2012A&A...543A..18L -
Astronomy and Astrophysics, volume 543A, 18-18 (2012/7-1)
O-star mass-loss rates at low metallicity.
LUCY L.B.
Abstract (from CDS):
Mass fluxes J are computed for the extragalactic O stars investigated by Tramper et al. (
2011ApJ...741....8C, TSKK). For one early-type O star, computed and observed rates agree within errors. However, for two late-type O stars, theoretical mass-loss rates underpredict observed rates by ∼1.6dex, far exceeding observational errors. A likely cause of the discrepancy is overestimated observed rates due to the neglect of wind-clumping. A less likely but intriguing possibility is that, in observing O stars with Z/Z
☉∼1/7, TSKK have serendipitously discovered an additional mass-loss mechanism not evident in the spectra of Galactic O stars because of their powerful radiation-driven winds. Constraints on this unknown mechanism are discussed. In establishing that the discrepancies, if real, are inescapable for purely radiation-driven winds, failed searches for high-J solutions are reported and the importance stressed of a numerical technique that cannot spuriously create or destroy momentum. The Z-dependences of the computed rates for Z/Z
☉∈(1/30,2) show significant departures from a single power law, and these are attributed to curve-of-growth effects in the differentially expanding reversing layers. The best-fitting power-law exponents range from 0.68-0.97.
Abstract Copyright:
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Journal keyword(s):
stars: early-type - stars: mass-loss - stars: winds, outflows
Simbad objects:
8
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