Unveiling the environment surrounding LMXB SAX J1808.4-3658

Low-mass X-ray binaries (LMXBs) are a natural workbench to study accretion disk phenomena and optimal background sources to measure elemental abundances in the Interstellar medium (ISM). In high-resolution XMM-Newton spectra, the LMXB SAX J1808.4-3658 showed in the past a neon column density significantly higher than expected given its small distance, presumably due to additional absorption from a neon-rich circumstellar medium (CSM). It is possible to detect intrinsic absorption from the CSM by evidence of Keplerian motions or outflows. For this purpose, we use a recent, deep (100 ks long), high-resolution Chandra/LETGS spectrum of SAX J1808.4-3658 in combination with archival data. We estimated the column densities of the different absorbers through the study of their absorption lines. We used both empirical and physical models involving photo- and collisional-ionization in order to determine the nature of the absorbers. The abundances of the cold interstellar gas match the solar values as expected given the proximity of the X-ray source. For the first time in this source, we detected neon and oxygen blueshifted absorption lines that can be well modeled with outflowing photoionized gas. The wind is neon rich (Ne/O>3) and may originate from processed, ionized gas near the accretion disk or its corona. The kinematics (v=500-1000 km/s) are indeed similar to those seen in other accretion disks. We also discovered a system of emission lines with very high Doppler velocities (v~24000 km/s) originating presumably closer to the compact object. Additional observations and UV coverage are needed to accurately determine the wind abundances and its ionization structure.Comment: 12 pages, 10 figures, accepted for publication on A&

Abundance and temperature distributions in the hot intra-cluster gas of Abell 4059

Using the EPIC and RGS data from a deep (~200 ks) XMM-Newton observation, we investigate the temperature structure (kT and sigma_T ) and the abundances of 9 elements (O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni) of the intra-cluster medium (ICM) in the nearby (z=0.046) cool-core galaxy cluster Abell 4059. Next to a deep analysis of the cluster core, a careful modelling of the EPIC background allows us to build radial profiles up to 12' (~650 kpc) from the core. Probably because of projection effects, the temperature ICM is found not to be in single phase, even in the outer parts of the cluster. The abundances of Ne, Si, S, Ar, Ca and Fe, but also O are peaked towards the core. Fe and O are still significantly detected in the outermost annuli; suggesting that the enrichment by both type Ia and core-collapse SNe started in the early stages of the cluster formation. However, the particularly high Ca/Fe ratio that we find in the core is not well reproduced by the standard SNe yield models. Finally, 2-D maps of temperature and Fe abundance are presented and confirm the existence of a denser, colder, and Fe-rich ridge southwest of the core, previously observed by Chandra. The origin of this asymmetry in the hot gas of the cluster core is still unclear, but might be explained by a past intense ram-pressure stripping event near the central cD galaxy.Comment: 17 pages, 13 figures, accepted for publication in A&

X-ray variability with WFXT: AGNs, transients and more

The Wide Field X-ray Telescope (WFXT) is a proposed mission with a high survey speed, due to the combination of large field of view (FOV) and effective area, i.e. grasp, and sharp PSF across the whole FOV. These characteristics make it suitable to detect a large number of variable and transient X-ray sources during its operating lifetime. Here we present estimates of the WFXT capabilities in the time domain, allowing to study the variability of thousand of AGNs with significant detail, as well as to constrain the rates and properties of hundreds of distant, faint and/or rare objects such as X-ray Flashes/faint GRBs, Tidal Disruption Events, ULXs, Type-I bursts etc. The planned WFXT extragalactic surveys will thus allow to trace variable and transient X-ray populations over large cosmological volumes.Comment: Proceedings of "The Wide Field X-ray Telescope Workshop", held in Bologna, Italy, Nov. 25-26 2009 (arXiv:1010.5889). To appear in Memorie della Societ\`a Astronomica Italiana 2010 - Minor corrections to text

Chemical Enrichment RGS cluster sample (CHEERS): Constraints on turbulence

Feedback from AGN, galactic mergers, and sloshing are thought to give rise to turbulence, which may prevent cooling in clusters. We aim to measure the turbulence in clusters of galaxies and compare the measurements to some of their structural and evolutionary properties. It is possible to measure the turbulence of the hot gas in clusters by estimating the velocity widths of their X-ray emission lines. The RGS Spectrometers aboard XMM-Newton are currently the only instruments provided with sufficient effective area and spectral resolution in this energy domain. We benefited from excellent 1.6Ms new data provided by the CHEERS project. The new observations improve the quality of the archival data and allow us to place constraints for some clusters, which were not accessible in previous work. One-half of the sample shows upper limits on turbulence less than 500km/s. For several sources, our data are consistent with relatively strong turbulence with upper limits on the velocity widths that are larger than 1000km/s. The NGC507 group of galaxies shows transonic velocities, which are most likely associated with the merging phenomena and bulk motions occurring in this object. Where both low- and high-ionization emission lines have good enough statistics, we find larger upper limits for the hot gas, which is partly due to the different spatial extents of the hot and cool gas phases. Our upper limits are larger than the Mach numbers required to balance cooling, suggesting that dissipation of turbulence may prevent cooling, although other heating processes could be dominant. The systematics associated with the spatial profile of the source continuum make this technique very challenging, though still powerful, for current instruments. The ASTRO-H and Athena missions will revolutionize the velocity estimates and discriminate between different spatial regions and temperature phases.Comment: 16 pages, 18 figures, 3 tables, accepted for publications in Astronomy and Astrophysic

A high-density relativistic reflection origin for the soft and hard X-ray excess emission from Mrk 1044

