New dwarf nova ASAS 023322-1047.0 - detection of early superhumps

 
Dwarf nova ASAS 023322-1047.0 (Cet) was discovered on 2006, Jan 20.121 UT at mag V= 12.08, using the ASAS3V instrument, by B. Pilecki, Warsaw University Astronomical Observatory. The object is located at RA: 02h33m21.4s and Decl.: -1047'04.6" (J2000), hence quite unfavourable as seen from Belgium (50 North).
 

CBA Belgium observations dd 2006, Jan 23/24

I started a time-series (unfiltered) CCD photometry session of this target on Jan 23.72 UT, using a 0.35-m f/6.3 telescope and ST-7XME camera at CBA Belgium Observatory. The session lasted for 3.6 hours, and shows the presence of a weak periodic signal, that might indicate the emergence of early superhumps, although still unsure at this moment. The linear trend of decline has been removed from the light curve below. 

 
A period analysis using Peranso's ANOVA method, yields a period of 0.055 +/- 0.005 d, with an amplitude of about 0.1 mag. If this signal relates to early superhumps, it would be amongst the shortest presently known. The object faded by approx. 0.04 mag over the course of my session. A period significance analysis, using a Fisher Randomization Test (with 200 Monte Carlo permutations), yields a false alarm probability close to 0%, hence indicating that the above signal is quite likely secure. 

 
CBA and AAVSO observations of the Early Superhump Stage

Following the above announcement, I received additional CCD observations of ASAS 023322-1047.0 from Tom Krajci, David Boyd, Berto Monard, Michael Armstrong, Tim Crawford and Diego Rodriguez Perez. Our dataset now comprises a total of 2222 observations, covering a time span of 5.8 days, i.e. the entire initial outburst stage.


Combined light curve (zero-averaged, detrended) with observations from Tom Krajci (black), 
David Boyd (red), Berto Monard (purple), Michael Armstrong (green), Tim Crawford (gray)
Diego Rodriguez Perez (aqua) and Tonny Vanmunster (blue)

A period analysis using the ANOVA method (Peranso) reveals a dominant signal at 0.05485 +/- 0.00026 d, that is clearly showing the signature of double-peaked "early superhumps". The average amplitude is just below 0.05 mag. I have created a phase diagram, folding all observations over the above mentioned period, and I then averaged the data per 10 observations. The resulting phase diagram is very nicely revealing the early superhump. Amazing to see how much detail we can derive by joining the observation sets of individual observers, taking into account that each session was relatively short.


ANOVA Period Window showing dominant signal at 0.054851 d


Phase Diagram created by folding all observations over a period of
0.054851d, then averaged per 10 obs. Double-peaked early superhumps clearly visible.

 
The object meanwhile has entered a next outburst stage

   

 
 

 

 

Copyright © 2006 - Tonny Vanmunster.