Using Photometry to Probe the Circumstellar Environment of delta Scorpii

TL;DR

This study uses Johnson BV photometry over multiple years to analyze the inner disk regions of delta Scorpii, revealing disk-building events, cyclical variability, and the impact of variable mass-loss rates.

Contribution

It provides a detailed analysis of delta Scorpii's circumstellar environment using photometry and models to link observed variability to mass-loss rate changes.

Findings

Detected multiple disk-building events and long-term brightening.

Observed cyclical variability with 60-100 day periods.

Modeled mass-loss rate variations reproduce observed brightness changes.

Abstract

We acquired Johnson BV photometry of the binary Be disk system delta~Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V-band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100 days. We were able to reproduce the changes in the magnitude and colour of delta Sco using our theoretical models and found that variable mass-loss rates in the range 2.5-7.0x10^{-9} M_{sun}/yr over ~35 days can reproduce the observed increase in brightness.