Search

The persistent Be/X-ray binary RXJ0440.9+4431 flared in 2010 and 2011 and has been followed by various X-ray facilities (Swift, RXTE, XMM-Newton, and INTEGRAL). We studied the source timing and spectral properties as a function of its X-ray luminosity to investigate the transition from normal to flaring activity. The source spectrumcan always be described by a bulk-motion Comptonization model of black body seed photons attenuated by a moderate photoelectric absorption. At the highest luminosity, we measured a curvature of the spectrum, which we attribute to a significant contribution of the radiation pressure in the accretion process. This allows us to estimate that the transition from a bulk-motion-dominated flow to a radiatively dominated one happens at a luminosity of ~ 2 x 1036 erg s-1. The luminosity dependency of the size of the black body emission region is found to be rBB α LX0.39±0.02. This suggests that either matter accreting onto the neutron star hosted in RXJ0440.9+4431 penetrates through closed magnetic field lines at the border of the compact object magnetosphere or that the size of the black-body emitting hotspot is larger than the footprint of the accretion column. This phenomenon can be due to illumination of the surface by a growing column or by a a structure of the neutron star magnetic field more complicated than a simple dipole at least close to the surface. [ABSTRACT FROM AUTHOR]

The emission characteristics of X-ray pulsars are governed by magnetospheric accretion within the Alfvén radius, leading to a direct coupling of accretion column properties and interactions at the magnetosphere. The complexity of the physical processes governing the formation of radiation within the accreted, strongly magnetized plasma has led to several sophisticated theoretical modelling efforts over the last decade, dedicated to either the formation of the broad band continuum, the formation of cyclotron resonance scattering features (CRSFs) or the formation of pulse profiles. While these individual approaches are powerful in themselves, they quickly reach their limits when aiming at a quantitative comparison to observational data. Too many fundamental parameters, describing the formation of the accretion columns and the systems' overall geometry are unconstrained and different models are often based on different fundamental assumptions, while everything is intertwined in the observed, highly phase-dependent spectra and energy-dependent pulse profiles. To name just one example: the (phase variable) line width of the CRSFs is highly dependent on the plasma temperature, the existence of B-field gradients (geometry) and observation angle, parameters which, in turn, drive the continuum radiation and are driven by the overall two-pole geometry for the light bending model respectively. This renders a parallel assessment of all available spectral and timing information by a compatible across-models-approach indispensable. In a collaboration of theoreticians and observers, we have been working on a model unification project over the last years, bringing together theoretical calculations of the Comptonized continuum, Monte Carlo simulations and Radiation Transfer calculations of CRSFs as well as a General Relativity (GR) light bending model for ray tracing of the incident emission pattern from both magnetic poles. The ultimate goal is to implement a unified fitting model for phase-resolved spectral and timing data analysis. We present the current status of this project. [ABSTRACT FROM AUTHOR]

We compiled X-ray and Optical observations of the accreting X-ray binary sytem A0535+26 since its discovery in 1975, that will allow us to shed light on the unpredictible behavior of this binary system. We present the data in terms of the Be-disc interaction with the neutron star companion. In addition, we show recent results from the continous monitoring of this source by the Gamma-ray Burst Monitor (GBM), on board the Fermi observatory, since its launch in 2008 June 11. [ABSTRACT FROM AUTHOR]

A transcriptome was constructed by pyrosequencing on the GS-FLX sequencer (Roche), for the whole body of the combined nymph and adult green stink bug, Acrosternum hilare (Say), collected from sites in North Carolina and Virginia, USA. The cDNA library for the combined sample was sequenced on one-half plate. The total output from the reads was 40, 500, 000 bps (base pairs) of data. The whole body library produced 162, 000 reads which were assembled using Roche software (Genome Sequencer FLX System GS De Novo Assembler, version 2.3, October 2009) into 1,598 contigs (contiguous sequences) with the assembly cutoff set at 400 bp, and into 2,534 contigs with the assembly cutoff set at 150 bp. BLASTp was used to compare contigs to the Uniprot database (January 3, 2010) to determine putative sequence identity. Of these contigs, 974 had an expect value of 1e-05 or lower. Of these, 876 had an assigned Uniprot GO (Gene Ontology) ID and were mapped and annotated. Wego software was used to translate the Uniprot GO ID for these contigs into GO Level 2 functional categories. Analysis of this recently-sequenced green stink bug transcriptome is aimed at the discovery of new insecticide targets for applications in plant, genetic pest management. [ABSTRACT FROM AUTHOR]

