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Mining the future of low-mass, core-He-burning hot subdwarfs

jjhermes
June 26, 2019

Mining the future of low-mass, core-He-burning hot subdwarfs

Conference presentation, 20 min. June 2019: 9th Hot Subdwarf Meeting, Hendaye, France.

jjhermes

June 26, 2019
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  1. Mining the Future of Low-Mass,
    Core-He-Burning Hot Subdwarfs
    http://jjherm.es
    @jotajotahermes
    J.J. Hermes

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  2. JJ Hermes, Boston University | sdOB9-Hendaye | 2
    David Schneider
    (on Tuesday)
    Let’s talk about non-canonical-mass hot subdwarfs!

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  3. • There is good evidence for <0.4 M¤
    sdBs
    • Core-He-burning subdwarfs descending from
    >2 M
    ¤
    stripped progenitors should exist
    • These sdBs will evolve into <0.4 M¤
    CO-core WDs
    • Is there evidence for <0.4 M¤
    CO-core WDs?
    • Gaia CMD
    • Asteroseismology
    • Eclipsing binaries
    JJ Hermes, Boston University | sdOB9-Hendaye | 3

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  4. Observational Evidence of Low-Mass Hot Subdwarfs
    2M 1533+3759
    0.376 ± 0.055 M¤
    0.166 ± 0.007 R¤
    JJ Hermes, Boston University | sdOB9-Hendaye | 4 For et al. 2010
    from lightcurve fits

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  5. Observational Evidence of Low-Mass Hot Subdwarfs
    2M 1938+4603
    0.372 ± 0.024 M¤
    (if e < 10-4)
    Barlow et al. 2012
    JJ Hermes, Boston University | sdOB9-Hendaye | 5
    from Rømer delay

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  6. Observational Evidence of Low-Mass Hot Subdwarfs
    TIC 278659026
    0.391 ± 0.013 M¤
    0.1694 ± 0.0081 R¤
    Charpinet et al. 2019
    (from Tuesday)
    JJ Hermes, Boston University | sdOB9-Hendaye | 6
    from seismology

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  7. Hot Subdwarfs Could Have Masses Down to 0.31 M
    ¤
    • Stripped progenitors >1.7 M¤
    can nondegenerately
    ignite He with core
    masses at ~0.31 M¤
    JJ Hermes, Boston University | sdOB9-Hendaye | 7 Han et al. 2013
    Han et al. 2012
    Z=0.02
    Z=0.02, normal tip of FGB
    Z=0.004
    First CE ejection
    First stable RLOF channel
    Merger

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  8. Hot Subdwarfs Could Have Masses Down to 0.31 M
    ¤
    • sdBs are the only way to make a <0.4 M¤
    CO-core WD
    JJ Hermes, Boston University | sdOB9-Hendaye | 8
    Prada Moroni &
    Straniero 2009
    Mass of the H-exhausted core
    see also Iben &
    Tutukov 1985

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  9. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    • CO-core white dwarfs have
    much smaller radii than
    He-core white dwarf of the
    same mass
    • At 17,000 K, an He-core WD
    has a >10% bigger radius
    than a CO-core WD
    JJ Hermes, Boston University | sdOB9-Hendaye | 9
    Prada Moroni &
    Straniero 2009

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  10. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    • Gaia CMD position of WDs w/ log(g) < 7.5 and high-
    quality (σ < 0.035 dex) spectroscopy
    JJ Hermes, Boston University | sdOB9-Hendaye | 10
    spectroscopic log(g)
    Montreal White
    Dwarf Database
    log(g) = 7.0
    log(g) = 7.5
    25kK
    5kK

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  11. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    JJ Hermes, Boston University | sdOB9-Hendaye | 11
    spectroscopic log(g) –
    photometric log(g)
    log(g) = 7.0
    log(g) = 7.5
    Smaller difference:
    WD is underluminous

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  12. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    • Asteroseismology is another precise way to determine
    mean stellar density
    • Asymptotic mean period spacing for l=1 dipole modes
    • 0.3 M¤
    He-core: Δπ = 75 s
    • 0.3 M¤
    CO-core: Δπ < 60 s
    JJ Hermes, Boston University | sdOB9-Hendaye | 12

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  13. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    JJ Hermes, Boston University | sdOB9-Hendaye | 13
    Known Pulsating WD

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  14. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    • Double-lined eclipsing (WD+dM) binaries
    JJ Hermes, Boston University | sdOB9-Hendaye | 14 Parsons et al. 2017
    He-core
    models
    C/O-core
    models
    Thick H (10-4)
    Thin H (10-10)

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  15. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    JJ Hermes, Boston University | sdOB9-Hendaye | 15 Hallakoun et al. 2016
    SDSSJ1152+0248: WD+WD from K2 Campaign 1
    T1
    = 25,500 ± 1000 K
    log(g)1
    = 7.42 ± 0.25 SED: T2
    = 14,340 K

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  16. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    JJ Hermes, Boston University | sdOB9-Hendaye | 16
    SDSSJ1152+0248
    Parsons et al. 2019
    (in prep., please no Tweets)
    X-shooter
    HiPERCAM

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  17. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    JJ Hermes, Boston University | sdOB9-Hendaye | 17
    SDSSJ1152+0248
    M1
    : 0.362 ± 0.014 M¤ M2
    : 0.325 ± 0.013 M¤
    R1
    : 0.0212 ± 0.0003 R¤ R2
    : 0.0191 ± 0.0004 R¤
    Parsons et al. 2019
    (in prep., please no Tweets)

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  18. Can We Find <0.4 M
    ¤
    CO-Core White Dwarfs?
    JJ Hermes, Boston University | sdOB9-Hendaye | 18
    21.9 min (1312 s)
    @ 0.5% amp
    ZZ Ceti pulsations!
    Parsons et al. 2019
    (in prep., please no Tweets)

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  19. Evidence for 0.3-0.4 M
    ¤
    sdBs Evolving Into 0.3-0.4 M
    ¤
    WDs
    JJ Hermes, Boston University | sdOB9-Hendaye
    • There is good evidence for <0.4 M¤
    sdBs
    • Core-He-burning subdwarfs descending from
    >2 M
    ¤
    stripped progenitors should exist
    • These sdBs will evolve into <0.4 M¤
    CO-core WDs
    • Is there evidence for <0.4 M¤
    CO-core WDs?
    • Gaia CMD
    • Asteroseismology
    • Eclipsing binaries
    possible CO-core WD(s) in
    the pulsating WD+WD
    binary SDSSJ1152+0248
    (maybe)

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