Epsilon Hydrae

ε Hydrae
Location of ε Hydrae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 8h 46m 46.51223s[1]
Declination +06° 25′ 07.6855″[1]
Apparent magnitude (V) AB: 3.38[2]
C: 7.5[3]
Characteristics
Spectral type AB: G5 III + F0 V[4]
C: F5[3]
U−B color index +0.37[5]
B−V color index +0.68[5]
Astrometry
Radial velocity (Rv)40.46±0.03[6] km/s
Proper motion (μ) RA: −228.11[1] mas/yr
Dec.: −43.82[1] mas/yr
Parallax (π)25.23 ± 0.98 mas[1]
Distance129 ± 5 ly
(40 ± 2 pc)
Absolute magnitude (MV)+0.39[7]
Orbit[8]
Primaryε Hya A
Companionε Hya B
Period (P)5,478.98 ± 93.19 days
Semi-major axis (a)0.226[9]″
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
Mass2.094+0.094
−0.129[10] M☉
Radius7.92±1.27[6] R☉
Luminosity44[6] L☉
Surface gravity (log g)3.00±0.05[6] cgs
Temperature5,084±15[6] K
Metallicity [Fe/H]−0.17±0.02[6] dex
Rotational velocity (v sin i)19[9] km/s
Age1.15+0.26
−0.22[6] Gyr
ε Hya B
Mass1.64[10][a] M☉
Other designations
Ashlesha, ε Hya, 11 Hydrae, BD+06 2036, HD 74874, HIP 43109, HR 3482, NSV 4244, SAO 117112.
Database references
SIMBADdata

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.[1]

The system consists of a binary pair designated Epsilon Hydrae AB, whose two components are themselves designated Epsilon Hydrae A (formally named Ashlesha /ɑːʃˈleɪʃə/)[11] 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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  10. ^ a b Cite error: The named reference Anguita-Aguero was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference IAU-LSN was invoked but never defined (see the help page).


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