Transgenic cotton varieties that express Bacillus thuringiensis (Bt) toxins have been adapted readily because they reduce the need of insecticide application, while their environmental impacts are minimal. Recently, pyramided cotton varieties that express two different Bt toxins have been introduced; these varieties may reduce the risk of resistance development in lepidopteran pests populations. However, resistance monitoring in Bt cotton fields are necessary and mandated. Based on a previously described feeding disruption test (FDT) from our laboratory, the objective of this project was to develop a bioassay that uses Bt toxin obtained directly from Bollgard II plant material. The technology under development should be applicable to other pyramided and single gene commercial plants. The assay hardware is a novel 16 well plastic plate with each well of the plate containing a hydrateable, artificial diet containing leaf extract from Bollgard II. Dose-response studies were conducted using a laboratory susceptible strain of the tobacco budworm, Heliothis virescens, where different concentrations of leaf extract were used to hydrate a standard meal pad in each well. From these studies, a diagnostic dose was determined of 1.3 µg cotton / meal pad, which essentially stopped the production of fecal pellets by neonates of the budworm after a 24 h incubation. This diagnostic dose was further evaluated using three different populations of H. virescens assayed directly from the field from central North Carolina, USA. The diagnostic dose was also evaluated with the Bt resistant, laboratory reared H. virescens strains, YHD2 and CxC. The bioassay developed is a practical, reliable monitoring tool that can be used to monitor Bt susceptibility as part of an integrated resistance program in pyramided cotton fields. [ABSTRACT FROM AUTHOR]

Separate transcriptomes were constructed by pyrosequencing on the GS-FLX sequencer (Roche), for the whole body and digestive system of the adult Tarnished plant bug, Lygus lineolaris, collected from the field in North Carolina, USA. Each cDNA library from the two samples examined were sequence on one-half plates each. The total ouput from the two reads was 116, 635, 527 bps of data. The whole body library produced 292,714 reads which were assembled using the GS Assembler ver. 1.1.02.15 (Roche) with default parameters into 5,529 contiguous sequences (contigs). The digestive system library produced 229,919 reads which was assembled into 3,549 contigs. Contigs were putatively identified using the Tera-BLASTX algorithm with DeCypher (TimeLogic) against Genbank nr and est databases that were downloaded on June 2008. The contigs obtained from the tarnished plant bug gut transcriptome were analyzed using the blast2go program (www.blast2go.org). Blast2go also blasted the contigs using its blastx function and performed the gene ontologies. The analysis of the results from the whole bug and gut transcroptomes are in its infancy. However, the gut library has some obvious messages that should be of interest to plant, genetic pest management. [ABSTRACT FROM AUTHOR]

With the eradication of the boll weevil, the development of narrow-spectrum insecticides for whitefly control, and the widespread adoption of Bt cotton in the last decade, several species of plant bugs (Miridae) and stink bugs (Pentatomidae) have become major pests of cotton. Reports of tarnished plant bug Lygus lineolaris (Palisot de Beauvois) resistance to several classes of cotton insecticides, and of variable insecticide susceptibilities of stink bug species that damage cotton, highlight the need for assays to monitor resistance. Assays in current use have several limitations. Topical assays used for plant bugs and stink bugs are limited to testing insecticides with contact activity. Except in the case of neonicotinoids, vial assays in current use for plant bugs require the addition of plant material as a food source and are limited to contact insecticides. Vial tests for stink bugs are limited to testing insecticides with contact activity. All of the topical and vial assays for these sucking pests rely on a mortality endpoint which is often not easy to read (requires probing the insect and/or discriminating between knockdown versus death) and un-necessarily extends the time to the assay endpoint. Feeding disruption test (FDT) bioassays circumvent these limitations. In FDT assays, insects feed on insecticide in rehydrateable artificial diet mealpads containing a blue indicator dye to mark feeding on the artificial diet. The assay endpoint is the dose-dependent amount of blue feces produced, usually within 24 hours. The objective of the work described in this paper was to determine the feasibility of developing FDT assays for plant bugs and stink bugs. Lab-strain adult tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), fed different concentrations of β-cyfluthrin and thiamethoxam in rehydrateable NI diet mealpads containing food-grade blue dye in FDT plates showed a dose-response in production of dyed feces for both insecticides. Lab-strain adult brown stink bugs, Euchistus servus (Say), fed different concentrations of thiamethoxam in nectar also showed a mortality dose response. Brown stink bugs fed NI diet containing food-grade blue dye produced dyed feces; this approach should also be applicable to resitance monitoring as was the case for the plant bug. [ABSTRACT FROM AUTHOR]

