χ Eridani

Location of χ Eridani (circled in red)
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

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]

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]

References