Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching

The James Webb Space Telescope (JWST) is predicted to make great advances in the field of exoplanet atmospheres. Its 25 m 2 mirror means that it can reach unprecedented levels of precision in observations of transit spectra, and can thus characterise the atmospheres of planets orbiting stars several hundred pc away. Its coverage of the infrared spectral region between 0.6 and 28 µm allows the abundances of key molecules to be probed during the transit of a planet in front of the host star, and when the same planet is eclipsed constraints can be placed on its temperature structure. In this work, we explore the possibility of using low-spectral-resolution observations by JWST/NIRSpec and JWST/MIRI-LRS together to optimise wavelength coverage and break degeneracies in the atmospheric retrieval problem for a range of exoplanets from hot Jupiters to super Earths. This approach involves stitching together non-simultaneous observations in different wavelength regions, rendering it necessary to consider the effect of time-varying instrumental and astrophysical systematics. We present the results of a series of retrieval feasibility tests examining the effects of instrument systematics and star spots on the recoverability of the true atmospheric state, and demonstrate that correcting for these systematics is key for successful exoplanet science with JWST.

[1]  Philipp Eigmüller,et al.  NGTS: a robotic transit survey to detect Neptune and super-Earth mass planets , 2012, Other Conferences.

[2]  S. Aigrain,et al.  HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b , 2013, 1309.5261.

[3]  Drake Deming,et al.  3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b , 2012, 1206.6887.

[4]  Alain Lecavelier des Etangs,et al.  THE DEEP BLUE COLOR OF HD 189733b: ALBEDO MEASUREMENTS WITH HUBBLE SPACE TELESCOPE/SPACE TELESCOPE IMAGING SPECTROGRAPH AT VISIBLE WAVELENGTHS , 2013, 1307.3239.

[5]  S. Aigrain,et al.  The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations , 2012, 1210.4163.

[6]  K. Heng,et al.  ATMOSPHERIC RETRIEVAL ANALYSIS OF THE DIRECTLY IMAGED EXOPLANET HR 8799b , 2013, 1307.1404.

[7]  Lothar Frommhold,et al.  Collision-induced infrared spectra of H2-He pairs involving 0-1 vibrational transitions and temperatures from 18 to 7000 K , 1989 .

[8]  J. Champion,et al.  Spherical top data system (STDS) software for the simulation of spherical top spectra , 1998 .

[9]  Sara Seager,et al.  ATMOSPHERIC RETRIEVAL FOR SUPER-EARTHS: UNIQUELY CONSTRAINING THE ATMOSPHERIC COMPOSITION WITH TRANSMISSION SPECTROSCOPY , 2012, 1203.4018.

[10]  A. Collier Cameron,et al.  The SuperWASP wide-field exoplanetary transit survey: candidates from fields 23 h < RA < 03 h , 2006 .

[11]  I. P. Waldmann,et al.  ON SIGNALS FAINT AND SPARSE: THE ACICA ALGORITHM FOR BLIND DE-TRENDING OF EXOPLANETARY TRANSITS WITH LOW SIGNAL-TO-NOISE , 2013, 1302.6714.

[12]  Andreas Seifahrt,et al.  TRANSMISSION SPECTROSCOPY OF THE HOT JUPITER WASP-12b FROM 0.7 TO 5 μm , 2013, 1305.1670.

[13]  Drake Deming,et al.  Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b , 2013, Nature.

[14]  Robert T. Zellem,et al.  THE 4.5 μm FULL-ORBIT PHASE CURVE OF THE HOT JUPITER HD 209458b , 2014, 1405.5923.

[15]  P. Drossart,et al.  Models of the global cloud structure on Venus derived from Venus Express observations , 2012 .

[16]  C. Sotin,et al.  Thermal Structure and Dynamics of Saturn’s Northern Springtime Disturbance , 2011, Science.

[17]  S. Aigrain,et al.  The transit spectra of Earth and Jupiter , 2014, 1408.3914.

[18]  Joanna K. Barstow,et al.  CLOUDS ON THE HOT JUPITER HD189733b: CONSTRAINTS FROM THE REFLECTION SPECTRUM , 2014, 1403.6664.

[19]  Nikole K. Lewis,et al.  SPITZER TRANSITS OF THE SUPER-EARTH GJ1214b AND IMPLICATIONS FOR ITS ATMOSPHERE , 2012, 1301.6763.

[20]  Drake Deming,et al.  Accepted for publication in the Astrophysical Journal Strong Infrared Emission from the Extrasolar Planet HD189733b , 2006 .

[21]  Michel Mayor,et al.  The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b , 2008, 0802.0845.

[22]  T. Fouchet,et al.  Retrievals of Jovian tropospheric phosphine from CassiniKIRS , 2004 .

