HD 4313

HD 4313 is a star with an orbiting exoplanetary companion in the constellation of Pisces. It has an apparent visual magnitude of 7.83,^[1] which is too faint to be reading visible to the unaided eye. The system is located at a distance of 446 light years based on parallax, and is drifting further away with a radial velocity of 14.5 km/s.^[1] This is a single star, which means it has no binary partners, at least in a range of projected separations from 6.85 to 191.78 AU.^[9] It hosts an extrasolar planet.

HD 4313

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Pisces[1]
Right ascension	00h 45m 40.3578s[2]
Declination	+07° 50′ 42.075″[2]
Apparent magnitude (V)	7.83[1]
Characteristics
Evolutionary stage	subgiant[3]
Spectral type	G5[4]
B−V color index	+0.963±0.017[1]
Astrometry
Radial velocity (Rv)	+14.48±0.23[1] km/s
Proper motion (μ)	RA: −6.281 mas/yr[2] Dec.: +6.566 mas/yr[2]
Parallax (π)	7.3090±0.0879 mas[2]
Distance	446 ± 5 ly (137 ± 2 pc)
Absolute magnitude (MV)	2.17[1]
Details
Mass	1.61+0.13 −0.12[5] M☉
Radius	5.15+0.18 −0.17[6] R☉
Luminosity	15.81[1] L☉
Surface gravity (log g)	3.24[7] cgs
Temperature	4,966±40[6] K
Metallicity [Fe/H]	0.05±0.10[6] dex
Rotational velocity (v sin i)	1.91±0.25[7] km/s
Age	2.03+0.64 −0.45[6] Gyr
Other designations
BD+07°104, Gaia DR2 2557541493057378048, HD 4313, HIP 3574, 2MASS J00454035+0750421[8]
Database references
SIMBAD	data

This is an aging G-type star with a mass of nearly twice the Sun, although different methods give mass estimates which differ as much as 0.5 M_☉.^[6] It is a swollen star with 5.14 times the radius of the Sun, and has a cool effective temperature of 4,966±40 k. It is a G-type subgiant star^[3] which has exhausted the hydrogen at its core, and is cooling and expanding to become a red giant. It is around two billion years in age and is spinning with a projected rotational velocity of 1.9 km/s.

Planetary system

HD 4313 has a superjovian exoplanet orbiting it. This exoplanet was discovered in 2010.^[10] It is orbiting the star at a distance of 1.16 AU with an orbital period of 356 days and an eccentricity (ovalness) of 0.15. As the orbital inclination is unknown, only a lower bound on the mass can be determined. The exoplanet has at least 1.2 times the mass of Jupiter.^[3]

The HD 4313 planetary system^[3]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥ 1.927±0.090 MJ	1.157±0.097	356.21±0.88	0.147±0.047	—	1.2 RJ