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Epsilon Octantis
from Wikipedia
ε Octantis
Location of ε Octantis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Octans
Right ascension 22h 20m 01.67970s[1]
Declination −80° 26′ 23.0947″[1]
Apparent magnitude (V) 4.58 - 5.30[2]
Characteristics
Spectral type M5III[3]
U−B color index +1.18[4]
B−V color index +1.47[4]
Variable type SRb[2]
Astrometry
Radial velocity (Rv)+11.70[5] km/s
Proper motion (μ) RA: +56.81[1] mas/yr
Dec.: −43.47[1] mas/yr
Parallax (π)11.22±0.23 mas[1]
Distance291 ± 6 ly
(89 ± 2 pc)
Absolute magnitude (MV)+0.34[6]
Details
Mass1.34[7] M
Radius112±15[8] R
Luminosity1,819[8] L
Surface gravity (log g)2.15[7] cgs
Temperature3,560±264[8] K
Other designations
BO Oct, ε Oct, CD−81°831, FK5 839, GC 31166, HD 210967, HIP 110256, HR 8481, SAO 258928
Database references
SIMBADdata

Epsilon Octantis, Latinized from ε Octantis, is a star in the southern circumpolar constellation of Octans. It is a faintly visible to the naked eye with an apparent visual magnitude of about 5. The annual parallax shift of 11.22[1] mas yields a distance estimate of around 291 light years. It is moving further from the Sun with a radial velocity of +11.7 km/s.[5]

A light curve for Epsilon Octantis, plotted from Hipparcos data[9]

This is an evolved, cool red giant star with a stellar classification of class M5III.[3] It is a semiregular variable with a magnitude range of 4.58 to 5.30 and a (poorly defined) period around 55 days.[2] The star has 1.34[7] times the mass of the Sun and has expanded to around 112[8] times the Sun's radius. It is radiating 1,819[8] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,560 K.[8]

Epsilon Octantis was found to be variable on a survey of the southern sky conducted by the Bamberg observatory, which was reported in 1966.[10] In 1972, it was assigned the variable star designation BO Octantis,[11] although this is now recognised as a mistake since stars with Bayer designations are not given a separate variable star designation.[2]

References

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