Quasi-static aberrations induced by laser guide stars in adaptive optics

Laser Guide Star Adaptive Optics (LGS AO) systems use the return from an artificial guide star to measure the wavefront aberrations in the direction of the science object. We observe quasi-static differences between the measured wavefront and the wavefront aberration of the science object. This paper quantifies and explains the source of the difference between the wavefronts measured using an LGS and a natural guide star at the W. M. Keck Observatory, which can be as high as 1000 nm RMS

The response of Li and Mg isotopes to rain events in a highly-weathered catchment

Storms are responsible for up to ~50% of total annual rainfall on tropical islands and result in rapid increases in discharge from rivers. Storm events are, however, notoriously under-sampled and their effects on weathering rates and processes are poorly constrained. To address this, we have undertaken high-frequency sampling of Quiock Creek catchment, a Critical Zone Observatory located in Guadeloupe, over a period of 21 days, encompassing several storm events. Chemical and isotopic (Li and Mg) analyses of different critical zone reservoirs (throughfall, soil pore water, groundwater and river water) were used to assess the interactions between rock, water and secondary minerals. The Li concentrations and δ7Li values of these different reservoirs range from 14 to 95 nmol/kg and 1.8 to 16.8‰, respectively. After several rain events, the average δ7Li value (13.3‰) of soil solutions from the lower part of the soil profile (>~150 cm below the surface) was unchanged, whereas in the upper part of the profile δ7Li values increased by ~2–4‰ due to increased contribution from throughfall. By contrast, the δ26Mg value of soil waters in the upper part of the soil profile were not significantly affected by the rain events with an average value of −0.90‰. The δ26Mg values of the different fluid reservoirs were generally close to the value of throughfall (~−0.90‰), but higher δ26Mg values (up to −0.58‰) were measured in the deeper parts of the soil profile, whereas groundwaters that have a long residence time had lower δ26Mg values (down to −1.48‰). These higher and lower values are attributed to, respectively, adsorption/desorption of light Mg isotopes on/from the surface of clay minerals. The δ7Li value of the river waters was ~9.3‰, with a Li concentration of 60 μmol/kg, but during a storm these values decreased to, respectively, 7.8‰ and 40 μmol/kg. This change in δ7Li is consistent with an increased contribution of Li from the soil solution. Thus, even in highly weathered catchments, changes in hydrological conditions can have a significant impact on weathering processes and therefore the composition of river waters delivered to the ocean

A New High Contrast Imaging Program at Palomar Observatory

We describe a new instrument that forms the core of a long-term high contrast imaging program at the 200-inch Hale Telescope at Palomar Observatory. The primary scientific thrust is to obtain images and low-resolution spectroscopy of brown dwarfs and young Jovian mass exoplanets in the vicinity of stars within 50 parsecs of the Sun. The instrument is a microlens-based integral field spectrograph integrated with a diffraction limited, apodized-pupil Lyot coronagraph, mounted behind the Palomar adaptive optics system. The spectrograph obtains imaging in 23 channels across the J and H bands (1.06 - 1.78 microns). In addition to obtaining spectra, this wavelength resolution allows suppression of the chromatically dependent speckle noise, which we describe. We have recently installed a novel internal wave front calibration system that will provide continuous updates to the AO system every 0.5 - 1.0 minutes by sensing the wave front within the coronagraph. The Palomar AO system is undergoing an upgrade to a much higher-order AO system ("PALM-3000"): a 3388-actuator tweeter deformable mirror working together with the existing 241-actuator mirror. This system will allow correction with subapertures as small as 8cm at the telescope pupil using natural guide stars. The coronagraph alone has achieved an initial dynamic range in the H-band of 2 X 10^-4 at 1 arcsecond, without speckle noise suppression. We demonstrate that spectral speckle suppression is providing a factor of 10-20 improvement over this bringing our current contrast at an arcsecond to ~2 X 10^-5. This system is the first of a new generation of apodized pupil coronagraphs combined with high-order adaptive optics and integral field spectrographs (e.g. GPI, SPHERE, HiCIAO), and we anticipate this instrument will make a lasting contribution to high contrast imaging in the Northern Hemisphere for years.Comment: Accepted to PASP: 12 pages, 12 figure

A Close Companion Search Around L Dwarfs Using Aperture Masking Interferometry and Palomar Laser Guide Star Adaptive Optics

We present a close companion search around 16 known early L dwarfs using aperture masking interferometry with Palomar laser guide star adaptive optics (LGS AO). The use of aperture masking allows the detection of close binaries, corresponding to projected physical separations of 0.6-10.0 AU for the targets of our survey. This survey achieved median contrast limits of ΔK ~ 2.3 for separations between 1.2λ/D-4λ/D and ΔK ~ 1.4 at 2/3λ/D. We present four candidate binaries detected with moderate-to-high confidence (90%-98%). Two have projected physical separations less than 1.5 AU. This may indicate that tight-separation binaries contribute more significantly to the binary fraction than currently assumed, consistent with spectroscopic and photometric overluminosity studies. Ten targets of this survey have previously been observed with the Hubble Space Telescope as part of companion searches. We use the increased resolution of aperture masking to search for close or dim companions that would be obscured by full aperture imaging, finding two candidate binaries. This survey is the first application of aperture masking with LGS AO at Palomar. Several new techniques for the analysis of aperture masking data in the low signal-to-noise regime are explored

Know The Star, Know the Planet. IV. A Stellar Companion to the Host star of the Eccentric Exoplanet HD 8673b

HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e=0.723). Based on two epochs of speckle interferometry a previous publication identified a candidate stellar companion. We observed HD 8673 multiple times with the 10 m Keck II telescope, the 5 m Hale telescope, the 3.63 m AEOS telescope and the 1.5m Palomar telescope in a variety of filters with the aim of confirming and characterizing the stellar companion. We did not detect the candidate companion, which we now conclude was a false detection, but we did detect a fainter companion. We collected astrometry and photometry of the companion on six epochs in a variety of filters. The measured differential photometry enabled us to determine that the companion is an early M dwarf with a mass estimate of 0.33-0.45 M?. The companion has a projected separation of 10 AU, which is one of the smallest projected separations of an exoplanet host binary system. Based on the limited astrometry collected, we are able to constrain the orbit of the stellar companion to a semi-major axis of 35{60 AU, an eccentricity ? 0.5 and an inclination of 75{85?. The stellar companion has likely strongly in uenced the orbit of the exoplanet and quite possibly explains its high eccentricity.Comment: Accepted to the Astronomical Journal, 6 Pages, 5 Figure

A low density of 0.8 g/cc for the Trojan binary asteroid 617 Patroclus

The Trojan population consists of two swarms of asteroids following the same orbit as Jupiter and located at the L4 and L5 Lagrange points of the Jupiter-Sun system (leading and following Jupiter by 60 degrees). The asteroid 617 Patroclus is the only known binary Trojan (Merline et al. 2001). The orbit of this double system was hitherto unknown. Here we report that the components, separated by 680 km, move around the system centre of mass, describing roughly a circular orbit. Using the orbital parameters, combined with thermal measurements to estimate the size of the components, we derive a very low density of 0.8 g/cc. The components of Patroclus are therefore very porous or composed mostly of water ice, suggesting that they could have been formed in the outer part of the solar system.Comment: 10 pages, 3 figures, 1 tabl

Ecosystems monitoring powered by environmental genomics: a review of current strategies with an implementation roadmap

A decade after environmental scientists integrated high-throughput sequencing technologies in their toolbox, the genomics-based monitoring of anthropogenic impacts on the biodiversity and functioning of ecosystems is yet to be implemented by regulatory frameworks. Despite the broadly acknowledged potential of environmental genomics to this end, technical limitations and conceptual issues still stand in the way of its broad application by end-users. In addition, the multiplicity of potential implementation strategies may contribute to a perception that the routine application of this methodology is premature or “in development”, hence restraining regulators from binding these tools into legal frameworks. Here, we review recent implementations of environmental genomics-based methods, applied to the biomonitoring of ecosystems. By taking a general overview, without narrowing our perspective to particular habitats or groups of organisms, this paper aims to compare, review and discuss the strengths and limitations of four general implementation strategies of environmental genomics for monitoring: (a) Taxonomy-based analyses focused on identification of known bioindicators or described taxa; (b) De novo bioindicator analyses; (c) Structural community metrics including inferred ecological networks; and (d) Functional community metrics (metagenomics or metatranscriptomics). We emphasise the utility of the three latter strategies to integrate meiofauna and microorganisms that are not traditionally utilised in biomonitoring because of difficult taxonomic identification. Finally, we propose a roadmap for the implementation of environmental genomics into routine monitoring programmes that leverage recent analytical advancements, while pointing out current limitations and future research needs.publishedVersio

Complex population structure and haplotype patterns in the Western European honey bee from sequencing a large panel of haploid drones:Sequencing haploid honey bee drones

International audienceHoney bee subspecies originate from specific geographical areas in Africa, Europe and the Middle East, and beekeepers interested in specific phenotypes have imported genetic material to regions outside of the bees' original range for use either in pure lines or controlled crosses. Moreover, imported drones are present in the environment and mate naturally with queens from the local subspecies. The resulting admixture complicates population genetics analyses, and population stratification can be a major problem for association studies. To better understand Western European honey bee populations, we produced a whole genome sequence and single nucleotide polymorphism (SNP) genotype data set from 870 haploid drones and demonstrate its utility for the identification of nine genetic backgrounds and various degrees of admixture in a subset of 629 samples. Five backgrounds identified correspond to subspecies, two to isolated populations on islands and two to managed populations. We also highlight several large haplotype blocks, some of which coincide with the position of centromeres. The largest is 3.6 Mb long and represents 21% of chromosome 11, with two major haplotypes corresponding to the two dominant genetic backgrounds identified. This large naturally phased data set is available as a single vcf file that can now serve as a reference for subsequent populations genomics studies in the honey bee, such as (i) selecting individuals of verified homogeneous genetic backgrounds as references, (ii) imputing genotypes from a lower-density data set generated by an SNP-chip or by low-pass sequencing, or (iii) selecting SNPs compatible with the requirements of genotyping chips

PALM-3000: Exoplanet Adaptive Optics for the 5 m Hale Telescope

We describe and report first results from PALM-3000, the second-generation astronomical adaptive optics (AO) facility for the 5.1 m Hale telescope at Palomar Observatory. PALM-3000 has been engineered for high-contrast imaging and emission spectroscopy of brown dwarfs and large planetary mass bodies at near-infrared wavelengths around bright stars, but also supports general natural guide star use to V ≈ 17. Using its unique 66 × 66 actuator deformable mirror, PALM-3000 has thus far demonstrated residual wavefront errors of 141 nm rms under ~1'' seeing conditions. PALM-3000 can provide phase conjugation correction over a 6."4 × 6."4 working region at λ = 2.2 μm, or full electric field (amplitude and phase) correction over approximately one-half of this field. With optimized back-end instrumentation, PALM-3000 is designed to enable 10^(–7) contrast at 1" angular separation, including post-observation speckle suppression processing. While continued optimization of the AO system is ongoing, we have already successfully commissioned five back-end instruments and begun a major exoplanet characterization survey, Project 1640