The earliest recorded eruption of luminous blue variables in Messier 33

Abstract

Luminous blue variables (LBVs) are extremely massive, evolved stars that can experience highly erratic instabilities and outbursts. During an eruption, they are capable of temporarily being the brightest star in their host galaxy. By careful examination of two drawings of Messier 33 (M33) made in 1850–1851 and 1857, the currently well-known LBVs Variable B and Variable 83 have been found. The drawings show that Variable 83 was visible on both while Variable B had faded below detection on the second. Comparing the limiting magnitude of the stars plotted on the earlier drawing indicates that Variable B was near the brightest it has ever been measured at while Variable 83 was experiencing a brighter eruption than has since been recorded. These are the first known recorded observations of an LBV in any galaxy beyond the Milky Way.