Dynamics in atmospheres and outflows of evolved stars Elvire De - PowerPoint PPT Presentation

Dynamics in atmospheres and outflows of evolved stars Elvire De Beck Wouter Vlemmings, Theo Khouri, Matthias Maercker, Hans Olofsson Department of Space, Earth and Environment, Chalmers University of Technology Onsala Space Observatory The Dynamical Universe for All Lund Observatory, 5th - 6th February 2018

Quick intro • Evolved stars in this talk 
 = Post-Main-Sequence Giants 
 Luminosity compared to the sun • < 8 M sun 
 AGB: asymptotic giant branch stars • >8 M sun 
 RSG: red supergiant stars 
 • Cool surface ~ 3000K • Luminous ~ 100 - 100,000 L sun • Mass loss ~ 10 -8 -10 -3 M sun /yr Surface temperature

Dynamics of AGB stars Review: Mass loss of stars on the asymptotic giant branch Mechanisms, models and measurements Hoefner & Olofsson, 2018, A&ARv 26:1 Evolution and appearance on AGB strongly affected by range of dynamical processes • large-scale convective flows 
 >> transport of newly formed chemical elements to the surface • stellar pulsations >> trigger shock waves in extended stellar atmosphere 
 • dust grain formation in upper atmosphere 
 >> acceleration through scattering/absorption and collisions with gas 
 • massive outflows of gas and dust These lead to • enrichment of ISM • evolution from giant 
 to white dwarf

Dynamics of AGB stars Review: Mass loss of stars on the asymptotic giant branch Mechanisms, models and measurements Hoefner & Olofsson, 2018, A&ARv 26:1 Observations of asymmetries and inhomogeneities • short-lived & small-scale: photosphere and dust-forming layers • long-lived & large-scale: circumstellar envelope High-angular resolution observations give information on e.g. dust condensation • location • chemical composition • size 
 “These are essential constraints for building realistic models of wind acceleration and developing a predictive theory of mass loss for AGB stars, which is a crucial ingredient of stellar and galactic chemical evolution models.”

Observations: large scales Large scales = circumstellar envelope (CSE) 
 >> spherical • entire outflow • shells ~17” (~0.02pc) Castro Carrizo et al. (2010) Olofsson et al. (2000) CO ( J =2-1), PdBI CO ( J =1-0), PdBI IK Tau, normal mass loss TT Cyg, detached shell

Observations: large scales 30 SiO, v =1(8-7) Large scales = circumstellar envelope (CSE) 
 30 SiO, v =1(4-3) >> spherical • entire outflow • shells 29 SiO, v =1(4-3) 2-1 2-1 4-3 4-3 6 5 -5 4 6 5 -5 4 SiO, v =3(4-3) 3-2 3-2 5-4 5-4 6 7 -5 6 6 7 -5 6 4-3 4-3 6-5 6-5 5 5 -4 4 5 5 -4 4 Normalised intensity Normalised intensity 7-6 7-6 5 6 -4 5 5 6 -4 5 8-7 8-7 5 4 -4 3 5 4 -4 3 4 4 -3 3 4 4 -3 3 SiO, v =2(7-6) 4 5 -3 4 4 5 -3 4 -20 -15 -10 -5 0 -15 -10 -5 0 0 5 10 15 20 SiO, v =2(6-5) -20 -10 0 10 20 -20 -10 0 10 20 -20 -10 0 10 20 Velocity [km s -1 ] Velocity [km s -1 ] Velocity [km s -1 ] SiO, v =2(4-3) De Beck & Olofsson (2018) SiO, v =1(7-6) APEX spectral survey at 0.8-1.9 mm R Dor, normal mass loss SiO, v =1(5-4) • main, smooth, spherical component • up to 4 extra components in the outflow SiO, v =1(4-3) • one at velocities >> wind expansion velocity • shells / rings / spiral / … ? -20 -10 0 10 20 Velocity [km s -1 ]

Observations: large scales Large scales = circumstellar envelope (CSE) 
 >> spherical • entire outflow • shells >> not so spherical • binary interaction -37 -35.5 -34 -32.5 -31 Maercker et al. (2012, 2014, 2016) R Scl, detached shell source CO( J =3-2), ALMA 
 -29.5 -28 -26.5 -25 -23.5 Dust-scattered stellar light, PolCor Dec. offset [arcsec] -22 -20.5 -19 -17.5 -16 • previously unknown binary companion 
 ~60 AU separation -14.5 -13 -11.5 -10 -8.5 • from spiral windings: 
 information on changes in velocity and mass loss on evolutionary timescales 1.5 20 -7 -5.5 -4 -2.5 -1 10 1 0 0.5 • Dust and gas dynamics comparable? -10 0 -20 20 10 0 -10 -20 R.A. offset [arcsec]

