[vsnet-chat 3761] Re: [AAVSO-DIS] Duration of eclipses

[Fraser Farrell <fraser@trilobytes.com.au>]

> IS IT POSSIBLE THAT A SECONDARY ECLIPSE (I mean  a "brighter" eclipse) 
LASTS
> LONGER THAN A PRIMARY??

Sebastian,

I can imagine two ways to make this happen.

1) The orbit is elliptical. In fact, the primary and 
secondary eclipses are of equal duration only for two 
special cases: 
 - circular orbit, or
 - if the major axis is in the plane of the sky

Separation of the eclipses by 0.5 of the period only 
occurs for:
 - circular orbit, or
 - major axis parallel to our line of sight.

One lightcurve could be explained by many different 
combinations of orbital parameters; so additional 
evidence (eg: orbital velocities) would be needed to 
pick the right numbers.


2) Either or both components change size for some 
reason eg: one is a cepheid. It is likely that in this 
case the system will show variation in addition to 
eclipses (eg: AR Pav).


And yes, I will be staying up late tonight to confirm 
(or disprove) the 27-day hypothesis for delta Vel.


cheers,
Fraser Farrell

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp