Abstract
Is there a stellar upper mass limit? Recent statistical work seems to indicate that there is and that it is in the vicinity of 150 M☉. In this paper we use HST and ground-based data to investigate the brightest members of the cluster Pismis 24, one of which (Pismis 24-1) was previously inferred to have a mass greater than 200 M☉, in apparent disagreement with that limit. We determine that Pismis 24-1 is composed of at least three objects, the resolved Pismis 24-1SW and the unresolved spectroscopic binary Pismis 24-1NE. The evolutionary zero-age masses of Pismis 24-1SW, the unresolved system Pismis 24-1NE, and the nearby star Pismis 24-17 are all ≈100 M☉, very large but under the stellar upper mass limit.
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Footnotes
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This article is based on data gathered with three facilities: the NASA/ESA Hubble Space Telescope (HST), the 6.5 m Magellan Telescopes at Las Campanas Observatory (LCO), and the 2.15 m J. Sahade telescope at Complejo Astronómico El Leoncito (CASLEO). The HST observations are associated with GO program 10602. HST is controlled from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. CASLEO is operated under agreement between CONICET, SeCyT, and the Universities of La Plata, Córdoba and San Juan, Argentina.