Stellar Winds and Circumstellar Envelopes

The velocity structure, mass loss rate, and ionization of the outflowing gas in late-type giants and supergiants can be inferred from high resolution spectra of optically thick lines in ultraviolet spectra and thermal radio emission. We are now developing wind models for hybrid-chromosphere stars and M supergiants. The winds of main sequence stars like the Sun are now being studied for the first time by analysis of Lyman alpha absorption produced in their astrospheres by the interaction of the stellar wind with the interstellar gas. The figure on the left shows the extra absorption by hydrogen in the astrosphere of Alpha Centauri B (K1 V) compared to Proxima Centauri (dM6e) that shows that the mass loss rate for Alpha Centauri B is much larger than for Proxima Centauri. Absorption by interstellar deuterium is seen toward both stars. Ultraviolet spectra of fluoresced molecular hydrogen in the circumstellar disks of T Tauri stars are providing new understanding of these circumstellar regions.

Research Objectives:

• Measure the mass loss rates for solar-like stars from Lyman alpha absorption in their astrospheres.
• Analyze high resolution stellar UV and far-UV spectra obtained with the GHRS and STIS instruments on HST and the FUSE satellite.
• Determine the physical properties and velocity structure of the winds of late-type giants, supergiants, and pre-main sequence stars
• Understand and model emission line of molecular hydrogen and other fluoresced molecules in the disks of T Tauri stars.
• Analyze and model the thermal radio emission from late-type giants and supergiants.

Recent Publications:

• Wood, Brian E., Izmodenov, Vladislav V., Linsky, Jeffrey L., and Alexashov, Dimitry: 2007, "Dependence of Heliospheric Ly-alpha Absorption on the Interstellar Magnetic Field", Astrophysical Journal, 659, 1784
• Wood, Brian E., Izmodenov, Vladislav V., Linsky, Jeffrey L., and Malama, Yuri G.: 2006, "Lyman-alpha absorption from heliosheath neutrals", Astrophysical Journal, 657, 609
• Herczeg, G.J., Linsky, J.L., Walter, F.M., Gahm, G.F., and Johns-Krull, C.M.: 2006, "The origins of fluorescent H2 emission from T Tauri stars", Astrophysical Journal Supplement Series, 165, 256
• Wood, B.E., Mueller, H.-R., Zank, G.P., Linsky, J.L., and Redfield, S.: 2005, "New mass loss measurements from astrospheric Ly$\alpha$ absorption", Astrophysical Journal Letters, 628, L143
• Wood, Brian E., Redfield, Seth, Linsky, Jeffrey .L., Muller, Hans-Reinhard, and Zank, Gary P.: 2005, "Stellar Lyman-alpha emission lines in the Hubble Space Telescope Archive: Intrinsic line fluxes and absorption from the heliosphere and astrospheres", Astrophysical Journal Supplements, 159, 118
• Herczeg, G.J., Walter, F.M., Linsky, J.L., Gahm, Gosta, Ardila, D.R., Brown, A., Johns-Krull, C.M., Simon, M., and Valenti, J.A.: 2005, "The loopy UV line profiles of RU Lupi: accretion, outflows, and fluorescence", Astronomical Journal, 129, 2777
• Wood, B.E., Muller, H.-R., Zank, G.P., Izmodenov, V.V., and Linsky, J.L.: 2004, "The heliospheric hydrogen wall and astrospheres", Advances in Space Research, 34, 66
• Wood, B.E., Redfield, S., Linsky, J.L., Muller, H.-R., and Zank, G.P.: 2004, "The winds of solar-like main sequence stars" in Proc. 13th Cool Stars Workshop, ed. F. Favata et al. ESA SP-560, 309
• Linsky, J.L. and Wood, B.E.: 2004, "Hydrogen walls: Mass loss of dwarf stars and the young Sun" in The Sun and the Heliosphere as an Integrated System, ed. S.T. Suess and G. Poletto, Kluwer Academic Publishers, in press
• Herczeg, G.J., Wood, B.E., Linsky, J.L., Valenti, J.A., and Johns-Krull, C.M.: 2004, "The FUV spectrum of TW Hya. II. Models of H2 fluorescence in a disk", Astrophysical Journal, 607, 369
• Linsky, J.L. and Wood, B.E.: 2003, "Measuring stellar mass loss rates at the femto level", Space Telescope Science Institute Newsletter, 20, issue4, p.18
• Wood, B.E., Linsky, J.L., Muller, H.-R., and Zank, G.P.: 2003, "A search for Lyman-alpha emission from the atmosphere of 40 Eridani A", Astrophysical Journal, 591, 1210
• Linsky, J.L., Wood, B.E., Muller, H.-R., and Zank, G.P.: 2003, "Measurements of the winds of solar-like stars and their influence on extrasolar planets", in Toward other Earths: DARWIN/TPF", ESA-539, 507
• Linsky, J.L., Wood, B.E., Muller, H.-R., and Zank, G.P.: 2003, "Winds of late-type stars -- Observational constraints", in Modelling of Stellar Atmospheres, IAU Symposium No. No. 210, ed. N.E. Piskunov, W.W. Weiss, and D.F. Gray, Astronomical Soc. Pacific, F14
• Bennett, P.D., Harper, G.M., Brown, A., and Linsky, J.L.: 2003, "NLTE radiative transfer in the extended atmospheres and winds of cool stars", in Modelling of Stellar Atmospheres, IAU Symposium No. No. 210, ed. N.E. Piskunov, W.W. Weiss, and D.F. Gray, Astronomical Soc. Pacific, 93
• Wood, B.E., Muller, H.-R., Zank, G.P., and Linsky, J.L.: 2002, "Measured mass loss rates of solar-like stars as a function of age and activity", Astrophysical Journal, 574, 412
• Herczeg, G.J., Linsky, J.L., Valenti, J.A., Johns-Krull, C.M., and Wood, B.E.: 2002, "The FUV spectrum of TW Hya. I. Observations of H2 fluorescence", Astrophysical Journal, 572, 310
• Herczeg, G.J., Linsky, J.L., Johns-Krull, C., and Valenti, J.: 2001, "Highly Excited UV H2 Emission around TW Hya", Young Stars Near the Earth: Progress and Prospects, ed. R. Jayawardhana and T. Greene, APS Conf. Series, 244, 265
• Harper, G.M., Wilkinson, E., Brown, A., Jordan, C., and Linsky, J.L.: 2001, "Identification of FeII emission lines in FUSE stellar spectra", Astrophysical Journal, 551, 486
• Grady, C.A., Devine, D., Woodgate, B., Kimble, R., Bruhweiler, F.C., Boggess, A., Linsky, J.L., Plait, P., Clampin, M., and Kalas. P.: 2001, "STIS coronographic imaging of the Herbig Ae star: HD 163296", Astrophysical Journal, 544, 895
• Wood, B.E., Linsky, J.L., Mueller, H.R., and Zank, G.P.: 2001, "Observational estimates for the mass-loss rates of Alpha Centauri and Proxima Centauri using HST Lyman Alpha spectra", Astrophysical Journal Letters, 547, L49
• Linsky, J.L., Harper, G.M., Valenti, J., Bennett, P.D., and Brown, A.: 2000, "Inferring mass loss rates from cool luminous stars from high-resolution GHRS spectra", in The Carbon Star Phenomenon, ed. R.F. Wing (Dordrecht: Kluwer), p. 303