We present a 0.6-4.1 micron spectroscopic sequence of M, L, and T dwarfs. The spectra have R~2000 from 0.9 to 2.4 microns and R=2500-200 from 2.9 to 4.1 microns. These new data nearly double the number of L and T dwarfs that have reported L-band spectra. The near-infrared spectra are combined with previously published red-optical spectra to extend the wavelength coverage to ~0.6 microns. Prominent atomic and molecular absorption features are identified including neutral lines of Al, Fe, Mg, Ca, Ti, Na, and K and 19 new weak CH_4 absorption features in the H-band spectra of mid- to late-type T dwarfs. In addition, we detect for the first time the 0-0 band of the A ^4\Pi - X ^4\Sigma^- transition of VO at ~1.06 microns in the spectra of L dwarfs and the P and R branches of the \nu_3 band of CH_4 in the spectrum of a T dwarf. The equivalent widths of the refractory atomic features all decrease with increasing spectral type and are absent by a spectral type of ~L0, except for the 1.189 micron Fe I line which persists to at least ~L3. We compute the bolometric luminosities of the dwarfs in our sample with measured parallaxes and find good agreement with previously published results that use L'-band photometry to account for the flux emitted from 2.5 to 3.6 microns. Finally, 2MASS J2224381-0158521 (L4.5) has an anomalously red spectrum and the strongest \Delta \nu=+2 CO bands in our sample. This may be indicative of unusually thick condensate clouds and/or low surface gravity.

An Infrared Spectroscopic Sequence of M, L and T Dwarfs

The OmegaCAM wide-field imager will start operations at the ESO VLT Survey Telescope at Paranal in 2007. The photometric calibration of OmegaCAM data depends on standard-star measurements that cover the complete 1 × 1 FoV of OmegeaCAM. A catalog fullfilling this requirement for 8 Landolt equatorial fields, denoted the OmegaCAM Secondary Standards Catalog, will be constructed from OmegaCAM observations during the first year of operations. Here we present the ‘Preliminary Catalog’ which will be used to bootstrap the construction of the OmegaCAM Secondary Standards Catalog. Thus the Preliminary Catalog will be used to assess the performance of OmegaCAM+VST early-on. The catalog is based on WFC data from the INT.

The Future of Photometric, Spectrophotometric and Polarimetric Standardization

Observations of circumstellar environments that look for the direct signal of exoplanets and the scattered light from disks have significant instrumental implications. In the past 15 years, major developments in adaptive optics, coronagraphy, optical manufacturing, wavefront sensing, and data processing, together with a consistent global system analysis have brought about a new generation of high-contrast imagers and spectrographs on large ground-based telescopes with much better performance. One of the most productive imagers is the Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE), which was designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE includes an extreme adaptive optics system, a highly stable common path interface, several types of coronagraphs, and three science instruments. Two of them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager and Spectrograph (IRDIS), were designed to efficiently cover the near-infrared range in a single observation for an efficient search of young planets. The third instrument, ZIMPOL, was designed for visible polarimetric observation to look for the reflected light of exoplanets and the light scattered by debris disks. These three scientific instruments enable the study of circumstellar environments at unprecedented angular resolution, both in the visible and the near-infrared. In this work, we thoroughly present SPHERE and its on-sky performance after four years of operations at the VLT.

