A model for high-mass microquasar jets under the influence of a strong stellar wind

Context. High-mass microquasars (HMMQs) are systems from which relativistic jets are launched. At the scales of several times the binary system size, the jets are expected to follow a helical path caused by the interaction with a strong stellar wind and orbital motion.Such a trajectory has its influence on the non-thermal emission of the jets, which also depends strongly on the observing angle due to Doppler boosting effects. Aims. We explore how the expected non-thermal emission of HMMQ jets at small scales is affected by the impact of the stellar wind and the orbital motion on the jet propagation. Methods. We studied the broadband non-thermal emission, from radio to gamma rays, produced in HMMQ jets up to a distance of several orbital separations, taking into account a realistic jet trajectory, different model parameters, and orbital modulation. The jet trajectory is computed by considering momentum transfer with the stellar wind. Electrons are injected at the position where a recollimation shock in the jets is expected due to the wind impact. Their distribution along the jet path is obtained assuming local acceleration at the recollimation shock, and cooling via adiabatic, synchrotron, and inverse Compton processes. The synchrotron and inverse Compton emission is calculated taking into account synchrotron self-absorption within the jet, free-free absorption with the stellar wind, and absorption by stellar photons via pair production. Results. The spectrum is totally dominated by the jet over the counter-jet due to Doppler boosting. Broadband emission from microwaves to gamma rays is predicted, with radio emission being totally absorbed. This emission is rather concentrated in the regions close to the binary system and features strong orbital modulation at high energies. Asymmetric light curves are obtained owing to the helical trajectory of the jets. Conclusions. The presence of helical shaped jets could be inferred from asymmetries in the light curves, which become noticeable only for large jet Lorentz factors and low magnetic fields. Model parameters could be constrained if accurate phase-resolved lightcurves from GeV to TeV energies were available. The predictions for the synchrotron and the inverse Compton radiation are quite sensitive of the parameters determining the wind-jet interaction structure

Gamma rays from jets interacting with BLR clouds in blazars

Context. The innermost parts of powerful jets in active galactic nuclei are surrounded by dense, high-velocity clouds from the broad-line region, which may penetrate into the jet and lead to the formation of a strong shock. Such jet-cloud interactions are expected to have measurable effects on the γ-ray emission from blazars. Aims. We characterise the dynamics of a typical cloud-jet interaction scenario, and the evolution of its radiative output in the 0.1-30 GeV energy range, to assess to what extent these interactions can contribute to the γ-ray emission in blazars. Methods. We use semi-analytical descriptions of the jet-cloud dynamics, taking into account the expansion of the cloud inside the jet and its acceleration. Assuming that electrons are accelerated in the interaction and making use of the hydrodynamical information, we then compute the high-energy radiation from the cloud, including the absorption of γ-rays in the ambient photon field through pair creation. Results. Jet-cloud interactions can lead to significant γ-ray fluxes in blazars with a broad-line region (BLR), in particular when the cloud expansion and acceleration inside the jet are taken into account. This is caused by 1) the increased shocked area in the jet, which leads to an increase in the energy budget for the non-thermal emission; 2) a more efficient inverse Compton cooling with the boosted photon field of the BLR; and 3) an increased observer luminosity due to Doppler boosting effects. Conclusions. For typical broad-line region parameters, either (i) jet-cloud interactions contribute significantly to the persistent γ-ray emission from blazars or (ii) the BLR is far from spherical or the fraction of energy deposited in non-thermal electrons is smal

Gamma-ray emission from interactions between jets and BLR clouds

Blazars -active galactic nuclei with a jet pointing towards the observer- are the most numerous γ-ray sources detected until date. In this work we show preliminary results of a model in which broad-line region (BLR) clouds penetrate in the jet, producing shocks capable of accelerating relativistic electrons; these electrons emit γ-rays when they interact with the photons coming from the BLR clouds. We calculate semi-analytically the dynamical evolution of a typical cloud inside the jet, the energy distribution of the locally accelerated electrons, and the high-energy emission the latter produce, taking into account relativistic effects. We estimate the dutycycle of these interactions in order to find whether they occur as discrete events or almost continuous. We compare the observed γ-ray fluxes with the ones predicted by our model and discuss the implications in terms of particle acceleration efficiency and mass-loading in the blazar jets

