[vsnet-alert 986] possible nova in Sco - on periodic variations

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

Taichi Kato wrote:

>     This object should be indeed a nova, as reported in [vsnet-alert 977].
> (http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-alert/msg00977.html)
> No dwarf nova can show such a high (~3200 km/s) ejection velocity in emission
> lines.  The observed width well corresponds to that of a fast nova.
> 
>     By assuming the optical maximum at the epoch of Liller's discovery,
> your observation suggest t3 of 3 - 4 days (!), which probably rivals the
> fastest nova, V1500 Cyg (Nova Cyg 1975, t3 = 3.6) and V838 Her (Nova Her
> 1991).  It would be probably interesting to search for any periodic
> modulation during this nova eruption, since V1500 Cyg showed a remarkable
> 0.141-day modulation, which is interpreted as the "searchlight effect"
> (cf. Stockman et al. Ap.J. 232, 282).  V838 Her is a neon nova, which showed
> deep eclipses even during the early decay.  As usual, observations are
> strongly recommended!

Since my thesis subject is young novae, let me add a few words.
If this object is indeed a nova, and a very fast one, periodic
variations may soon be detected. In Nova V838 Her 1991, it was
discovered from about 3 weeks after the outburst (Leibowitz et al. 
1992, Ap. J. 385, L49). They interpreted the eclipse in this system 
as an eclipse of the accretion disk by the secondary. 

Well, in this nova, we were lucky to have a very high inclination, 
but even if the inclination is small, periodic variations can be 
found shortly after the outburst.

Our preprint on Nova V1425 Aquilae 1995, which will be presented 
in a poster in the Jackson workshop states that the orbital period 
of this nova was detected about 3 months after maximum light. Who 
knows, it might have been there long before. The amplitudes there
are about 1%, so it's probably a low inclination system.

Periodic variations were also discovered in other young novae.
In Nova V1974 Cyg 1992 (DeYoung & Schmidt 1994, Ap.J. 431, L47)
and Nova V705 Cas 1993 (Retter & Leibowitz, 1995, IAUC 6234) 
they were observed about 2 years after the eruption, however, again
they might have been there before, and there were not so fast novae.

I think, that it is very interesting to follow periodic variations
in young novae. See for example the photometric papers on V1974 Cyg
(DeYoung & Schmidt 1994, Ap.J. 431, L47, Semeniuk et al. 1994, Acta
Astro., 44, 277, Semeniuk et al. 1995, Acta Astro., 45, 365, Skillman 
et. al., 1997, PASP, 109, 114 and Retter, Leibowitz & Ofek, 1997, MNRAS, 
286, 745). The case of Nova V1500 Cyg 1975, mentioned by Kato is another
beautiful example.

Our hands are tied for this purpose, since we are at the north
here at the Wise Observatory (dec=30), however for those of you
interested in continuous photometry on this object, I suggest to use
red filters, either for a reflection effect or for an eclipse of the
accretion disk, which might be deeper in the red.

Good luck, and see you in Jackson!

Alon Retter
Wise Obs.

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