/pdf/sphere-the-exoplanet-imager-for-the-very-large-telescope-1mlo24tsno.pdf

SPHERE: the exoplanet imager for the Very Large Telescope

High-contrast adaptive optics imaging is a powerful technique to probe the architectures of planetary systems from the outside-in and survey the atmospheres of self-luminous giant planets. Direct imaging has rapidly matured over the past decade and especially the last few years with the advent of high-order adaptive optics systems, dedicated planet-finding instruments with specialized coronagraphs, and innovative observing and post-processing strategies to suppress speckle noise. This review summarizes recent progress in high-contrast imaging with particular emphasis on observational results, discoveries near and below the deuterium-burning limit, and a practical overview of large-scale surveys and dedicated instruments. I conclude with a statistical meta-analysis of deep imaging surveys in the literature. Based on observations of 384 unique and single young ($\approx$5--300~Myr) stars spanning stellar masses between 0.1--3.0~\Msun, the overall occurrence rate of 5--13~\Mjup \ companions at orbital distances of 30--300~AU is 0.6$^{+0.7}_{-0.5}$\% assuming hot-start evolutionary models. The most massive giant planets regularly accessible to direct imaging are about as rare as hot Jupiters are around Sun-like stars. Dividing this sample into individual stellar mass bins does not reveal any statistically-significant trend in planet frequency with host mass: giant planets are found around 2.8$^{+3.7}_{-2.3}$\% of BA stars, $<$4.1\% of FGK stars, and $<$3.9\% of M dwarfs. Looking forward, extreme adaptive optics systems and the next generation of ground- and space-based telescopes with smaller inner working angles and deeper detection limits will increase the pace of discovery to ultimately map the demographics, composition, evolution, and origin of planets spanning a broad range of masses and ages.

Imaging Extrasolar Giant Planets

Context . The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation.Aims . We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT.Methods . We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96–3.8 μ m). We use different atmospheric models covering a large parameter space in temperature, log g , chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b.Results . PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at ~22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000–1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 R J with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr.Conclusions . This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.

https://www.aanda.org/articles/aa/pdf/2018/09/aa33584-18.pdf

Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk

GJ 758 B is a brown dwarf companion to a nearby (15.76%) solar-type, metal-rich (M/H = +0.2 dex) main-sequence star (G9V) that was discovered with Subaru/HiCIAO in 2009. From previous studies, it has drawn attention as being the coldest (similar to 600 K) companion ever directly imaged around a neighboring star. We present new high-contrast data obtained during the commissioning of the SPHERE instrument at the Very Large Telescope (VLT). The data was obtained in Y-, J-, H-, and K-s-bands with the dual-band imaging (DBI) mode of IRDIS, thus providing a broad coverage of the full near-infrared (near-IR) range at higher contrast and better spectral sampling than previously reported. In this new set of high-quality data, we report the re-detection of the companion, as well as the first detection of a new candidate closer-in to the star. We use the new eight photometric points for an extended comparison of GJ 758 B with empirical objects and four families of atmospheric models. From comparison to empirical object, we estimate a T8 spectral type, but none of the comparison objects can accurately represent the observed near-IR fluxes of GJ 758 B. From comparison to atmospheric models, we attribute a T-eff = 600 +/- 100 K, but we find that no atmospheric model can adequately fit all the fluxes of GJ 758 B. The lack of exploration of metal enrichment in model grids appears as a major limitation that prevents an accurate estimation of the companion physical parameters. The photometry of the new candidate companion is broadly consistent with L-type objects, but a second epoch with improved photometry is necessary to clarify its status. The new astrometry of GJ 758 B shows a significant proper motion since the last epoch. We use this result to improve the determination of the orbital characteristics using two fitting approaches: Least-Squares Monte Carlo and Markov chain Monte Carlo. We confirm the high-eccentricity of the orbit (peak at 0.5), and find a most likely semi-major axis of 46.05 AU. We also use our imaging data, as well as archival radial velocity data, to reject the possibility that this is a false positive effect created by an unseen, closer-in, companion. Finally, we analyze the sensitivity of our data to additional closer-in companions and reject the possibility of other massive brown dwarf companions down to 4-5 AU.

/pdf/first-light-of-the-vlt-planet-finder-sphere-i-detection-and-fx9ljfpwq0.pdf

First light of the VLT planet finder SPHERE: I. Detection and characterization of the substellar companion GJ 758 B

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First light of the VLT planet finder SPHERE: I. Detection and characterization of the substellar companion GJ 758 B