delta Scorpii 2011 Periastron: Visual and Digital Photometric Campaign (Poster abstract)

Volume 40 number 1 (2012)

Costantino! Sigismondi Sapienza

University of Rome and CIRA, International Center for Relativistic Astrophysics, Rome, Italy; costantino.sigismondi@gmail.com

Abstract

(Abstract only) Approximately a hundred observations of d Scorpii, from April to September 2011, made for the 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 d Sco, a spectroscopic double star, experienced a close periastron in July 2011 within the outer atmospheres of the two giant components. The whole luminosity of d Sco 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 magnitude occuring over 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.