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 :