The cooling, mass and radius of the neutron star in EXO 0748-676 in quiescence with XMM-Newton

We analyse four XMM-Newton observations of the neutron-star low-mass X-ray binary EXO 0748$-$676 in quiescence. We fit the spectra with an absorbed neutron-star atmosphere model, without the need for a high-energy (power-law) component; with a 95 per cent confidence the power-law contributes less than 1 per cent to the total flux of the source in $0.5-10.0$ keV. The fits show significant residuals at around 0.5 keV which can be explained by either a hot gas component around the neutron star or a moderately broad emission line from a residual accretion disc. The temperature of the neutron-star has decreased significantly compared to the previous observation, from 124 eV to 105 eV, with the cooling curve being consistent with either an exponential decay plus a constant or a (broken) power law. The best-fitting neutron-star mass and radius can be better constrained if we extend the fits down to the lowest possible energy available. For an assumed distance of 7.1 kpc, the best-fitting neutron-star mass and radius are $2.00_{-0.24}^{+0.07}~M_\odot$ and $11.3_{-1.0}^{+1.3}$ km if we fit the spectrum over the $0.3-10$ keV range, but $1.50_{-1.0}^{+0.4}~M_\odot$ and $12.2_{-3.6}^{+0.8}$ km if we restrict the fits to the $0.5-10$ keV range. We finally discuss the effect of the assumed distance to the source upon the best-fitting neutron-star mass and radius. As systematic uncertainties in the deduced mass and radius depending on the distance are much larger than the statistical errors, it would be disingenuous to take these results at face value.Comment: 12 pages, 6 figure

Systematic Uncertainties in the Spectroscopic Measurements of Neutron-Star Masses and Radii from Thermonuclear X-ray Bursts. III. Absolute Flux Calibration

Many techniques for measuring neutron star radii rely on absolute flux measurements in the X-rays. As a result, one of the fundamental uncertainties in these spectroscopic measurements arises from the absolute flux calibrations of the detectors being used. Using the stable X-ray burster, GS 1826-238, and its simultaneous observations by Chandra HETG/ACIS-S and RXTE/PCA as well as by XMM-Newton EPIC-pn and RXTE/PCA, we quantify the degree of uncertainty in the flux calibration by assessing the differences between the measured fluxes during bursts. We find that the RXTE/PCA and the Chandra gratings measurements agree with each other within their formal uncertainties, increasing our confidence in these flux measurements. In contrast, XMM-Newton EPIC-pn measures 14.0$\pm$0.3 % less flux than the RXTE/PCA. This is consistent with the previously reported discrepancy with the flux measurements of EPIC-pn, compared to EPIC-MOS1, MOS2 and ACIS-S detectors. We also show that any intrinsic time dependent systematic uncertainty that may exist in the calibration of the satellites has already been implicity taken into account in the neutron star radius measurements.Comment: Accepted for publication in the Astrophysical Journa

Influencia de la Imagen del Establecimiento Comercial en el Valor de Marca: Estudio Estadístico y de Marketing

El desarrollo de la investigación se centra particularmente en la forma cómo la imagen del establecimiento, que es parte del merchandising y de la gestión de distribución, influye en el valor de marca. Esto bajo el supuesto que los consumidores ven reflejada la imagen del establecimiento comercial en la imagen de marca. Con el modelo propuesto se establecerán las hipótesis, a partir de las variables, las cuales serán verificadas al final del estudio. Cada variable está conformada por ítems que forman grupos de escalas, una vez validadas por medio de un análisis de fiabilidad se utilizará el análisis de componentes principales. El fin de ambos análisis es construir variables latentes, para posteriormente realizar una regresión que pueda comprobar las hipótesis planteadas y determinar información relevante sobre el grupo de datos.Palabras clave: Imagen del establecimiento comercial, valor de marca, proceso de selección de compra, modelo de componentes principales, calidad percibida, lealtad de marca, notoriedad, imagen de marca

