HD 11506

HD 11506 is a star in the equatorial constellation of Cetus. It has a yellow hue and can be viewed with a small telescope but is too faint to be visible to the naked eye, having an apparent visual magnitude of 7.51.^[2] The distance to this object is 167 light-years based on parallax, but it is drifting closer to the Sun with a radial velocity of −7.5 km/s.^[1] It has an absolute magnitude of 3.94.^[2]

HD 11506

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cetus
Right ascension	01h 52m 50.53442s[1]
Declination	−19° 30′ 25.1082″[1]
Apparent magnitude (V)	7.51[2]
Characteristics
Spectral type	G0V[3]
B−V color index	0.607±0.015[2]
Astrometry
Radial velocity (Rv)	−7.53±0.13[1] km/s
Proper motion (μ)	RA: 22.039(22) mas/yr[1] Dec.: −97.904(16) mas/yr[1]
Parallax (π)	19.5342±0.0221 mas[1]
Distance	167.0 ± 0.2 ly (51.19 ± 0.06 pc)
Absolute magnitude (MV)	3.94[2]
Details[4]
Mass	1.22±0.02[5] M☉
Radius	1.06±0.01 R☉
Luminosity	1.17±0.01 L☉
Surface gravity (log g)	4.43±0.02 cgs
Temperature	5,833±28 K
Metallicity [Fe/H]	+0.30±0.06[5] dex
Rotation	~15 days[5]
Rotational velocity (v sin i)	5.5±0.5[5] km/s
Age	1.6±0.9 Gyr
Other designations
BD−20°358, HD 11506, HIP 8770, SAO 148079[6]
Database references
SIMBAD	data
Exoplanet Archive	data

This object is an ordinary G-type main-sequence star with a stellar classification of G0V,^[3] which indicates it is generating energy via hydrogen fusion at its core. It is around 1.6^[4] billion years old and is spinning with a projected rotational velocity of 5 km/s.^[7] The star has 112% of the mass of the Sun and 106% of the Sun's radius. The spectrum shows a higher than solar abundance of elements other than hydrogen and helium – what astronomers term the metallicity.^[8] The star is radiating 117% of the Sun's luminosity from its photosphere at an effective temperature of 5,833 K.^[4]

Planetary system

The superjovian planet HD 11506 b was discovered orbiting the star by the N2K Consortium in 2007 using the Doppler spectroscopy method.^[3] In 2009, a second planet discovery was claimed based on Bayesian analysis of the original data.^[9] However, in 2015 additional radial velocity measurements showed that the planetary parameters were significantly different than those determined by Bayesian analysis. An additional linear trend in the radial velocities indicated a stellar or planetary companion on a long term orbit.^[8]

In 2022, the presence of a third planet was confirmed, and the mass and inclination of both planet b and the new planet d were measured via astrometry.^[10] A 2024 study also confirmed HD 11506 d, but found a significantly wider orbit and greater mass than previously estimated. This object orbits with a 73-year period, and at about 13 times the mass of Jupiter, it is at the borderline of being a brown dwarf.^[5]

The HD 11506 planetary system^[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
c	≥0.40±0.02 MJ	0.771±0.004	223.92±0.37	0.228±0.054	—	—
b	4.80±0.08 MJ	2.885±0.016	1,617.7±1.9	0.379±0.009	113+23 −53[10]°	—
d	12.8+0.6 −0.5 MJ	18.20+0.06 −0.09	26,517+256 −292	0.29+0.02 −0.03	90+6 −5°	—