Observations: large scales Large scales = circumstellar envelope (CSE) 
 >> spherical • entire outflow • shells >> not so spherical • binary interaction 1 Maercker et al. (2012, 2014, 2016) 20 R Scl, detached shell source CO( J =3-2), ALMA 
 15 0.8 Dust-scattered stellar light, PolCor 10 Dec. offset [arcsec] Dec. offset [arcsec] 5 0.6 • previously unknown binary companion 
 0 ~60 AU separation 0.4 − 5 − • from spiral windings: 
 − 10 − information on changes in velocity and mass loss 0.2 − 15 − on evolutionary timescales − 20 − 0 • Dust and gas dynamics comparable? 20 10 0 − 10 − 20 − − R.A. offset [arcsec]

Observations: large scales Large scales = circumstellar envelope (CSE) 
 >> spherical • entire outflow • shells >> not so spherical • binary interaction • disk 43.0 km/s 1.6 1.4 5 O ff set [arcsec] 1.2 Jy/beam 1 0 0.8 0.6 − − 5 0.4 0.2 − 10 5 0 − 5 − 10 − East O ff set [arcsec] Ramstedt et al. (2014) Kervella et al. (2014, 2015, 2016) Mira, 0.5” (~45 AU) binary separation L2 Pup CO( J =3-2), ALMA, “bubble” in the AGB wind ALMA, VLT (NACO/SPHERE), edge-on disk

Observations: small scales • Small scales • upper atmospheric layers (warm molecular layer) 
 i.e. before wind acceleration Khouri et al. (2016) CO( v =1, J =3-2), ALMA • inverse P-Cygni profiles indicate infall motion • multiple epochs reflect changes of the upper atmosphere • temperature • density • motion

Observations: small scales • Small scales • upper atmospheric layers 
 i.e. before wind acceleration • dust formation region Khouri et al. (2016), SPHERE/ZIMPOL, R Dor • Top 
 variable morphology in continuum 
 = changing opacity of TiO in extended atmosphere 
 • Bottom 
 polarised light from ~annular region around central star. • density profile steeper than constant- v wind • upper limit for the d/g ~2 × 10 -4 at 5.0 R � , consistent with minimum required by wind- driving models

Observations: small scales • Small scales • upper atmospheric layers 
 i.e. before wind acceleration • dust formation region • surface imaging Paladini et al. (2018, Nature ) π 1 Gruis, VLTI/PIONIER surface granulation due to convection Vlemmings et al. (2017, Nature Astro. ) W Hya, ALMA heating of the upper atmosphere due to shocks chromosphere?

Conclusions Mass loss dominates appearance and evolution on AGB >> critical to have predictive description as input for models of • stellar evolution • galactic chemical evolution >> strongly dependent on variety of dynamical processes Observations show • asymmetries and inhomogeneities • on large spatial scales & long timescales • on small spatial scales & short timescales • dust location, size, composition • surface structure for stars other than our Sun (!) 
 constraining 5 • convection and pulsation motions 0 • dust growth − − 5 • wind acceleration − • mass-loss rates − − − and heading for a deeper understanding of the dynamics of evolved stars.

Theoretical models 500 • ] y [R O 0 -500 Freytag et al. (2017) star-in-a-box models 500 • ] y [R O 0 -500 500 • ] y [R O 0 -500 500 surface granulation due to convection • ] y [R O 0 -500 t= 0.0 d t= 28.9 d t= 57.9 d t= 86.8 d t= 112.9 d 600 400 200 • ] y [R O 0 500 -200 • ] y [R O 0 -400 -600 -500 t= 141.8 d t= 170.7 d t= 199.7 d t= 228.6 d t= 257.5 d 600 400 200 500 • ] y [R O 0 • ] y [R O 0 -200 -400 -500 -600 -500 0 500 -500 0 500 -600-400-200 0 200 400 600 -600-400-200 0 200 400 600 -600-400-200 0 200 400 600 -600-400-200 0 200 400 600 -600-400-200 0 200 400 600 x [R O • ] x [R O • ] x [R O • ] x [R O • ] x [R O • ] x [R O • ] x [R O • ] temperature density