V883 Sco Period determination

Presented by Mark Blackford, Neil Butterworth and Tom Richards

In 2015 Neil Butterworth attempted to record eclipses of V833 Scorpii however predicted eclipse times using the accepted 1.29484 day period and HJD 2443285.794 epoch were clearly wrong. In order to determine the correct period we needed a large set of homogeneous, high quality observations recorded over several years. The All Sky Automated Survey is an excellent source of such observations for stars between V magnitudes 6 and 12, or so. Data for V833 Sco from the ASAS archive was imported into David Benn’s excellent VStar light curve plotting and analysis software. After rejecting several obviously discrepant data points (possibly due to clouds or image artifacts), the Discrete Fourier Transform algorithm in VStar was employed to find candidate periods. The strongest signal from the DFT analysis was for a period of 2.1706 d, however this produced a folded light curve with two overlapping eclipses. Replotting with period twice that (4.3412 d) worked very well, showing slightly shallower secondary eclipses offset from the midpoint between successive primary eclipses. This period was further refined to 4.341164(11) d using data from INTEGRAL-OMC and Neil’s DSLR observations.