HD 233731, or HAT-P-22, is a suspected multiple star system in the northern circumpolar constellation of Ursa Major. It is invisible to the naked eye, having an apparent visual magnitude of 9.732.[2] This system is located at a distance of 267 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +13 km/s.[1]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 10h 22m 43.5923s[1] |
| Declination | +50° 07′ 42.062″[1] |
| Apparent magnitude (V) | 9.732[2] |
| Characteristics | |
| Spectral type | G5V[3] |
| B−V color index | 0.86[3] |
| Astrometry | |
| Radial velocity (Rv) | 12.86(15)[1] km/s |
| Proper motion (μ) | RA: −26.110(14) mas/yr[1] Dec.: 83.806(16) mas/yr[1] |
| Parallax (π) | 12.2731 ± 0.0155 mas[1] |
| Distance | 265.7 ± 0.3 ly (81.5 ± 0.1 pc) |
| Absolute magnitude (MV) | 5.22±0.14[2] |
| Details[3] | |
| Mass | 0.936+0.028 −0.033 M☉ |
| Radius | 1.062+0.046 −0.013 R☉ |
| Luminosity | 0.77±0.09[2] L☉ |
| Surface gravity (log g) | 4.357+0.039 −0.005 cgs |
| Temperature | 5,314±50 K |
| Metallicity [Fe/H] | 0.30±0.09 dex |
| Rotation | 28.7±0.4 d |
| Rotational velocity (v sin i) | 1.65±0.26 km/s |
| Age | 9.0+1.4 −2.2 Gyr[3] 12.4±2.6[2] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The stellar classification of the primary is G5V,[3] matching an ordinary G-type main-sequence star. The star has a low level of stellar activity with an estimated age of 9 to 12 billion years old. Its metallicity is twice that of the Sun, unusual for its advanced age.[3] HD 233731 has a similar mass and radius as the Sun, and is spinning with a rotation period of 28.7 days.[3] It is radiating 77%[2] of the luminosity of the Sun from its photosphere at an effective temperature of 5314 K.[3]
A faint stellar companion (2MASS J10224397+5007504) with a red hue is located at an angular separation of 9 arcseconds from the primary.[2] In 2015, a spectroscopic stellar companion was reported with a semimajor axis of less than 33 AU. This star has an effective temperature of 4,000+250
−400 K with a mass of 0.63+0.07
−0.17 M☉.[5]
Planetary system
In 2010 a transiting hot Jupiter like planet was detected, designated HAT-P-22b.[2] It has an equilibrium temperature of 1,463±19 K, and planetary atmosphere is cloudy.[6] 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, with a misalignment angle equal to 25°±18°.[3]
In 2017, analysis of additional HARPS data showed a long-term trend that suggested the presence of an additional orbiting companion, HAT-P-22c.[7]
| 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 |
| c (unconfirmed) | ≥3.0 MJ | — | ≥20.8 years | — | — | — |