The Local Stellar Population of Novae Regions in the Large Magellanic Cloud

The distribution of novae across the face of the Large Magellanic Cloud (LMC) is presented. The star formation history of nearby regions around them is also studied using photometric data of stars and star clusters in the OGLE II survey and star cluster catalogues. The nova population in the LMC belong, predominantly, to the fast category, with only 11.8% belonging to the slow nova population. The distribution of novae shows that most of the novae are located in or near the Bar of LMC, with a high concentration near the south and east of the Bar. All the novae detected within the Bar are fast novae. The age of the stellar population within a few arcmin around novae regions are estimated using isochrone fits to the V vs (V−I) colour-magnitude diagrams. The fraction of stars in various evolutionary states are compared using luminosity functions of the main-sequence stars and the red giant stars. Of the 15 regions studied, excepting the one around the slow nova LMC 1948, all the other regions do not show stellar population in the range 4 – 10 Gyr. In these regions, star formation is found to have started between 4 – 2.0 Gyr, with a majority of regions starting the star formation at 3.2 Gyr. This star formation event lasted until 1.6 – 0.8 Gyr. Based on the star formation history, it is estimated that the parent population of the fast and moderately fast novae are likely to be in the age range 3.2 – 1.0 Gyr. The region around the slow nova shows continuous star formation between 1 – 10 Gyr, with a good fraction belonging to the older population. It is thus likely that the slow nova belongs to an older population. The red clump stars in the LMC are also found to be in the age range of 3.2 – 1.0 Gyr, implying that the parent population of fast and moderately fast novae and the red clump stars are similar. The high concentration of novae seen near the south-east edge of the Bar suggests a higher concentration of the progenitor population in this region. Further, the presence of novae in the vicinity of the Bar as well as within the Bar suggests the Bar is as old as the progenitor population, i.e., at least 4 Gyr old.