GSC 3693:1720, a new variable near UV Per

On November 10th, 2003, Finish amateur astronomer Arto Oksanen (CBA Finland) announced his discovery of a new variable star, very close to UV Per [cba-news, 10 nov 2003]. The star has GSC identification 3693:1720, and is listed at mag. 10.077 Vt. Arto writes : "... The variability is about 0.05 magnitudes and period is about 0.164 days. The star seems to be either Delta Scuti or Beta Cephei type, both having low amplitude and short period. The final classification will need spectroscopic observations". More information on the object is given by Arto Oksanen on his website.

Upon request of Arto, I started a photometric analysis of GSC 3693:1720 using my UV Per images (in outburst in November 2003, and the direct cause of GSC 3693:1720's variability detection). Below is an overview of my November 2003 CCD observations of GSC 3693:1720. All unfiltered CCD images have been acquired at CBA Belgium Observatory, using an ST-7 CCD and 0.35-m f/6.3 telescope. Photometric conditions were as follows :

2003, November 04/05 : good
2003, November 10/11 : poor (cirrus clouds)
2003, November 11/12 : good
2003, November 14/15 : good

The light curve below (fig. 1) is a compilation of 4 nights of observations, with a total of 2458 datapoints. The detailed light curves of each individual night are presented at the end of this page (fig. 5-8). Using a beta version of a period determination programme, that I have been developing in Visual Basic over the course of the past months (and that is specifically aiming at multi-night / multi-site photometry data reduction), I have calculated the periodicity of GSC 3693:1720 on the basis of the PDM technique (fig. 2) and the Lomb periodogram Fourier analysis (fig. 3). In both cases, I got a value of  0.1531 +/- 0.0004 d, which is still a bit different from the initial value mentioned by Arto (see above). The corresponding phase diagram is shown in fig. 4 and yields an average amplitude of 0.04 mag. 

Belgian amateur-astronomer Patrick Wils, who is a specialist in the analysis of multi-period Delta Scuti stars, commented as follows on our initial GSC 3693:1720 observations : "Given the period and amplitude of the object, it has to be a Delta Scuti variable, or another elliptical variable (e.g., a low inclination EW). The Tycho catalogue lists B-V=0.55 and 2MASS yields J-K=0.27, indicating a (nearly) F5-star, which is again typical for Delta Scuti stars".

Fig. 1 - overall light curve of GSC 3693:1720, consisting of 2458 observations collected at CBA Belgium Observatory.

Fig. 2 - PDM analysis using the above observations, indicating a period of 0.1531 d


Fig. 3 - Lomb periodogram using the same observations, yielding a similar period

Fig. 4 - Phase diagram corresponding to a period of 0.1531 d


The figures below (Fig. 5-8) show the light curves of each individual night.








Copyright © 2003 - Tonny Vanmunster.