328 0.016±0.009 86.46±0.41° 1.060±0.048 RJ

References
  1. HD 233731 -- High proper-motion Star
  2. The GAPS programme with HARPS-N at TNG XVI. Measurement of the Rossiter-McLaughlin effect of transiting planetary systems HAT-P-3, HAT-P-12, HAT-P-22, WASP-39, and WASP-60, 2018, arXiv:1802.03859
  3. FRIENDS OF HOT JUPITERS III:AN INFRARED SPECTROSCOPIC SEARCH FOR LOW-MASS STELLAR COMPANIONS, 2015, arXiv:1510.08062
  4. HAT-P-20b--HAT-P-23b: Four Massive Transiting Extrasolar Planets, 2010, arXiv:1008.3388
  5. Ground-based near-UV observations of 15 transiting exoplanets: Constraints on their atmospheres and no evidence for asymmetrical transits, 2016, arXiv:1603.02587

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