Non-thermal emission in hyper-velocity and semi-relativistic stars

Context. There is a population of runaway stars that move at extremely high speeds with respect to their surroundings. The fast motion and the stellar wind of these stars, plus the wind-medium interaction, can lead to particle acceleration and non-thermal radiation. Aims. We characterise the interaction between the winds of fast runaway stars and their environment, in particular to establish their potential as cosmic-ray accelerators and non-thermal emitters. Methods. We model the hydrodynamics of the interaction between the stellar wind and the surrounding material. We self-consistently calculate the injection and transport of relativistic particles in the bow shock using a multi-zone code, and compute their broadband emission from radio to γ-rays. Results. Both the forward and reverse shocks are favourable sites for particle acceleration, although the radiative efficiency of particles is low and therefore the expected fluxes are in general rather faint. Conclusions. We show that high-sensitivity observations in the radio band can be used to detect the non-thermal radiation associated with bow shocks from hyper-velocity and semi-relativistic stars. Hyper-velocity stars are expected to be modest sources of sub-TeV cosmic rays, accounting perhaps for ∼0.1% of that of galactic cosmic rays

Multi-zone non-thermal radiative model for stellar bowshocks

Context. Runaway stars produce bowshocks that are usually observed at infrared (IR) wavelengths. Non-thermal radio emission has been detected so far only from the bowshock of BD+43°3654, whereas the detection of non-thermal radiation from these bowshocks at high energies remains elusive. Aims. We aim at characterising in detail the radio, X-ray, and γ-ray emission from stellar bowshocks accounting for the structure of the region of interaction between the stellar wind and its environment. Methods. We develop a broadband-radiative, multi-zone model for stellar bowshocks that takes into account the spatial structure of the emitting region and the observational constraints. The model predicts the evolution and the emission of the relativistic particles accelerated and streaming together with the shocked flow. Results. We present broadband non-thermal spectral energy distributions for different scenarios, synthetic radio-cm synchrotron maps that reproduce the morphology of BD+43°3654, and updated predictions in X-ray and γ-ray energy ranges. We also compare the results of the multi-zone model applied in this work with those of a refined one-zone model. Conclusions. A multi-zone model provides better constraints than a one-zone model on the relevant parameters, namely the magnetic field intensity and the amount of energy deposited in non-thermal particles. However, one-zone models can be improved by carefully characterising the intensity of the IR dust photon field and the escape rate of the plasma from the shocked region. Finally, comparing observed radio maps with those obtained from a multi-zone model enables constraints to be obtained on the direction of stellar motion with respect to the observer

Evidence for non-thermal X-ray emission from the double Wolf-Rayet colliding-wind binary Apep

Context. Massive colliding-wind binaries (CWBs) can be non-thermal sources. The emission produced in their wind-collision region (WCR) encodes information of both the shock properties and the relativistic electrons accelerated in them. The recently discovered system Apep, a unique massive system hosting two Wolf-Rayet stars, is the most powerful synchrotron radio emitter among the known CWBs. It is an exciting candidate in which to investigate the non-thermal processes associated with stellar wind shocks. Aims. We intend to break the degeneracy between the relativistic particle population and the magnetic field strength in the WCR of Apep by probing its hard X-ray spectrum, where inverse-Compton (IC) emission is expected to dominate. Methods. We observed Apep with NuSTAR for 60 ks and combined this with a reanalysis of a deep archival XMM-Newton observation to better constrain the X-ray spectrum. We used a non-thermal emission model to derive physical parameters from the results. Results. We detect hard X-ray emission consistent with a power-law component from Apep. This is compatible with IC emission produced in the WCR for a magnetic field of ≈105–190 mG, corresponding to a magnetic-to-thermal pressure ratio in the shocks of ≈0.007–0.021, and a fraction of ∼1.5 × 10−4 of the total wind kinetic power being transferred to relativistic electrons. Conclusions. The non-thermal emission from a CWB is detected for the first time in radio and at high energies. This allows us to derive the most robust constraints so far for the particle acceleration efficiency and magnetic field intensity in a CWB, reducing the typical uncertainty of a few orders of magnitude to just within a factor of a few. This constitutes an important step forward in our characterisation of the physical properties of CWBs

Genetic differentiation of North-East Argentina populations based on 30 binary X chromosome markers

