stellar and exoplanetary masses and radii · conclusions •precise model-independent stellar...

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

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

2/25/2016 D.J. Stevens -- SPHEREx Workshop 2016 2

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)


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


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


Why Precise Masses and Radii?

• Exoplanet composition

• F dwarf rotational

mixing

Fulton+15

Can use single-lined

EBs found from planet

searches!


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!


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)


Complementary Constraints

• Primary log(g)

• Spectroscopy

• Asteroseismology

• Flicker

• Primary radius

• Parallax + SED

Winn (2010)


1 AU

Precise Parameters from Parallax

• Linear error propagation:

• Precise radii easier than masses, but still difficult!

• How low can we go?


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


KELT Follow-up Network


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)


KELT

Hipparcos

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)


Example: KELT-3

• V = 9.8

• P = 2.7 days

• 9mmag transit

• 25min ingress

• d ~ 180 pc

Pepper+13


Example: KELT-3 Pepper+13


Gaia

SPHEREx

• Now:

Observations

miss 20% of

flux

• SPHEREx

+ Gaia:

Only miss

2%!

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


KELT-3 SED: + SPHEREx + Gaia

• Assuming:

• Shot noise

dominates

• 0.2%

systematic

• 50%

throughputs

• 10nm per

Gaia

element


• 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:

Bonus: Extinction


Av = 0.0

Av = 1.0

Can measure extinction!


• 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

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)


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


stellar and exoplanetary masses and radii · conclusions •precise model-independent stellar...

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