Stellar and Exoplanetary Masses and Radii · Conclusions •Precise model-independent stellar...
Transcript of Stellar and Exoplanetary Masses and Radii · Conclusions •Precise model-independent stellar...
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MASSES AND RADII OF
STARS AND EXOPLANETS
Daniel J. Stevens1
B. Scott Gaudi1 & Keivan G. Stassun2
SPHEREx Science Community Workshop
February 25, 2016
1The Ohio State University 2Vanderbilt University
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State of the Art: eSB2s: ~only way to
directly measure M, R
Torres et al. (2010)
• 94 eSB2s + aCen
• 3% precision on
mass and radius
Problems:
• 4 stars < 0.5 M_sun
• Few with
metallicities
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Why Precise Masses and Radii?
1. Inflated M dwarf radii
Birkby+12 • Bad models?
• (e.g. Mann+15,
Boyajian+12)
• Stellar activity?
• (Lopez-Morales
07, Birkby+12)
• Binary physics?
• (Kraus+11,
Birkby+12)
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Inflated M Dwarf Radii – Binary Physics?
• Kraus+11: Inflation
decreases for
P_orb > 3 days
• Birkby+12: Bigger
sample, inflation at
higher periods
• Large errors
Birkby+12
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Single vs. Binary Stars
• Interferometric M dwarfs are also inflated
• Uncorrelated with activity (Mann+15)
Boyajian+12
EB
Single
• Single-binary
comparisons are
difficult:
• EB Teffs lower by 200-
300K
• Single star masses
from M-L relation
(Delfosse+00)
• 5% scatter
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Why Precise Masses and Radii?
• Exoplanet composition
• F dwarf rotational
mixing
Fulton+15
Can use single-lined
EBs found from planet
searches!
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Why Single-lined Eclipsing Systems?
Like Double-lined EBs:
• Exoplanet transit/RV
surveys find them for free
• Large sample volume
• Hundreds of pc
• Masses without models or
empirical relations
Unlike Double-lined EBs:
• One set of spectral lines
• Easier primary log(g), Teff,
[Fe/H]
• Tougher for companion
• Need more than
RV+eclipse…
• Transiting/RV exoplanets!
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How it Works
• From transit/eclipse:
• Measure period, depth,
FHWM/ingress durations
• => a/R_1, R_2/R_1
• Infer primary density:
• RV semiamplitude:
Winn (2010)
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Complementary Constraints
• Primary log(g)
• Spectroscopy
• Asteroseismology
• Flicker
• Primary radius
• Parallax + SED
Winn (2010)
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1 AU
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Precise Parameters from Parallax
• Linear error propagation:
• Precise radii easier than masses, but still difficult!
• How low can we go?
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Kilodegree Extremely Little Telescope
Aperture: 42 mm
CCD: Apogee AP16E 4k x 4k
Pixel Size: 9 microns
Field-of-View: 26x26 sq. deg.
Plate Scale: 23 arcsec/pixel
KELT-North (Sonoita, AZ) KELT-South
(Sutherland, S. Africa)
• All-sky transit survey
• 7.5 > V > 12
• 9 published planets
• >200 eSB1 candidates
• 0.5d < P_orb < 30d
• ~80 could have M dwarf
companions
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KELT Follow-up Network
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Parallax: Gaia
(ESA-D. Ducros, 2013)
(ESA)
• 5-10 micro-arcsec
for bright stars
(de Bruijne+15, de
Bruijne 12)
• ~unaffected by
ice/straylight
• ~0.1% distances for
KELT stars
• (<~300pc)
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KELT
Hipparcos
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SED Bolometric Fluxes and More
• SPHEREx spectrophotometry
• Bands 1-3: 750nm – 4.1 microns (R = 41.5)
• Band 4: 4.1 microns – 4.8 microns (R = 150)
• Rayleigh-Jeans tail
• More flux for K and M dwarfs
• Gaia low-resolution spectrophotometry
• Blue-pass (BP): 330nm – 680nm
• Red-pass (RP): 640nm – 1050nm
• SED peak
• SPHEREx + Gaia: Measure most of the energy!
(spherex.caltech.edu)
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Example: KELT-3
• V = 9.8
• P = 2.7 days
• 9mmag transit
• 25min ingress
• d ~ 180 pc
Pepper+13
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Example: KELT-3 Pepper+13
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Gaia
SPHEREx
• Now:
Observations
miss 20% of
flux
• SPHEREx
+ Gaia:
Only miss
2%!
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KELT-3 SED: Literature Observations
• F_bol :
2.94x10^-9
erg/s/cm^2
• ~6% error
• Av = 0.02 + 0.02
• Teff = 6350 + 150 K
• log(g) = 4.0 + 0.5
• Fe/H = 0.0 +0.5-1.0
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KELT-3 SED: + SPHEREx + Gaia
• Assuming:
• Shot noise
dominates
• 0.2%
systematic
• 50%
throughputs
• 10nm per
Gaia
element
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• Av = 0.00 +0.01-0.00
• Teff = 6306 + 5 K
• log(g) = 4.0 + 0.2
• [Fe/H] = 0.0 + 0.1
• Av = 0.02 + 0.02
• Teff = 6350 + 150 K
• log(g) = 4.0 + 0.5
• [Fe/H] = 0.0 +0.5-1.0
SPHEREx+Gaia: Without:
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Bonus: Extinction
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Av = 0.0
Av = 1.0
Can measure extinction!
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• log(g):
• 21% radius
• 65% mass
• Parallax:
• 6% F_bol
• 5.6% radius
• 18% mass
• SPHEREx +
Gaia:
• 2% F_bol
• 1% radius
• 8% mass
Constraining KELT-3 Host
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Next Steps
1. SPHEREx+Gaia error estimates
• Correlated and systematic errors in/between each channel
2. Account for covariances between input parameters
3. Fit mock data
1. Modified ExoFAST/MultiFAST (Eastman 2012)
4. Follow up and fit KELT eSB1s
5. Add more parameters
1. Abundances (SDSS-APOGEE)
2. log(g) (APOGEE, TESS)
3. Companion Teff from secondary eclipses (TESS)
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Conclusions
• Precise model-independent stellar masses and radii:
reconcile observations and models
• Turn transit false signals into robust anchors for empirical
stellar and planetary relations
• SPHEREx + Gaia => exquisite radii (Fbol, Teff, distance)
• Directly constrain extinction
• Compare atmosphere model accuracy
• Long-term: Catalog of exceptionally well-characterized
stars and exoplanets
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