On the mass distribution of neutron stars

The distribution of masses for neutron stars is analyzed using the Bayesian statistical inference, evaluating the likelihood of proposed gaussian peaks by using fifty-four measured points obtained in a variety of systems. The results strongly suggest the existence of a bimodal distribution of the masses, with the first peak around $1.37 {M_{\odot}}$, and a much wider second peak at $1.73 {M_{\odot}}$. The results support earlier views related to the different evolutionary histories of the members for the first two peaks, which produces a natural separation (even if no attempt to "label" the systems has been made here), and argues against the single-mass scale viewpoint. The bimodal distribution can also accommodate the recent findings of $\sim M_{\odot}$ masses quite naturally. Finally, we explore the existence of a subgroup around $1.25 {M_{\odot}}$, finding weak, if any, evidence for it. This recently claimed low-mass subgroup, possibly related to $O-Mg-Ne$ core collapse events, has a monotonically decreasing likelihood and does not stand out clearly from the rest of the sample.Comment: 11 pp., 3 figures, submitted to MNRAS Letter

Trade-off between reproduction and mobility prolongs organisms' survival in rock-paper-scissors models

We study the spatial rock-paper-scissors model, where resource competitors' cyclic dominance impacts organisms' energy levels. Our model assumes that failed selection interactions can lead to energy loss, reducing the chances of success in the spatial game and hastening decline. To prevent death by energy insufficiency, organisms of one out of the species strategically perform a trade-off between reproduction and mobility. When prioritising exploring more extensive areas, organisms aim to maximise the chances of acquiring resources to regain high energy levels. Through simulation, we examine the effect of survival behaviour on species segregation and spatial patterns. Our outcomes show that the trade-off between offspring generation and accelerated movement effectively protects individuals from death due to lack of energy. Moreover, the risk of being eliminated by an enemy in the cyclic game reduces due to the behavioural strategy. Considering a three-state model, we quantify how the trade-off parameter controls the organisms' energy recovery. Computing the median organisms' survival time, we find that although individuals performing the trade-off strategy may live longer, the organisms of other species are negatively affected by a life expectancy reduction. Our research may elucidate the role of adaptive survival strategies in species persistence and provide valuable insights for ecologists.Comment: 7 pages, 5 figure

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue

AGN are known to have complex X-ray spectra that depend on both the properties of the accreting SMBH (e.g. mass, accretion rate) and the distribution of obscuring material in its vicinity ("torus"). Often however, simple and even unphysical models are adopted to represent the X-ray spectra of AGN. In the case of blank field surveys in particular, this should have an impact on e.g. the determination of the AGN luminosity function, the inferred accretion history of the Universe and also on our understanding of the relation between AGN and their host galaxies. We develop a Bayesian framework for model comparison and parameter estimation of X-ray spectra. We take into account uncertainties associated with X-ray data and photometric redshifts. We also demonstrate how Bayesian model comparison can be used to select among ten different physically motivated X-ray spectral models the one that provides a better representation of the observations. Despite the use of low-count spectra, our methodology is able to draw strong inferences on the geometry of the torus. For a sample of 350 AGN in the 4 Ms Chandra Deep Field South field, our analysis identifies four components needed to represent the diversity of the observed X-ray spectra: (abridged). Simpler models are ruled out with decisive evidence in favour of a geometrically extended structure with significant Compton scattering. Regarding the geometry of the obscurer, there is strong evidence against both a completely closed or entirely open toroidal geometry, in favour of an intermediate case. The additional Compton reflection required by data over that predicted by toroidal geometry models, may be a sign of a density gradient in the torus or reflection off the accretion disk. Finally, we release a catalogue with estimated parameters such as the accretion luminosity in the 2-10 keV band and the column density, $N_{H}$, of the obscurer.Comment: 28 pages, 18 figures, catalogue available from https://www.mpe.mpg.de/~jbuchner/agn_torus/analysis/cdfs4Ms_cat/, software available from https://github.com/JohannesBuchner/BX

The post-migration sexual citizenship of Latino gay men in Canada

The Cuéntame! Study interviewed 25 Spanish-speaking gay and bisexual men in Toronto. Their migration experiences are traversed by economic rationales, security concerns, and the embodied experiences of race, gender, culture, and sexuality. Most express narratives of empowered opportunity in distancing themselves from restrictive sexual regimes of their place of origin, but at the same time, many migrants trade a new sense of social acceptance as gay for marginalized statuses defined by diminished social and economic capital. The social participatory rights of citizenship are particularly affected by sexuality and social class. The need and desire to establish social and sexual connections in a new environment often characterized by economic vulnerability shape experiences of social capital and citizenship rights

Competição de leguminosas introduzidas no agreste de Pernambuco - município de Surubim.

Efeito da adubação fosfatada em 3 níveis e a variação na produção de massa verde nas estações seca e chuvosa

Squeezing generation and revivals in a cavity-ion system in contact with a reservoir

We consider a system consisting of a single two-level ion in a harmonic trap, which is localized inside a non-ideal optical cavity at zero temperature and subjected to the action of two external lasers. We are able to obtain an analytical solution for the total density operator of the system and show that squeezing in the motion of the ion and in the cavity field is generated. We also show that complete revivals of the states of the motion of the ion and of the cavity field occur periodically.Comment: 9 pages, 3 figure