Delta Scorpii 2011 periastron: visual and digital photometric campaign

TL;DR

This study presents a detailed photometric campaign of Delta Scorpii during its 2011 periastron, demonstrating the effectiveness of digital and visual observations in capturing luminosity variations and rapid fluctuations in bright variable stars.

Contribution

It introduces a differential photometry method using CMOS cameras for bright stars, highlighting its potential for monitoring stellar variability during close stellar encounters.

Findings

Delta Scorpii's luminosity increased from Mv=1.8 to 1.65 during periastron.

Detected rapid brightness fluctuations of 0.2-0.3 magnitudes over 20 days.

The method shows promise for studying other bright variable stars like Betelgeuse and Antares.

Abstract

Hundred observations of Delta Scorpii, from April to September 2011, made for AAVSO visually and digitally with a commercial CMOS camera have been plotted. The three most luminous pixels either of the target star and the two reference stars are used to evaluate the magnitude through differential photometry. The main sources of errors are outlined. The system of Delta Scorpii, a spectroscopic double star, has experienced a close periastron in July 2011 within the outer atmospheres of the two giant components. The whole luminosity of Delta Scorpii increased from about Mv=1.8 to 1.65 peaking around 5 to 15 July 2011, but there are significant rapid fluctuations of 0.2-0.3 magnitudes occuring in 20 days that seem to be real, rather than a consequence of systematic errors due to the changes of reference stars and observing conditions. This method is promising for being applied to other bright variable stars like Betelgeuse and Antares.