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Page 1: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space Telescope

Spitzer Meets K2M.Werner, J.Livingston, V.Gorjian, JPL/Caltech;

C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci;

J.Krick, SSC;

I.Crossfield, U.Arizona;

J.Schlieder, NASA-Ames;

H.Knutson, B.Benneke, I.Wong, E.Petigura, K.Deck, Caltech

Page 2: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space Telescope

Overview of Spitzer Meets K2

• 450 Hour Cycle 11 Spitzer GO Proposal– Main thrust is K2 candidate exoplanets around late stars– Our team screens and selects candidates for Spitzer study– 4.5um is wavelength of choice

• Have scheduled/executed 20 observations through K2 field 2– 16 exoplanets, 13 stars– First results to be reported here [Beichman et al, Benneke et al]

• Main science thrusts- Improved transit parameters based on better sampling , reduced limb brightening and higher S/N – Improved timing for JWST and other recovery followup– Search for TTVs

Page 3: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space TelescopeNominal Temperatures and Radii of Spitzer Meets K2 Exoplanet Targets

Page 4: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space Telescope

Stellar Colors and Exoplanet Orbital Radii for K2 Sample

Page 5: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space Telescope

Measured Transits for Two Planets Orbiting K2-3

an M0 Star with [4.5] = 8.4

K2-3bRadius = 2.04 RearthTransit depth = .0012T = 800K

K2-3dRadius = 1.53 RearthTransit depth = .00051T = 300K

Page 6: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Confirmation of the Transiting Habitable Zone Super-Earth K2-18b – Bjoern Benneke

• K2-18b is the first habitable zone exoplanet amenable to atmospheric characterization

• Only two transits observed by K2

Earth: 1370 W/m2

K2-18b: 1300 W/m2

K2-18

Page 7: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Detection of Third Transit

Transit occurs 7σ (1.8 hours) before predicted transit time! Spitzer transit will constrain eclipse/planet geometry much more effectively than did the K2 observations alone.

Predictedmid-transit timebased on K2(Montet et al. 2015)

Page 8: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Global Analysis of K2 + Spitzer Photometry

• Previously unidentified outlier in K2 data led to inaccurate ephemeris

No TTVK2

Spitzer

Page 9: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

K2-18b would have been lost for future characterizations

• Long observation time possible from Spitzer facilitated recovery• Ephemeris from K2 could have led to non-detections with HST and JWST

Page 10: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space Telescope

Summary of Initial Results• Spitzer at 4.5um confirms K2 measurements of transit depths for

exoplanets K2-3 b,c,d; K2-18b; and 20208328b

• Further analysis of Spitzer data will provide improved constraints on transit geometry and exoplanet properties for these and other systems, including small HZ planets– TTV analysis of K2-3 system in process by Kat Deck, results to be

included in Beichman et al paper

• First round of Spitzer measurements reduce uncertainty in transit times for JWST era. Most dramatically, the transits of K2-18b will occur ~six hours earlier at the time of the JWST launch than K2 ephemeris alone would predict

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Spitzer Space Telescope

K2-3b is a Promising Target for JWST Spectroscopy

Simulations by Mike Line and Tom Greene of the JWST transmission spectrum of K2-3b for several atmosphere models

Page 12: Spitzer Space Telescope Spitzer Meets K2 M.Werner, J.Livingston, V.Gorjian, JPL/Caltech; C.Beichman, D.Ciardi, J.Christiansen, R.Akeson, NExSci; J.Krick,

Spitzer Space Telescope

Conclusions• Spitzer followup of K2 promises to be very productive

scientifically and to set the stage for JWST

• Observations of K2-3, K2-18b, & 20209328b have:• Confirmed transit depths• Provided better data for exoplanet characterization• Improved ephemerides for JWST work

• Future plans• 8 additional exoplanets already queued up for observation • Several hundred hours still to be scheduled – we invite

suggestions of targets we may overlook • Program expanded to include FGK stars• Extend Spitzer through Senior Review to go beyond K2

field 5

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Spitzer Space Telescope

K2 Exoplanets observed or currently planned for observation with Spitzer

K2-22b