Delta Scorpii is a bright variable of the gamma Cassiopeiae type. The gamma Cas stars are a class of Be stars, which are young, hot, massive stars believed to be rapidly rotating and losing mass. While Be stars undergo small amplitude variations, the gamma Cas variables also undergo occasional outbursts. Delta Sco underwent such an outburst in mid-2000, an event that was recorded for the first time by a visual observer, Sebastian Otero. He was observing delta Sco as part of a project to understand the relationship between his visual observations and the Johnson V bandpass, and alerted the astronomical community to this unique event. Since then, observers around the world have tracked delta Scorpii's variations, both large and small.
You can read more about delta Scorpii and its discovery as a variable in Sebastian Otero's Variable Star of the Season article (English/Español).