HD 203473 is a star in the equatorial constellation Equuleus. With an apparent magnitude of 8.23,[2] it’s only visible by using an amateur telescope. The star is located at a distance of 237 light years[1] based on its parallax shift but is drifting closer at a high rate of 61.7 km/s.[1] As of 2014, no stellar companions have been detected around the star.[7]
| Observation data Epoch J2000 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Equuleus |
| Right ascension | 21h 22m 18.87390s[1] |
| Declination | +05° 01′ 24.9072″[1] |
| Apparent magnitude (V) | 8.23[2] |
| Characteristics | |
| Spectral type | G6 V[3] |
| B−V color index | +0.66[2] |
| Astrometry | |
| Radial velocity (Rv) | −61.70±0.13[1] km/s |
| Proper motion (μ) | RA: 180.093±0.035 mas/yr[1] Dec.: 0.098±0.031 mas/yr[1] |
| Parallax (π) | 13.7402 ± 0.0370 mas[1] |
| Distance | 237.4 ± 0.6 ly (72.8 ± 0.2 pc) |
| Absolute magnitude (MV) | +4.2[2] |
| Details | |
| Mass | 0.82[4] M☉ |
| Radius | 1.48+0.05 −0.02[5] R☉ |
| Luminosity | 2.31±0.01[5] L☉ |
| Surface gravity (log g) | 4.25[4] cgs |
| Temperature | 5847+35 −94[5] K |
| Metallicity [Fe/H] | +0.18[4] dex |
| Rotational velocity (v sin i) | 1[6] km/s |
| Age | 5.2[4] or 8.5[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 203473 is an ordinary G-type main-sequence star with 82% the mass of the Sun,[4] but is 48% larger than the latter.[5] This star is over luminous and hot for its class, with it radiating at 2.31 the luminosity of the Sun[5] and an effective temperature of 5,847 K.[5] HD 203473 has different age estimates, either being 5[4] or 8[6] billion years old. The higher luminosity and low projected rotational velocity of 1 km/s[6] favors the older age estimate. Like many planetary hosts, HD 203473 has an enhanced metallicity, with an iron abundance 1.51 times that of the Sun.[4]
Companion
In 2018, the N2K project discovered an object, initially thought to be a planet, orbiting the star via Doppler spectroscopy. Due to the detection method, its inclination and true mass were initially unknown.[8] In 2022, the inclination and true mass of this companion were measured via astrometry, revealing it to be 96 MJ and thus either a massive brown dwarf or low-mass star. The companion's orbital period was also found to be twice as long as originally thought.[9]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 95.886+8.523 −8.864 MJ |
4.161+0.172 −0.190 |
8.103+0.014 −0.016 |
0.404±0.007 | 141.240+0.949 −0.909° |
— |
References
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