THEORETICAL TRANSIT SPECTRA FOR GJ 1214b AND OTHER “SUPER-EARTHS”

We present new calculations of transit spectra of super-Earths that allow for atmospheres with arbitrary proportions of common molecular species and haze. We test this method with generic spectra, reproducing the expected systematics and absorption features, then apply it to the nearby super-Earth GJ 1214b, which has produced conflicting observational data, leaving the questions of a hydrogen-rich versus hydrogen-poor atmosphere and the water content of the atmosphere ambiguous. We present representative transit spectra for a range of classes of atmosphere models for GJ 1214b. Our analysis supports a hydrogen-rich atmosphere with a cloud or haze layer, although a hydrogen-poor model with 10% water is not ruled out. Several classes of models are ruled out, however, including hydrogen-rich atmospheres with no haze, hydrogen-rich atmospheres with a haze of ~0.01 μm tholin particles, and hydrogen-poor atmospheres with major sources of absorption other than water. We propose an observational test to distinguish hydrogen-rich from hydrogen-poor atmospheres. Finally, we provide a library of theoretical transit spectra for super-Earths with a broad range of parameters to facilitate future comparison with anticipated data.

[1]  D. Queloz,et al.  Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer , 2011, 1105.0415.

[2]  C. Moutou,et al.  Detection of atmospheric haze on an extrasolar planet: the 0.55–1.05 μm transmission spectrum of HD 189733b with the Hubble Space Telescope , 2007, 0712.1374.

[3]  et al,et al.  The CoRoT space mission : early results Special feature Transiting exoplanets from the CoRoT space mission VIII . CoRoT-7 b : the first super-Earth with measured radius , 2009 .

[4]  Adam Burrows,et al.  Theoretical Spectra and Atmospheres of Extrasolar Giant Planets , 2003 .

[5]  Joshua N. Winn,et al.  THE TRANSIT LIGHT CURVE PROJECT. XIII. SIXTEEN TRANSITS OF THE SUPER-EARTH GJ 1214b , 2010, 1012.0376.

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

[7]  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.

[8]  James W. Head,et al.  The surface of Venus , 2003 .

[9]  S. Seager,et al.  Mass-Radius Relationships for Solid Exoplanets , 2007, 0707.2895.

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

[11]  C. Sotin,et al.  Mass–radius curve for extrasolar Earth-like planets and ocean planets , 2007 .

[12]  J. Schneider,et al.  Constraints on the exosphere of CoRoT-7b , 2010, 1009.5500.

[13]  T. Barman,et al.  HIGH-RESOLUTION, DIFFERENTIAL, NEAR-INFRARED TRANSMISSION SPECTROSCOPY OF GJ 1214b , 2011, 1104.1173.

[14]  A. D. Etangs,et al.  Rayleigh scattering in the transit spectrum of HD 189733b , 2008, 0802.3228.

[15]  Drake Deming,et al.  Infrared radiation from an extrasolar planet , 2005, Nature.

[16]  K. F. Palmer,et al.  Optical constants of sulfuric Acid; application to the clouds of venus? , 1975, Applied optics.

[17]  K. Kinemuchi,et al.  KEPLER-10 c: A 2.2 EARTH RADIUS TRANSITING PLANET IN A MULTIPLE SYSTEM , 2011, 1105.4647.

[18]  R. Kudritzki,et al.  THE DISTANCE TO THE MASSIVE ECLIPSING BINARY LMC-SC1-105 IN THE LARGE MAGELLANIC CLOUD , 2011, 1101.1953.

[19]  Jacob L. Bean,et al.  A ground-based transmission spectrum of the super-Earth exoplanet GJ 1214b , 2010, Nature.

[20]  Jie Li,et al.  Kepler-22b: A 2.4 EARTH-RADIUS PLANET IN THE HABITABLE ZONE OF A SUN-LIKE STAR , 2011, The Astrophysical Journal.

[21]  A. Burrows,et al.  Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres , 1999 .

[22]  Diana Valencia,et al.  Detailed Models of Super-Earths: How Well Can We Infer Bulk Properties? , 2007, 0704.3454.

[23]  Xavier Bonfils,et al.  A super-Earth transiting a nearby low-mass star , 2009, Nature.

