The December 2003 superoutburst of TY Vul

Informal joint CBA-AAVSO Campaign

Contributing observers :

Dave Messier (CBA Connecticut)
Keith Graham (AAVSO)
Arne Henden (USNO Flagstaff)
David Boyd (BAA VSS, AAVSO)
Arto Oksanen (CBA Finland)
Tonny Vanmunster (CBA Belgium)

TY Vul is a little studied dwarf nova. It was last seen in outburst in 1999, when P. Schmeer reported the object on September 1st [vsnet-alert 3436] at unfiltered mag 15.7. It had not been seen anymore since it was studied in 1980 by Meinunger [Veröff. Sternwarte Sonneberg, 9, 197].  The variable reached a maximum magnitude of  V=14.6 on September 1st, 1999. It rapidly faded on the night of September 2nd, 1999 [IBVS 4787]. On subsequent nights, the object could no longer be distinguished from USNO 1125.16991372, an optical binary of TY Vul.

On December 02.063 UT, 2003, TY Vul was detected in outburst by P. Schmeer, who reported an unfiltered magnitude of 14.9. Given the unkown characteristics of TY Vul, the object was immediately promoted a high-priority target by the CBA and AAVSO. Thanks to the multi-longitudinal coverage of the variable, resulting from this campaign, relatively good datasets are being obtained, despite the quite unfavourable location of TY Vul in the December evening skies.

Dave Messier (CBA Connecticut) was the first to report the detection of superhumps in TY Vul (cba-news dd. 04 Dec 2003), hence establishing this variable as a new member of the UGSU-type dwarf novae.  Figure 1 below shows a compilation of 1067 CCD observations of TY Vul, collected by the observers listed on the top of this page. Keith Graham, David Boyd and Arne Henden obtained filtered observations, while Dave Messier, Arto Oksanen and Tonny Vanmunster worked unfiltered. 


Fig. 1 - overall light curve of TY Vul ('zero averaged')

Using this dataset and a period determination program, that I have been developing in Visual Basic over the course of the past months (aimed at multi-night / multi-site photometry data reduction), I have calculated the average superhump period of TY Vul on the basis of the PDM technique (fig. 2) and the Lomb periodogram Fourier analysis. In both cases, I got a value of  0.0804 +/- 0.0001 d. The corresponding phase diagram is shown in fig. 3 and yields an average amplitude of 0.40 mag.

As one may easily conclude from the overall light curve of Fig. 1, the superhump amplitude started to decrease quite significantly around JD +2984, corresponding with the decline stage of the outburst.  By JD +2986.3 (Dec 12), the amplitude was merely 0.095 mag. 

Splitting the observing interval in 2 equally long sections, we observe following evolution in the average superhump period and  average amplitude :

JD Start

JD End

Avg Psh

Avg Ampl



0.0807 +/- 0.0002d

0.34 mag



0.0800 +/- 0.0002d

0.40 => 0.095 mag

+2977.0 +2986.5 0.0804 +/- 0.0001d -

This indicates that the superhump period Psh is showing a 'typical' decrease over the entire observing period, consistent with other UGSU-type dwarf novae.

Fig. 2 - PDM analysis using the above observations, indicating an average Psh of 0.0804 d


Fig. 3 - Average Phase diagram corresponding to a period of 0.0804 d





Copyright © 2003 - Tonny Vanmunster.