[vsnet-chat 151] AC Sco and others

[Taichi Kato <tkato>]

Berto Monard wrote:
> AC Sco also a non-cv? It's a close neighbour to AF Sco. Is it not
> strange that often similar peculiar stars or stars with similar
> records are close neighbours (in the sky), and that novae seem to
> occur in certain regions during brief periods and occur in other
> regions during later periods.

    AC Sco is most likely identical with a GSC star of mag 13.3 at
164635.17 -272316.3 (2000.0), which could be identified with IRAS 16434-2717.
This star is probably a red variable.  IRAS variability index = 31%.

    Yes, novae do seem to cluster.  Good examples may be a pair of CK Vul
and LV Vul, SS Cyg (dwarf nova) and V1668 Cyg - pairs a little too
meaningless?, GR Sgr and V441 Sgr, V990 Sgr and V3889 Sgr and many, many..
Stars in Sco do not seem so particular.  Apart from letting it a product
of mistaken impression, these associations might be physically explained
as a result of inhomogenous variable star (nova) surveys and inhomogenous
interstellar extinction -- novae should tend to appear in less obscured
regions.  Improper classifications in the original discovery papers may
be also responsible.  Novae are often classified as such only based on
the non-recurring eruptive nature; in poorly sampled (in time series)
surveys, variable stars of other types appearing on only a few plates
may be easily mistaken for novae (candidates).  It's my own speculation,
though.

    I wonder why 'true' dwarf novae are so rare in Sgr or Sco regions.

Regards,
Taichi Kato

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