DSLR Photometry of the High Amplitude delta Scuti Stars V1338 Centauri, V1430 Scorpii and V1307 Scorpii

Presented by Roy Axelsen

V1338 Centauri, V1430 Scorpii and V1307 Scorpii are high amplitude delta Scuti stars for which the last period determinations were made in 2006, 2004 and 2001 respectively. In view of the elapse of time since, DSLR photometry was taken from April to August 2015. Fourier analysis with the software PERIOD04 identified the dominant frequencies of pulsation to be 7.6372 +/- 0.0001 c/d (cycles/day), 11.93629 (+/- 0.00004) c/d and 8.54475 (+/- 0.0007) c/d respectively, corresponding to periods similar to those found by other authors. For all three stars, additional harmonic frequencies were found, integer multiples of each of the dominant oscillations, representing the extent to which the light curves are skewed from pure sinusoids. Furthermore, an additional low amplitude frequency of 18.4335 (+/- 0.0008) c/d was identified for the star V1430 Sco, which is a new discovery. Subtle shoulders were identified on the descending limbs of the light curves of V1338 Cen and V1430 Sco. Precise times of the peaks of the light curves were calculated with the software PERANSO. Using these times of maximum and those reported previously in the literature, new linear ephemerides were calculated, yielding the following periods, similar to those reported by other authors, but now with greater precision: 0.13093808 (+/- 0.00000003) d for V1338 Cen, 0.08377709 (+/- 0.00000001) d for V1430 Sco, and 0.11703066 (+/- 0.00000001) d for V1307 Sco. High-amplitude delta Scuti stars are suitable objects for study by amateur astronomers, who can make significant contributions to the literature using modest equipment.