17,840 research outputs found
Sustainable management of miombo woodlands in the Northern part of Mozambique (Niassa National Reserve - NNR).
Poster presented at Commiting Science to Global Development. Lisbon (Portugal). 29-30 Sep 2009
Dinâmica de características físicas e químicas de solos em diferentes sistemas de manejo/uso da terra em áreas de pequenos produtores.
Caracterização química dos solos e a dinâmica dessas características em diferentes sistemas de manejo/uso da terra em áreas de pequenos produtores.
Caracterização morfológica, física e química dos solos e a dinâmica dessas características em diferentes sistemas de manejo e uso da terra em áreas de pequenos produtores.
Evidence for reduced magnetic braking in polars from binary population models
We present the first population synthesis of synchronous magnetic cataclysmic variables, called polars, taking into account the effect of the white dwarf (WD) magnetic field on angular momentum loss. We implemented the reduced magnetic braking (MB) model proposed by Li, Wu & Wickramasinghe into the Binary Stellar Evolution (BSE) code recently calibrated for cataclysmic variable (CV) evolution. We then compared separately our predictions for polars and non-magnetic CVs with a large and homogeneous sample of observed CVs from the Sloan Digital Sky Survey. We found that the predicted orbital period distributions and space densities agree with the observations if period bouncers are excluded. For polars, we also find agreement between predicted and observed mass transfer rates, while the mass transfer rates of non-magnetic CVs with periods ≳3 h drastically disagree with those derived from observations. Our results provide strong evidence that the reduced MB model for the evolution of highly magnetized accreting WDs can explain the observed properties of polars. The remaining main issues in our understanding of CV evolution are the origin of the large number of highly magnetic WDs, the large scatter of the observed mass transfer rates for non-magnetic systems with periods ≳3 h, and the absence of period bouncers in observed samples
Galactic Archaeology with CoRoT and APOGEE: Creating mock observations from a chemodynamical model
In a companion paper, we have presented the combined
asteroseismic-spectroscopic dataset obtained from CoRoT lightcurves and APOGEE
infra-red spectra for 678 solar-like oscillating red giants in two fields of
the Galactic disc (CoRoGEE). We have measured chemical abundance patterns,
distances, and ages of these field stars which are spread over a large radial
range of the Milky Way's disc. Here we show how to simulate this dataset using
a chemodynamical Galaxy model. We also demonstrate how the observation
procedure influences the accuracy of our estimated ages.Comment: 5 pages, 6 figures. To appear in Astronomische Nachrichten, special
issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
Montalb\'an, and M. Steffe
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