Modelling the variable broad-band optical/UV/X-ray spectrum of PG1211+143: Implications for the ionized outflow

We present the results from a detailed analysis of the 2007 Swift monitoring campaign of the quasar PG1211+143. We constructed broad-band, optical/UV/X-ray spectral energy distributions over three X-ray flux intervals. We fitted them with a model which accounts for the disc and the X-ray coronal emission and the warm absorber (well established in this source). The three flux spectra are well fitted by the model we considered. The disc inner temperature remains constant at ~2 eV, while X-rays are variable both in spectral slope and normalization. The absorber covers almost 90% of the central source. It is outflowing with a velocity less than 2.3*10^4 km/s (3sigma upper limit), and has a column density of ~10^23.2. Its ionization parameter varies by a factor of 1.6, and it is in photo-ionizing equilibrium with the ionizing flux. It is located at a distance of less than 0.35 pc from the central source and its relative thickness, DR/R is less than 0.1. The absorber' s ionization parameter variations can explain the larger than average amplitude of the X-ray variations. The absence of optical/UV variations (consistent with the high black hole mass estimate) argues against the presence of inward propagating disc fluctuations and strong X-ray illumination of the disc (in agreement with the low ratio of X-ray over the bolometric luminosity of ~20-35). We estimate an upper limit for the mass outflow of ~5 solar masses per year (~2.3 times the Eddington mass accretion rate). If the outflow rate is indeed that high, then it must be a short-lived episode in the quasar's life time. Finally, we estimate an upper limit for the kinetic power of the outflow of ~1.4*10^43 ergs/s. This outflow cannot deploy significant mechanical energy to the surrounding ISM of the quasar's host galaxy, but is sufficient to heat the ISM to 10^7 K and to produce a fast decline to the star formation rate of the galaxy.Comment: Accepted for publication by A&

A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in the Milky Way

Without a source of new gas, our Galaxy would exhaust its supply of gas through the formation of stars. Ionized gas clouds observed at high velocity may be a reservoir of such gas, but their distances are key for placing them in the Galactic halo and unraveling their role. We have used the Hubble Space Telescope to blindly search for ionized high-velocity clouds (iHVCs) in the foreground of Galactic stars. We show that iHVCs with 90 < |v_LSR| < 170 km/s are within one Galactic radius of the sun and have enough mass to maintain star formation, while iHVCs with |v_LSR|>170 km/s are at larger distances. These may be the next wave of infalling material.Comment: This paper is part of a set of three papers on circumgalactic gas observed with COS and STIS on HST, to be published in Science, together with related papers by Tripp et al. and Tumlinson et al., in the November 18, 2011 edition. This version has not undergone final copyediting. Please see Science online for the final printed versio

A New Method for Obtaining Binary Pulsar Distances and its Implications for Tests of General Relativity

We demonstrate how measuring orbital period derivatives can lead to more accurate distance estimates and transverse velocities for some nearby binary pulsars. In many cases this method will estimate distances more accurately than is possible by annual parallax, as the relative error decreases as t^-5/2. Unfortunately, distance uncertainties limit the degree to which nearby relativistic binary pulsars can be used for testing the general relativistic prediction of orbital period decay to a few percent. Nevertheless, the measured orbital period derivative of PSR B1534+12 agrees within the observational uncertainties with that predicted by general relativity if the proper-motion contribution is accounted for.Comment: 4 pages, latex, uuencoded compressed postscript + source, no figures, uses aaspptwo.sty and dec.sty, accepted for publication in ApJL, omitted reference now include

Movement behaviour and mortality in invasive and indigenous mussels: resilience and resistance strategies at different spatial scales

