L’evoluzione stellare: l’orologio Evoluzione di stelle di massa piccola, intermedia e alta Features sul HRD particolarmente importanti per il problema Sistematica con la metallicita’ Caveats June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Evolutionary Tracks 1MO 2.5 MO 5 MO 20 MO 1 MO 100 MO PAGB0.6 MO To WD ZAHB ZAMS RGB PN Padova 94 set Z=Zo Y=0.28 Lines of constant radii: R=1,10,100,1000 Ro R=0.008,0.013,0.014 Ro (MWD=1,0.6,0.5 Mo) Fagotto 94 Zsun tracks; solid are 0.6,0.8,1,2.2,2.5,5,20 and 100 Msun PAGB tracks are dug out from UVdir Purple lines are const R/Rsun of 0.0142,0.013 and 0.008, should become late evol. of 0.55,0.6 and 1 Msun Dashed black lines are const R/Rsun of 1,10,100,1000 June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations RGB evolution Back to HRD RGB Bump 0.8 Mo 2 Mo 100Ro 10 Ro Enlargement of low mass tracks (Fagotto 94, Zo) to show bump appearance and location June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Back to HRD RGB : bump and LF 1.2 Mo 1 Mo Sx: show why bump generates excess on LF. Plotted here are: 1 and 1.2 Mo versus t/t_tip. Notice that bump does not occur at the same phase, but almost. Dx: RGB LFs from synthetic tracks with Z=0.004. The RGB base masses are 1.127,1.365,1.47,1.796. There would have been the 0.941 with tau_tip=10 Gyr, but it was white and went off with bckg. Notice shape of the LF, location of the bump..anticipate retreatment of TRGB. June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Flash and After Back to HRD M tr RGB tip RGB base RGB tip 10 Ro 1 Ro P-EAGB 100 Ro 0.03 0.07 0.12 Discuss concept of M_tr ; discuss L_tip as distance indicator: will be better illustrated later. Dx: HB dispersion, and HB + E-AGB evolution. Plotted tracks are (Zo): M=0.5 0.55 0.6 0.8 1 1.2 1.4 2 whose Menv= 0.03 0.07 0.12 0.476 0.52 0.72 0.79 1.56 June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Clump and Loops Back to HRD TRGB ZAHB 2.2 Mo 9 Mo 4 7 6 5 3 15 10 Ro Age indicator Distance ind Lmax,He Lmin,He June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations AGB Bump BUMP RGB 2.2 Mo 5 Mo 4 Mo 3 Mo 1 Mo with cost=-1 1.5 Mo with cost=-0.5 June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Bump Clump PMS LF RGB HB AGB June 2006 Lectures on Stellar Populations

A Field in the Halo of Centaurus A (Rejkuba et al 2005) June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations First Pulse and TAGB TAGB Ist Pulse TRGB First Pulse luminosity and AGB tip: age indicators. TAGB from bertelli isochs, with Zo. Depend on mass loss. June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Massive Stars Evolution affected by MASS LOSS OVERSHOOTING First Pulse luminosity and AGB tip: age indicators. TAGB from bertelli isochs, with Zo. Depend on mass loss. Chiosi and Maeder 1986 June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations Back to HRD Where the Stars are WR C stars Miras Clump Ceph HB RRLyr WD BSG RSG Dots are equally spaced in There are 1000 dots along each track Would be nice to pop up P-L relations..next time June 2006 Lectures on Stellar Populations

Dependence on Metallicity 30 Mo 15 Mo 5 Mo 3 Mo 0.9 Mo Clumps 0.5 Mo 0.55 Mo 0.6 Mo AGB Manque’ Post E-AGB Clumps Nel diagramma di destra ci sono anche le tracce delle tre 0.9 masse June 2006 Lectures on Stellar Populations

Evolutionary Lifetimes tot MS overshooting RGB phase transition rgb He burning Overshooting change of lambda at arounf 1.45 msun; transition at 1.9 – 2.2 Msun June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations RGB Luminosities Base TIP Notice behaviour at transition; notice Mtr and tau_tr June 2006 Lectures on Stellar Populations

Helium Burning and beyond Ist Pulse He burn L-band RGB trans June 2006 Lectures on Stellar Populations

Isochrones Girardi et al. 2002 As Z increases: isochrones get fainter and redder loops get shorter WR stars are more easily produced June 2006 Lectures on Stellar Populations

Uncertainties and wish list Core Convection: affects star’s luminosity H and He lifetimes shape of tracks around Mhook first H shell burning and runway for intermediate mass stars MS width location of RGB bump values of Mtr and Mup ratios N(HB)/N(AGB) loops extension Mass Loss: on the RGB affects Temperature extension of HB on the AGB affects value of Mup and TAGB for massive stars affects surface abundances, upper limit of Red SGs, productions of WR .. Opacity: affects MS width occurrence and extension of loops Blue to Red ratio Mixing Length, rotation, diffusion, meridional circulation, nuclear reactions… Separate dependence on Y and Z is important June 2006 Lectures on Stellar Populations

Lectures on Stellar Populations What have we learnt To place on the HRD whatever mass at whatever age we want to pay attention to: Mtr Mup Mhook : lifetimes and tracks discontinuities Place correctly RGB Tip (as distance indicator) Describe accurately the evolution in core He burning close to RGB transition (Lum extension during evolution) Allow spread of envelope masses for HB stars Describe extension of the loops, location of BSG, Back-to-the-Blue evolution of high mass stars …………. AND if we include a metallicity spread Correctly describe all these systematics as a function of Metallicity June 2006 Lectures on Stellar Populations