Winds and Chromospheres of Cool (Super-) Giants Wind Acceleration, Structure and Energy Balance What we know, don’t know, and what we can do about it Graham Harper, CASA, University of Colorado

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session2 What we know wind acceleration is mostly gradual in K & early-M stars very good discriminator for theoretical models mass-loss rates are a weak discriminator wind emissivity is lower than the chromosphere wind base filling factor <1 wind ionization declines with T eff Winds do not start at Mg II dividing-line (e.g. HR 6902 G9 IIb) eclipsing binary systems still yielding new results strong evidence for magnetic fields (O VI, SiO masers) stellar properties becoming better constrained new Hipparcos reduction, angular diameters, SED

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session3 What we don’t know We don’t know [1] nature of wind acceleration close to star [2] geometry of chromosphere and wind [3] wave energy spectrum [4] nature of acceleration in metal poor stars Why is this important [1] acceleration is good discriminator of theory empirically we need to get it right [2] geometry controls wave damping thermodynamics [2,3] boundary conditions for theoretical models [4] test new extreme of parameter space

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session4 Magnetohydrodynamic Models Falceta-Gonçalves et al. 2006, MNRAS, 368, 1145 Carpenter et al. 1999, ApJ, 521, 382 Baade et al. 1996, ApJ, 466, 979

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session5 Magnetohydrodynamic Models Time dependent Alfvén waves in super-radial flux tubes Suzuki (2007 ApJ, 659, 1592) Symbiotics: Vogel/Crowley (2006 PhD), γ Cru Carpenter et al.

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session6 What do we need? Spatial Resolution – any way you can! Gradients -> physics High Spectral Resolution: resolve smallest scales possible Include geometric structure in wind acceleration models Improved model ionization and therefore energy balance Inputs from convection, granulation, and dynamo models e.g. AGB input physics Freytag & Hofner (2008, A&A, 483, 571) Continue to learn from solar physics (spicule Alfvén waves) Hinode: De Pontieu et al Science, 318, 1574

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session7 Spectro-Interferometry: the 3 rd spectrum Provide excellent test of theoretical models Left: Betelgeuse VTLI/MIDI R=30 (Perrin et al A&A, 474, 599) Right: HST/STIS R=15,000 (CS15)

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session8 Future Potential of Eclipsing Binaries Similar radial excitation temperatures: Eaton (2007, AJ, 133, 2669) & Crowley (2006 PhD) Different radial density scale heights: Schröder et al. (1988, A&A, 202, 136) [Analytic solar magnetic field model: Banaszkiewicz et al. 1998, A&A, 337, 940]

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session9 High Spectral Resolution … Courtesy of P. Bennett Line bifurcation (stable extended fine-structure) Ca II H & K (R. Elizabeth Griffin 2005 CS13, p. 595)

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session10 A Way Forward To make progress we DO require access to significant resources dedicated multi-wavelength multiple sites often on oversubscribed telescope facilities need to demonstrate to community that we really mean business Form interdisciplinary teams working toward common goals observers, modellers, theoreticians (all flavours) Identify key projects with specific goals and outcomes, e.g., theoretical model grids for specific stars identifying spectral signatures of super-radial flows differential study of wind acceleration in Pop II and Pop I stars constraining the filling factors of Molspheres

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session11 A Way Forward We cannot choose stars to match the theoretical models – the models need to move to the stars (anon, 2008) help theoreticians make relevant model grids Single Stars Select stars that are to be the focus of mass-loss studies Identify single stars that are proxies for eclipsing binary primaries Make database of stellar parameters and atmospheric properties parameters to be critically evaluated by Teams identify missing crucial data (e.g., vsini, g *, isotopic abundances) make observations to remedy missing data make database open Eclipsing Binaries obtain good time-series during ingress & egress deconstruct the chromosphere and wind, establish symmetries

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session12 Matching spectral-types Eclipse spectra: K4 Ib star + scattered light ~ tau : Bennett (2006 ASP Conf. Ser., 348, 254) ζ Aur chromospheric heating rates same as spectral-type proxies: Eaton (1992, MNRAS, 258, 473)

Tuesday, June 09, 2015 Cool Stars XV - Splinter Session13 Specific Challenges For Cool Stars16 Theoretical models + spectrum of Mult. C II] 2325 Ang for real stars. low mass K-M giants (EG And, αTau, αBoo) intermediate mass (ζAur systems, λVel K4 Ib-II) Accurately measure vsini(i) for primaries of eclipsing systems clues to structure from where the wind decouples from the star? St. Andrews: What kind of magnetic fields required for line splitting? Large scale prominences? Projection + ΔV both ➱ R *