[vsnet-campaign-news 120] AstroAlert: HV Vir extremely rare outburst

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

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             HV Virginis -- Extremely Rare Outburst of
                     a WZ Sge-Type Dwarf Nova
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    Patrick Schmeer (Germany) reported the detection of an outburst of
the WZ Sge-type dwarf nova HV Vir, currently in the morning sky.
The only known outbursts of HV Vir occurred in 1929, 1970 and 1992
(and possible faint outbursts in 1939 and 1981).  The long (about 10 yr)
interval of outbursts, the large outburst amplitude (7 mag) and the
presence of two types of superhumps signify HV Vir as a member of
small group of cataclysmic variables, called WZ Sge stars.
[Readers may remember that WZ Sge itself has undergone a remarkable
outburst last year].  HV Vir is reported to be currently at magnitude 12.

    CCD observers are strongly requested to observe this target as frequently
as possible (every 30 sec or less), in order to record superhumps.
WZ Sge-type stars are known to show "early superhumps" during the
earliest epoch of their superoutbursts.  So emergent observations are
most wanted!

    The object is located at RA = 13h21m03s.15, Dec = +01d53'28".6.

    Finding chart, see links at:
    http://vsnet.kusastro.kyoto-u.ac.jp/pub/vsnet/gcvs/VIRHV.html

    Regarding general CCD time-series photometry, our WZ Sge page would be
helpful:

    http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/wzsge01.html

    The paper on the 1992 outburst of HV Vir [T. Kato, Y. Sekine and
R. Hirata, PASJ 53, 1191 (2001)] is available at:

    http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/HV_Vir/

    or astro-ph/0110207
    http://arXiv.org/abs/astro-ph/0110207

Regards,
Taichi Kato
On behalf of the VSNET Collaboration team

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  VSNET (Variable Star Network) is an international variable star observing
network, covering various areas of novae, supernovae, cataclysmic variables
(CVs), X-ray transients, and other classical eruptive, pulsating, and
eclipsing variables.  VSNET is one of invited contributing organizations
to the SkyPub AstroAlert system.

       VSNET Home Page: http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/

CCD observations of such targets are a relatively easy task for a 20-40cm
telescope; simply take as many CCD frames (with exposure times 10-30 sec)
as possible, spanning several hours per night.  The only requirements are
the weather and your patience!  If you need more help on the observing
technique, please feel free to ask on the vsnet-campaign list.

   We would sincerely appreciate volunteers who would join the VSNET
Collaboration team to study the wonders of these exotic variable stars.
To join the VSNET campaign collaborative list, send an e-mail to

         vsnet-adm@kusastro.kyoto-u.ac.jp (VSNET administrator)

with a line "SUBSCRIBE vsnet-campaign." or your comment to join the
collaboration team.

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