Delta Scorpii 2011 periastron: worldwide observational campaign and preliminary photometric analysis

TL;DR

This paper reports on a global observational campaign of Delta Scorpii during its 2011 periastron, revealing irregular luminosity variations possibly caused by interactions between the binary stars.

Contribution

It presents the first preliminary photometric analysis of Delta Scorpii during its 2011 periastron, highlighting observed luminosity irregularities and potential shock phenomena.

Findings

Irregular luminosity behavior observed during periastron

Small luminosity increase detected on July 5, 2011

Potential shock interactions between the stars inferred

Abstract

Delta Scorpii is a double giant Be star in the forefront of the Scorpio, well visible to the naked eye, being normally of magnitude 2.3. In the year 2000 its luminosity rose up suddenly to the magnitude 1.6, changing the usual aspect of the constellation of Scorpio. This phenomenon has been associated to the close periastron of the companion, orbiting on a elongate ellipse with a period of about 11 years. The periastron, on basis of high precision astrometry, is expected to occur in the first decade of July 2011, and the second star of the system is approaching the atmosphere of the primary, whose circumstellar disk has a H-alpha diameter of 5 milliarcsec, comparable with the periastron distance. The preliminary results of a photometric campaign, here presented in the very days of the periastron, show an irregular behavior of the star's luminosity, which can reflect some shocks between material around the two stars. The small luminosity increasement detected in the observation of 5 of July 2011 at 20 UT may suggest that the periastron phenomena are now going to start.