[vsnet-alert 89] GW Lib and V592 Her

[tkato@kusastro.kyoto-u.ac.jp]

  Dear Colleagues,

  As P. Schmeer and C. Scovil noticed, GW Lib seems to be observed at
around mv=14-15.  Since I am now at a remote terminal, the following
information is based on my memory -- perhaps contains some errors.
GW Lib was discovered as a possible nova by Gonzalez in 1983.  The only
available photometric data in IAUC suggests that the object reached
at least 9th mag, and faded rather rapidly.  No spectroscopic information
during outburst was available.  This discovery lead to a quiescent
identification of mpg~18 star.  The spectrum of this quiescent counter-
part showed rather broad strong emission lines of H-alpha etc., and more
resembled the spectrum of a dwarf nova in quiescence rather than that of
a nova.  Therefore some authors suspected this object to be a WZ Sge-type
dwarf nova or a TOAD (tremendous outburst amplitude dwarf nova).
No confirmed outburst has been recorded since its discovery in spite of
close monitoring by visual observers.  If the present possible brightening
of GW Lib really reflects its outburst activity, it will surely provide
a long-awaited opportunity in clarifying the nature of this poorly known
cataclysmic variable.  Confirmatory observations, spectroscopy, and
photometry (time-resolved one, if possible), are most emergently requested.
The finding chart can be found in many familiar articles such as the
atlas by Duerbeck.  A PostScript file is also available from our anonymous
ftp service (ftp.kusastro.kyoto-u.ac.jp, presently 130.54.52.121, file
pub/tkato/chart/pscht/libgw.ps).  Note that this chart was based on GSC,
but will be surely helpful in identifying the variable by visual observers.
GW Lib itself was record at mag 16.6 on Mar. 19, 1993.

  A PostScript file for V592 Her is also available (herv592.ps in the same
directory).  This chart contains faint comparison stars down to V=17.8.
Note that the quiescent identification by Duerbeck should be replaced by
more recent one published in IBVS (sorry I don't remember the number).
Our chart is based on this correct identification.  V592 Her is also
suspected to be a WZ Sge-type dwarf nova with a very long recurrence
time and an exceptionally large (~10 mag) outburst amplitude.  Other
classifications, however, can not be ruled out.  Please keep a close watch.

Regards,
Taichi Kato

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