A sample of long-period variables in the bar of the Large Magellanic Cloud and evidence for a recent burst of star formation

Infrared JHK photometry and spectral types have been obtained for a sample of long-period variables in, and to the north of, the bar of the LMC. It is found that the carbon stars and the oxygen-rich stars obey different period-luminosity relations. The period-luminosity distribution of the long-period variables in the central bar of the LMC suggests that (1) the bulk of the stars in this region have main-sequence masses Mms ⪉ 1.6 M_sun; and ages ⪆109yr, and (2) there is a distinct group of stars in this region with Mms ≡ 5 - 6 M_sun; and age ≡6×107yr. The period and luminosity distributions of the Cepheid variables in the central LMC bar also suggest that a burst of star formation occurred in the bar of the LMC ≡6×107yr ago.