We present the first results from a detailed spectral-timing analysis of a long ($\sim$130 ks) XMM-Newton observation and quasi-simultaneous NuSTAR and Swift observations of the highly-accreting narrow-line Seyfert 1 galaxy Mrk 1044. The broadband (0.3$-$50 keV) spectrum reveals the presence of a strong soft X-ray excess emission below $\sim$1.5 keV, iron K$_{\alpha}$ emission complex at $\sim$6$-$7 keV and a `Compton hump' at $\sim$15$-$30 keV. We find that the relativistic reflection from a high-density accretion disc with a broken power-law emissivity profile can simultaneously explain the soft X-ray excess, highly ionized broad iron line and the Compton hump. At low frequencies ($[2-6]\times10^{-5}$ Hz), the power-law continuum dominated 1.5$-$5 keV band lags behind the reflection dominated 0.3$-$1 keV band, which is explained with a combination of propagation fluctuation and Comptonization processes, while at higher frequencies ($[1-2]\times10^{-4}$ Hz), we detect a soft lag which is interpreted as a signature of X-ray reverberation from the accretion disc. The fractional root-mean-squared (rms) variability of the source decreases with energy and is well described by two variable components: a less variable relativistic disc reflection and a more variable direct coronal emission. Our combined spectral-timing analyses suggest that the observed broadband X-ray variability of Mrk~1044 is mainly driven by variations in the location or geometry of the optically thin, hot corona.Comment: 23 pages, 19 figures, 4 tables, Published in MNRA

Influence of abiotic factors on the resistance of plants to insects

Abstract. Plant resistance is considered as an important pillar of Integrated Pest Management (IPM), being a highly targeted method since is a less harmful method to the environment, if compared to other tactics such as chemical control. Abiotic factors are those related to the environment and have a direct influence on the dynamics of interaction between insects and plants. The abiotic factors such as altitude, temperature, humidity, luminosity, wind and soil fertility, among others, do not act alone, but in a complex net that leads insect population dynamics in agroecosystems. How the variations of these factors can be studied in the same context? First, it is important to consider how each abiotic factors act separately and then in a coexistence influence over the populations dynamics of insects and plants. In this study, the literature about the influence of abiotic factors on insect herbivory has been reviewed, focusing mainly on the mechanisms in which the plants use in the defense against insects. Influência de fatores abióticos na resistência de plantas a insetos Resumo. A resistência de plantas é considerada um importante pilar no contexto do Manejo Integrado de Pragas (MIP), sendo um método bastante visado por ser menos nocivo ao meio ambiente, quando comparado a outras táticas como o controle químico. Os fatores abióticos são aqueles relacionados ao ambiente e têm influência direta na dinâmica de interação entre insetos e plantas. Os fatores abióticos como altitude, temperatura, umidade, luminosidade, ventos e fertilidade do solo, por exemplo, não atuam sozinhos, mais sim em um complexo de fatores coexistentes que regem as dinâmicas populacionais nos diversos agroecosistemas. Como as variações destes fatores podem ser estudadas em um mesmo contexto? Primeiramente, é importante conhecer como cada uma atua individualmente para então contextualizar em uma situação de coexistência sobre as dinâmicas populacionais de insetos e plantas. Neste artigo, a literatura sobre a influência de fatores abióticos na herbivoria de insetos foi revisada, focando principalmente nos mecanismos em que as plantas utilizam na defesa contra insetos

Searching for cool and cooling X-ray emitting gas in 45 galaxy clusters and groups

We present a spectral analysis of cool and cooling gas in 45 cool-core clusters and groups of galaxies obtained from Reflection Grating Spectrometer (RGS) XMM-$Newton$ observations. The high-resolution spectra show FeXVII emission in many clusters, which implies the existence of cooling flows. The cooling rates are measured between the bulk Intracluster Medium (ICM) temperature and 0.01 keV and are typically weak, operating at less than a few tens of $\rm M_{\odot}\rm yr^{-1}$ in clusters, and less than 1 $\rm M_{\odot}\rm yr^{-1}$ in groups of galaxies. They are 10-30% of the classical cooling rates in the absence of heating, which suggests that AGN feedback has a high level of efficiency. If cooling flows terminate at 0.7 keV in clusters, the associated cooling rates are higher, and have a typical value of a few to a few tens of $\rm M_{\odot}\rm yr^{-1}$. Since the soft X-ray emitting region, where the temperature $kT<1$ keV, is spatially associated with H$\alpha$ nebulosity, we examine the relation between the cooling rates above 0.7 keV and the H$\alpha$ nebulae. We find that the cooling rates have enough energy to power the total UV-optical luminosities, and are 5 to 50 times higher than the observed star formation rates for low luminosity objects. In 4 high luminosity clusters, the cooling rates above 0.7 keV are not sufficient and an inflow at a higher temperature is required. Further residual cooling below 0.7 keV indicates very low complete cooling rates in most clusters.Comment: 17 pages, 10 figures, accepted for publication in MNRA

The inner gas mass-temperature profile in the core of nearby galaxy clusters

We present a mass-temperature profile of gas within the central 10 kpc of a small sample of cool core clusters. The mass of the hottest gas phases, at 1.5 and 0.7 keV, is determined from X-ray spectra from the XMM Reflection Grating Spectrometers. The masses of the partially ionized atomic and the molecular phases are obtained from published H α and CO measurements. We find that the mass of gas at 0.7 keV in a cluster is remarkably similar to that of the molecular gas. Assuming pressure equilibrium between the phases, this means that they occupy volumes differing by 105. The molecular gas is located within the H α nebula which is often filamentary and coincides radially and in position angle with the soft X-ray emitting gas