[vsnet-alert 10087] V2491 Cyg spectrum: comparision with those of recurrent novae

[Taichi Kato]

>    Fujii-san's new spectrum of V2491 Cyg:
>
> http://www1.harenet.ne.jp/~aikow/etc/v2491_cyg_20080420.gif
>
>    Strong broad emission lines were present.  N III/He II around 4640,
> N II([O III]?) 5001, N II 5679, Na I 5892 were strong.

   This spectrum is worth comparing with those of V394 CrA.
The overall feature looks similar to the latter spectrum on
1987 Aug 3.75.

http://adsabs.harvard.edu/abs/1989MNRAS.236..611S

   The 2000 outburst of CI Aql was not recorded at the very early
epoch, but the overall feature of the spectrum was also similar.

   If V2491 Cyg is a recurrent nova with an evolved subgiant secondary
as in above systems, the small outburst amplitude can be naturally
explained.  The relatively long recurrence times of V394 CrA and CI Aql
might explain why no previous outburst had been reported in V2491 Cyg.