Lab-strain tobacco budworm (Heliothis virescens) moths were fed different concentrations of permethrin and spinosyn in 10% sucrose containing 0.2 mg/ml trypan blue dye to obtain dose-mortality, dose-nectar-ingestion, and dose-fecal production responses. Percent mortality increased with increasing concentration of permethrin. Ingestion (g of treatment solution per moth) declined with increasing concentration of permethrin. Trends in percent mortality and ingestion for permethrin were consistent with prior results reported for spinosyn (van Kretschmar et al., 2007). Blue-dyed fecal production declined with increasing concentration of both insecticides. These results demonstrate the feasibility of using dyed sucrose solution in an adult-based feeding disruption test to monitor Lepidoptera for development of resistance to chemical insecticides. [ABSTRACT FROM AUTHOR]

Lab-strain tobacco budworm (Heliothis virescens) moths were fed different concentrations of spinosyn and permethrin in 10% sucrose to obtain dose-mortality responses. Percent mortality increased with increasing concentration of both insecticides. Ingestion (g of treatment solution per moth) declined with increasing concentration of both insecticides. When trypan blue dye was added to an insecticide solution fed to moths, it provided a dramatic visual marker of disrupted fecal production. These results demonstrate the feasibility of an adult-based feeding disruption test to monitor Lepidoptera for development of resistance to chemical insecticides. [ABSTRACT FROM AUTHOR]

The Galactic Bulge region is a rich host of variable high-energy point sources. These sources include bright and relatively faint X-ray transients, X-ray bursters, persistent neutron star and black-hole candidate binaries, X-ray pulsars, etc.. We have a program to monitor the Galactic Bulge region regularly and frequently with the γ-ray observatory INTEGRAL. As a service to the scientific community the high-energy light curves of all the active sources as well as images of the region are made available through the WWW. We show the first results of this exciting new program. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Feeding disruption tests (FDTs) were developed for monitoring insect resistance to three Bt proteins--Cry1Ab, Cry1Ac and Cry1F. The tests were designed to minimize false positives and negatives for resistance. The assays rely on a diagnostic dose of Bt toxin in a hydrateable meal pad containing a blue indicator dye. Insects resistant to Bt are able to consume the artificial diet and produce blue feces on a white background. Fecal production was inversely correlated with Bt concentration in the hydrated meal pad. The diagnostic dose for resistance determined by FDT for Cry1Ab against Heliothis virescens (Hv) was 15 micrograms a.i./ml hydration solution and for Helicoverpa zea (Hz) was 500 micrograms per ml; Cry1Ac: Hv=10, Hz=40; and Cry1F: Hv=20, Hz=200. The assays were successfully tested against Bt resistant tobacco budworms (YHD2 strain) and on H. virescens collected as eggs from tobacco in North Carolina. The kits were also evaluated by cooperators (results reported). FDT kits provide an easy-to-use (off-the-shelf) standard assay method for monitoring insect resistance to Bt and chemical insecticides. The technology has other applications in high-throughput insecticide screening, routine insect rearing and the evaluation of the insecticidal activity of Bt transgenic crops. [ABSTRACT FROM AUTHOR]