The responses of indigenous and exotic species to environmental factors can differ across spatial and temporal scales, and it is this difference that determines invasion success and the dynamics of co-existence, In South Africa, the indigenous Perna perna and the invasive Mytilus galloprovincialis are the dominant intertidal mussels on the southern coast, where they co-exist. We compared their movement behaviour over 6 mo at small scales (within and at the edge of mussel beds) and at meso scales (in bays and on the open coast). M, galloprovincialis moved more and had higher mortality rates than did P. perna. For both species, mortality was greater at the edge than at the centre of beds, and on the open coast than in bays. Mussels at the edge of beds moved more than those within beds, but, while this was true for M. galloprovincialis in both habitats, P. perna did not show a position effect on the open coast. Cross-correlation analysis showed that movement rates of both species were correlated with mortality rates after a lag of 1. mo. These results suggest that following mortality events, mussels react to increased availability of space and decreased attachment to neighbours by increasing their movement to reorganise into a safer arrangement. However, P. perna and M. galloprovincialis effectively adopt resistance and resilience strategies, respectively. The effectiveness of each strategy depends on environmental conditions in different habitats, influencing the possibility of co-existence. The higher hydrodynamic stresses experienced in open coast habitats and at the edge of a mussel bed are disadvantageous to the more active, less strongly attached invasive species.Claude Harris Leon Foundation; Rhodes University; National Research Foundation of South Afric

Spectral catalogue of bright gamma-ray bursts detected with the BeppoSAX/GRBM

The emission process responsible for the so-called "prompt" emission of gamma-ray bursts is still unknown. A number of empirical models fitting the typical spectrum still lack a satisfactory interpretation. A few GRB spectral catalogues derived from past and present experiments are known in the literature and allow to tackle the issue of spectral properties of gamma-ray bursts on a statistical ground. We extracted and studied the time-integrated photon spectra of the 200 brightest GRBs observed with the Gamma-Ray Burst Monitor which flew aboard the BeppoSAX mission (1996-2002) to provide an independent statistical characterisation of GRB spectra. The spectra were fit with three models: a simple power-law, a cut-off power law or a Band function. The typical photon spectrum of a bright GRB consists of a low-energy index around 1.0 and a peak energy of the nuFnu spectrum E_p~240 keV in agreement with previous results on a sample of bright CGRO/BATSE bursts. Spectra of ~35% of GRBs can be fit with a power-law with a photon index around 2, indicative of peak energies either close to or outside the GRBM energy boundaries. We confirm the correlation between E_p and fluence, with a logarithmic dispersion of 0.13 around the power-law with index 0.21+-0.06. The low-energy and peak energy distributions are not yet explained in the current literature. The capability of measuring time-resolved spectra over a broadband energy range, ensuring precise measurements of parameters such as E_p, will be crucial for future experiments (abridged).Comment: 28 pages, 20 figures, 3 tables, accepted to A&

Levantamento de dados agropecuários da região metropolitana de Campinas: principais produtos e sua importância para fundamentar o atlas ambiental escolar.

Este trabalho pretende descrever os principais produtos agropecuários presentes na Região Metropolitana de Campinas (RMC). A descrição foi baseada em levantamento e organização de dados primários de acesso público.O trabalho de coleta de dados integra o projeto ?Geotecnologias como apoio à elaboração de material didático para o ensino fundamental: Atlas Ambiental Escolar da Região Metropolitana de Campinas (GeoAtlas)?. Este projeto visa elaborar, em conjunto com professores da rede municipal de Campinas, um material de apoio para estudantes do ensino fundamental com enfoque para a agropecuária como um agente modificador da paisagem (EMBRAPA MONITORAMENTO POR SATÉLITE, 2010). O atlas utilizará a RMC como estudo de caso, inserindo o local de vivência dos alunos em seu aprendizado.A coleta de dados primários é fundamental para a compreensão das atividades agropecuárias presentes na região. O uso de materiais e dados de acesso público permitirá que a metodologia desenvolvida para a elaboração do atlas possa ser disseminada para outros municípios do Brasil.Os dados censitários serão analisados, buscando compreender quais são os produtos agrícolas mais importantes na paisagem dos municípios que integram a RMC