HAT-P-15

HAT-P-15 is a G-type main-sequence star about 630 light-years away. The star is older than Sun yet has a concentration of heavy elements roughly 190% of solar abundance.^[4] The star has no noticeable starspot activity.^[6]

HAT-P-15 / Berehynia

Observation data Epoch J2000      Equinox J2000
Constellation	Perseus[1]
Right ascension	04h 24m 59.5350s[2]
Declination	+39° 27′ 38.313″[2]
Apparent magnitude (V)	12.41
Characteristics
Spectral type	G5V
Variable type	planetary transit[3]
Astrometry
Radial velocity (Rv)	31.21 km/s
Proper motion (μ)	RA: 14.233(21) mas/yr[2] Dec.: −9.407(15) mas/yr[2]
Parallax (π)	5.1856±0.0166 mas[2]
Distance	629 ± 2 ly (192.8 ± 0.6 pc)
Details[4]
Mass	1.013±0.043 M☉
Radius	1.080±0.039 R☉
Luminosity	1.00±0.11 L☉
Surface gravity (log g)	4.38±0.03 cgs
Temperature	5684±25 K
Metallicity	0.272±0.031
Rotational velocity (v sin i)	2.0±0.5 km/s
Age	6.8+2.5 −1.6 Gyr
Other designations
Berehynia, Gaia DR3 179498266829041664, TYC 2883-1687-1, GSC 02883-01687, 2MASS J04245952+3927382[5]
Database references
SIMBAD	data

The spectroscopic survey in 2015 have failed to find any stellar companions to it,^[7] yet imaging survey have identified a possibly two companion red dwarf stars at projected separations 1210 and 1370 AU, respectively.^[8]

The star was named Berehynia in December 2019 by Ukrainian amateur astronomers.^[9]

Planetary system

In 2010 a transiting hot superjovian planet b (named Tryzub in 2019^[9]) was detected. It has an equilibrium temperature of 904±20 K.^[3] An orbital simulation shows that any planets inward of the orbit of b would spiral inward and be destroyed within a time-span of less than a billion years.^[10] The planetary orbit is well aligned with the equatorial plane of the star, misalignment equal to 13±6 degrees.^[11]

Size comparison of HAT-P-15 b and Jupiter

The HAT-P-15 planetary system^[3]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b / Tryzub	1.946±0.066 MJ	0.0964±0.0014	10.863502±0.000027	0.19±0.019	89.1±0.2°	1.072±0.043 RJ