[23]  Drake Deming,et al.  Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet , 2014, Nature.

[24]  Jonathan Tennyson,et al.  HITEMP, the high-temperature molecular spectroscopic database , 2010 .

[25]  S. Tashkun,et al.  CDSD-1000, the high-temperature carbon dioxide spectroscopic databank , 2003 .

[26]  S. Aigrain,et al.  Hst hot jupiter transmission spectral survey: Detection of water in HAT-P-1b from WFC3 near-IR spatial scan observations , 2013, 1308.2106.

[27]  Ansgar Reiners,et al.  A new extensive library of PHOENIX stellar atmospheres and synthetic spectra , 2013, 1303.5632.

[28]  G. Laughlin,et al.  Discovery and Characterization of Transiting Super Earths Using an All-Sky Transit Survey and Follow-up by the James Webb Space Telescope , 2009, 0903.4880.

[29]  S. Calcutt,et al.  The NEMESIS planetary atmosphere radiative transfer and retrieval tool , 2008 .

[30]  Y. Yung,et al.  Atmospheric Radiation: Theoretical Basis , 1989 .

[31]  David Charbonneau,et al.  The 3.6-8.0 μm Broadband Emission Spectrum of HD 209458b: Evidence for an Atmospheric Temperature Inversion , 2007, 0709.3984.

[32]  Sara Seager,et al.  Constraining Exoplanet Mass from Transmission Spectroscopy , 2013, Science.

[33]  Mark Clampin,et al.  Discovery and Characterization of Transiting SuperEarths Using an All-Sky Transit Survey and Follow-Up by the James Webb Space Telescope , 2010 .

[34]  Lothar Frommhold,et al.  Collision-induced infrared spectra of H2-He pairs at temperatures from 18 to 7000 K. II - Overtone and hot bands , 1989 .

[35]  A. Collier Cameron,et al.  Thermal emission at 4.5 and 8 μm of WASP-17b, an extremely large planet in a slightly eccentric orbit , 2011, 1101.5620.

[36]  Drake Deming,et al.  EXOPLANET TRANSIT SPECTROSCOPY USING WFC3: WASP-12 b, WASP-17 b, AND WASP-19 b , 2013, 1310.2949.

[37]  Norman Murray,et al.  BROADBAND TRANSMISSION SPECTROSCOPY OF THE SUPER-EARTH GJ 1214b SUGGESTS A LOW MEAN MOLECULAR WEIGHT ATMOSPHERE , 2011, 1104.0011.

[38]  Sara Seager,et al.  THE OPTICAL AND NEAR-INFRARED TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ 1214b: FURTHER EVIDENCE FOR A METAL-RICH ATMOSPHERE , 2011, 1109.0582.

[39]  Laurence S. Rothman,et al.  HITRAN HAWKS and HITEMP: high-temperature molecular database , 1995, Defense, Security, and Sensing.

[40]  Joanna K. Barstow,et al.  Constraining the atmosphere of GJ 1214b using an optimal estimation technique , 2013, 1306.6567.

[41]  Mark Clampin,et al.  INFRARED TRANSMISSION SPECTROSCOPY OF THE EXOPLANETS HD 209458b AND XO-1b USING THE WIDE FIELD CAMERA-3 ON THE HUBBLE SPACE TELESCOPE , 2013, 1302.1141.

[42]  A. Borysow,et al.  Collision-induced absorption coefficients of H2 pairs at temperatures from 60 K to 1000 K , 2002 .

[43]  R. Gilliland,et al.  Detection of an Extrasolar Planet Atmosphere , 2001, astro-ph/0111544.

[44]  A. Lacis,et al.  A description of the correlated k distribution method for modeling nongray gaseous absorption, thermal emission, and multiple scattering in vertically inhomogeneous atmospheres , 1991 .

[45]  F. Selsis,et al.  Potential biosignatures in super-Earth atmospheres II. Photochemical responses. , 2013, Astrobiology.

[46]  E. Gaidos,et al.  NARROW-K-BAND OBSERVATIONS OF THE GJ 1214 SYSTEM , 2013, 1308.4404.

[47]  Lothar Frommhold,et al.  A new computation of the infrared absorption by H2 pairs in the fundamental band at temperatures from 600 to 5000 K , 1990 .

[48]  Joanna K. Barstow,et al.  On the potential of the EChO mission to characterise gas giant atmospheres , 2012, 1212.5020.

[49]  Mark Clampin,et al.  Transiting Exoplanet Survey Satellite (TESS) , 2014, Astronomical Telescopes and Instrumentation.

[50]  Patrick G. J. Irwin,et al.  Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy , 2011, 1110.2934.