Extremely rare supreoutburst of EG Cnc

Initial call for monitoring posted to vsnet

(vsnet-alert 599)

Visual magnitude estimates by P. Schmeer, Bischmisheim, Germany:

Nov. 21.23  UT, (13.7 ;
     30.917 UT,  12   ;   (low altitude, clouds, wind)
     30.951 UT,  12.0 ;   (clouds, wind, moon nearby)
     30.989 UT,  11.8 ;   (moon nearby)
Sequence:   Hubble GSC 
Instrument: 203-mm SCT

Herewith I wish to report my detection of the first visually observed (confirmed) outburst of EG Cnc, a probable SU UMa-type dwarf with long outburst intervals. The only previously known outburst (apparently a supermaximum) was recorded by Dr. Huruhata; EG Cnc reached a maximum brightness of mpv= 11.9 on 1977 Nov. 12 (IBVS 2401, 2926). The current maximum has been confirmed by Tonny Vanmunster (Belgium), who observed EG Cnc at mv= 12.1 (GSC seq.) on Dec. 1.021 UT. High-speed photometry and spectroscopy are urgently required.


(CVC 115, also vsnet-obs 4461)

EG Cnc [NL/UG:, 11.9v - 17:v]

We have been informed by Patrick Schmeer, Germany about an outburst of EG Cnc. This most interesting object, called Huruhata's Variable, has been seen only once before (in November 1977). A confirmative visual observation has been made by Tonny Vanmunster, Belgium. Here are some details :

1996 Nov. 30.917 UT,  12.5  (P. Schmeer, 0.20-m SCT, Seq: GSC);
     Nov. 30.951 UT,  12.0  (P. Schmeer);
     Nov. 30.989 UT,  11.8  (P. Schmeer);
     Dec. 01.021 UT,  12.1  (T. Vanmunster, 0.35-m refl., seq: GSC);

Given the long recurrence time of this object, it is most likely that this a UGWZ-type dwarf nova. Therefor, follow-up observations at each stage of the light curve are of utmost importance. Time series CCD photometry is highly encouraged.

Tonny Vanmunster

(vsnet-alert 601)

EG Cnc

Congratulations to P. Schmeer on his discovery of a long-awaited outburst of EG Cnc!

Looking back into our record, EG Cnc was suspected to be in outburst last year bt T. Watanabe (vsnet-obs 1398 ). His observation:

> CNCEG          951022.825   134  Wnt.VSOLJ (*1)
> (*1): magnitude based on CCD (V) by Kato.  Wantanabe comments he could see
>       both 12.9, 14.0 stars near EG Cnc in Huruhata's chart.

L. Szentasko (vsnet-obs 1404) reported a negative observation fainter than 14.2 on 1995 Oct. 23.12 UT.

After some discussion with him and his subsequent confirmation of the field, I am fairly confident of the reality of his sighting. If the present bright outburst really turns out to be a superoutburst, Watanabe's sighting may correspond to a short, normal outburst, which suspicion may not contradict Szentasko's negative data.

According to IBVS 2401 (M. Huruhata), the course of the 1977 outburst was as follows.

         UT          mpg
   --------------   ------
   1977 Nov.  9.8   <12.0
             12.8    11.9
             18.8    12.5:
             19.7    12.4
             20.7    12.3
             20.8    12.0
             21.7    12.3
             22.8    12.4
        Dec.  3.8    14.0:
              4.7    14.0:
              6.7   <14.0
              7.9    14.1
              8.7   <14.0
             10.7   <14.0

Looking forward to hearing your successful observations with expectations of the most fruitful closing of the year 1996!

Taichi Kato

Outburst CCD images (courtesy by K. Matsumoto)

VSNET chart (revised)

Detection of superhumps -- A WZ Sge-type dwarf nova?

We obtained a continuous (four hours) CCD V-band light curve of EG Cnc last night. The observed light curve shows superhumps with a low amplitude, approximately between 0.03 and 0.04 magnitude. A preliminary analysis yielded a period of 0.058 day, which is one of the shortest known among dwarf novae.

The long interval of outbursts and the large amplitude support the WZ Sge-type classification of EG Cnc; the observed doubly-humped feature of superhumps strongly suggests that the object was observed in the earlier stage of a superoutburst. Further follow-up observations are encourged.

Katsura Matsumoto (Osaka Kyoiku Universiry, Japan)
e-mail: katsura@quasar.cc.osaka-kyoiku.ac.jp

Development of superhumps

Repeated post-outburst re-brightenings!

EG Cnc - first one?

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