[vsnet-chat 475] Nova RW UMi 1956 and pre and post magnitudes of novae

[Alon Retter <alon@wise.tau.ac.il>]

Dear Dr. Kato,
 
> 
>     I think the original claim of the possible faint state of this post-
> outburst nova should be checked (any images available?) before reaching
> any definite conclusion.  As you have shown, I would not wonder if the star
> (assuming the below-the-gap nature) wanders between 'high' (permanent
> superhumper) and 'low' (SU UMa) states.  If so proven, this object may
> become the first such.
>

I'll forward this qustion to Steve Howell, the source for this claim.

>     I am pleased to know this object is so intensively monitored.  It would
> be very interesting to know its true orbital period, since the object
> is suspected to belong to the old population (from its high-Z), and the
> orbital period might provide a test for the evolutionary model of halo CVs.
> Any indication of a coherent signal?
> 

I don't think that 1 case can tell a lot about the whole picture.
Anyway our data were not enough for determine the period/s.  In the
power spectrum, there are about 3 structure of peaks at about 1.25-1.5,
2-2.5, 4-6 hr, and few more. Not all of them are really significant.
Aditionally, two different parts of the data show a similar patern, but
the numbers and aliases are somewhat different. Right now, My guess is
that it is an intermediate polar, and the 3 main peaks are the spin,
beat and orbital periods.  However, it might be changed with more
data.  Finding the right period/s of a system for the first time, is a
perfect target fo collaboration, especially if the object is faint. A
longer run will eliminate the aliases.

>     My notion was not that above-the-gap novae should return to their
> pre-outburst states, but that above-the-gap novae might have been normal
> novalike (NL) variables before nova eruption.  So I don't wonder if these
> novae had high mass-transfer rates before eruption as they do today.
> This is probably not the case for below-the-gap novae.  If they had high
> mass-transfer rates before eruption, we need a (new) mechanism of
> maintaining such high mass-transfer rates, since they unlikely have
> nova-heated secondary stars before eruption, which are sometimes thought
> to be the cause of enhanced mass-transfer.
> 
>     By the way, are there any established cases of above-the-gap novae
> (aside from the peculiar magnetic nova, V1500 Cyg) which show much brighter
> quiescence after the nova explosion?  It is interesting even the fastest
> nova (V838 Her) has returned to its pre-outburst magnitude.
> 

I agree that pre-nova are naturally not well studied, and that the
evolutionary picture is still not well understood. Duerbeck (1992,
MNRAS, 258, 629) showed that the brightness of a few old novae is
increased! a few decades after outburst, so these novae are probably,
above their pre-outburst state. GK Per with Porb=2d is one of them,
together with DI Lac and V841 Oph, for which, to my knowledge, the
orbital periods are unknown. Duerbeck has data on many more old nova,
and he's still working on this in collaboration with the Wise Obs.
(Elia Leibowitz).

I didn't know that V1500 Cyg is above its pre-nova mag., but as far as
I remember it still decays, and it might have not reached its final
quiescent state.


Regards,
Alon Retter

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