Open questions in our knowledge of the evolution of Galactic OB stars

Size: px

Start display at page:

Download "Open questions in our knowledge of the evolution of Galactic OB stars"

Joy Montgomery
5 years ago
Views:

Open questions in our knowledge of the evolution of Galactic OB stars Georges Meynet Geneva Observatory, Geneva University Andre Maeder (Uni. Geneva, Switzerland) Sylvia Ekström (Uni.

1 Open questions in our knowledge of the evolution of Galactic OB stars Georges Meynet Geneva Observatory, Geneva University Andre Maeder (Uni. Geneva, Switzerland) Sylvia Ekström (Uni. Geneva, Switzerland) José Groh (Uni. Geneva, Switzerland) Fabio Barblan (Uni. Geneva, Switzerland) Cyril Georgy (Uni. Keele, UK) Phil Massey (Flagstaff, USA) Norbert Pruybilla (Zni. Innsbruck, Austria) Hideyuki Saio (Uni. Sendai, Japan) Rolf Kudritzki (IfA, USA) Heng Song (Uni. Ghuizou, China)

2 MASSIVE STARS M > 8-10 Msol, core collapse supernovae, neutron stars and black holes Only a few 3/ Msol/1000 Msol But large impact: short lifetimes (2-30 Myr) strong mass loss (Z) high luminosity large amounts of new chemical elements injected into ISM (O) remnant 10 Msol/1000 Msol A UNIVERSE WITHOUT MASSIVE STARS. returned 130 Msol/1000 Msol New elements 40 Msol/1000 Msol

3 2015 MNRAS Non-rotating models, 15, 20 and 25 Msun Surface abundances at the end of core He-burning, OK s-process, end of He-core, in agreement within 30% Smaller than the impact of nuclear physics uncertainty Three models gives consistent results for the yields at the end of the core helium-burning. Mixing processes remain the main uncertainty of the models

4 IMPORTANT EFFECTS MASS LOSS winds, mass transfer MIXING rotation, magnetic fields CONVECTION criterion, overshooting

5 Mixing vs. mass loss : μm T ~ R R ~μ 0.5 T ~ M M Higher M M 1 ρ ~ 3 ~ 1.1 R M P rad MASS LOSS : Higher T Lower 3 T ~ P gas ρ MIXING: shear ~ thermal diffusivity 3 4 ac T K= 2 3 CP κ ρ Mass loss and mixing strongly favoured!

6 1) SOME CHALLENGES

7 Massey 2003

8 Eldridge et al. 2008

9 B=OBA supergiants B=B supergiants 8-30 Msol Eggenberger et al. AA, 386, 576 (2002); Cf discussion in Langer and Maeder AA 373, 555 (1995)

10 CONSISTENT WITH MODELS More fast More Rotators RSG

11 2) BLUE SUPERGIANTS

12 BLUE SUPERGIANTS Msol Teff ~ K Mv ~ -9.5 mag AS BRIGHT AS A Globular Cluster OR A DWARF GALAXY

13 SPECTROSCOPY intrinsic energy distribution reddening and metallicity AGE BETWEEN 5 and 13 millions years not too much concentrated in their birth region, smaller crowding effects than for O-type stars Short lifetimes little chance to have two (non resolved) stars which spectroscopically would appear as a single blue supergiants

14 Blue Supergiants As standard candles Kudritzki et al Kudritzki et al. 2008ab Urbaneja et al U et al Kudritzki et al Kudritzki et al Kudritzki et al Hosek et al. 2014

15 WHY DO WE HAVE SUCH A WELL DEFINED RELATION? IF THE BLUE SUPERGIANTS FOLLOW A MASS-LUMINOSITY RELATION OF THE TYPE log L= α * log M + b

