[vsnet-chat 381] possible nova in Sco - on periodic variations

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

Taichi Kato wrote:

>    The case of V838 Her = Nova Her 1991 was extremely interesting.
> I was prompted by its rapidness of decline to test any possible indication
> of V1500 Cyg-type variation.  The nova instead proved to be an eclipsing one!
> The first indication of deep eclipses were observed on 1991 April 22
> (cf. IAUC 5262), which was 29 days after the optical maximum.
> There were also some indication of shallow secondary minima (at phase 0.5)
> on April 20 and 21, and some hint of a shallow primary eclipse on
> April 14.  The observation on April 12 covered this phase, but was
> inconclusive because of the heavy cloud interference.
> 
>    My 1991 August observations showed a very steep eclipse ingress and
> egress, just as in detatched subdwarf binaries, indicating the eclipsed
> source was very compact, probably indicating the contribution from the
> accretion disk was negligible.
> 
>    Regarding eclipses in young novae, the fast nova V1668 Cyg presents
> another interesting example.  While a 0.4271-day periodicity was observed
> during decline, the nova was later found to be an eclipsing binary
> of 0.1384 day (Kaluzny, MNRAS 245,547).  The observed period is close
> to three times of Porb, but the relation between them is unknown.
> I wonder what was the case during the nova decline of the well-observed


The observations on Nova V838 Her 1991 at the Wise obs. indicated that
the eclipse was seen during 10-13/4/91, although none of the 4 observed
nights had a full cycle. Our analysis and the shape of the light curve
support the presence of a bright spot and an accretion disk.  However,
I agree that that the case of Nova V1974 Cyg 1992 - permanent
superhumps is much more convincing for the presence of the disk.

Nova V1668 Cyg 1978 is indeed an intriguing case. I saw somewhere (I
think that in Warner's book) that the 10.5-hr period (0.4392 d and not
0.4271-d !) was interpreted as oscillations of the common enveloppe. I
found this nova very interesing also because the periodicity found
about 3 yr after the outburst (Piccioni et al., 1984, 34/4, 473-485)
was half the later detected by Kaluzny in 1989. There were also signs
for these periods even from about 40 d after maximum light (see
Voloshina and Cherepashchuk 1980 Astron. Circ. 1942, 1-6 - sorry it's
in russian, and Blitzstein et al., 1980, PASP, 92, 338-344).

No doubt that observations on young novae are fruitfull.
I envy you southerns for the chance to observe Nova Sco. 1997.

Since I'm leaving tomorrow night to the states, let us continue this
chat there.

Alon Retter
Wise Obs.

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