Chi Eridani
Star in the constellation Eridanus
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χ Eridani (Latinised as Chi Eridani) is a binary star[10] system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.70.[2] The distance to this system, as determined using the parallax method, is around 58 light years.[1] The pair had an angular separation of 5.0 arcseconds as of 1994. This corresponds to a projected separation of around 128 AU.[3]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 01h 55m 57.45606s[1] |
| Declination | −51° 36′ 31.9736″[1] |
| Apparent magnitude (V) | 3.70[2] / 10.7[3] |
| Characteristics | |
| Spectral type | G8IV[4] or G8IIIb CNIV[5] |
| U−B color index | +0.46[2] |
| B−V color index | +0.85[2] |
| Astrometry | |
| Radial velocity (Rv) | –6.30[6] km/s |
| Proper motion (μ) | RA: +682.281[1] mas/yr Dec.: −295.332[1] mas/yr |
| Parallax (π) | 57.3774±0.3291 mas[1] |
| Distance | 56.8 ± 0.3 ly (17.43 ± 0.10 pc) |
| Absolute magnitude (MV) | 2.39 / 9.4[3] |
| Details[7] | |
| A | |
| Mass | 1.58[8] 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 |
| B | |
| Mass | ~0.7 M☉ |
| Radius | ~0.7 R☉ |
| Other designations | |
| χ Eri, CD−52 394, FK5 68, GJ 81, HD 11937, HIP 9007, HR 566, SAO 232573[9] | |
| Database references | |
| SIMBAD | data |
| ARICNS | A |
| B | |
The primary component is an evolving G-type subgiant star with a stellar classification of G8 IV.[4] It is about 1.6 times the mass of the Sun and has 4 times the Sun's radius.[8] The star shines with 10 times the solar luminosity from its outer atmosphere at an effective temperature of 5,115 K.[7] 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.[8]
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.[8]