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[vsnet-campaign-news 61] AstroAlert: AL Com: extremely rare outburst!
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Extremely Rare Outburst of AL Comae Berenices
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We have been informed by Steve Kerr (Australia) that the WZ Sge-type
dwarf nova AL Com is undergoing an extremely rare outburst. WZ Sge-type
dwarf novae are a subgourp of SU UMa-type dwarf novae, but their
outbursts are extremely rare (typically once in decade), and almost
all outbursts are superoutburst (see MM Hya and precedent issues for
the explanation of superoutburst and superhumps).
The last outburst was in 1995 April, and the last secure outburst of
AL Com before 1995 date back to 1976!! On the occasion of the 1995
superoutburst, an extensive VSNET campaign yielded a very fruitful result,
including detections of so-called "early superhumps", evolution of
superhumps, sudden fade and subsequent recovery, and long fading tail.
The observation was the most extensive one ever made in WZ Sge-type
dwarf novae. AL Com was even selected as the "star of the year" in
1995, at the conference held in the UK next year.
The VSNET Collaboration team has already started another extensive
campaign, which has already most likely covered the early rise to maximum,
which was not observed in 1995! The object may brighten further, and will
be an excellent target for long time-series CCD photometry with small
telescopes. Spectroscopy with large telescopes to catch the signal
of the secondary star, or the structure in the accretion disk, is
also highly encouraged. Happy observing, and please report your progress
to vsnet-campaign-dn, important detections to vsnet-alert and vsnet-campaign.
Raw data should be sent to the campaign coordinator, R. Ishioka
(ishioka@kusastro.kyoto-u.ac.jp) or to vsnet-campaign-data.
AL Com is located close to M88, and was initially discovered as a
possible supernova. Supernova searchers may have to pay attention to
this "new star".
On-line reference:
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/alcom1.html
(this URL only provides likes to the messages in 1995, but will be
useful in determining the strategy on the current outburst).
related papers:
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/AL_Com/
http://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/preprints/AL_Com-2/
Data received up to now:
YYYYMMDD(UT) mag observer
20010509.962 <154 (M. Reszelski)
20010511.922 <139 (E. Muyllaert)
20010511.940 <139 (H. McGee)
20010512.917 <154 (M. Reszelski)
20010512.928 <139 (E. Muyllaert)
20010512.955 <139 (H. McGee)
20010512.960 <155 (C. P. Jones)
20010513.017 <155 (G. Poyner)
20010513.235 <139 (M. Simonsen)
20010513.410 <135 (R. Stubbings)
20010513.501 <139 (H. Itoh)
20010513.939 <148 (P. A. Dubovsky)
20010514.481 <135 (R. Stubbings)
20010514.867 <154 (M. Reszelski)
20010514.887 <148 (P. A. Dubovsky)
20010515.515 <135 (R. Stubbings)
20010516.887 <154 (M. Reszelski)
20010516.917 <139 (E. Muyllaert)
20010516.921 <148 (P. A. Dubovsky)
20010516.965 <155 (G. Poyner)
20010517.898 <154 (M. Reszelski)
20010518.510 134 (S. Kerr)
20010518.882 129 (E. Muyllaert)
20010518.902 128 (C. P. Jones)
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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