A 0.3% measurement of orbital decay in the 12.75-min WD+WD J0651+2844

Conference presentation, 20 min. July 2019: The Beginnings and Ends of Double White Dwarfs, Copenhagen, Denmark.

Transcript

1. http://jjherm.es
   @jotajotahermes
   J.J. Hermes
   A 0.3% measurement of orbital decay
   in the 12.75-min WD+WD J0651+2844
   with Warren R. Brown, Mukremin Kilic, Keaton J. Bell,
   Zachary Vanderbosch, Alex Gianninas, Don Winget,
   Tom Marsh, Samuel T. Harrold, Karen Winget,
   and Barbara Castanheira
   

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2. JJ Hermes, Boston University | WD+WD | 2
   A syzygy (from the Ancient Greek σύζυγος,
   'yoked together') is a (roughly) straight-line
   configuration of three or more celestial bodies.
   @jotajotahermes
   

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3. J0651+2844: The 12.75-min WD+WD Binary
   Average distance between the Earth and the Moon: 384,400 km
   M
   2
   = 0.51 M¤
   M
   1
   = 0.26 M¤
   JJ Hermes, Boston University | WD+WD | 3
   J0651+2844
   

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4. J0651+2844: The 12.75-min WD+WD Binary
   JJ Hermes, Boston University | WD+WD | 4
   Brown et al. 2011,
   ApJ, 737, L23
   “We discovered that J0651 is a compact
   binary system when back-to-back
   spectra separated by six minutes showed a
   1300 km/s change in radial velocity.”
   

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5. phase = 0
   • Eclipses detected on 01 April 2011 from the
   2.1m at McDonald Observatory
   J0651+2844: The 12.75-min WD+WD Binary
   Brown et al. 2011,
   ApJ, 737, L23
   JJ Hermes, Boston University | WD+WD | 5
   

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6. Photo by Taylor Chonis
   Eclipses were detected on 1 April 2011 from the 2.1m telescope at
   McDonald Observatory on the first night of a 14-night run
   JJ Hermes, Boston University | WD+WD | 6
   John Kuehne
   

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7. The Rock House fire
   started on 9 April 2011
   near Marfa, TX
   It eventually burned
   >310,000 acres
   (>1270 km2)
   Photos I took on 9 April 2011
   JJ Hermes, Boston University | WD+WD | 7
   

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8. Photo by Don Winget on 11 April 2011
   JJ Hermes, Boston University | WD+WD | 8
   

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9. We re-started monitoring the 12.75-min binary on 13 April 2011,
   the first photons collected at McDonald after the Rock House fire started.
   Photo by Frank Cianciolo on 17 April 2011
   JJ Hermes, Boston University | WD+WD | 9
   

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10. Within 13 Months We Confirmed Orbital Decay
    JJ Hermes, Boston University | WD+WD | 10
    Hermes et al. 2012,
    ApJ, 757, L21
    In 2012:
    dPorb
    /dt = (-0.31 ± 0.09) ms/yr
    

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11. O-C Diagrams Measure Tiny Period Changes
    Hermes 2013 JJ Hermes, Boston University | WD+WD | 11
    Imagine a leaky faucet, dripping exactly every 12 min, but sediment
    buildup is slowing the drip by 0.5 ms every year:
    Drip 1: 1 January 2014,
    at UT 00:00:00
    

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12. O-C Diagrams Measure Tiny Period Changes
    Hermes 2013 JJ Hermes, Boston University | WD+WD | 12
    Imagine a leaky faucet, dripping exactly every 12 min, but sediment
    buildup is slowing the drip by 0.5 ms every year:
    Drip 1: 1 January 2014,
    at UT 00:00:00
    Drip 43801: 1 January 2015,
    at UT 00:00:11
    P0
    in 2014: 12 min (720 s)
    P in 2015: 12.00000833 min (720.0005 s)
    

