Epsilon Hydrae

Epsilon Hydrae (ε Hydrae, abbreviated Epsilon Hya, ε Hya) is a multiple star system of a combined third magnitude in the constellation of Hydra. Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly 129 light-years (40 parsecs) distant from the Sun.

ε Hydrae
Location of ε Hydrae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 8h 46m 46.51223s
Declination +06° 25′ 07.6855″
Apparent magnitude (V) AB: 3.38
C: 7.5
Characteristics
Spectral type AB: G5 III + F0 V
C: F5
U−B color index +0.37
B−V color index +0.68
Astrometry
Radial velocity (Rv)+36.4 km/s
Proper motion (μ) RA: −228.11 mas/yr
Dec.: −43.82 mas/yr
Parallax (π)25.23 ± 0.98 mas
Distance129 ± 5 ly
(40 ± 2 pc)
Absolute magnitude (MV)+0.39
Orbit
Primaryε Hya A
Companionε Hya B
Period (P)5,478.98 ± 93.19 days
Semi-major axis (a)0.226″
Eccentricity (e)0.652 ± 0.020
Inclination (i)49.3°
Periastron epoch (T)2437060.85 ± 63.86
Argument of periastron (ω)
(secondary)		74.66 ± 0.21°
Semi-amplitude (K1)
(primary)		8.05 ± 0.14 km/s
Details
ε Hya A
Mass2.5 M☉
Luminosity67 L☉
Temperature5,620 K
Metallicity [Fe/H]−0.08 dex
Rotational velocity (v sin i)19 km/s
ε Hya B
Mass1.7 M☉
Other designations
Ashlesha, ε Hya, 11 Hydrae, BD+06 2036, HD 74874, HIP 43109, HR 3482, NSV 4244, SAO 117112.
Database references
SIMBADdata

The system consists of a binary pair designated Epsilon Hydrae AB, whose two components are themselves designated Epsilon Hydrae A (formally named Ashlesha /ɑːʃˈleɪʃə/) and B, orbited by a spectroscopic binary designated Epsilon Hydrae C. A possible fourth component, designated Epsilon Hydrae D, shares a common proper motion with the other components and thus is most likely a gravitationally-bound member of the system.

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