Evolution of Massive Stars

Norbert Langer (Bonn University)

with

Matteo Cantiello (UCSB)

Chris Evans (Edinburgh)

Sung-Chul Yoon (Seoul)

Alex de Koter (Amsterdam)

Swetlana Hubrig (Potsdam)

Fabian Schneider (Bonn)

Luca Fossati (Bonn)

Alexander Heger (Melbourne)

Selma de Mink (Carnegie)

Hugues Sana (Amsterdam)

Rob Izzard (Bonn)

Ines Brott (Vienna)

Bruxelles, 2-12-13 – p.1/25

Evolution of Massive Stars : Magetic Fields

Norbert Langer (Bonn University)

with

Matteo Cantiello (UCSB)

Chris Evans (Edinburgh)

Sung-Chul Yoon (Seoul)

Alex de Koter (Amsterdam)

Swetlana Hubrig (Potsdam)

Fabian Schneider (Bonn)

Luca Fossati (Bonn)

Alexander Heger (Melbourne)

Selma de Mink (Carnegie)

Hugues Sana (Amsterdam)

Rob Izzard (Bonn)

Ines Brott (Vienna)

Bruxelles, 2-12-13 – p.1/25

Massive Star Evolution

Bruxelles, 2-12-13 – p.2/25

Three kinds of B-fields in OB stars

large scaledirectly observable, “dipoles”,spin-down

small scaleindirectly observable; “spots”

toroidalinternal, not directly observable,j-transport, mixing

Bruxelles, 2-12-13 – p.3/25

Toroidal fields: ubiquitous?

differential rotation → Spruit-Taylor dynamo?Spruit 2002, A&A, 381, 923

slowly rotating Solar coreEggenberger 2005, A&A, 440, L9

slowly rotating cores of red giantsMosser et al. 2012, A&A, 548, A10

slowly rotating WDs and NSsSuijs et al. 2008, A&A 481, L87

Bruxelles, 2-12-13 – p.4/25

Core spin-down in red giants

Mosser et al. 2012, A&A, 548, A10

Bruxelles, 2-12-13 – p.5/25

B-fields in “non-magnetic” stars

Suijs, NL, Poelarends, et al. 2008, A&A 481, L87Bruxelles, 2-12-13 – p.6/25

Low Mass Stars (< 1.5M⊙)

convective envelopes

rotation↑ ↔ B↑ ↔ age↓example: Sun

concerns 100% of starsexceptions: tidal binaries

Bruxelles, 2-12-13 – p.7/25

Low Mass Stars (< 1.5M⊙)

convective envelopes

rotation↑ ↔ B↑ ↔ age↓example: Sun

concerns 100% of starsexceptions: tidal binaries

αΩ-dynamoα ↓ or Ω ↓ → B↓

Bruxelles, 2-12-13 – p.7/25

Intermed. Mass Stars (< 10M⊙)

radiative envelopesrotation↓ ↔ B↑concerns ∼10% of stars Ap, Bp stars→ 90% are non-magnetic

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Intermed. Mass Stars (< 10M⊙)

radiative envelopesrotation↓ ↔ B↑concerns ∼10% of stars Ap, Bp stars→ 90% are non-magneticstable large scale fields (no dynamo)Braithwaite & Spruit 2004, Nature 431, 819

Bruxelles, 2-12-13 – p.8/25

Massive Stars (> 10M⊙)

convective envelopes

αΩ-fields → spots

in all stars

Bruxelles, 2-12-13 – p.9/25

Massive Stars (> 10M⊙)

convective envelopes

αΩ-fields → spots

in all stars

stable large scale fieldsin 10% stars

Bruxelles, 2-12-13 – p.9/25

Massive stars: convective envelops

Cantiello, NL, Brott et al. 2009, A&A 499, 279 Bruxelles, 2-12-13 – p.10/25

Massive stars: microturbulence

Cantiello et al. 2009 Bruxelles, 2-12-13 – p.11/25

Stochastic pulsations: KEPLER

Belkacem, Samadi, Goupil, et al. 2009, Science, 324, 1540 Bruxelles, 2-12-13 – p.12/25

Massive stars: magnetic spots

sub-surface αΩ-dynamo

buoyant rise of B-fieldsCantiello et al. 2009

localized, small scale: bright spots

Discrete Absorption Components→ ubiquitous in O stars!

no spin-down

Bruxelles, 2-12-13 – p.13/25

Massive stars: large scale fields

Grunhut, Wade et al. 2012, ASPC, 465, 42 Bruxelles, 2-12-13 – p.14/25

LMC early B stars

6.8

7

7.2

7.4

7.6

7.8

8

0 50 100 150 200 250 300 350

12 +

log

[N/H

]

v sini [km/s]

M ≤ 10 Msun10 < M ≤ 12 Msun

12 < M ≤ 15 Msun15 < M ≤ 20 Msun

M > 20 Msunbinary

1

10

100

1000

Num

ber

of s

imul

ated

sta

rs p

er b

in

Box 1(a)

(b)

Box 2 Box 4

Box 3

Box 5

Brott, Evans, Hunter, et al. 2011, A&A 530, A116Bruxelles, 2-12-13 – p.15/25

Box 2 - stars: magnetic?

10% of early B stars: very slowrotators, N-rich

similar population in the Galaxy:B-field detected in most of them!Morel, Hubrig & Briquet 2008, A&A, 481, 453

O-stars? –> ESO Tarantula Survey(PI: Chris Evans)

Bruxelles, 2-12-13 – p.16/25

The rotation rates: early B stars

Dufton, NL, Dunstall et al. 2013, A&A 550, A109Bruxelles, 2-12-13 – p.17/25

Origin of large scale fields

“fossil”: how? why 10%?

binary induced:binaries −→ 10%magnetic MS, WD: mostly singleMS WD NS: 10% magneticMS: N-enrichmentobs. examples (e.g., HD 148937;Plaskett’s star)

Bruxelles, 2-12-13 – p.18/25

Close binaries: O stars

eectivelysingle

envelopestrippingenvelopestripping

merge

accretion & spin up or CE

accretion & spin up or CE

~29%

~24%

~14%

~33%

Sana, de Mink, de Koter, NL, et al. , 2012, Science, 337, 444Bruxelles, 2-12-13 – p.19/25

Pre-MS merger

Korntreff, Kaczmarek & Pfalzner 2012, A&A 543, A126Bruxelles, 2-12-13 – p.20/25

HD 148937

Bruxelles, 2-12-13 – p.21/25

Dipoles from dynamical events?

binary merger: strong differential rotationimposed on dynamical time scale

Polars (=magnetic WDs in CVs) very tight:almost-mergerPotter & Tout 2010

ordinary neutron stars: dynamical collapsewith rotationDuncan & Thompson 1992

Bruxelles, 2-12-13 – p.22/25

Advanced evolution

Can stable large scale fields prevail?

intermediate mass stars:magnetic Herbig AeBe (10%) → Ap/Bp star(10%) → magnetic WD (10%)

massive stars:magnetic OB (10%) → magnetar (10% ?)

flux conservation: B-fields scale within uncertain-

ties

Bruxelles, 2-12-13 – p.23/25

Advanced evolution

Heger et al. 2000, ApJ 528, 368Bruxelles, 2-12-13 – p.24/25

Conclusions

torroidal fields ubiquitous in stars→ core spin-down

small scale fields: ubiquitous in low and highmass stars

strong large scale fields in ∼ 10% of: Herbigstars, intermdiate mass and massive mainsequence stars, WDs, NS (?)

binary merger → large-scale fields

rotating core collapse → NS fields (?)

survival of large scale fields: magnetic WDs& magnetars?

Bruxelles, 2-12-13 – p.25/25