The atmosphere of 2M1207 b

The highest resolution near-IR spectrum of the imaged planetary mass companion 2M1207 b
http://arxiv.org/abs/1003.4507

Abstract wrote:

Direct-imaging searches for planets reveal wide orbit planets amenable to spectroscopy, and their atmospheres represent an important comparison to the irradiated atmospheres of Hot Jupiters. Using AO integral field spectroscopy of 2M1207 b, the shape of the continuum emission over the J, H, and K bands from the atmosphere of this young, planetary mass companion is measured in order to compare with atmospheric and evolutionary models, and objects of similar temperature in young clusters and the field. The 2M1207 b spectrum has the highest spectral resolution (R~300-1500) and largest wavelength coverage, including the first J-band spectrum, for this benchmark object. The high signal-to-noise of the data allow a clear identification of signatures of low surface gravity, and comparison with a grid of AMES-Dusty models reveals a best-fit effective temperature of Teff=1600 K with a preferred surface gravity of log g=4.5. The J-band flux is depressed relative to nearly all L-type objects, and the detailed shape of the absorption features across the H-band exhibit differences from the model predictions. The possible origins of 2M1207 b and its low luminosity are examined with the new data and analysis which suggest that extinction from a disk with large grains is a viable scenario and is preferred over scatttering off an optically thick disk. The 2M1207 b spectrum presents an important comparison for the types of features which may be present in upcoming spectra of the atmospheres of planets imaged in orbit around stellar primaries.

Further study of the under-luminosity of 2M1207b: apparently thick clouds may do a better job of explaining this than an edge-on disc. Implies that the sub-luminous brown dwarfs (e.g. HD 203030B, HN Pegasi B, the HR 8799 planets) may be cooler and less massive than thought.

Evidence Against an Edge-On Disk Around the Extrasolar Planet 2MASS 1207 b and a New Thick Cloud Explanation for its Under-Luminosity

The Young Planet-mass Object 2M1207b: a cool, cloudy, and methane-poor atmosphere
http://arxiv.org/abs/1106.1201

Quote :

The properties of 2M1207b, a young (~ 8 Myr) planet-mass companion, have lacked a satisfactory explanation for some time. The combination of low luminosity, red near-IR colors, and L-type near-IR spectrum (previously consistent with Teff ~ 1600K) imply an abnormally small radius. Early explanations for the apparent underluminosity of 2M1207b invoked an edge-on disk or the remnant of a recent protoplanetary collision. The discovery of a second planet-mass object (HR8799b) with similar luminosity and colors as 2M1207b indicate that a third explanation, one of a purely atmospheric nature, is more likely. By including clouds, non-equilibrium chemistry and low-gravity, an atmosphere with effective temperature consistent with evolution cooling-track predictions is revealed. Consequently 2M1207b, and others like it, require no new physics to explain nor do they belong to a new class of objects. Instead they most likely represent the natural extension of cloudy substellar atmospheres down to low Teff and log(g). If this atmosphere only explanation for 2M1207b is correct, then very young planet-mass objects with near-IR spectra similar to field T dwarfs may be rare.

Discovery of Rotational Modulations in the Planetary-Mass Companion 2M1207b: Intermediate Rotation Period and Heterogeneous Clouds in a Low Gravity Atmosphere
http://arxiv.org/abs/1512.02706

Quote :

Rotational modulations of brown dwarfs have recently provided powerful constraints on the properties of ultra-cool atmospheres, including longitudinal and vertical cloud structures and cloud evolution. Furthermore, periodic light curves directly probe the rotational periods of ultra-cool objects. We present here, for the first time, time-resolved high-precision photometric measurements of a planetary-mass companion, 2M1207b. We observed the binary system with HST/WFC3 in two bands and with two spacecraft roll angles. Using point spread function-based photometry, we reach a nearly photon-noise limited accuracy for both the primary and the secondary. While the primary is consistent with a flat light curve, the secondary shows modulations that are clearly detected in the combined light curve as well as in different subsets of the data. The amplitudes are 1.36% in the F125W and 0.78% in the F160W filters, respectively. By fitting sine waves to the light curves, we find a consistent period of 10.7+1.2−0.6 hours and similar phases in both bands. The J- and H-band amplitude ratio of 2M1207b is very similar to a field brown dwarf that has identical spectral type but different J-H color. Importantly, our study also measures, for the first time, the rotation period for a directly imaged extra-solar planetary-mass companion.

http://www.nasa.gov/feature/goddard/2016/hubble-directly-measures-rotation-of-cloudy-super-jupiter

Hubble Directly Measures Rotation of Cloudy 'Super-Jupiter'
(press release)