Basic data (System:560)

Identifiers:

Orbit

Note

This star was formerly known as 21 Hya. After the discovery that its light
varies, the star received the designation KW Hya. In some catalogues, however,
it was erroneously listed as KM Hya and appears under that name in the paper by
Andersen and Vaz. These authors later drew attention to the error themselves
(Astron. Astrophys., 175, 355, 1987). The new observations supersede the orbit
formerly determined by M.-T. Chauville (Astron. Astrophys., 40, 207, 1975).
There is general agreement that the primary spectrum is an Am spectrum. Curchod
and Hauck give A5, A7 and A9 from the K line, hydrogen lines and metallic lines
respectively, but Andersen and Vaz favour slightly earlier types. They do not
give a precise classification for the secondary spectrum, which is certainly
later than the primary. The epoch is the time of primary minimum. The orbital
eccentricity and time of periastron derived from the velocity-curve are in good
agreement with the same quantities derived from the light-curve. The latter
values are given in the Catalogue, and the other elements were derived with
those quantities fixed. Andersen and Vaz have found an appreciably larger value
for K2 than did Chauville. The value given for V0 is that appropriate to the
primary component. The small difference in the two values of V0 is probably not
significant. Analysis of the light-curve leads to an orbital inclination close
to 88 deg and a difference of visual magnitude, between the components, of
1.44m. Andersen and Vaz find it difficult to determine a unique evolutionary
state for the two components of this system.

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