Binaries with total eclipses in the LMC: potential targets for spectroscopy

35 Eclipsing binaries presenting unambiguous total eclipses were selected from a subsample of the list of Wyrzykowski et al. (2003). The photometric elements are given for the I curve in DiA photometry, as well as approximate Teff and masses of the components. The interest of these systems is stressed in view of future spectroscopic observations.Comment: 4 pages, 1 figure; poster presented at the conference "Close binaries in the 21st Century: new opportunities and challenges", Syros, 27-30 June 200

Estudio preliminar de las binarias eclipsantes RT Hydri y V594 Centauri

Se presentan las primeras observaciones fotoeléctricas UBV de dos sistemas binarios eclipsantes de corto período orbital: RT Hydri y V594 Centauri. Se determinan nuevos tiempos de mínimo y se actualizan las efemérides, incluyendo posibles variaciones del período. Las curvas de luz derivadas de las presentes observaciones exhiben las características típicas de las binarias tipo W UMa, con apreciables profundidades en los mínimos. Un análisis preliminar de las curvas en magnitud V permite clasificar a los dos sistemas estudiados dentro del gtupo de las binarias cerradas de contacto marginal.Asociación Argentina de Astronomí

Measuring Black Hole Spin using X-ray Reflection Spectroscopy

I review the current status of X-ray reflection (a.k.a. broad iron line) based black hole spin measurements. This is a powerful technique that allows us to measure robust black hole spins across the mass range, from the stellar-mass black holes in X-ray binaries to the supermassive black holes in active galactic nuclei. After describing the basic assumptions of this approach, I lay out the detailed methodology focusing on "best practices" that have been found necessary to obtain robust results. Reflecting my own biases, this review is slanted towards a discussion of supermassive black hole (SMBH) spin in active galactic nuclei (AGN). Pulling together all of the available XMM-Newton and Suzaku results from the literature that satisfy objective quality control criteria, it is clear that a large fraction of SMBHs are rapidly-spinning, although there are tentative hints of a more slowly spinning population at high (M>5*10^7Msun) and low (M<2*10^6Msun) mass. I also engage in a brief review of the spins of stellar-mass black holes in X-ray binaries. In general, reflection-based and continuum-fitting based spin measures are in agreement, although there remain two objects (GROJ1655-40 and 4U1543-475) for which that is not true. I end this review by discussing the exciting frontier of relativistic reverberation, particularly the discovery of broad iron line reverberation in XMM-Newton data for the Seyfert galaxies NGC4151, NGC7314 and MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk reflection, this detection of reverberation demonstrates that future large-area X-ray observatories such as LOFT will make tremendous progress in studies of strong gravity using relativistic reverberation in AGN.Comment: 19 pages. To appear in proceedings of the ISSI-Bern workshop on "The Physics of Accretion onto Black Holes" (8-12 Oct 2012). Revised version adds a missing source to Table 1 and Fig.6 (IRAS13224-3809) and corrects the referencing of the discovery of soft lags in 1H0707-495 (which were in fact first reported in Fabian et al. 2009

Analysis of a Two-Class FCFS Queueing System with Interclass Correlation

This paper considers a discrete-time queueing system with one server and two classes of customers. All arriving customers are accommodated in one queue, and are served in a First-Come-First-Served order, regardless of their classes. The total numbers of arrivals during consecutive time slots are i.i.d. random variables with arbitrary distribution. The classes of consecutively arriving customers, however, are correlated in a Markovian way, i.e., the probability that a customer belongs to a class depends on the class of the previously arrived customer. Service-time distributions are assumed to be general but class-dependent. We use probability generating functions to study the system analytically. The major aim of the paper is to estimate the impact of the interclass correlation in the arrival stream on the queueing performance of the system, in terms of the (average) number of customers in the system and the (average) customer delay and customer waiting time

Análisis fotométrico de la binaria de contacto BF Pav

Se presenta el análisis de las observaciones fotométricas BV de la binaria de corto período BF Pav, llevadas a cabo entre 1987 y 1993. El estudio de los tiempos de mínimo define un período de 0.3023186 días, probablemente creciente a una tasa de 0.015 s/año. Las curvas de luz B y V obtenidas son analizadas mediante el método de Wilson y Devinney en un amplio rango de razones de masas. Se bata de un sistema de contacto moderado con una relación de masas q = 1.4 ± 0.2. Se presentan los parámetros fotométricos de las distintas soluciones y se comparan los resultados con los obtenidos para otros sistemas binarios similares. Se estiman parámetros estelares absolutos de las componentes y se discuten las probables características físicas y evolutivas del objeto.Asociación Argentina de Astronomí

Luz de America: comunidad y biodiversidad Amazonica

Problems with governance of forests are closely linked to incompatible interests between different stakeholders. Having a clearer understanding of the relative importance of forest landscape functions among stakeholders can bring much clarity about why governance problems persist. The voice of the weakest actors is often insufficiently heard in decision-making processes that affect how stakeholders can use forests. CIFOR has developed potentially rapid and efficient assessment procedures that, as far as possible, explicitly identify and describe what landscape functions that are most important for forest dependent communities. This Multidisciplinary Landscape Assessment (MLA) set of methods was developed in East Kalimantan, Indonesia. The “Stakeholders and biodiversity in the forest of the future project” tested and further developed the MLA methods in Bolivia (humid forest) and Mozambique (woodlands)

Expansion and equity in Australian higher education: three propositions for new relations

This article outlines three broad propositions for student equity in Australian higher education (HE), arising from the Australian Government's recent policy announcement to expand and widen student participation. The first is that a new relationship between student demand for places and their supply is on the horizon, unlike any other in Australia's history. Specifically, demand will struggle to match the intended supply. Given these new arrangements between government, institution and applicant, the article's second proposition is that governments and universities will need to develop a new regard for the people they seek to attract. And, following on from this, they will need to pay more attention to the nature of HE and its appeal to people who traditionally have not been all that interested. Informing this account are an examination of statistical data, analysis of university outreach programs, and a comparison of current principles of effective teaching in HE. The article concludes that advancing student equity in the current context will require new relations between institutions and students, which include a more sophisticated appreciation for the diversity of students and their communities, and for what they potentially contribute to HE