On Mon, 2 Apr 2007 22:34:19 +0100, "George Dishman"
wrote:


"Henri Wilson" HW@.... wrote in message
.. .
On Sun, 1 Apr 2007 15:04:46 +0100, "George Dishman"

Given that you now accept the huff-puff nature, you
need to reconsider your justification for saying
that Cepheids that are currently thought of as
isolated might actually be part of a binary.

Every one I read about seems to have a companion star.

Put "solitary cepheid" into Google and you get a number
of hits. At least one was a survey listing both categories
with similar numbers of entries. I looked it up earlier
at work and don't have the reference here and it was in
postscript but I'm sure you can find a readable version
with a little hunting.

I'm sure there are many that have very slow orbit periods.

If you are now switching to say they are single stars, why
on Earth would your software be modelling binary systems
and restricting the solutions to Keplerian orbits when the
motion of the surface is due to internal pressure?

I think it is my turn to say you are getting very confused
Henry.

It is a fact that most 'cepheids' appear to have a companion...

It is a fact that something around half of _all_ stars
are in binary systems so there is no reason why Cepheids
should be an exception.

...all stars are obiting some kind of mass centre.

They all orbit the galaxy, so what. The orbital period
needs to be a few years or less for any significant
effects to show up.

They orbit all kinds of objects, not just the galaxy...and other objects orbit
them.
Many orbits will involve more than one other object and will be unstable.


It is certainly possible, especially for close binaries,
but less likely for those with greater separations.

and
distorted into some kind of dumbell shape,

No, each would be more like an egg shape. Look up "Roche Lobe".

Yes, egg shaped...that would cause a brightness variation at double the
orbit
frequency.

leading to a brightness variation as
they orbit....but that wouldn't account for the short periods of many of
them.

It wouldn't account for any where the period of the Cepheid
differs from the orbital period, nor does it account for those
that are not in binary systems.

That is true. That's why I accept the possibility.
However it doesn't make any difference to the fact that the brightness
variation of huff-puff stars conforms with BaTh.

First you need to model them correctly. Your new program
should do that if you match the red velocity curve to the
published data. The grreen curve then gives the luminosity
variation due to c+v and any extra is intrinsic. So Henry,
revisit your matches and tell me how much is c+v and how
much is intrinsic for some examples 1.5 magnitude variation

It isn't difficult to produce variations of 1.5 mag. ..but 3 is about the limit
with the BaTh before the critical distance is reached and the curves become
peaked.
There still appears to be no theory that explains any intrinsic brightness
variation of huff-puff stars.

In every paper I have read about cepheids, the authors admit the have no
theory
to link the surface movement to the brightness curve.

I won't comment on that without doing some study for myself.

George



Einstein's Relativity - the greatest HOAX since jesus christ's mother.