HD 203473
High proper motion star in the constellation Equuleus
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HD 203473 is a star in the equatorial constellation Equuleus. With an apparent magnitude of 8.23,[1] it’s only visible by using an amateur telescope. The star is located at a distance of 237 light years[2] based on its parallax shift but is drifting closer at a high rate of 61.7 km/s.[2] As of 2014, no stellar companions have been detected around the star.[7]
| Observation data Epoch J2000 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Equuleus[1] |
| Right ascension | 21h 22m 18.87390s[2] |
| Declination | +05° 01′ 24.9072″[2] |
| Apparent magnitude (V) | 8.23[1] |
| Characteristics | |
| Evolutionary stage | subgiant[2] |
| Spectral type | G6 V[3] |
| B−V color index | +0.66[1] |
| Astrometry | |
| Radial velocity (Rv) | −61.70±0.13[2] km/s |
| Proper motion (μ) | RA: 180.093±0.035 mas/yr[2] Dec.: 0.098±0.031 mas/yr[2] |
| Parallax (π) | 13.7402±0.0370 mas[2] |
| Distance | 237.4 ± 0.6 ly (72.8 ± 0.2 pc) |
| Absolute magnitude (MV) | +4.2[1] |
| Details | |
| Mass | 1.12[4] M☉ |
| Radius | 1.52[5] R☉ |
| Luminosity | 2.31[5] L☉ |
| Surface gravity (log g) | 4.11[4] cgs |
| Temperature | 5,780[5] K |
| Metallicity [Fe/H] | +0.19[4] dex |
| Rotation | 28 days[6] |
| Rotational velocity (v sin i) | 1.27[6] km/s |
| Age | 6.0[6] Gyr |
| Other designations | |
| AG+04°2898, BD+04°4656, HD 203473, HIP 105521, SAO 126740, GSC 00536-00696 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 203473 is an ordinary G-type main-sequence star with 112% the mass of the Sun,[4] but is 52% larger than the latter.[5] This star is over luminous and hot for its reported spectral class, with it radiating at 2.3 times the luminosity of the Sun and an effective temperature of 5,780 K.[5] HD 203473 is about six billion years old.[6] Like many planetary hosts, HD 203473 has an enhanced metallicity, with an iron abundance 1.55 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 |
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