The 2001 Superoutburst of AL Com

(Light curve of AL Com superoutburst 2001. The magnitude scale is adjusted to that of Kyoto system. (preliminary result))

Outburst detection on May 18

(vsnet-outburst 2251)

AL Com appears to be visible tonight,

COMAL 20010518.51 13.4

25cm Newtonian 180X.

Steve Kerr - RASNZ = Kf

(Combined CCD image of AL Com obtained at Brno by P. Sobotka and R. Novak)

(CCD images of AL Com on May 18, 19 and 20 by the Kyoto team with 25-cm Schmidt-Cassegrain telescope + SBIG ST-7 CCD camera)

(vsnet-alert 5891)

As Steve Kerr reported in [vsnet-outburst 2251], the WZ Sge-type dwarf nova AL Com is undergoing a rare outburst ( ~13.3mag). The last outburst of AL Com was observed in 1995 April. We started the observation of this object at 16:00 May 18 (UT).
Follow-up time-series observations are strongly encouraged.

VSNET Collaboration team

Early superhump!

(Averaged early superhumps observed on May 19 by Kyoto team.)

(Averaged early superhumps observed on May 19, 20, 21, and 22 by VSNET collaboration team.)

(vsnet-alert 5901)

AL Com early superhumps are evolving!

Dear Colleagues,

A quick look at the partially analyzed data of May 19 (vsnet-alert 5897) shows that there is a clear signature of evolving early superhumps. The outburst is thus very likely a superoutburst of a WZ Sge-type dwarf nova caught at the earliest stage (probably the earliest ever observed). The amplitude of variation is still small. At the same time, the object is slowly fading. We will report later as the analysis becomes more complete.

Looking forward to hearing your successful observations!

VSNET Collaboration team

(vsnet-alert 5906)

AL Com early superhumps and decline

Dear Colleagues,

More analysis (still ongoing) of the May 19 data has revealed the rapid fading at a rate of 0.80 mag/d. Early superhumps are present, as already reported. The best period from the presently available data is very slightly shorter than the orbital period, but the difference is marginally within errors of respective measurements. This observation may be the first indication of "negative superhumps" in the earliest stage of WZ Sge-type superoutburst. The full amplitude of early superhumps is 0.04-0.05 mag, and humps are singly peaked. This makes striking contrast to early superhumps observed in the 1995 superoutburst. This may be an indicatation that we are witnessing the earlier stage of evolution of these humps than in 1995. More detailed analysis will be later presented by Ishioka-san et al. Intensive observations are very encouraged.

Taichi Kato
VSNET Collaboration team

(vsnet-campaign 920)

Dear Colleagues,

Combined the data kindly sent to the VSNET collaboration team (vsnet-campaign 918), we have performed preliminary analysis of these early obsevations.
We performed period analysis using May 19 data (the Kyoto team and the R. Novak & P. Sobotka) and May 20 data (the Kyoto team), and obtained the best candidate of the period of early superhumps of 0.05673 (8) d which is consistent with the orbital period within its error. The profile has double peaks (~0.1mag) per one period. The light curve by R. Novak and P. Sobotka clearly shows this feature. The double-peak profile can be also sometimes seen in the Kyoto data, but not constantly. This may imply that the amplitude of these humps are variable.
The light curve on May 20 taken by R. Novak & P. Sobotka shows a relatively large (~0.2mag) hump with a single peak. The phase of this peak is quite different from that of earlier humps, so we should consider these have an essentially different nature. According to the light curve on May 21 by Gary W. Billings and R. Novak & P. Sobotka, this large hump seems to be diminished and the light curve has become more smooth, and no prompt periodic variations are not seen.
The object is now gradually faded with 0.08mag/d. We will see the evolution of normal superhumps within these days, so follow-up obsevations are strongly urged.

M. Uemura, R. Ishioka, T. Kato, R. Novak, P. Sobotka, and G. W. Billings
on behalf of the VSNET AL Com collaboration team

Normal superhump!!

(Left: growing superhumps observed on May 28. Right: averaged superhump profile during May 30 - June 2)

(vsnet-alert 5904)

AL Com superhumps are growing!

Dear Colleagues,
The waited superhumps of AL Com are coming! The data on May 28 at Kyoto clearly show the evolution of superhumps. More detailed analysis will be presented by Ishioka-san and Uemura-san et al.

VSNET Collaboration team

Rapid fading!!!

(CCD images taken at Kyoto on June 2 and June 11, showing the sudden fading of AL Com (marked))

(vsnet-alert 5972)

AL Com: rapidly decline!!

Dear colleagues,

Our yesterdays observation shows that AL Com is rapidly fading. Its magnitude is ~16.7 mag. At 8 June, the object was still bright at ~14.8 mag. So the decline rate during these three days is ~0.6 mag/day (before 8 June, the decline rate was ~0.1 mag/day).
AL Com was 14.7 at 10.949 June (UT) in the report of visual observations from Gary Poyner. Probably, the rapid decline occured during 10.949 and 11.5 (UT): 24 dars after the onset of the current outburst. In the 1995 outburst, another long lasting outburst started following the rapid decline 28 days after the the onset of the outburst.
More observations in this phase are strongly needed.

Ryoko Ishioka
VSNET Collaboration team

Recovering from the temporal dip !!!!

(vsnet-alert 5978)

AL Com rapid recovery again!

The short duration of the temporary fading strongly suggests that the object is entering a stage of the second superoutburst (if it follows the course of the 1995 superoutburst). Observations at this stage is extremely important. Please make time-resolved photometry as long as possible.

VSNET Collaboration team

From: (Jochen Pietz)
Subject: [vsnet-campaign-dn 900] RE: AL Com: rapidly decline!!

Results from the last two nights:

2001-06-12.879 17.0C:
2001-06-13.883 15.5C

Jochen Pietz

VSNET Campaign News about AL Com
Alert of the Outburst
Early Phase Activity
Impressive Image and Successful Observing Campaign
Normal Superhump Evolution
Rapid Fading
Rapid Recovery

VSNET light curve (requires Java)

Light curve

VSNET data search



Initial letter on AL Com/WZ Sge 2001 by the VSNET Collaboration (Ishioka et al.) Initial letter on AL Com/WZ Sge 2001 by the VSNET Collaboration (Ishioka et al.) (PDF)

The 1995 super outburst

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