Search

The characterization of a physically-diverse set of transiting exoplanets isan important and necessary step towards establishing the physical propertieslinked to the production of obscuring clouds or hazes. It is those planets withidentifiable spectroscopic features that can most effectively enhance ourunderstanding of atmospheric chemistry and metallicity. The newly-commissionedLDSS-3C instrument on Magellan provides enhanced sensitivity and suppressedfringing in the red optical, thus advancing the search for the spectroscopicsignature of water in exoplanetary atmospheres from the ground. Using dataacquired by LDSS-3C and the Spitzer Space Telescope, we search for evidence ofwater vapor in the transmission spectrum of the Neptune-mass planet HAT-P-26b.Our measured spectrum is best explained by the presence of water vapor, a lackof potassium, and either a high-metallicity, cloud-free atmosphere or asolar-metallicity atmosphere with a cloud deck at ~10 mbar. The emergence ofmulti-scale-height spectral features in our data suggests that futureobservations at higher precision could break this degeneracy and reveal theplanet's atmospheric chemical abundances. We also update HAT-P-26b's transitephemeris, t_0 = 2455304.65218(25) BJD_TDB, and orbital period, p =4.2345023(7) days.

We observed 15 transits of the planet GJ 1214b with the Wide Field Camera 3 (WFC3) instrument on the Hubble Space Telescope (HST) between 27 September 2012 and 22 August [...], Recent surveys have revealed that planets intermediate in size between Earth and Neptune ('super-Earths') are among the most common planets in the Galaxy (1-3). Atmospheric studies are the next step towards developing a comprehensive understanding of this new class of object (4-6). Much effort has been focused on using transmission spectroscopy to characterize the atmosphere of the super-Earth archetype GJ 1214b (refs 7-17), but previous observations did not have sufficient precision to distinguish between two interpretations for the atmosphere. The planet's atmosphere could be dominated by relatively heavy molecules, such as water (for example, a 100 per cent water vapour composition), or it could contain high-altitude clouds that obscure its lower layers. Here we report a measurement of the transmission spectrum of GJ 1214b at near-infrared wavelengths that definitively resolves this ambiguity. The data, obtained with the Hubble Space Telescope, are sufficiently precise to detect absorption features from a high mean-molecular-mass atmosphere. The observed spectrum, however, is featureless. We rule out cloud-free atmospheric models with compositions dominated by water, methane, carbon monoxide, nitrogen or carbon dioxide at greater than 5σ confidence. The planet's atmosphere must contain clouds to be consistent with the data.

We present ground-based measurements of the transmission and emission spectra of the hot-Jupiter WASP-19b in nine spectroscopic channels from 1.25 to 2.35 μm. The measurements are based on the combined analysis of time-series spectroscopy obtained during two complete transits and two complete secondary eclipses of the planet. The observations were performed with the MMIRS instrument on the Magellan II telescope using the technique of multi-object spectroscopy with wide slits.We compare the transmission and emission data to theoretical models to constrain the composition and thermal structure of the planet's atmosphere. Our measured transmission spectrum exhibits a scatter that corresponds to 1.3 scale heights of the planet's atmosphere, which is consistent with the size of spectral features predicted by theoretical models for a clear atmosphere. We detect the secondary eclipses of the planet at significances ranging from 2.2σ to 14.4σ. The secondary eclipse depths, and the significances of the detections increase toward longer wavelengths. Our measured emission spectrum is consistent with a 2250 K effectively isothermal one-dimensional model for the planet's dayside atmosphere. This model also matches previously published photometric measurements from the Spitzer Space Telescope and ground-based telescopes. These results demonstrate the important role that ground-based observations using multi-object spectroscopy can play in constraining the properties of exoplanet atmospheres, and they also emphasize the need for high-precision measurements based on observations of multiple transits and eclipses. [ABSTRACT FROM AUTHOR]

