Chi Eridani
χ Eridani (Latinised as Chi Eridani) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.70. The distance to this system, as determined using the parallax method, is around 58 light years. The pair had an angular separation of 5.0 arcseconds as of 1994. This corresponds to a projected separation of around 128 AU.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 01h 55m 57.45606s |
| Declination | −51° 36′ 31.9736″ |
| Apparent magnitude (V) | 3.70 / 10.7 |
| Characteristics | |
| Spectral type | G8IV or G8IIIb CNIV |
| U−B color index | +0.46 |
| B−V color index | +0.85 |
| Astrometry | |
| Radial velocity (Rv) | –6.30 km/s |
| Proper motion (μ) | RA: +682.281 mas/yr Dec.: −295.332 mas/yr |
| Parallax (π) | 57.3774 ± 0.3291 mas |
| Distance | 56.8 ± 0.3 ly (17.43 ± 0.10 pc) |
| Absolute magnitude (MV) | 2.39 / 9.4 |
| Details | |
| A | |
| Mass | 1.58 M☉ |
| Radius | 3.993±0.027 R☉ |
| Luminosity | 9.84±0.39 L☉ |
| Surface gravity (log g) | 3.42±0.10 cgs |
| Temperature | 5,115±49 K |
| Metallicity [Fe/H] | −0.18±0.07 dex |
| Rotational velocity (v sin i) | 4.50 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
| ARICNS | A |
| B | |
The primary component is an evolving G-type subgiant star with a stellar classification of G8 IV. It is about 1.6 times the mass of the Sun and has 4 times the Sun's radius. The star shines with 10 times the solar luminosity from its outer atmosphere at an effective temperature of 5,115 K. Unusually for a star of this class, it shows a photometric variability of 0.04 in magnitude, which may be due to a previous mass transfer from the secondary companion, or else from an undiscovered third companion.
The companion is about 7 magnitudes fainter than the primary and may be the source of the X -ray emission from this system. This emission has a luminosity of 504.4×1027 erg s−1.