False Positives and Shallow Eclipsing Binaries · 2015-04-21 · (PSPM WP132,300, PLATO field...
Transcript of False Positives and Shallow Eclipsing Binaries · 2015-04-21 · (PSPM WP132,300, PLATO field...
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False Positives andShallow Eclipsing Binaries
as will be seen by PLATO 2.0
P. Rowden, E. Farrell, R. Farmer, U. KolbThe Open University
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FALSE POSITIVEa signal mimicking that arising from an exoplanet but
actually arising from another astrophysical body
Typicallyl a grazing eclipsing binary
l a white dwarf or brown dwarfl blends with a background eclipsing binary
PLATO 2.0 will have a large pixel size of 15” x 15”so there will be a significant blending problem.
Research question (part of PLATO Input Catalogue work packages(PSPM WP132,300, PLATO field contaminants, led by U. Kolb)):
How close to the Galactic plane can PLATO 2.0 gaze,
allowing more genuine exoplanets to be detected,
before the numbers of false positives become unmanageable?
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Blends: why are they a problem?
log(2δ) = –0.4Δmmax
This is the maximum eclipse depth in an MS/MS system
log
flux
Foreground star
Background Eclipsing Binary
Δm
δ
Measured eclipse depth
+ =
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PLATO 2.0 proposed fields of view
Red squares: the two “Long Look” fields: PLATO 2.0 will spend2-3 years observing these fields.
Grey squares: Step-and-stare phase, up to five months per field.
PLATO 2.0 is ESA’s M3 mission, due for launch in 2024 and will operate at the L2 position.
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Binary Population Synthesis with BiSEPSprevious applications include
“The True Stellar parameters of the Kepler Target List”, Farmer et al (2013)
log Teff [K]
log g
[cm
s-2]
The distribution of the Kepler Q2 data set from the Kepler Stellar Classification Program (SCP).The contour indicates the region covered by the synthetic distribution after processing,while the grey-shaded area indicates the true parameters of the synthetic distribution.
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PLATO 2.0 follow-up observations
Based on The PLATO 2.0 Mission, 2014, Rauer et al, p 51
Lightcurve Vetting
High AngularResolution Image
Precise RadialVelocities
False positivesintrinsic variations; transits by WD;
blends from background binaries, triple systemsand giant planet transits
No Characterisationhot stars; high rotation;
active stars; other
ConfirmedPlanets
SpectroscopicReconnaisance
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Measured eclipsing binary depths from 2 x 10-2 to 1 x 10-5
mr ≤ 16 (measured), l = 64.5°-65.5°, b = 6.5°-15.0°. Binning: b = 0.17° , Δm ≈ 0.25.
Gal
actic
latit
ude/
°
Magnitude difference
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BlendedeclipsingbinariesStrip size:l = 64.5-65.5 (1°)b = 6.5-54.5 (48°)
All systems
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BlendedeclipsingbinariesStrip size:l = 64.5-65.5 (1°)b = 6.5-54.5 (48°)
All systems
MS/MS systems
Evolutionary primary is an RGB
Evolutionary primary is a WD
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–10 –8 –6 –4 –2 0log10 Maximum Eclipse Depth
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–10 –8 –6 –4 –2 0log10 Maximum Eclipse Depth
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–10 –8 –6 –4 –2 0log10 Maximum Eclipse Depth
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–10 –8 –6 –4 –2 0log10 Maximum Eclipse Depth
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WHERE NEXT?l Extend the coverage to the full sky at low latitudes (≤ b = 55°)
l Study the nature of the systems that may form false positives
l Extend BiSEPS to cover triple systems
l Consider contamination by giant planets ofterrestrial planet signals
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SUMMARYl PLATO 2.0 seeks to discover Earth-like planets.
l The large point spread function means thatfalse positives are a serious issue,
especially at lower Galactic latitudes.
l We use binary population synthesis tools(BiSEPS) to study this problem.
l Early results indicate that,especially at low latitudes,
systems that produce an Earth-like signalwill probably have Δm ≈ 8and will be MS/MS systemswith a non-grazing eclipse.
Image:NASA/Goddard
Space Flight CenterScientific Visualisation Studio