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[vsnet-campaign-news 58] AstroAlert: MM Hya: probable superoutburst of a dwarf nova
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Probable Superoutburst the dwarf nova MM Hya
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Rod Stubbings and Andrew Pearce (Australia) reports that the SU UMa-type
dwarf nova MM Hya = PG 0911-066 is undergoing a rare, bright outburst.
The reported brightness (13.0 mag) suggests that the present outburst
is a superoutburst. MM Hya is known as a ultra-short period cataclysmic
binary, and show infrequent outbursts. Time-resolved photometry with CCD
will be able to catch "superhumps" which are the signature of a
superoutburst. Superhumps are small-amplitude (0.1-0.3 mag) variations
with a period slightly longer than the binary orbital period.
Observations of superhumps will tell much about the nature of the binary
system, structure of the accretion disk, and the mechanism of outburst
and superoutburst.
In the case of MM Hya, a continuous run of 2-3 hours in the evening
(take as many exposures as possible starting in the evening twilight;
the recommended exposure time is 20-60 seconds, depending on the telescope
aperture). Please continue the observation until MM Hya fades away,
probable 10-15 days after this alert.
MM Hya is located at 09h 14m 13.97s, -06o 47' 45.0" (J2000.0)
For more information of superhumps, see
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/CVs/suumas.html
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/superhump.html
We have been undertaking on photometric campaigns on several super-
outbursting dwarf novae and peculiar variable stars. News and call for
observations on these objects will be issued on our regular weekly
"News from VSNET" bulletins. Those who immediately need information
should make an access to the VSNET website, and click on VSNET campaign
list.
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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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