Very Thick, High Clouds of Salt or Sulfides can Produce Flat Transmission Spectra on Mini Neptunes and SuperEarths

THERMAL EMISSION AND REFLECTED LIGHT SPECTRA OF SUPER EARTHS WITH FLAT TRANSMISSION SPECTRA

Authors:

Morley et al

Abstract:

Planets larger than Earth and smaller than Neptune are some of the most numerous in the galaxy, but observational efforts to understand this population have proved challenging because optically thick clouds or hazes at high altitudes obscure molecular features. We present models of super Earths that include thick clouds and hazes and predict their transmission, thermal emission, and reflected light spectra. Very thick, lofted clouds of salts or sulfides in high metallicity (1000× solar) atmospheres create featureless transmission spectra in the near-infrared. Photochemical hazes with a range of particle sizes also create featureless transmission spectra at lower metallicities. Cloudy thermal emission spectra have muted features more like blackbodies, and hazy thermal emission spectra have emission features caused by an inversion layer at altitudes where the haze forms. Close analysis of reflected light from warm (~400–800 K) planets can distinguish cloudy spectra, which have moderate albedos (0.05–0.20), from hazy models, which are very dark (0.0–0.03). Reflected light spectra of cold planets (~200 K) accessible to a space-based visible light coronagraph will have high albedos and large molecular features that will allow them to be more easily characterized than the warmer transiting planets. We suggest a number of complementary observations to characterize this population of planets, including transmission spectra of hot ($\gtrsim 1000$ K) targets, thermal emission spectra of warm targets using the James Webb Space Telescope, high spectral resolution (R ~ 105) observations of cloudy targets, and reflected light spectral observations of directly imaged cold targets. Despite the dearth of features observed in super Earth transmission spectra to date, different observations will provide rich diagnostics of their atmospheres.

The jet and Disk of Protostar HH 212 is VERY Sulfur Enriched

The jet and the disk of the HH 212 low-mass protostar imaged by ALMA: SO and SO2 emission

Authors:

Podio et al

Abstract:

To investigate the disk formation and jet launch in protostars is crucial to comprehend the earliest stages of star and planet formation. We aim to constrain the properties of the molecular jet and the disk of the HH 212 protostellar system at unprecedented angular scales through ALMA observations of sulfur-bearing molecules, SO 9(8)-8(7), SO 10(11)-10(10), SO2 8(2,6)-7(1,7). SO 9(8)-8(7) and SO2 8(2,6)-7(1,7) show broad velocity profiles. At systemic velocity they probe the circumstellar gas and the cavity walls. Going from low to high blue-/red-shifted velocities the emission traces the wide-angle outflow and the fast (~100-200 km/s) and collimated (~90 AU) molecular jet revealing the inner knots with timescales less than 50 years. The jet transports a mass loss rate greater than 0.2-2e-6 Msun/yr, implying high ejection efficiency ( greater than 0.03-0.3). The SO and SO2 abundances in the jet are ~1e-7-1e-6. SO 10(11)-10(10) emission is compact and shows small-scale velocity gradients indicating that it originates partly from the rotating disk previously seen in HCO+ and C17O, and partly from the base of the jet. The disk mass is greater than 0.002-0.013 Msun, and the SO abundance in the disk is ~1e-8-1e-7. SO and SO2 are effective tracers of the molecular jet in the inner few hundreds AU from the protostar. Their abundances indicate that 1% - 40% of sulfur is in SO and SO2 due to shocks in the jet/outflow and/or to ambipolar diffusion at the wind base. The SO abundance in the disk is 3-4 orders of magnitude larger than in evolved protoplanetary disks. This may be due to an SO enhancement in the accretion shock at the envelope-disk interface or in spiral shocks if the disk is partly gravitationally unstable.

Water and Sulfide Clouds in Brown Dwarf J085510.83-071442.5

Indications of Water Clouds in the Coldest Known Brown Dwarf

Authors:

Faherty et al

Abstract:

We present a deep near-infrared image of the newly discovered brown dwarf WISE J085510.83-071442.5 (W0855) using the FourStar imager at Las Campanas Observatory. Our detection of J3=24.8+0.33 -0.53 (J_MKO=25.0+0.33-0.53) at 2.6sigma -- or equivalently an upper limit of J3 greater than 23.8 (J_MKO greater than 24.0) at 5sigma makes W0855 the reddest brown dwarf ever categorized (J_MKO - W2 = 10.984+0.33 - 0.53 at 2.6sigma -- or equivalently an upper limit of J_MKO - W2 > 9.984 at 5sigma) and refines its position on color magnitude diagrams. Comparing the new photometry with chemical equilibrium model atmosphere predictions, we demonstrate that W0855 is 4.5sigma from models using a cloudless atmosphere and well reproduced by partly cloudy models (50%) containing sulfide and water ice clouds. Non-equilibrium chemistry or non-solar metallicity may change predictions, however using currently available model approaches, this is the first candidate outside our own solar system to have direct evidence for water clouds.