Mass-losing semiregular variable stars in Baade's windows

C. Alard, J. A.D.L. Blommaert, C. Cesarsky, N. Epchtein, M. Felli, P. Fouque, S. Ganesh, R. Genzel, G. Gilmore, I. S. Glass, H. Habing, A. Omont, M. Perault, S. Price, A. Robin, M. Schultheis, G. Simon, J. Th Van Loon, C. Alcock, R. A. AllsmanD. R. Alves, T. S. Axelrod, A. C. Becker, D. P. Bennett, K. H. Cook, A. J. Drake, K. C. Freeman, M. Geha, K. Griest, M. J. Lehner, S. L. Marshall, D. Minniti, C. Nelson, B. A. Peterson, P. Popowski, M. R. Pratt, P. J. Quinn, W. Sutherland, A. B. Tomaney, T. Vandehei, D. L. Welch

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52 Citations (Scopus)


By cross-correlating the results of two recent large-scale surveys, the general properties of a well-defined sample of semiregular variable stars have been determined. ISOGAL mid-infrared photometry (7 and 15 μm) and MACHO V and R light curves are assembled for approximately 300 stars in the Baade's windows of low extinction toward 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 P-Mbo1 relation or set of such relations. Approximate mass-loss rates Ṁ in the range of ∼1 × 10-8 to 5 × 10-7 M⊙ yr-1 are derived from ISOGAL mid-infrared photometry and models of stellar spectra adjusted for the presence of optically thin circumstelkr silicate dust. Mass-loss rates depend on luminosity and pulsation period. Some stars lose mass as rapidly as short-period Mira variables but do not show Mira-like amplitudes. A period of 70 days or longer is a necessary but not 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 can be expressed as Ṁ ∝ TαLβ, where α = -8.80+0.96-0.24 and β = +1.74+0.16-0.24, 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 and ignore T as a variable, we get the general result for AGB stars that Ṁ ∝ L2.7, valid for AGB stars with 10-8 < Ṁ < 10-4 M yr-1.

Original languageEnglish
Pages (from-to)289-308
Number of pages20
JournalAstrophysical Journal
Issue number1 PART 1
Publication statusPublished - 1 May 2001

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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