Outflow Legacy Accretion Survey: unveiling the wind driving mechanism in BHXRBs

Transient black-hole X-ray binaries viewed at high inclinations display blue-shifted absorption lines in their X-ray spectra. These features are the signatures of powerful, hot and equatorial accretion disk winds being driven from these systems in their luminous soft states. Remarkably, blue-shifted absorption lines have recently also been discovered in optical and NIR recombination lines and ultraviolet resonance features. These features must also be produced in an outflow, but the physical conditions traced by these outflows are different. Despite this, the characteristic Doppler velocities of all three types of signatures are comparable, yet they have never been observed simultaneously. It is therefore completely unclear if they are associated with distinct outflows (e.g. driven by different mechanisms) or simply with different regions/phases within the same outflow. Here, we propose to answer this question by carrying out simultaneous time-resolved spectroscopy of a high-inclination system in the X-ray, ultraviolet and optical bands, in its two distinct physical configurations (hard- and soft-states). This will allow us to test if the three types of wind features are present simultaneously, and, if so, whether they display correlated variability and/or velocity structure

Accretion in Stellar-Mass Black Holes at High X-ray Spectral Resolution

Accretion disks around stellar-mass black holes are optimal regimes in which to make observational tests of seminal theory that applies across the mass scale. High X-ray spectral resolution will enable the most incisive tests. This white paper briefly reviews the key ideas and examines three case studies

The high energy Universe at ultra-high resolution: the power and promise of X-ray interferometry

We propose the development of X-ray interferometry (XRI), to reveal the Universe at high energies with ultra-high spatial resolution. With baselines which can be accommodated on a single spacecraft, XRI can reach 100 μ as resolution at 10 Å (1.2 keV) and 20 μ as at 2 Å (6 keV), enabling imaging and imaging-spectroscopy of (for example) X-ray coronae of nearby accreting supermassive black holes (SMBH) and the SMBH ‘shadow’; SMBH accretion flows and outflows; X-ray binary winds and orbits; stellar coronae within ∼100 pc and many exoplanets which transit across them. For sufficiently luminous sources XRI will resolve sub-pc scales across the entire observable Universe, revealing accreting binary SMBHs and enabling trigonometric measurements of the Hubble constant with X-ray light echoes from quasars or explosive transients. A multi-spacecraft ‘constellation’ interferometer would resolve well below 1 μ as, enabling SMBH event horizons to be resolved in many active galaxies and the detailed study of the effects of strong field gravity on the dynamics and emission from accreting gas close to the black hole

APICAMPUS, a project on Urban beekeeping developed at the University of Malaga

Urban beekeeping has ourished in the last years, with many institutions interested in creating colonies on their roofs. Bees and other animal pollinators contribute to increase food production, making bees essential for agriculture and plant life, in general. And, as bee populations decline, the need for secondary sources of pollinators for agricultural production grows. The Vice-rectorate of Smart-Campus of the University of Malaga focuses on two fundamen tal aspects: understanding the UMA campus as a Smart City in itself and marking new lines of action at the academic level that will make the UMA an international benchmark in Sustainability. Framed in the program above mentioned, APICAMPUS is a pilot and interdisciplinary project that involves researchers and students belonging to 4 departments of 2 university faculties together with Bee Garden Malaga, a multi-disciplinary environmental company with thematic areas on beekeeping. The project aims to promote the development of beekeeping in urban environments, raising awareness about the importance of the bees as pollinating insects, as well as the use of the beehive products. For the above mentioned, two beehives Langstroth type, were installed at the roof of the Faculty of Science, a traditional wooden one, and another made of polystyrene. The main interest of this project lies in the monitoring of the hives by means of temperature and humidity sensors, electronic scales for weight control, video cameras located inside and outside of them, together with the use of bee-marking systems. Additionally, analysis for characterizing and study the origin and the properties of the beehive products will be carried out, as well as field monitoring to highlight the situation of pollinators at the University Campus of Teatinos. Although the samplings have barely begun, this communication intends to be the offcial presentation of the project APICAMPUS to the scientific community.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech