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Properties of massive binaries interacting during core hydrogen burning�

Koushik Sen

in collaboration with N. Langer, A. Menon, C. Schurmann, P. Marchant, C. Wang, Xiao-Tian Xu, L. Mahy, H. Sana, S. de Mink

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Overview

Typical evolution of a Case A binary system.
Why study this phase of evolution in massive star binaries?
Method to study Case A evolution
Results (Main-Sequence evolution)
Discussion of the uncertainties
Conclusion

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Typical evolution*

M1 = 17.8 Msun

M2/M1 = 0.8

period ∼2.66 days

*during the Main Sequence - ‘Algol’ phase

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Why should we care?

1. More than 50% of massive stars are in binaries (Sana et. al. 2012, Moe and di Stefano 2017).

2. Unreliable predictions from rapid binary evolution codes for this stage.

3. Can be progenitors of high mass and supergiant X-ray binaries (Qin 2019, Walter et. al. 2015, Quast 2019).

5. Mass transfer at a nuclear timescale.

6. To constrain mass transfer efficiency (Langer et. al. 2003, de Mink et. al. 2007).

Kruckow et. al. (2018)

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Previous work

Nelson & Eggleton (2001): Sub-classification of Case A systems.
de Mink et. al. (2007, 2014): mass transfer efficiency, fraction of ‘Algol’ binaries in a star population
Mennekens and Vanbeveren (2017): orbital period and mass ratio distributions
Wang (2017): on surface nitrogen enhancements during the slow Case A mass transfer phase

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Methods

Investigate ~10,000 models at LMC metallicity.
M1 ~ 10 – 40 Msun;
q (M2/M1) = 0.275 – 0.975;
Pi ~ 1.41 – 1000 days;
Create distributions of observable properties of massive binaries during the nuclear timescale slow Case A mass transfer phase.
Compile a list of observed semi-detached binaries in the LMC and Galaxy.

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Observed period distribution

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Observed mass ratio distribution

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Mass-mass diagram

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Orb. period-q diagram

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Mass transfer efficiency

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Conservative models

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Timescale of mass transfer

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Number of ‘Algol’ systems in the LMC

From the grid, 3% of all (?) core hydrogen burning massive binaries are in the semi-detached configuration.
25% of all stars in the LMC is in the Tarantula region. Number of O stars in the Tarantula region ~ 570 (Langer et. al. 2020).
Accounting for a Saltpeter IMF and lifetime, B stars ~ 4000 in the Tarantula region (Langer et. al. 2020).
Total of 6000 O+B stars in the LMC.
~90 binaries in the ‘Algol’ configuration (assuming 50% binary fraction) above 10 Msun.

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Helium surface abundance

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Nitrogen surface enhancement

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Rotation and nitrogen enhancement

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Uncertainties

Stability of mass transfer (Wang et. al. 2020)
Angular momentum lost from the binary (Mennekens & Vanbeveren 2017)
Extent of envelope stripping (Mahy 2011, Raucq 2016, Martins et. al. 2017, Wang et. al. 2017)

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Conclusions & future prospects

~90 semi-detached systems out of ~3000 massive binaries in the LMC above 10 Msun.
The orbital period and mass ratio distribution match reasonably well with observations.
The nitrogen abundances are underpredicted by our models when compared to observations.
Look at the post Case AB mass transfer phase where these systems will correspond to short period Wolf Rayet and HM/SG X-Ray binaries.

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Observed ‘Algol’ binaries

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