[vsnet-chat 3430] Re: Permanent Superhumpers...

[Taichi Kato <tkato>]

Re: [vsnet-chat 3429] Permanent Superhumpers...

> To my opinion permanent superhumps occur in permanent superhumpers. 
> They occur when the system is tidally and thermally unstable. I agree 
> that there is some confusion in terminology as the field is relatively 
> new. For example is a permanent superhumper a nova like or are these two
> groups separate?

   Looking at literatures, a number of researchers carefully avoid using
these terms interchangeably.  This apparent segregation of usage seems to
stem from the history and the achived consensus level regarding the underlying
mechanism.

> As far as I understand there is no difference between a permanent
> superhumper below the gap and above the gap.

   It seems (also from the paragraphs above and below) that you assume
"the observed signals in long-period systems having periods different
from orbital periods" are the same superhumps as those in short-period
systems.  Yes, this may be a matter of the definition of the "superhump"
terminology, but it is not well established whether this modulation is
caused by the same mechanism which produces well-established SU UMa-type
superhumps.  For example, period vs. "superhump" excess relation is
different from that of short-period systems.  This might suggests that
a completely different mechanism may be relevant.  In such a case, the
classification based on tidal stability may make no sense.  The in-the-gap
system V795 Her is perfectly on the SU UMa-type superhump excess relation;
this is why this system is a natural extension of SU UMa systems toward
novalike or longer period systems, but the situation is less clear in
even longer period systems.  Some recent simulations suggest that these
"superhumps" need to be reconsidered (not on the naive extension of
short-period systems) using more detailed fluid treatment [NB the original
tidal instability does not require fluid as an essential part].
Remebering this, one should be more conservative in observationally
determining the tidal stability limit from "superhumps" in long-period
systems.

   Keeping this and original definition in mind, Osaki's "permanent
superhumpers" should be better understood in a narrower sense, as thermally
stable systems which show superhumps having the same properties as our
familiar SU UMa-type superhumps.

Regards,
Taichi Kato

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