HAT-P-21
HAT-P-21 is a G-type main-sequence star about 910 light-years away. The star has amount of metals similar to solar abundance. The survey in 2015 has failed to detect any stellar companions.[4] The star is rotating rapidly, being spun up by the tides of giant planet on close orbit.[3]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 11h 25m 05.9858s[1] |
| Declination | +41° 01′ 40.6692″[1] |
| Apparent magnitude (V) | 11.46[1] |
| Characteristics | |
| Spectral type | G3V |
| Astrometry | |
| Radial velocity (Rv) | -51.98 km/s |
| Proper motion (μ) | RA: -1.088 mas/yr Dec.: 13.243 mas/yr |
| Parallax (π) | 3.5781 ± 0.0410[1] mas |
| Distance | 910 ± 10 ly (279 ± 3 pc) |
| Details[2][3] | |
| Mass | 0.947±0.042 M☉ |
| Radius | 1.105±0.083 R☉ |
| Luminosity | 1.06+0.20 −0.16 L☉ |
| Surface gravity (log g) | 4.33±0.06 cgs |
| Temperature | 5634±67 K |
| Metallicity | 0.04±0.08 |
| Rotation | 15.9±0.8 d |
| Rotational velocity (v sin i) | 3.5±0.5 km/s |
| Age | 10.2±2.5 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Naming
In 2019, the HAT-P-21 star havs received a proper name Mazalaai and planet HAT-P-21b - Bambaruush at an international NameExoWorlds contest.[5]. These names mean the Mongolian name for the endangered Gobi bear subspecies, and Mongolian term for 'bear cub', respectively.
Planetary system
In 2010 a transiting hot super-Jovian planet on moderately eccentric orbit was detected.[6] Its equilibrium temperature is 1283±50 K. The transit-timing variation survey in 2011 have failed to rule out or confirm the existence of additional planets in the system, until the orbital parameters of HAT-P-21b are known with better precision.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (Bambaruush) | 4.063±0.161 MJ | 0.0494±0.0007 | 4.124481±0.000007 | 0.228±0.016 | 88.6° | 1.08±0.18 RJ |
References
- HAT-P-21 -- Star
- ACCURATE, EMPIRICAL RADII AND MASSES OF PLANETS AND THEIR HOST STARS WITH GAIA PARALLAXES, 2016, arXiv:1609.04389
- A comparison of gyrochronological and isochronal age estimates for transiting exoplanet host stars, 2015, arXiv:1503.09111
- A Lucky Imaging search for stellar companions to transiting planet host stars, 2015, arXiv:1507.01938
- IAU 100 NameExoWorlds Approved Names
- HAT-P-20b–HAT-P-23b: FOUR MASSIVE TRANSITING EXTRASOLAR PLANETS, 2010, arXiv:1008.3388
- Prospecting transit duration variations in extrasolar planetary systems, 2011, arXiv:1109.0936
- Light Curve Analysis of Ground‐Based Data from Exoplanets Transit Database, 2019, arXiv:1910.11438