16 GROUP 1 BSG= BSG HAVING DIRECTLY EVOLVED FROM THE MS FOR A GIVEN MASS L~cst Actual mass~cst

17 GROUP 1 BSG= BSG HAVING DIRECTLY EVOLVED FROM THE MS

18 GROUP 1 BSG= BSG HAVING DIRECTLY EVOLVED FROM THE MS

19 USING SYCLIST PROBABILITY DENSITY (cst SFR) Rotating stellar models Z=0.014 (only grouo 1 BSG) Meynet, Kudritzki, Georgy, A& A, in press

20 Rotating models Z=0.002

21 Rotating models at Z=0.002

22 THUS GOOD AGREEMENTS

23 3) THE SMALL OBSERVED SCATTER OF THE FGLR AS A CONSTRAINT FOR THE POST MS MASSIVE STAR EVOLUTION

24 GROUP 2 BSG= POST RED SUPERGIANT BSG WHERE WOULD BE THESE STARS IN THE FWGL?

25 GROUP 2 BSG= POST RED SUPERGIANT BSG WHERE WOULD BE THESE STARS IN THE FWGL?

26 BEST MATCH BETWEEN THEORY AND OBSEVATION IS FOR ROTATING STELLAR MODELS WITH MAINLY GROUP 1 BSG Non-rotating models Z=0.014

27 Meynet et al. 2014

28 Meynet et al. 2014

29 HIGH MASS LOSS RATES DURING THE RSG PHASE SEEM TO BE EXCLUDED AS BEING THE MOST FREQUENT CASES

30 4) CLOSE BINARY EVOLUTION AND THE SMALL OBSERVED SCATTER OF THE FGLR

31 THE CASE OF THE PROGENITOR OF THE SN 1987A 20 Msun at LMC metallicity STAR EVOLVED TO THE BLUE AT THE VERY END OF ITS EVOLUTION (RED BLUE MAY BE TRIGGERED BY A RLOF IN A CLOSE BINARY)

32 THE CASE OF THE PROGENITOR OF THE SN 1987A HIGH MASS LOSS RATES TRIGGERED BY MASS TRANSFER DURING THE RSG PHASE MAY PRODUCE BLUE SN PROGENITORS HAVING A VERY LIMITED 20 M POPULATIONS at LMC metallicity IMPACT ON BSG sun STAR EVOLVED TO THE BLUE AT THE VERY END OF ITS EVOLUTION (RED BLUE MAY BE TRIGGERED BY A RLOF IN A CLOSE BINARY)

34 Barblan et al. in preparation

36 HIGH MASS LOSS RATES TRIGGERED BY MASS TRANSFER BEFORE THE RSG MIGHT NOT BE TOO FREQUENT BUT MORE MODELS NEEDED TO CONFIRM THAT POINT

CONCLUSIONS THE CHALLENGES: GLOBAL TRENDS WITH Z RSG/WR RSG/Be BSG/RSG AN INTERESTING GLOBAL CONSTRAINT ON STELLAR MODELS THE SMALL OBSERVED SCATTER OF THE FGLR SMALL SCATTER WELL

37 CONCLUSIONS THE CHALLENGES: GLOBAL TRENDS WITH Z RSG/WR RSG/Be BSG/RSG AN INTERESTING GLOBAL CONSTRAINT ON STELLAR MODELS THE SMALL OBSERVED SCATTER OF THE FGLR SMALL SCATTER WELL REPRODUCED BY ROTATING MODELS WITH NO OR ONLY VERY FEW GROUP 2 BSG CONTINUOUS HIGH MASS LOSS RATES DURING THE RSG PHASE IS NOT THE RULE MASS TRANSFER BEFORE THE RSG PHASE IS LIKELY NOT THE RULE.

Effects of low metallicity on the evolution and spectra of massive stars

Jose Groh (Geneva Observatory, Switzerland) Image credits: NASA/ESA/J. Hester & A. Loll, Arizona State U. (Crab Nebula) Effects of low metallicity on the evolution and spectra of massive stars Take Away: