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Mass-Losing Semiregular Variable Stars in Baade's Windows | | C.Alard
; J.Blommaert
; C.Cesarsky
; N.Epchtein
; M.Felli
; P.Fouque
; S.Ganesh
; R.Genzel
; G.Gilmore
; I.Glass
; H.Habing
; A.Omont
; M.Perault
; S.Price
; A.Robin
; M.Schultheis
; G.Simon
; J.van Loon
; C.Alcock
; R.Allsman
; D.Alves
; T.Axelrod
; A.Becker
; D.Bennett
; K.Cook
; A.Drake
; K.Freeman
; M.Geha
; K.Griest
; M.Lehner
; S.Marshall
; D.Minniti
; C.Nelson
; B.Peterson
; P.Popowski
; M.Pratt
; P.Quinn
; W.Sutherland
; A.Tomaney
; T.Vandehei
; D.Welch
; | | Date: |
7 Dec 2000 | | Subject: | astro-ph | | Affiliation: | ISOGAL Collaboration), C.Alcock, R.Allsman, D.Alves, T.Axelrod, A.Becker, D.Bennett, K.Cook, A.Drake, K.Freeman, M.Geha, K.Griest, M.Lehner, S.Marshall, D.Minniti, C.Nelson, B.Peterson, P.Popowski, M.Pratt, P.Quinn, W.Sutherland, A.Tomaney, T.Vandehei | | Abstract: | By cross-correlating the results of two recent large-scale surveys, the general properties of a well defined sample of semi-regular variable stars have been determined. ISOGAL mid-infrared photometry and MACHO lightcurves are assembled for approximately 300 stars in the Baade’s Windows of low extinction towards the Galactic bulge. These stars are mainly giants of late M spectral type, evolving along the asymptotic giant branch (AGB). They are found to possess a wide and continuous distribution of pulsation periods and to obey an approximate log~period -- bolometric magnitude relation or set of such relations. Approximate mass-loss rates in the range of 1e-8 to 5e-7 M_sun per year are derived from ISOGAL mid-infrared photometry and models of stellar spectra adjusted for the presence of optically-thin circumstellar silicate dust. Mass-loss rates depend on luminosity and pulsation period. Some stars lose mass as rapidly as short-period Miras but do not show Mira-like amplitudes. A period of 70 days or longer is a necessary but not a sufficient condition for mass loss to occur. For AGB stars in the mass-loss ranges that we observe, the functional dependence of mass-loss rate on temperature and luminosity is found to be in agreement with recent theoretical predictions. If we include our mass-loss rates with a sample of extreme mass-losing AGB stars in the Large Magellanic Cloud, we get the general result for AGB stars that mass-loss rate is proportional to luminosity^{2.7}, valid for AGB stars with 10^{-8} to 10^{-4} M_sun per year (Abridged). | | Source: | arXiv, astro-ph/0101094 | | Services: | Forum | Review | PDF | Favorites | |
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