HIP 5158 is a star with a pair of orbiting substellar companions, located in the equatorial constellation of Cetus,[1] the whale. It has the older designation CD-23 395, which is derived from the Cordoba Durchmusterung catalogue of southern stars.[6] Based on parallax measurements, it is located 169 light years from the Sun. It has an absolute magnitude of 7.11,[1] but at that distance the star has an apparent visual magnitude of 10.16,[1] which is too dim to be visible to the naked eye. The system is receding with a radial velocity of 15.3 km/s,[4] and it has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.205″·yr−1.[7]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cetus[1] |
Right ascension | 01h 06m 02.050s[2] |
Declination | –22° 27′ 11.35″[2] |
Apparent magnitude (V) | 10.16[1] |
Characteristics | |
Spectral type | K5V[3] |
Apparent magnitude (B) | 11.238[1] |
B−V color index | 1.078±0.001[1] |
Astrometry | |
Radial velocity (Rv) | 15.28±0.23[4] km/s |
Proper motion (μ) | RA: 203.818±0.025 mas/yr[2] Dec.: −106.926±0.032 mas/yr[2] |
Parallax (π) | 19.3199 ± 0.0198 mas[2] |
Distance | 168.8 ± 0.2 ly (51.76 ± 0.05 pc) |
Absolute magnitude (MV) | 7.11[1] |
Details | |
Mass | 0.75±0.01[5] M☉ |
Radius | 0.69±0.02[5] R☉ |
Luminosity | 0.19±0.01[5] L☉ |
Surface gravity (log g) | 4.63±0.02[5] cgs |
Temperature | 4,571±14[5] K |
Metallicity [Fe/H] | 0.10±0.07[3] dex |
Rotation | 42.3 days[3] |
Age | 4.5±3.2[5] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
Exoplanet Archive | data |
The spectrum of HIP 5158 matches an ordinary K-type main-sequence star,[8] an orange dwarf, with a stellar classification of K5V.[3] The age of this star is poorly constrained, but it appears to be comparable to the Sun.[5] It is spinning slowly with a rotation period of around 42.3 days. Based on the abundance of iron, this star appears metal rich, having concentration of heavy elements equal to 125% of solar abundance.[3] It has 75% of the mass of the Sun and 60% of the Sun's radius. The star is radiating just 19% of the luminosity of the Sun from its photosphere at an effective temperature of 4,571 K.[5]
In 2009, a gas giant planet HIP 5158 b was found in orbit around the star. The quadratic drift in the radial velocities did indicate the presence of an additional outer planet in the system,[3] which was confirmed in 2011. The large uncertainty in the mass of HIP 5158 c leaves in question whether this is an exoplanet or a brown dwarf.[8]
Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | ≥1.42 MJ | 0.89 | 345.72 ± 5.37 | 0.52 ± 0.08 | — | — |
c | ≥15.04 MJ | 7.7±1.88 | 9,018±3181 | 0.14±0.1 | — | — |