Radiative braking in the extended exosphere of GJ 436 b

An evaporating planet in the wind: stellar wind interactions with the radiatively braked exosphere of GJ 436 b

Observations of the warm Neptune GJ 436 b were performed with HST/STIS at three different epochs (2012, 2013, 2014) in the stellar Lyman-α line. They showed deep, repeated transits that were attributed to a giant exosphere of neutral hydrogen. The low radiation pressure from the M-dwarf host star was shown to play a major role in the dynamics of the escaping gas and its dispersion within a larg...

Telescope transit light curve for GJ 436 b

We present time series photometry for six partial transits of GJ 436b obtained with the Fine Guidance Sensor instrument on the Hubble Space Telescope (HST). Our analysis of these data yields independent estimates of the host star's radius R ⋆ = 0.505

The M Dwarf GJ 436 and its Neptune - Mass Planet

We determine stellar parameters for the M dwarf GJ 436 that hosts a Neptunemass planet. We employ primarily spectral modeling at low and high resolution, examining the agreement between model and observed optical spectra of five comparison stars of type, M0-M3. Modeling high resolution optical spectra suffers from uncertainties in TiO transitions, affecting the predicted strengths of both atomi...

Hydrogen in the extended Venus exosphere

Transit Infrared Spectroscopy of the Hot Neptune Around GJ 436 with the Hubble Space

The nearby transiting system GJ 436b offers a unique opportunity to probe the structure and atmosphere of an extra-solar “hot Neptune”. In this Letter, we present the main results of observations covering two transit events with the NICMOS camera on the Hubble Space Telescope. The data consist of high-cadence time series of grism spectra covering the 1.1-1.9 μm spectral range. We find Rpl = 4.0...