12 research outputs found
Stellar convective cores as dark matter probes
The recent detection of a convective core in a main-sequence solar-type star
is used here to test particular models of dark matter (DM) particles, those
with masses and scattering cross sections in the range of interest for the DM
interpretation of the positive results in several DM direct detection
experiments. If DM particles do not effectively self-annihilate after
accumulating inside low-mass stars (e.g. in the asymmetric DM scenario) their
conduction provides an efficient mechanism of energy transport in the stellar
core. For main-sequence stars with masses between 1.1 and 1.3 Msun, this
mechanism may lead to the suppression of the inner convective region expected
to be present in standard stellar evolution theory. The asteroseismic analysis
of the acoustic oscillations of a star can prove the presence/absence of such a
convective core, as it was demonstrated for the first time with the Kepler
field main-sequence solar-like pulsator, KIC 2009505. Studying this star we
found that the asymmetric DM interpretation of the results in the CoGeNT
experiment is incompatible with the confirmed presence of a small convective
core in KIC 2009505.Comment: to appear on Physical Review
Deforestation and Carbon Stock Loss in Brazil’s Amazonian Settlements
We estimate deforestation and the carbon stock in 2740 (82 %) of the 3325 settlements in Brazil’s Legal Amazonia region. Estimates are made both using available satellite data and a carbon map for the “pre-modern” period (prior to 1970). We used data from Brazil’s Project for Monitoring Deforestation in Amazonia updated through 2013 and from the Brazilian Biomes Deforestation Monitoring Project (PMDBBS) updated through 2010. To obtain the pre-modern and recent carbon stocks we performed an intersection between a carbon map and a map derived from settlement boundaries and deforestation data. Although the settlements analyzed occupied only 8 % of Legal Amazonia, our results indicate that these settlements contributed 17 % (160,410 km2) of total clearing (forest + non-forest) in Legal Amazonia (967,003 km2). This represents a clear-cutting of 41 % of the original vegetation in the settlements. Out of this total, 72 % (115,634 km2) was in the “Federal Settlement Project” (PA) category. Deforestation in settlements represents 20 % (2.6 Pg C) of the total carbon loss in Legal Amazonia (13.1 Pg C). The carbon stock in remaining vegetation represents 3.8 Pg C, or 6 % of the total remaining carbon stock in Legal Amazonia (58.6 Pg C) in the periods analyzed. The carbon reductions in settlements are caused both by the settlers and by external actors. Our findings suggest that agrarian reform policies contributed directly to carbon loss. Thus, the implementation of new settlements should consider potential carbon stock losses, especially if settlements are created in areas with high carbon stocks. © 2016, The Author(s)