Location of τ4 Eridani (circled) | |
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
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Constellation | Eridanus |
Right ascension | 03h19m 31.0006s [1] |
Declination | −21° 45′ 28.315″ [1] |
Apparent magnitude (V) | 3.65[2] |
Characteristics | |
Evolutionary stage | asymptotic giant branch[3] |
Spectral type | M3/4 III[4] |
U−B color index | +1.79[2] |
B−V color index | +1.61[2] |
Variable type | Lb[5] |
Astrometry | |
Radial velocity (Rv) | +41.7±0.7[6] km/s |
Proper motion (μ) | RA: +52.774 mas/yr[1] Dec.: +32.718 mas/yr[1] |
Parallax (π) | 10.6153 ± 0.3213 mas[1] |
Distance | 307 ± 9 ly (94 ± 3 pc) |
Absolute magnitude (MV) | −0.79[7] |
Details | |
Mass | 1.95[8] M☉ |
Radius | 103[9] R☉ |
Luminosity | 1,537[10] L☉ |
Surface gravity (log g) | 0.91[8] cgs |
Temperature | 3,770[8] K |
Other designations | |
τ4 Eridani, τ4 Eri, 16 Eridani, BD-22° 584, HD 20720, HIP 15474, HR 1003, SAO 168460.[11] | |
Database references | |
SIMBAD | data |
Tau4 Eridani (τ4 Eridani, τ4 Eri) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.65.[2] The distance to this star can be estimated using the parallax method, which yields a value of roughly 300 light years. [1]
This is an evolved red giant star currently on the asymptotic giant branch[3] with a stellar classification of M3/4 III.[4] It is a slow irregular variable star of type Lb, undergoing changes in magnitude over the range 3.57−3.72[5] with a periodicity of 23.8 d.[12] The measured angular diameter of Tau4 Eridani is 10.58±1.00 mas.[13] At its estimated distance, this yields a physical size of about 106 times the radius of the Sun.[14] It shines with 1,537[10] times the luminosity of the Sun from an outer atmosphere at an effective temperature of 3,770 K.[8]
This is most likely a binary star system.[15] The companion is a magnitude 9.5 star at an angular separation of 5.7″ along a position angle of 291°, as of 2013.[16]
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