Alu insertions, INDELs, and SNPs in the X chromosome can be useful not only for revealing relationships among populations but also for identification purposes. We present data of 10 Alu insertions, 5 INDELs, and 15 SNPs of X-chromosome from three Argentinian north-east cities in order to gain insight into the genetic diversity of the X chromosome within this region of the country. Data from 198 unrelated individuals belonging to Posadas, Corrientes, and Eldorado cities were genotyped for Ya5DP62, Yb8DP49, Ya5DP3, Ya5NBC37, Ya5DP77, Ya5NBC491, Ya5DP4, Ya5DP13, Yb8NBC634, and Yb8NBC102 Alu insertions, for MID193, MID1705, MID3754, MID3756 and MID1540 Indels and for rs6639398, rs5986751, rs5964206, rs9781645, rs2209420, rs1299087, rs318173, rs933315, rs1991961, rs4825889, rs1781116, rs1937193, rs1781104, rs149910, and rs652 SNPs. No deviations from Hardy-Weinberg equilibrium were observed for Posadas and Corrientes. However, Eldorado showed significant values, and it was found to have an internal substructuring with two groups of different origin, one showing higher similarity with European countries, and the other with more similarities to Posadas and Corrientes. Fst pairwise genetic distances emerged for some markers among the studied populations and also between our data and those from other countries and continents. Of particular interest, Alu insertions demonstrated the most differences, and could be of use in ancestry studies for these populations, while INDELs and SNPs variation were informative for differentiation within the country

Gamma rays from clumpy wind-jet interactions in high-mass microquasars

Context. The stellar winds of the massive stars in high-mass microquasars are thought to be inhomogeneous. The interaction of these inhomogeneities, or clumps, with the jets of these objects may be a major factor in gamma-ray production. Aims. Our goal is to characterize a typical scenario of clump-jet interaction, and calculate the contribution of these interactions to the gamma-ray emission from these systems. Methods. We use axisymmetric, relativistic hydrodynamical simulations to model the emitting flow in a typical clump-jet interaction. Using the simulation results we perform a numerical calculation of the high-energy emission from one of these interactions. The radiative calculations are performed for relativistic electrons locally accelerated at the jet shock, and the synchrotron and inverse Compton radiation spectra are computed for different stages of the shocked clump evolution. We also explore different parameter values, such as viewing angle and magnetic field strength. The results derived from one clump-jet interaction are generalized phenomenologically to multiple interactions under different wind models, estimating the clump-jet interaction rates, and the resulting luminosities in the GeV range. Results. If particles are efficiently accelerated in clump-jet interactions, the apparent gamma-ray luminosity through inverse Compton scattering with the stellar photons can be significant even for rather strong magnetic fields and thus efficient synchrotron cooling. Moreover, despite the standing nature or slow motion of the jet shocks for most of the interaction stage, Doppler boosting in the postshock flow is relevant even for mildly relativistic jets. Conclusions. For clump-to-average wind density contrasts greater than or equal to ten, clump-jet interactions could be bright enough to match the observed GeV luminosity in Cyg X-1 and Cyg X-3 when a jet is present in these sources, with required non-thermal-to-total available power fractions greater than 0.01 and 0.1, respectively

Archivo sobre cardiopatías congénitas. Grupo GECAR-AVEPA

En este artículo se presentan los objetivos y las pautas para la elaboración de un archivo sobre cardiopatías congénitas en pequeños animales a nivel nacional, elaborados por una comisión de miembros del Grupo de Especialistas en Cardiorrespiratorio (GECAR) de AVEPA.

Prevalence and Intensity of Soil-transmitted Helminthiasis in the City of Portoviejo (Ecuador)

We studied the stool samples of 151 school children in a district of the city of Portoviejo (Ecuador) in order to determine the prevalence and intensity of soil-transmitted helminthiasis (STH) and their relationships with anthropometric indices. The samples were analyzed with the semiquantitative Kato-Katz technique and the intensity of infections was categorized as light, moderate or high according to the thresholds set by the World Health Organization. Prevalence of soil transmitted helmintiasis was 65% (92 out of 141 collected samples), Ascaris lumbricoides was the most common STH (63%) followed by Trichuris trichiura (10%) and hookworm (1.4%). Heavy intensity infections were found in 8.5% of the stool samples, with T. trichiura showing higher worm burdens than A. lumbricoides. Sixteen percent of the children were below the third percentile for weight (wasted), while 27% were below the third percentile for height (stunted). A significant relationship was found between the worm burden and the degree of stunting. This study suggests that the periodic administration of an antihelminthic drug should be targeted to preschool and school children to allow a normal growth spurt and prevent stunting