Three New Eclipsing White-dwarf - M-dwarf Binaries Discovered in a Search for Transiting Planets Around M-dwarfs

We present three new eclipsing white-dwarf / M-dwarf binary systems discovered during a search for transiting planets around M-dwarfs. Unlike most known eclipsing systems of this type, the optical and infrared emission is dominated by the M-dwarf components, and the systems have optical colors and discovery light curves consistent with being Jupiter-radius transiting planets around early M-dwarfs. We detail the PTF/M-dwarf transiting planet survey, part of the Palomar Transient Factory (PTF). We present a Graphics Processing Unit (GPU)-based box-least-squares search for transits that runs approximately 8X faster than similar algorithms implemented on general purpose systems. For the discovered systems, we decompose low-resolution spectra of the systems into white-dwarf and M-dwarf components, and use radial velocity measurements and cooling models to estimate masses and radii for the white dwarfs. The systems are compact, with periods between 0.35 and 0.45 days and semimajor axes of approximately 2 solar radii (0.01 AU). We use the Robo-AO laser guide star adaptive optics system to tentatively identify one of the objects as a triple system. We also use high-cadence photometry to put an upper limit on the white dwarf radius of 0.025 solar radii (95% confidence) in one of the systems. We estimate that 0.08% (90% confidence) of M-dwarfs are in these short-period, post-common-envelope white-dwarf / M-dwarf binaries where the optical light is dominated by the M-dwarf. Similar eclipsing binary systems can have arbitrarily small eclipse depths in red bands and generate plausible small-planet-transit light curves. As such, these systems are a source of false positives for M-dwarf transiting planet searches. We present several ways to rapidly distinguish these binaries from transiting planet systems.Comment: 14 pages, 14 figures, submitted to Ap

Degradation of haloaromatic compounds

An ever increasing number of halogenated organic compounds has been produced by industry in the last few decades. These compounds are employed as biocides, for synthetic polymers, as solvents, and as synthetic intermediates. Production figures are often incomplete, and total production has frequently to be extrapolated from estimates for individual countries. Compounds of this type as a rule are highly persistent against biodegradation and belong, as "recalcitrant" chemicals, to the class of so-called xenobiotics. This term is used to characterise chemical substances which have no or limited structural analogy to natural compounds for which degradation pathways have evolved over billions of years. Xenobiotics frequently have some common features. e.g. high octanol/water partitioning coefficients and low water solubility which makes for a high accumulation ratio in the biosphere (bioaccumulation potential). Recalcitrant compounds therefore are found accumulated in mammals, especially in fat tissue, animal milk supplies and also in human milk. Highly sophisticated analytical techniques have been developed for the detection of organochlorines at the trace and ultratrace level

Silencing cuticular pigmentation genes enables RNA FISH in intact insect appendages

Optical imaging of gene expression by fluorescence in situ hybridisation (FISH) in insects is often impeded by their pigmented cuticle. Since most chemical bleaching agents are incompatible with FISH, we developed a RNA interference-based method for clearing cuticular pigmentation which enables using whole-mount body appendages for RNA FISH. Silencing laccase2 or tyrosine hydroxylase in two leaf beetles species (Chrysomela populi, Phaedon cochleariae) cleared their pigmented cuticle and decreased light absorbance. Subsequently, intact appendages (palps, antennae, legs) from RNAi-cleared individuals were used to image expression and spatial distribution of antisense mRNA of two chemosensory genes (gustatory receptor, odorant-binding protein). Imaging did neither work for RNAi-controls due to retained pigmentation, nor for FISH-controls (sense mRNA). Several bleaching agents were incompatible with FISH, either due to degradation of RNA, lack of clearing efficacy or long incubation times. Overall, silencing pigmentation genes is a significant improvement over bleaching agents enabling FISH in intact appendages

Near Infrared PICNIC Imager (NIPI) -A Progress Report

Abstract. In the AS1 2002 meeting we presented a preliminary design of Near Infrared PICNIC Imager Keywords : PICNIC -near infrared -imager -IUCAA Telescope Optical Design, Hardware and Software The optical design has now been finalised and the orders for all the optical components have been placed with various vendors. The design was modified to loosen the tolerances on lens thicknesses and the seperation between the lenses (Fischer et al, 2000), which had the effect that the total track from telescope focus to detector increased to 900mm. The optical design has been folded using three mirrors to reduce the flexure. We have also put aluminium spacers at the appropriate places to account for the effect of lens mounts on the design. The radii of the lenses have been matched with the test plates of International Scientific Products, Optics. The entire optics would sit inside a standard size dewar. The filter wheel would be driven by a stepper motor. On the basis of timings of the wheel, the torque required by stepper motor was calculated (Kenjo, 1984) and the correct motor identified. The clock and bias signals for reading out the PICNIC array have been tested on the oscilloscope. We have also made arrangements for testing the PICNIC array inside a dewar and for multiplexer testing at room temperature. The cable for sending the signals from the controller to the array (which sits in a socket on a PCB) has been made and tested