AG Car: Variability, Extinction, Distance and Luminosity

Abstract

AG Car is one of the few Luminous Blue Variables (LBV’s) in our galaxy. The star is a photometric variable which had a recent outburst in 1981 (Whitelock et al., 1983; Wolf and Stahl, 1982) and is surrounded by a resolved ring nebula (Thackeray, 1950; Paresce, 1989). These properties indicate that AG Car is a typical LBV. However, at its canonical distance of 2-2.5 kpc, derived from its assumed membership of the Car OBI or OB2 association, AG Car has a bolometric luminosity of M _bol -8.5 to -9.0 and is located significantly below the Humphreys-Davidson limit, and also below the upperlimit for red supergiants (RSG). This implies that AG Car might have been a RSG and that the ring might be due to the interaction of the RSG wind and the LBV wind.