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13. Hermes et al. 2012,
    ApJ, 757, L21
    T
    eff,1
    = 16,700 ± 200 K
    M
    1
    = 0.261 ± 0.010 M¤
    K
    1
    = 617.9 ± 5.8 km s-1
    i = 86.3 ± 1.0 deg
    T
    eff,2
    = 10,370 ± 360 K
    M
    2
    = 0.509 ± 0.029 M¤
    Updated Spectroscopy of J0651+2844
    JJ Hermes, Boston University | WD+WD | 13
    6.5m MMT 10m Keck
    J0651+2844 is a
    single-lined binary
    

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14. P
    spin,1
    > 6.7 min
    A Search for Primary Rotation in J0651+2844
    JJ Hermes, Boston University | WD+WD | 14
    Hermes et al. 2019,
    (nearly) submitted
    10m Keck
    We do not detect the
    Rossiter-McLaughlin
    effect around
    primary eclipses:
    

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15. Updated Light Curve Modeling of J0651+2844
    JJ Hermes, Boston University | WD+WD | 15
    Hermes et al. 2019,
    (nearly) submitted
    best-fit model
    using lcurve
    R
    1
    = 0.03596
    ± 0.00091 R¤
    (implies M
    1
    =
    0.252 ± 0.010 M¤
    in line with
    0.261 M¤ from
    surface gravity)
    R
    2
    = 0.01319
    ± 0.00033 R¤
    i = 86.3 ± 1.0 deg
    d
    LC
    = 1050 ± 120 pc
    d
    Gaia
    = 1080+930 pc
    -400
    

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16. We expect dPorb
    /dt = (-0.263 ± 0.020) ms/yr from GR (point masses) and
    observe (-0.28688 ± 0.00072) ms/yr!
    – a 0.3% measurement!
    Hermes et al. 2019,
    (nearly) submitted JJ Hermes, Boston University | WD+WD | 16
    χ2
    red
    = 0.962
    

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17. We expect dPorb
    /dt = (-0.263 ± 0.020) ms/yr from GR (point masses) and
    observe (-0.2879 ± 0.0022) ms/yr!
    using a sine fit to half the orbital period (ellipsoidal variations)
    Hermes et al. 2019,
    (nearly) submitted JJ Hermes, Boston University | WD+WD | 17
    χ2
    red
    = 1.20
    

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18. Hermes et al. 2019,
    (nearly) submitted
    JJ Hermes, Boston University | WD+WD | 18
    Expected dPorb
    /dt =
    (-0.263 ± 0.020) ms/yr from GR
    Observed dPorb
    /dt =
    (-0.28688 ± 0.00072) ms/yr!
    M
    tot
    = 0.770 ± 0.039 M¤
    L
    GW
    = 2.85 L¤
    L
    EM
    = 0.05 L¤
    Tides expected to
    increase dPorb
    /dt by 5%
    see Piro 2011, Benaquista 2011,
    Burkart et al. 2013, Fuller & Lai
    2013, Dall’Osso & Rossi 2014
    

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19. Hermes et al. 2019,
    (nearly) submitted
    JJ Hermes, Boston University | WD+WD | 19
    t0
    = -0.50 ± 0.13 s
    from primary
    eclipse times
    t0
    = -0.14 ± 0.38 s
    from ellipsoidal
    variations
    Tidal bulge is aligned with
    syzygy to at least 0.4 s
    (0.05% of orbit)
    

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20. J0651+2844: The 12.75-min WD+WD Binary
    • 8 years since discovery: dPorb
    /dt = (-0.28688 ± 0.00072) ms/y
    – The GW luminosity exceeds the EM luminosity by factor of >50!
    • This is 1.2σ consistent with pure GR: (-0.263 ± 0.020) ms/yr
    – This uncertainty is dominated by the uncertainty in M2
    • f
    orb
    = 2.6136734171(89) mHz, an exceptional LISA verification!
    • We will know dPorb
    /dt to 0.1% by 2021
    D. Berry, GSFC
    JJ Hermes, Boston University | WD+WD
    

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