catalogues and names

The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version)

SKY2000 - Master Star Catalog

Smithsonian Astrophysical Observatory Star Catalog

The Washington Visual Double Star Catalog, 1996.0

4th Catalog of Orbits of Visual Binaries

Combined General Catalogue of Variable Stars (Vol. I-III)

catalogues and names

catalogues and names	e Hya, eps Hya, 11 Hya, HR 3482, HD 74874, SAO 117112, BD +6 2036, WDS 08468+0625A
constellation	Hydra

data from The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991)

position, motion, parallax:

position (J2000)	RA: 8h 46min 46.6sec	DEC: +6° 25' 8''
position (2000.72)	RA: 8h 46min 49sec	DEC: +6° 24' 58''
position (B1900)	RA: 8h 41min 28.8sec	DEC: +6° 47' 9''
proper motion (J2000)	RA: -0.189 arcsec/a	DEC: -0.051 arcsec/a
radial velocity	36 km/s note: spectroscopic binaries note: orbital data avaible
rotational velocity	19 km/s (uncertain) (variable)
trigonometric parallax	0.027 arcsec
galactic coordinates	longitude: 220.72°	latitude: 28.53°

note (category: dynamical parallaxes):

0.018".

magnitude

visual magnitude

3.38 (V on UBV Johnson system)

spectral / color information

spectral class	G5III
B-V-magnitude	0.68
U-B-magnitude	0.36
R-I-magnitude
IR-note	object is infrared source (NASA merged infrared catalogue, Schmitz et al., 1978)

note (category: spectra):

Secondary has been classified dF7, later A8IV.

variability information

variable star identification

Eps Hya

double/multiple star system information

number of components of multiple star system	6
separation	0.2 arcsec
mag difference (of double or brightest multiple)	0.9
component ID	AB

note (category: double and multiple data):

AB 3.8 G5III, 4.7 A8IV or F0V, 15.05y, a = 0.238". Speckle interferometric sep. 0.263-0.272", 1980-3. Combined mag., colors. ABxC, 3.4, 7.8, dF7 at 3" from AB, 890y, a = 4.536". Component D, 12.7v at 19" from A, in hyperbolic orbit about ABC, periastron distance, 29".

note (category: spectroscopic binaries):

ADS 6993B, 5492d, K 7.3k/s, V0 +36.4k/s, asini 437. Secondary period 70d suspected. ADS 6993C, SB 9.9047d, K 35.0k/s, V0 +31.2, asini 3.74.

data from SKY2000 - Master Star Catalog (Myers+ 1997)

position, motion, parallax:

position (J2000)	RA: 8h 46min 46.587sec	DEC: +6° 25' 7.53''	±1.24 arcsec	source: 29
position (2000.72)	RA: 8h 46min 49sec	DEC: +6° 24' 58''	JD: 2451809.16
proper motion (J2000)	RA: -0.0127 arcsec/a	DEC: -0.051 arcsec/a		source: 25
radial velocity	36 km/s			source: 25
trigonometric parallax	0.027 arcsec		±0.003 arcsec	source: 25
galactic coord. (B1950)	longitude: 220.73°	latitude: 28.53°

magnitude:

visual	3.38 (observed)	source: 25
photovisual	3.5	source: 2
photographic	4	source: 2

spectral information:

spectral class	F8		source: 96
Morgan-Keenan	K1III:+F0V		source: 25
B-magnitude	4.06 ±0.05	B-V-magnitude	0.68
U-magnitude	4.42 ±0.05	U-B-magnitude	0.36

variability information:

source of data: 27

variability type	440
var. amplitude	0.1

double/multiple star system information:

source of data: 19

magnitude difference between brightest and second brightest component

1.5

component	magnitude	spectral class	catalogue(s)/name(s)
A	3.38	F8	e Hydrae, 11 Hya, HR 3482, HD 74874, SAO 117112
B	9.67	F0

sources:

