The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit - Astrophysics > Solar and Stellar Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Spectroscopic analyses of H-rich WN5-6 stars within the young star clustersNGC 3603 and R136 are presented, using archival HST and VLT spectroscopy, and highspatial resolution near-IR photometry. We derive high T* for the WN stars inNGC 3603 T*~42+-2 kK and R136 T*~53+-3 kK plus clumping-corrected dM-dt ~2-5x10^-5 Msun-yr which closely agree with theoretical predictions. These starsmake a disproportionate contribution to the global budget of their hostclusters. R136a1 alone supplies ~7% of NLyC of the entire 30 Dor region.Comparisons with stellar models calculated for the main-sequence evolution of85-500 Msun suggest ages of ~1.5 Myr and M init in the range 105 - 170 Msun for 3systems in NGC 3603, plus 165-320 Msun for 4 stars in R136. Our high stellarmasses are supported by dynamical mass determinations for the components of NGC3603 A1. We consider the predicted L X of the R136 stars if they were close,colliding wind binaries. R136c is consistent with a colliding wind binarysystem. However, short period, colliding wind systems are excluded for R136a WNstars if mass ratios are of order unity. Widely separated systems would havebeen expected to harden owing to early dynamical encounters with other massivestars in such a dense environment. From simulated star clusters, whoseconstituents are randomly sampled from the Kroupa IMF, both clusters areconsistent with a tentative upper mass limit of ~300 Msun. The Arches clusteris either too old, exhibits a deficiency of very massive stars, or more likelystellar masses have been underestimated - M init for the most luminous stars inthe Arches cluster approach 200 Msun according to contemporary stellar andphotometric results. The potential for stars greatly exceeding 150 Msun withinmetal-poor galaxies suggests that such pair-instability SNe could occur withinthe local universe, as has been claimed for SN 2007bi abridged.



Autor: Paul A Crowther Sheffield, Olivier Schnurr Sheffield, AIP, Raphael Hirschi Keele, Tokyo, Norhasliza Yusof Malaya, Richard J Parke

Fuente: https://arxiv.org/







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