Massive Star Content of OB association Lucke-Hodge 41 (NGC 1910) in the Large Magellanic Cloud

The Large Magellanic Cloud's (LMC) rich OB association LH41 (NGC 1910) is home to an abundance of O and B type stars, as well S Doradus, the prototypic Luminous Blue Variable, a surprising number of Wolf-Rayet stars, and interesting evolved supergiants. LH41 is the second most active star forming region in the LMC after the famous 30 Doradus, and like its big cousin, is a hotbed for young, massive stars. We have studied this association with HST UV imaging, B- and V-band ground-based photometry, and Magellan 6.5-m optical spectroscopy to determine the massive star content and age of the association. Spectroscopy and modeling using FASTWIND yielded spectral types and effective temperatures for select O and B stars in LH41. This allowed us to apply bolometric corrections to our photometric data and get luminosities and temperatures of the remaining LH41 stars. We eliminated foreground stars using astrometric data from GAIA DR2. The resulting HR Diagram shows a large age spread of O and B type stars, as well as a significant number of evolved supergiants, indicating that LH41 is not strictly coeval. Our findings challenge the current understanding of OB associations as temporary collections of young, hot stars. This work was supported by the National Science Foundation (AST-1852478 and AST-1612874), and by NASA/Space Telescope Science Institute (GO-14707, GO-12940).