2	HD and HDE Catalogs
Cannon, A.J., and E.C. Pickering, Harvard Annals, Vols 91-99, 1918-24, Cambridge, Massachusetts: Harvard University; Cannon, A.J., Harvard Annals, Vol. 100, 1925-36, Cambridge, Massachusetts: Harvard University; and Cannon, A.J., and M. Walton Mayall, Harvard Annals, Vol. 112, 1949, Cambridge, Massachusetts: Harvard University
19	WDS Catalog
Worley, C.E., and G.G. Douglass, Washington Catalog of Visual Double Stars 1996.0, United States Naval Observatory, 1996
25	Bright Star Catalogue, 5th edition
Hoffleit, D. and Warren, W.H. Jr., The Bright Star Catalogue, 5th Revised Edition, Version 2, 1994
27	Catalog of Red Magnitudes (CRM)
Warren, W.H. Jr., Northern Hemisphere Catalog of Red Magnitudes, 1994
29	SAOJ2000
SAO on FK5 at J2000, 1989
96	SAO or HD/HDE Catalog
Reference from Value 1 or Reference from Value 2

data from Smithsonian Astrophysical Observatory Star Catalog (SAO Staff 1966; USNO, ADC 1990)

position and proper motion:

position (B1950)	RA: 8h 44min 7.755sec	DEC: +6° 36' 12.41''	±0.007 arcsec
position (2000.72)	RA: 8h 46min 50sec	DEC: +6° 25' 0''	JD: 2451809.16
position (J2000)	RA: 8h 46min 46.587sec	DEC: +6° 25' 7.53''
proper motion B1950 (FK4)	RA: -0.0128 arcsec/a	DEC: -0.055 arcsec/a	±0.001 arcsec/a in RA ±0.001 arcsec/a in DEC
proper motion J2000 (FK5)	RA: -0.0127 arcsec/a	DEC: -0.051 arcsec/a
source of proper motion data	Determined by source catalog

magnitude:

visual	3.5 (accuracy: 2 decimals)
source of visual magnitude data	Combined magnitude of component stars.

spectral information:

spectral class	F8
source of spectral data	Taken from the HD with M stars reclassified by Miss Cannon.

remarks for duplicity and variability

Double star - see source catalog for source

catalogues

source catalogue	FK3, catalogue number: 329
Durchmusterung	BD+06 2036
Boss General Catalogue	12102
Henry Draper Catalogue	74874

data from The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996)

position and proper motion:

position (J2000)	RA: 8h 46.8min	DEC: +6° 25'
proper motion (J2000)	RA: -0.194 arcsec/a	DEC: -0.054 arcsec/a

double/multiple star system information:

component	year	number of measures	position angle	angular separation	magnitude of 1st component	magnitude of 2nd component	spectral class(es)	discoverer code
AB	1888	often	°	''	3.8	5.3	F8V	SP 1
AB-C	1825	often	195°	3.2''	-	7.8	-	STF1273
	1994		292°	3''
AB-D	1878	16	192°	20''	-	12.5	-	STF1273
	1978		199°	18.7''
AB-E	1921	3	359°	338''	-	10.1	-	STF1273
	1984		1°	-
AB-F	1921	3	265°	424.5''	-	10.2	-	STF1273
	1984		-	412.1''

discoverer information:

discoverer code	discoverer	reference
SP 1	Schiaparelli, G.	(Publ. Brera Milan No.33; 1888.)
STF1273	Struve, F.G.W.	-

notes:

note	Epsilon Hya. AB: P = 15.05yr., a = 0.255", motion direct. AB is variable. AB-C: P = 890yr., a = 4.54", motion direct. C is a spectroscopic binary, and D is physical. Hence quintuple.

data from 4th Catalog of Orbits of Visual Binaries (Worley+, 1983)

position:

position (B1900)

RA: 8h 41.5min

DEC: +6° 47'

magnitudes, spectral classes, orbital elements:

author:	W.D. Heintz	W.D. Heintz
date of observation:	1961	1961
magnitude of component A:	3.8	3.4
magnitude of component B:	3.8	3.4
spectral class component B:	G5III
spectral class component B:	G5III
period [y]:	15.05	890
semi-major axis [arcsec]:	0.238	4.536
inclination [deg]:	49.3	42
node [deg]:	109.3 (ascending)	55.5 (ascending)
equinox of node:	2000	2000
eccentricity:	0.67	0.29
time of periastron passage:	1961.05	1933
dates of ephemeris:	1 rev.	1 rev.
grade:	definitive	preliminary
reference:	Z. Astrophys. 57, 159; 1963.	Ibid.

notes

Quintuple. The elements for AB are combined visual-spectroscopic. C is a single-lined spectroscopic pair, P = 9.905 d. Star D is in slow direct motion (mag. 12.72, 19").