We present an investigation of the transmission spectrum of the 6.5 M⊕ planet GJ 1214b based on new ground-based observations of transits of the planet in the optical and near-infrared, and on previously published data. Observations with the VLT + FORS and Magellan + MMIRS using the technique of multi-object spectroscopy with wide slits yielded new measurements of the planet's transmission spectrum from 0.61 to 0.85 µm, and in the J, H, and K atmospheric windows. We also present a new measurement based on narrow-band photometry centered at 2.09 µm with the VLT + HAWKI. We combined these data with results from a reanalysis of previously published FORS data from 0.78 to 1.00 µm using an improved data reduction algorithm, and previously reported values based on Spitzer data at 3.6 and 4.5 µm. All of the data are consistent with a featureless transmission spectrum for the planet. Our K-band data are inconsistent with the detection of spectral features at these wavelengths reported by Croll and collaborators at the level of 4.1σ. The planet's atmosphere must either have at least 70% H2O by mass or optically thick high-altitude clouds or haze to be consistent with the data. [ABSTRACT FROM AUTHOR]

Lowrance et al. (2000) found a faint companion candidate about 4 arcsec south of the young A0-type star HR 7329. Its spectral type of M7-8 is consistent with a young brown dwarf companion. Here we report spectroscopic J band observations using the integral field spectrograph SINFONI at VLT, enabling a new estimation of effective temperature, extinction and surface gravity of the object and hence its mass. Although the data were reduced carefully, the presence of a spike within the point spread function of the object in each spectral image hampered the precise estimation of the properties of HR 7329. Nevertheless, we will show with the example of this sub-stellar companion how mass estimates independent of evolutionary models of directly imaged sub-stellar companions can be obtained, after removing most of the strong influence of the spike in the present data, and present a new mass estimation of HR 7329 B/b based on the values gained. [ABSTRACT FROM PUBLISHER]

We present our search program for substellar companions using high-precision relative astronomy. Due to its orbital motion around the star, an unseen substellar companion would produce a periodic “wobble” of the host star, which is the astrometric signal of the unseen companion. By measuring the separation between the components of stellar double and triple systems, we want to measure this astrometric signal of a possible unseen companion indirectly as a relative and periodic change of these separations. Using a new observation mode (the “cube-mode”) where the frames were directly saved in cubes with nearly no loss of time during the readout, an adaptive optics system to correct for atmospheric noise and an infrared narrow band filter in the near infrared to suppress differential chromatic refraction (DCR) effects we achieve for our first target (the double star HD 19994) a relative precision for the separation measurements of about 100. . . 150μas per epoch. To reach a precision in the μas-regime, we use a statistical approach. We take several thousand frames per target and epoche and after a verification of a Gaussian distribution the measurement precision can be calculated as the standard deviation of our measurements divided by the square root of the number of Gaussian distributed measurements. Our first observed target is the stellar binary HD 19994 A & B, where the A component has a known radial velocity planet candidate. [ABSTRACT FROM PUBLISHER]

We present findings for DoAr 24E, a binary system that includes a classical infrared companion. We observed the DoAr 24E system with the Spitzer Infrared Spectrograph (IRS), with high-resolution, near-infrared spectroscopy of CO vibrational transitions, and with mid-infrared imaging. The source of high extinction toward infrared companions has been an item of continuing interest. Here we investigate the disk structure of DoAr 24E using the column densities, temperature, and velocity profiles of two CO absorption features seen toward DoAr 24Eb. We model the spectral energy distributions found using T-ReCS imaging and investigate the likely sources of extinction toward DoAr 24Eb. We find the lack of silicate absorption and small CO column density toward DoAr 24Eb suggest that the mid-infrared continuum is not as extinguished as the near-infrared, possibly due to the mid-infrared originating from an extended region. This, along with the velocity profile of the CO absorption, suggests that the source of high extinction is likely due to a disk or disk wind associated with DoAr 24Eb. [ABSTRACT FROM AUTHOR]