Stellar Winds and Circumstellar Envelopes

We have developed the astrospheres technique for infering the mass-loss rate of cool main sequence stars based on the analysis of Lyman-alpha absorption produced where the stellar wind interacts 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), which 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 STIS, COS and GHRS 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 lines 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.

Important Results and Discoveries:

• Developed a new technique for measuring the mass-loss rates of G-M stars using the excess absorption on the blue side of interstellar absorption in the Lyman-alpha line. This provided the first measurements of mass-loss rates from dwarf stars. The results of this technique are widely used to study stellar winds and text theoretical models.
• Determined the first scaling relation between stellar mass-loss rate and X-ray surface flux.
• Showed that the many molecular hydrogen emission lines in the ultraviolet spectra of T Tauri stars are produced by fluorescence driven mostly by the stellar Lyman-alpha line. In some T Tauri stars the pumping molecular hydrogen lines are seen in absorption against the Lyman-alpha emission line.
• Wrote several review papers and book chapters on stellar winds.

Papers published in refereed journals since 2000:

• Herbst, K., Baalmann, L.R., Bykov, A., Linsky, J.L., et al.: 2022, " Astrospheres of Planet-Hosting Cool Stars and Beyond ⋅ When Modeling Meets Observations", Space Science Reviews, 218, 29
• Wood, B.E., Muller, H.-R., Redfield, S., Konow, F., Vannier, V., Linsky, J.L., et al.: 2021, "New Observational Constraints on the Winds of M dwarf Stars", Astrophysical Journal, 915, 37
• Ardila, D.R., Herczeg, G.J., Linsky, J.L. et al.: 2013, "Hot gas lines in T Tauri stars", Astrophysical Journal Supplement Series, 207, 1
• France, K., Schindhelm, E., Linsky, J.L. et al.: 2012, "A Hubble Space Telescope survey of H2 emission in the circumstellar environments of young stars", Astrophysical Journal, 756, 171
• France, K., Burgh, E.B., Linsky, J.L. et al.:2012, "CO and H2 in the AA Tauri circumstellar shell", Astrophysical Journal, 744, 22
• Yang, H., Herczeg, G.J., Linsky, J.L. et al.: 2012, "A far-ultraviolet atlas of low-resolution Hubble Space Telescope spectra of T Tauri stars", Astrophysical Journal, 744, 121
• Ingleby, L., Calvet, N., Linsky, J.L. et al.: 2011, "NUV excess in slowly accreting T Tauri stars: Limits imposed by chromospheric emission", Astrophysical Journal, 743, 105
• France, K., Schindhelm, E., Linsky, J.L. et al.: 2011, "The far-ultraviolet 'continuum' and in protoplanetary disk systems II. CO fourth positive emission and absorption", Astrophysical Journal, 734, 31
• Yang, H., Linsky, J.L., and France, K.: 2011, "HST/COS spectra of DF Tau and V4046 Sgr: First detection of molecular hydrogen absorption against the Lyman alpha emission line", Astrophysical Journal, 730, L10
• France, K., Yang, H., and Linsky, J.L.: 2011, "The far-ultraviolet 'continuum' and in protoplanetary disk systems I. Electron-impact H2 and accretion shocks", Astrophysical Journal, 729, 7
• Linsky, J.L., Wood, B.E., and Redfield, S.: 2011, "The solar wind in time", in Comparative Magnetic Minima: Characterizing Quiet Times in the Sun and Stars: Proceedings of IAU Symposium No. 286, ed. C.H. Mandrini and D.F. Webb, IAU, p. 286
• France, K., Linsky, J.L., Brown, A., Froning, C.S., and Beland, S.: 2010, "Metal depletion and warm H2 in the brown dwarf 2M1207 accretion disk", Astrophysical Journal, 715, 596
• Linsky, J.L., Herczeg, G., and Wood, B.E.: 2008, "Reverse engineering a spectrum: using fluorescent spectra of molecular hydrogen to recreate the missing Lyman-alpha line of pre-main sequence stars", Physics Scripta, T133, 014018
• Wood, Brian E., Izmodenov, Vladislav V., Linsky, Jeffrey L., and Alexashov, D.: 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
• 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
• 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
• 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
• 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

Review Papers and conference papers since 2000:

• Wood, B. E. and Linsky, J.L.:2016, "Astrospheres, stellar winds, and the interstellar medium", in Heliosphysics: Active Stars, their Astrospheres, and Impacts on Planetary Environments, ed. C Schrijver, F. Bagenal, and J.J. Sojka, Cambridge University Press, 56
• Wood, B.E., Linsky, J.L. and Guedel, M.: 2015, "Stellar winds in time", in Characterizing Stellar and Exoplanetary Environments ed. H. Lammer and M. Khodachenko, Astrophysics and Space Science Library 411, 19
• Linsky, J.L. and Wood, B.E.: 2014, "Lyman-alpha observations of astrospheres", in Wind Bubbles, Astrospheres and the Heliosphere: Environments and Cosmic Rays, ASTRA Proceedings, 1, 43
• Linsky, J.L., Wood, B.E., and Redfield, S.: 2011, "The solar wind in time", in Comparative Magnetic Minima: Characterizing Quiet Times in the Sun and Stars, ed. C.H. Mandrini and D.F. Webb, Proceedings of IAU Symposium No. 286, Cambridge Univ. Press, p. 286
• Yang, H., Linsky, J.L., and France, K.: 2011, "HST/COS spectra of DF Tau and V4046 Sgr: First detection of molecular hydrogen absorption against the Lyman alpha emission line", in The 16th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun, ed. C.M. Johns-Krull, M.K. Browning, and A.A. West, ASP Conf. Series, 448, 69
• 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, Astrophysics and Space Science Library, 317,1
• 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
• 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
• 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
• 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