# The low wind expansion velocity of metal-poor carbon stars in the Halo and the Sagittarius stream - Astrophysics > Solar and Stellar Astrophysics

The low wind expansion velocity of metal-poor carbon stars in the Halo and the Sagittarius stream - Astrophysics > Solar and Stellar Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: We report the detection, from observations using the James Clerk MaxwellTelescope, of CO J $=$ 3$\to$ 2 transition lines in six carbon stars, selectedas members of the Galactic Halo and having similar infrared colors. Just oneHalo star had been detected in CO before this work. Infrared observations showthat these stars are red J-K $>$3, due to the presence of large dustycircumstellar envelopes. Radiative transfer models indicates that these starsare losing mass with rather large dust mass-loss rates in the range 1-3.3$\times$$10^{-8}$M${\odot}$yr$^{-1}$, similar to what can be observed in theGalactic disc. We show that two of these stars are effectively in the Halo, oneis likely linked to the stream of the Sagittarius Dwarf Spheroidal galaxy SgrdSph, and the other three stars certainly belong to the thick disc. The windexpansion velocities of the observed stars are low compared to carbon stars inthe thin disc and are lower for the stars in the Halo and the Sgr dSph streamthan in the thick disc. We discuss the possibility that the low expansionvelocities result from the low metallicity of the Halo carbon stars. Thisimplies that metal-poor carbon stars lose mass at a rate similar to metal-richcarbon stars, but with lower expansion velocities, as predicted by recenttheoretical models. This result implies that the current estimates of mass-lossrates from carbon stars in Local Group galaxies will have to be reconsidered.

Autor: Eric Lagadec, Albert Zijlstra, Nicolas Mauron, Gary Fuller, Eric Josselin, G.C. Sloan, A.J.E. Riggs

Fuente: https://arxiv.org/