[24]  Austin,et al.  KEPLER'S FIRST ROCKY PLANET: KEPLER-10b , 2011, 1102.0605.

[25]  J. Fortney,et al.  THE NATURE OF THE ATMOSPHERE OF THE TRANSITING SUPER-EARTH GJ 1214b , 2010, 1001.0976.

[26]  Jaymie M. Matthews,et al.  A SUPER-EARTH TRANSITING A NAKED-EYE STAR , 2011, 1104.5230.

[27]  J. Koppenhoefer,et al.  Optical to near-infrared transit observations of super-Earth GJ 1214b: water-world or mini-Neptune? , 2011, 1111.2628.

[28]  A. Burrows,et al.  Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres , 2006, astro-ph/0607211.

[29]  A. Burrows,et al.  Giant Planet Atmospheres and Spectra , 2009, 0910.0248.

[30]  B. Jackson,et al.  RECENT TRANSITS OF THE SUPER-EARTH EXOPLANET GJ 1214b , 2010, 1008.1748.

[31]  David Charbonneau,et al.  THE GJ1214 SUPER-EARTH SYSTEM: STELLAR VARIABILITY, NEW TRANSITS, AND A SEARCH FOR ADDITIONAL PLANETS , 2010, 1012.0518.

[32]  Extrasolar Carbon Planets , 2005, astro-ph/0504214.

[33]  F. Murgas,et al.  Narrow band Hα photometry of the super-Earth GJ 1214b with GTC/OSIRIS tunable filters , 2012, 1206.6619.

[34]  L. Arnold,et al.  Transmission spectrum of Venus as a transiting exoplanet , 2011, 1112.0572.

[35]  Mercedes Lopez-Morales,et al.  55 CANCRI: STELLAR ASTROPHYSICAL PARAMETERS, A PLANET IN THE HABITABLE ZONE, AND IMPLICATIONS FOR THE RADIUS OF A TRANSITING SUPER-EARTH , 2011, 1106.1152.

[36]  J. Fortney,et al.  THE ATMOSPHERIC CHEMISTRY OF GJ 1214b: PHOTOCHEMISTRY AND CLOUDS , 2011, 1104.5477.

[37]  Carl Sagan,et al.  Tholins: organic chemistry of interstellar grains and gas , 1978, Nature.

[38]  D. Sasselov,et al.  THE ATMOSPHERIC SIGNATURES OF SUPER-EARTHS: HOW TO DISTINGUISH BETWEEN HYDROGEN-RICH AND HYDROGEN-POOR ATMOSPHERES , 2008, 0808.1902.

[39]  Gautam Vasisht,et al.  The presence of methane in the atmosphere of an extrasolar planet , 2008, Nature.

[40]  S. Seager,et al.  THREE POSSIBLE ORIGINS FOR THE GAS LAYER ON GJ 1214b , 2009, 0912.3243.

[41]  E. Ganor,et al.  Shape and optical properties of aerosols formed by photolysis of acetylene, ethylene, and hydrogen cyanide , 1988 .

[42]  G. Marcy,et al.  Detection of a Transiting Low-Density Super-Earth , 2011, 1109.2549.

[43]  Mark S. Marley,et al.  Planetary Radii across Five Orders of Magnitude in Mass and Stellar Insolation: Application to Transits , 2006 .

[44]  M. W. Williams,et al.  Optical constants of organic tholins produced in a simulated Titanian atmosphere: From soft x-ray to microwave frequencies , 1984 .

[45]  E. Agol,et al.  APOSTLE OBSERVATIONS OF GJ 1214b: SYSTEM PARAMETERS AND EVIDENCE FOR STELLAR ACTIVITY , 2010, 1012.1180.

[46]  K. Menou.  ATMOSPHERIC CIRCULATION AND COMPOSITION OF GJ1214b , 2011, 1109.1574.

[47]  J. Fortney,et al.  OBSERVATIONAL EVIDENCE FOR A METAL-RICH ATMOSPHERE ON THE SUPER-EARTH GJ1214b , 2011, 1103.2370.

[48]  W. C. Bowman,et al.  A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b , 2010, Nature.

[49]  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.