Ultraviolet and X-ray variability of NGC 4051 over 45 days with XMM-Newton and Swift

We analyse 15 XMM-Newton observations of the Seyfert galaxy NGC 4051 obtained over 45 days to determine the ultraviolet (UV) light curve variability characteristics and search for correlated UV/X-ray emission. The UV light curve shows variability on all time scales, however with lower fractional rms than the 0.2-10 keV X-rays. On days-weeks timescales the fractional variability of the UV is Fvar ~ 8%, and on short (~ hours) timescales Fvar ~ 2%. The within-observation excess variance in 4 of the 15 UV observations was found be much higher than the remaining 11. This was caused by large systematic uncertainties in the count rate masking the intrinsic source variance. For the four "good" observations we fit an unbroken power-law model to the UV power spectra with slope -2.0 +/- 0.5. We compute the UV/X-ray Cross-correlation function for the "good" observations and find a correlation of ~ 0.5 at time lag of ~ 3 ks, where the UV lags the X-rays. We also compute for the first time the UV/X-ray Cross-spectrum in the range 0-28.5 ks, and find a low coherence and an average time lag of ~ 3 ks. Combining the 15 XMM-Newton and the Swift observations we compute the DCF over +/-40 days but are unable to recover a significant correlation. The magnitude and direction of the lag estimate from the 4 "good" observations indicates a scenario where ~ 25 % of the UV variance is caused by thermal reprocessing of the incident X-ray emission.Comment: 11 pages, 8 figures. Accepted for publication in MNRA

The flux-dependent X-ray time lags in NGC 4051

We present an analysis of the X-ray time lags for the highly variable Seyfert 1 galaxy NGC 4051, based on a series of XMM-Newton observations taken in 2009. We investigate the Fourier frequency dependent time lags in the light curves between the 0.3--1.0 keV and 2.0--5.0 keV energy bands as a function of source flux, including simultaneous modelling of the resulting lag-frequency spectra. We find the shape of the lag-frequency spectra to vary significantly and systematically with source flux. We model the lag-frequency spectra using simple transfer functions, and find that two time lag components are required, one in each energy band. The simplest acceptable fits have only the relative contribution of the lagged component in the hard band varying with flux level, which can be associated with changes in the energy spectrum. We discuss the interpretation of these results in terms of the currently popular models for X-ray time lags.Comment: 9 pages, 4 figures. Accepted for publication in MNRA

All-aromatic biphenylene end-capped polyquinoline and polyimide matrix resins

Biphenylene end-capped polyquinoline and polyimide resins afford low void content graphite-reinforced composites with good initial properties. However, with both resins, rapid degradation occurs during oxidative isothermal aging at elevated temperatures. The degradation is not observed during isothermal aging under a nitrogen atmosphere which suggests that the biphenylene end-cap (or the resulting crosslink/chain extension structures) is not particularly thermooxidatively stable. The nature of the thermooxidative instability is currently under investigation

Effects of graphite fiber stability on the properties of PMR polyimide composites

The effect of the stability of graphite fibers on composite properties after exposure in air at 600 F was investigated. Composites were fabricated from PMR-15 and PMR-2 monomer solutions, using HTS-2 and Celion 6000 graphite fibers as the reinforcement. The effect of long-term exposure in air at 600 F on composite weight loss and mechanical properties was determined. These composites exhibited a significantly increased lifetime at that temperature compared to composites fabricated from HTS fiber sold prior to 1975. The effect of the PMR-15 and PMR-II resin compositions on long-term composite performance at 600 F is also discussed

PMR polyimides-review and update

Fiber reinforced PMR polyimides are finding increased acceptance as engineering materials for high performance structural applications. Prepreg materials based on this novel class of highly processable, high temperature resistant polyimides are commercially available and the PMR concept is used by other investigators. The current status of first and second generation PMR polyimides were reviewed. Emphasis is given to the chemistry, processing and applications of the first generation material known as PMR-15

Must naive realists be relationalists?

Relationalism maintains that perceptual experience involves, as part of its nature, a distinctive kind of conscious perceptual relation between a subject of experience and an object of experience. Together with the claim that perceptual experience is presentational, relationalism is widely believed to be a core aspect of the naive realist outlook on perception. This is a mistake. I argue that naive realism about perception can be upheld without a commitment to relationalism

Anti-Kaon Induced Reactions on the Nucleon

Using a previously established effective Lagrangian model we describe anti-kaon induced reactions on the nucleon. The dominantly contributing channels in the cm-energy region from threshold up to 1.72 GeV are included (K N, \pi \Sigma, \pi \Lambda). We solve the Bethe-Salpeter equation in an unitary $K$-matrix approximation.Comment: 21 pages, 13 figures, minor typos corrected, accepted for publication in Phys. Rev.

NuSTAR and Suzaku observations of the hard state in Cygnus X-1: locating the inner accretion disk

We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in the hard state. This is the first time this state has been observed in Cyg X-1 with NuSTAR, which enables us to study the reflection and broad-band spectra in unprecedented detail. We confirm that the iron line cannot be fit with a combination of narrow lines and absorption features, and instead requires a relativistically blurred profile in combination with a narrow line and absorption from the companion wind. We use the reflection models of Garcia et al. (2014) to simultaneously measure the black hole spin, disk inner radius, and coronal height in a self-consistent manner. Detailed fits to the iron line profile indicate a high level of relativistic blurring, indicative of reflection from the inner accretion disk. We find a high spin, a small inner disk radius, and a low source height, and rule out truncation to greater than three gravitational radii at the 3{\sigma} confidence level. In addition, we find that the line profile has not changed greatly in the switch from soft to hard states, and that the differences are consistent with changes in the underlying reflection spectrum rather than the relativistic blurring. We find that the blurring parameters are consistent when fitting either just the iron line or the entire broad-band spectrum, which is well modelled with a Comptonized continuum plus reflection model.Comment: 12 pages, 7 figures, accepted for publication in Ap

Revealing criterial vagueness in inconsistencies

Sixty undergraduate students made category membership decisions for each of 132 candidate exemplar-category name pairs (e.g., chess – Sports) in each of two separate sessions. They were frequently inconsistent from one session to the next, both for nominal categories such as Sports and Fish, and ad hoc categories such as Things You Rescue from a Burning House. A mixture model analysis revealed that several of these inconsistencies could be attributed to criterial vagueness: participants adopting different criteria for membership in the two sessions. This finding indicates that categorization is a probabilistic process, whereby the conditions for applying a category label are not invariant. Individuals have various functional meanings of nominal categories at their disposal and entertain competing goals for ad hoc categories