We present results from simultaneous observations of Cyg X-1 with INTEGRAL and RXTE in 2002 November and December, employing the new RXTE calibration from HEASOFT 5.3. The broad-band X-ray/γ-ray spectrum is well described by Comptonization spectra with an additional reflection component. The temperature of the Comptonizing plasma is kTe ∼ 60–80 keV and its optical depth is τ ∼ 0.8–1.2. The covering factor of the reflector is Ω/2π ∼ 0.1. There is a possible soft excess below 10 keV, interpreted as emission from the accretion disk. The spectral parameters are slightly different from those obtained by us earlier due to the different RXTE-PCA calibration. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A great deal of emphasis on timing in the RXTE era has been on pushing toward higher and higher frequency phenomena, particularly kHz QPOs. However, the large areas of the RXTE pointed instruments provide another capability which is key for the understanding of accreting X-ray pulsars — the ability to accumulate high quality spectra in a limited observing time. For the accreting X-ray pulsars, with their relatively modest spin frequencies, this translates into an ability to study broad band spectra as a function of pulse phase. This is a critical tool, as pulsar spectra are strong functions of the geometry of the “accretion mound” and the observers’ viewing angle to the ∼1012 G magnetic field. In particular, the appearance of “cyclotron lines” is sensitively dependent on the viewing geometry, which must change with the rotation of the star. These spectral features, seen in only a handful of objects, are quite important, as they give us our only direct measure of neutron star magnetic fields. Furthermore, they carry a great deal of information as to the geometry and physical conditions in the accretion mound. In this paper, we review the status of cyclotron line studies with the RXTE. We present an overview of phase-averaged results and give examples of observations which illustrate the power of phase-resolved spectroscopy. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present light curves and spectra of a ∼35ksec RXTE observation of Vela X-1 and a ∼300 ksec observation of Cen X-3. Both light curves show strong absorption which increases from no absorption at low orbital phases to large values at high orbital phases; in the case of Vela X-1 by a factor of almost 100. Superimposed are absorption dips which can be observed at any orbital phase, though mostly at high orbital phases. We study an unusually strong dip in Vela X-1 during which the flux is reduced by ∼90% and almost no pulses are detectable. The increase of N[sub H] and the scattered component show the in- and egress of material in the line of sight. A similar behaviour is observed in a pre-eclipse dip in Cen X-3. [ABSTRACT FROM AUTHOR]

We present the spectral analysis of our 35 ksec continuous RXTE observation of the High Mass X-ray Binary Vela X-1. The spectral models used normally to describe pulsar spectra like a power law with an exponential cutoff or the NPEX model (Negative Positive EXponential), do not work for our data. Our successful model consists of two NPEX components: one is heavily absorbed, while the other is due to reflection. But we still find large deviations around ∼21 keV and ∼50 keV. We interpret the feature at ∼55 keV as a cyclotron absorption line while the lower deviation might be due to instrument calibration problems around 25 keV in the PCA. [ABSTRACT FROM AUTHOR]

We present results from a 20 h RXTE observation of Vela X-1, including a peculiar low state of a few hours duration, during which the pulsation of the X-ray emission ceased, while significant non-pulsed emission remained. This “quiescent state” was preceded by a “normal state” without any unusual signs and followed by a “high state” of several hours of increased activity with strong, flaring pulsations. While there is clear spectral evolution from the normal state to the low state, the spectra of the following high state are surprisingly similar to those of the low state. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

© 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The INTEGRAL Science Data Center (ISDC) is designed as an interface between the INTEGRAL data and the user community. Its main task is to receive and process all the INTEGRAL data in order to (1) detect GRBs and other bright transient sources, for alerting the astronomical community and for initiating possible INTEGRAL Target Of Opportunity (TOO) observation, and (2) produce and archive a set of standard data products, and to distribute them to the observers. It is also foreseen to provide help and support to the observers in analyzing INTEGRAL data. The ISDC is funded by a consortium of European and US institutes. It is located in Versoix near Geneva. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A preface to the January 2014 issue of "EPJ Web of Conferences," which is dedicated to physics, is presented.