Spitzer Observations of Black Hole Low-mass X-ray Binaries: Assessing the Non-stellar Infrared Component

We have combined ground-based optical and near-infrared data with Spitzer Space Telescope mid-infrared data for five black hole (BH) soft X-ray transients (SXTs) in order to determine the levels of near- and mid-infrared emission from sources other than the secondary star. Mid-infrared emission from an accretion disk, circumbinary dust, and/or a jet could act as sources of near-infrared contamination, thereby diluting ellipsoidal variations of the secondary star and affecting determined BH mass estimates. Based on optical to mid-infrared spectral energy distribution modeling of the five SXTs along with the prototype, V616 Mon, we detected mid-infrared excesses in half of the systems, and suggest that the excesses detected from these systems arise from non-thermal synchrotron jets rather than circumbinary dust disks

Stellar or Non-Stellar Light? Determining Near-Infrared Contamination in Low Mass X-ray Binaries

Low-mass X-ray binary (LMXB) systems are comprised of a low-mass, K or M dwarflike star orbiting a compact object. Stellar black hole masses and their distributions are important inputs for binary evolution and supernova models. Currently, the main limiting factor in determining accurate black hole masses in LMXBs is the uncertainty of the orbital inclination angle due to an unknown amount of contaminating light in the near infrared. If present, this light dilutes the ellipsoidal variations of the low-mass secondary star, and thus gives the appearance of a lower orbital inclination system. It has been generally thought that the near infrared ellipsoidal light curves of these systems were relatively uncontaminated and represented primarily the light from the low-mass secondary star; however, recent disk and jet models have thrust this thinking into question. We combine our data from the Spitzer Space Telescope with our ground-based optical and near infrared data for several LMXBs to characterize and derive the amount of light contaminating the near-infrared ellipsoidal variations of the low-mass secondary star

A Potential Super-Venus in the Kepler-69 System

Transiting planets have greatly expanded and diversified the exoplanet field. These planets provide greater access to characterization of exoplanet atmospheres and structure. The Kepler mission has been particularly successful in expanding the exoplanet inventory, even to planets smaller than the Earth. The orbital period sensitivity of the Kepler data is now extending into the habitable zones of their host stars, and several planets larger than the Earth have been found to lie therein. Here we examine one such proposed planet, Kepler-69c. We provide new orbital parameters for this planet and an in-depth analysis of the habitable zone. We find that, even under optimistic conditions, this 1.7 R_⊕ planet is unlikely to be within the habitable zone of Kepler-69. Furthermore, the planet receives an incident flux of 1.91 times the solar constant, which is similar to that received by Venus. We thus suggest that this planet is likely a super-Venus rather than a super-Earth in terms of atmospheric properties and habitability, and we propose follow-up observations to disentangle the ambiguity

Novel Biomarkers Associated with Deep Venous Thrombosis: A Comprehensive Review

Primary and recurrent venous thromboembolic disease (VTE, deep venous thrombosis and pulmonary embolism) remain a significant source of morbidity and mortality in the hospitalized patient. Non-specific subjective complaints and lack of specific objective findings related to acute deep venous thrombosis (DVT) and pulmonary embolism (PE) complicate the diagnosis. There remains no single serum marker available to exclusively confirm the diagnosis of VTE. While D-dimer is highly sensitive and useful for diagnostic exclusion, it lacks the specificity necessary for diagnostic confirmation resulting in the need for a variety of additional studies (i.e.: duplex ultrasound, venography, V/Q scanning, helical thoracic and pelvic CT scans and pulmoary angiography). There is evolving research supporting the utility of various plasma markers as novel “biomarkers” for VTE including selectins, microparticles, interleukin-10 and other cytokines. This review attempts to examine recent literature assessing the utility of P-selectin, microparticles, D-dimer, E-selectin, thrombin, interleukins and fibrin monomers in the diagnosis and guidance of therapy for VTE

The Low Mass X-ray Binary - Globular Cluster Link and its Implications

Studies of nearby elliptical and S0 galaxies reveal that roughly half of the low mass X-ray binaries (LMXBs), which are luminous tracers of accreting neutron star or black hole systems, are in clusters. There is a surprising tendency of LMXBs to be preferentially associated with metal-rich globular clusters (GCs), with metal-rich GCs hosting three times as many LMXBs as metal-poor ones. There is no convincing evidence of a correlation with GC age so far. In some galaxies the LMXB formation rate varies with GC color even within the metal-rich peak of the typical bimodal cluster metallicity distribution. This provides some of the strongest evidence to date that there are metallicity variations within the metal-rich GC peak, as is expected in hierarchical galaxy formation scenarios. We also note that apparent correlations between the interaction rates in GCs and LMXB frequency may not be reliable because of the uncertainties in some GC parameters. We argue in fact that there are considerable uncertainties in the integrated properties of even the Milky Way clusters that are often overlooked.Comment: To be be published in the proceedings of, "A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environments", eds. Bandyopadhyay et a

