Paparazzi lightning: 68 million images of white dwarfs from space

Conference presentation, 20 min. October 2019: White Dwarfs as probes of fundamental physics and tracers of planetary, stellar & galactic evolution, IAU Symposium 357, Hilo, HI, USA.

Transcript

1. http://jjherm.es
   @jotajotahermes
   J.J. Hermes
   Paparazzi lightning: 68 million
   images of white dwarfs from space
   with help from Boris Gänsicke, Steve Kawaler, Sandra
   Greiss, Pier-Emmanuel Tremblay, Nicola Pietro
   Gentile Fusillo, Roberto Raddi, Keaton J. Bell, Erik
   Dennihy, Bart Dunlap, Chris Clemens, Mike
   Montgomery, Don Winget, Tom Marsh, Seth Redfield,
   Mukremin Kilic, Matt Burleigh, Ian Braker, Stéphane
   Charpinet, Noemi Giammichele, Judi Provencal, et al.
   

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2. Accounting for 68 million WD images in Kepler & K2
   All K2 selection was done without Gaia DR2
   (Hundreds more candidate WDs were observed by programs
   led by Matt Burleigh, Steve Kawaler, Mukremin Kilic, John
   Lewis, and Seth Redfield but turned out to be non-WDs)
   JJ Hermes, Boston University | IAU 357: WD Tracers | 2
   2212 unique WDs with long-
   cadence (30-min) exposures:
   7.1 million frames
   572 unique WDs with short-
   cadence (1-min) exposures:
   61.5 million frames
   All numbers up to
   Campaign 18
   

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3. JJ Hermes, Boston University | IAU 357: WD Tracers | 3
   Hermes et al. 2020,
   in prep.
   The 2212 WDs observed by Kepler/K2 as seen by Gaia
   7.5
   log(
   g
   ) = 9 8.5 8.0
   Grey: Only photometry
   Black: 72% of WDs with spectra
   

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4. JJ Hermes, Boston University | IAU 357: WD Tracers | 4
   The 2212 WDs observed by Kepler/K2 as seen by Gaia
   7.5
   9 8.5 8.0
   Hermes et al. 2020,
   in prep.
   Red: WD+MS from SDSS
   

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5. The 2212 WDs observed by Kepler/K2 as seen by Gaia
   JJ Hermes, Boston University | IAU 357: WD Tracers | 5
   7.5
   8.5 8.0
   Hermes et al. 2020,
   in prep.
   Blue: SC Pulsations
   Orange: Spots
   9
   

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6. How pulsating and spotted WDs look from space
   0.0 0.5 1.0 1.5 2.0
   Rotational Phase
   °3
   °2
   °1
   0
   1
   Relative Flux (%)
   1
   0
   -1
   -2
   -3
   EC 14012-1446 (EPIC 212395381, Campaign 6), g=15.7 mag
   SDSSJ0344+1705 (EPIC 210609259, Campaign 4), g=17.7 mag
   2.04-day,
   stable signal
   Relative Flux (%)
   Rotational Phase
   JJ Hermes, Boston University | IAU 357: WD Tracers | 6
   0.0 0.5 1.0 1.5 2.0
   

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7. JJ Hermes, Boston University | IAU 357: WD Tracers | 7
   Rotation rates fall directly from K2 data of pulsators
   Assume Ck,l
   =0.47 in all
   cases for modes
   l
   =1
   Hermes et al. 2017 k2wd.org
   

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8. Isolated pulsating WDs rotate between 0.5-2.2 days
   JJ Hermes, Boston University | IAU 357: WD Tracers | 8
   1 d 2 d 4 d
   None of the stars are
   currently in binaries:
   representative of
   single-star
   evolution of
   mostly 1-3 M¤
   stars
   Hermes et al. 2017 k2wd.org
   

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9. Magnetic spotted WDs can reach extreme rotation rates
   JJ Hermes, Boston University | IAU 357: WD Tracers | 9
   1 d 2 d 4 d
   

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10. A strongly magnetic WD observed in K2
    Long-cadence (30-min)
    exposures showed a
    significant peak in FT
    at 3 ppt = 0.3%
    5 hr 2 hr 1 hr
    SDSS
    ν
    Nyq
    JJ Hermes, Boston University | IAU 357: WD Tracers | 10
    SDSSJ082547.52+174818.4
    g=18.9 mag
    DC in Nicola’s DR10 catalog
    K2 Campaign 5
    

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11. A strongly magnetic WD rotating at 18 min!
    JJ Hermes, Boston University | IAU 357: WD Tracers | 11
    0.0 0.5 1.0 1.5 2.0
    Rotational Phase
    °6
    °4
    °2
    0
    2
    4
    6
    Relative Flux (%)
    ν
    Nyq
    2ν
    Nyq
    3ν
    Nyq
    18.04410 min dark spot
    2 hr 30 min 20 min
    Folded SOAR
    High-speed photometry from
    SOAR shows this was a
    superNyquist signal at 18 min!
    K2 Campaign 5
    SOAR, 5-pt smoothed
    

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12. A confluence of failures: the fastest-rotating isolated WD
    JJ Hermes, Boston University | IAU 357: WD Tracers | 12
    1. Kepler broke, giving us the
    K2 mission along the ecliptic
    (Only 46 WDs observed in
    original Kepler mission.)
    

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13. A confluence of failures: the fastest-rotating isolated WD
    JJ Hermes, Boston University | IAU 357: WD Tracers | 13
    2. In K2 Campaign 10,
    CCD Module 4 failed
    one week into the
    campaign
    ν
    Nyq
    1% FAP
    Reding et al., in prep.
    

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14. A confluence of failures: the fastest-rotating isolated WD
    JJ Hermes, Boston University | IAU 357: WD Tracers | 14 Reding et al., in prep.
    A 315.96 s (5.3 min) signal!
    3. On 24 April 2018,
    the SOAR Goodman slit
    mask motor burned
    out, forcing us to do
    photometry instead of
    spectroscopy.
    ν
    Nyq 3
    ν
    Nyq 7
    ν
    Nyq 11
    ν
    Nyq
    

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15. The fastest-rotating isolated WD has modulated emission!
    JJ Hermes, Boston University | IAU 357: WD Tracers | 15
    Spectrum changes occur along the
    315.96 s (5.3 min) spin period!
    5.1 MG
    Joins GD 356 as a DAe!
    SOAR
    Reding et al., in prep.
    

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16. Magnetic spotted WDs: Failed SN Ia, mergers
    JJ Hermes, Boston University | IAU 357: WD Tracers | 16
    7.5
    log(
    g
    ) = 9 8.5 8.0
    18-min spot
    

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17. Magnetic spotted WDs: Failed SN Ia, mergers
    JJ Hermes, Boston University | IAU 357: WD Tracers | 17
    7.5
    log(
    g
    ) = 9 8.5 8.0
    18-min spot
    5-min spot
    

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18. Tons of science from 68 million images of WDs from space
    JJ Hermes, Boston University | IAU 357: WD Tracers
    e.g. Anomalously fast-rotating WDs are often strongly
    magnetic and likely connect to failed SN Ia
    The stars have
    set on K2,
    which observed
    >2000 WDs
    TESS picks up
    the torch: we
    are monitoring
    >3500 WDs with
    GRP
    < 16.5 mag
    

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