Spitzer Observations of GX17+2: Confirmation of a Periodic Synchrotron Source

GX17+2 is a low-mass X-ray binary (LMXB) that is also a member of a small family of LMXBs known as "Z-sources" that are believed to have persistent X-ray luminosities that are very close to the Eddington limit. GX17+2 is highly variable at both radio and X-ray frequencies, a feature common to Z-sources. What sets GX17+2 apart is its dramatic variability in the near-infrared, where it changes by ΔK ~ 3 mag. Previous investigations have shown that these brightenings are periodic, recurring every 3.01 days. Given its high extinction (A_V≥9 mag), it has not been possible to ascertain the nature of these events with ground-based observations. We report mid-infrared Spitzer observations of GX17+2 which indicate a synchrotron spectrum for the infrared brightenings. In addition, GX17+2 is highly variable in the mid-infrared during these events. The combination of the large-scale outbursts, the presence of a synchrotron spectrum, and the dramatic variability in the mid-infrared suggest that the infrared brightening events are due to the periodic transit of a synchrotron jet across our line of sight. An analysis of both new, and archival, infrared observations has led us to revise the period for these events to 3.0367 days. We also present new Rossi X-Ray Timing Explorer (RXTE) data for GX17+2 obtained during two predicted infrared brightening events. Analysis of these new data, and data from the RXTE archive, indicates that there is no correlation between the X-ray behavior of this source and the observed infrared brightenings. We examine various scenarios that might produce periodic jet emission

Enabling I/O Automata Using Omniscient Archetypes

Many cyberinformaticians would agree that, had it not been for IPv6, the technical unification of digital-to-analog converters and Byzantine fault tolerance might never have occurred. Given the trends in constant-time theory, hackers worldwide famously note the study of randomized algorithms, which embodies the confirmed principles of cryptography. In our research we describe new game-theoretic archetypes (Sinner), showing that Byzantine fault toler- ance and the producer-consumer problem are mostly incompatible. Even though such a hypothesis might seem perverse, it fell in line with our expectations

Dynamic association between perfusion and white matter integrity across time since injury in Veterans with history of TBI.

ObjectiveCerebral blood flow (CBF) plays a critical role in the maintenance of neuronal integrity, and CBF alterations have been linked to deleterious white matter changes. Although both CBF and white matter microstructural alterations have been observed within the context of traumatic brain injury (TBI), the degree to which these pathological changes relate to one another and whether this association is altered by time since injury have not been examined. The current study therefore sought to clarify associations between resting CBF and white matter microstructure post-TBI.Methods37 veterans with history of mild or moderate TBI (mmTBI) underwent neuroimaging and completed health and psychiatric symptom questionnaires. Resting CBF was measured with multiphase pseudocontinuous arterial spin labeling (MPPCASL), and white matter microstructural integrity was measured with diffusion tensor imaging (DTI). The cingulate cortex and cingulum bundle were selected as a priori regions of interest for the ASL and DTI data, respectively, given the known vulnerability of these regions to TBI.ResultsRegression analyses controlling for age, sex, and posttraumatic stress disorder (PTSD) symptoms revealed a significant time since injury × resting CBF interaction for the left cingulum (p < 0.005). Decreased CBF was significantly associated with reduced cingulum fractional anisotropy (FA) in the chronic phase; however, no such association was observed for participants with less remote TBI.ConclusionsOur results showed that reduced CBF was associated with poorer white matter integrity in those who were further removed from their brain injury. Findings provide preliminary evidence of a possible dynamic association between CBF and white matter microstructure that warrants additional consideration within the context of the negative long-term clinical outcomes frequently observed in those with history of TBI. Additional cross-disciplinary studies integrating multiple imaging modalities (e.g., DTI, ASL) and refined neuropsychiatric assessment are needed to better understand the nature, temporal course, and dynamic association between brain changes and clinical outcomes post-injury

The quantitative trait linkage disequilibrium test: a more powerful alternative to the quantitative transmission disequilibrium test for use in the absence of population stratification

Linkage analysis based on identity-by-descent allele-sharing can be used to identify a chromosomal region harboring a quantitative trait locus (QTL), but lacks the resolution required for gene identification. Consequently, linkage disequilibrium (association) analysis is often employed for fine-mapping. Variance-components based combined linkage and association analysis for quantitative traits in sib pairs, in which association is modeled as a mean effect and linkage is modeled in the covariance structure has been extended to general pedigrees (quantitative transmission disequilibrium test, QTDT). The QTDT approach accommodates data not only from parents and siblings, but also from all available relatives. QTDT is also robust to population stratification. However, when population stratification is absent, it is possible to utilize even more information, namely the additional information contained in the founder genotypes. In this paper, we introduce a simple modification of the allelic transmission scoring method used in the QTDT that results in a more powerful test of linkage disequilibrium, but is only applicable in the absence of population stratification. This test, the quantitative trait linkage disequilibrium (QTLD) test, has been incorporated into a new procedure in the statistical genetics computer package SOLAR. We apply this procedure in a linkage/association analysis of an electrophysiological measurement previously shown to be related to alcoholism. We also demonstrate by simulation the increase in power obtained with the QTLD test, relative to the QTDT, when a true association exists between a marker and a QTL