CARMA interferometric observations of 2MASS J044427+2512: the first spatially resolved observations of thermal emission of a brown dwarf disk

We present CARMA 1.3 mm continuum data of the disk surrounding the young brown dwarf 2MASS J044427+2512 in the Taurus molecular cloud. The high angular resolution of the CARMA observations (0.16 arcsec) allows us to spatially resolve for the first time the thermal emission from dust around a brown dwarf. We analyze the interferometric visibilities and constrain the disk outer radius adopting disk models with power-law radial profiles of the dust surface density. In the case of a power-law index equal to or lower than 1, we obtain a disk radius in the range of about 15 - 30 AU, while larger disks are inferred for steeper radial profiles. By combining this information on the disk spatial extent with the sub-mm spectral index of this source we find conclusive evidence for mm-sized grains, or larger, in this brown dwarf disk. We discuss the implications of our results on the models of dust evolution in proto-planetary disks and brown dwarf formation.Comment: 14 pages, 3 figures, Accepted for publication in ApJ Letter

Helioseismology and Beryllium neutrino

We derive a lower limit on the Beryllium neutrino flux on earth, $\Phi(Be)_{min} = 1\cdot 10^9 cm^{-2} s^{-1}$, in the absence of oscillations, by using helioseismic data, the B-neutrino flux measured by Superkamiokande and the hydrogen abundance at the solar center predicted by Standard Solar Model (SSM) calculations. We emphasize that this abundance is the only result of SSMs needed for getting $\Phi(Be)_{min}$. We also derive lower bounds for the Gallium signal, $G_{min}=(91 \pm 3)$ SNU, and for the Chlorine signal, $C_{min}=(3.24\pm 0.14)$ SNU, which are about $3\sigma$ above their corresponding experimental values, $G_{exp}= (72\pm 6)$ SNU and $C_{exp}= (2.56\pm 0.22)$ SNU.Comment: 10 pages plus 1 ps figure, RevTeX styl

Connectivity Influences on Nonlinear Dynamics in Weakly-Synchronized Networks: Insights from Rössler Systems, Electronic Chaotic Oscillators, Model and Biological Neurons

Natural and engineered networks, such as interconnected neurons, ecological and social networks, coupled oscillators, wireless terminals and power loads, are characterized by an appreciable heterogeneity in the local connectivity around each node. For instance, in both elementary structures such as stars and complex graphs having scale-free topology, a minority of elements are linked to the rest of the network disproportionately strongly. While the effect of the arrangement of structural connections on the emergent synchronization pattern has been studied extensively, considerably less is known about its influence on the temporal dynamics unfolding within each node. Here, we present a comprehensive investigation across diverse simulated and experimental systems, encompassing star and complex networks of Rössler systems, coupled hysteresis-based electronic oscillators, microcircuits of leaky integrate-and-fire model neurons, and finally recordings from in-vitro cultures of spontaneously-growing neuronal networks. We systematically consider a range of dynamical measures, including the correlation dimension, nonlinear prediction error, permutation entropy, and other information-theoretical indices. The empirical evidence gathered reveals that under situations of weak synchronization, wherein rather than a collective behavior one observes significantly differentiated dynamics, denser connectivity tends to locally promote the emergence of stronger signatures of nonlinear dynamics. In deterministic systems, transition to chaos and generation of higher-dimensional signals were observed; however, when the coupling is stronger, this relationship may be lost or even inverted. In systems with a strong stochastic component, the generation of more temporally-organized activity could be induced. These observations have many potential implications across diverse fields of basic and applied science, for example, in the design of distributed sensing systems based on wireless coupled oscillators, in network identification and control, as well as in the interpretation of neuroscientific and other dynamical data

Bond diluted Levy spin-glass model and a new finite size scaling method to determine a phase transition

A spin-glass transition occurs both in and out of the limit of validity of mean-field theory on a diluted one dimensional chain of Ising spins where exchange bonds occur with a probability decaying as the inverse power of the distance. Varying the power in this long-range model corresponds, in a one-to-one relationship, to change the dimension in spin-glass short-range models. Using different finite size scaling methods evidence for a spin-glass transition is found also for systems whose equivalent dimension is below the upper critical dimension at zero magnetic field. The application of a new method is discussed, that can be exported to systems in a magnetic field.Comment: 8 pages, 8 figures, 1 tabl

Reactor Antineutrinos Signal all over the world

We present an updated estimate of reactor antineutrino signal all over the world, with particular attention to the sites proposed for existing and future geo-neutrino experiment. In our calculation we take into account the most updated data on Thermal Power for each nuclear plant, on reactor antineutrino spectra and on three neutrino oscillation mechanism.Comment: 4 pages including 1 figur

ALMA observations of the debris disk around the young Solar Analog HD 107146

We present ALMA continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the $\sim$ 100 Myr old solar analog HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyze the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parametrized as i) a single power-law, ii) a single power-law with a gap, and iii) a double power-law. We find that models with a gap of radial width $\sim 8$ AU at a distance of $\sim 80$ AU from the central star, as well as double power-law models with a dip in the dust surface density at $\sim 70$ AU provide significantly better fits to the ALMA data than single power-law models. We discuss possible scenarios for the origin of the HD 107146 debris disk using models of planetesimal belts in which the formation of Pluto-sized objects trigger disruptive collisions of large bodies, as well as models which consider the interaction of a planetary system with a planetesimal belt and spatial variation of the dust opacity across the disk. If future observations with higher angular resolution and sensitivity confirm the fully-depleted gap structure discussed here, a planet with a mass of approximately a few Earth masses in a nearly circular orbit at $\sim 80$ AU from the central star would be a possible explanation for the presence of the gap.Comment: (38 pages, 7 figures, accepted for publication in ApJ

On the gas content of transitional disks: a VLT/X-Shooter study of accretion and winds

Transitional disks (TDs) are thought to be a late evolutionary stage of protoplanetary disks with dust depleted inner regions. The mechanism responsible for this depletion is still under debate. To constrain the models it is mandatory to have a good understanding of the properties of the gas content of the inner disk. Using X-Shooter broad band -UV to NIR- medium resolution spectroscopy we derive the stellar, accretion, and wind properties of a sample of 22 TDs. The analysis of these properties allows us to put strong constraints on the gas content in a region very close to the star (<0.2 AU) which is not accessible with any other observational technique. We fit the spectra with a self-consistent procedure to derive simultaneously SpT,Av,and mass accretion rates (Macc) of the targets. From forbidden emission lines we derive the wind properties of the targets. Comparing our findings to values for cTTs, we find that Macc and wind properties of 80% of the TDs in our sample, which is strongly biased towards strongly accreting objects, are comparable to those of cTTs. Thus, there are (at least) some TDs with Macc compatible with those of cTTs, irrespective of the size of the dust inner hole.Only in 2 cases Macc are much lower, while the wind properties are similar. We do not see any strong trend of Macc with the size of the dust depleted cavity, nor with the presence of a dusty optically thick disk close to the star. In the TDs in our sample there is a gas rich inner disk with density similar to that of cTTs disks. At least for some TDs, the process responsible of the inner disk clearing should allow for a transfer of gas from the outer disk to the inner region. This should proceed at a rate that does not depend on the physical mechanism producing the gap seen in the dust emission and results in a gas density in the inner disk similar to that of unperturbed disks around stars of similar mass.Comment: Accepted on Astronomy & Astrophysics. Abstract shortened to fit arXiv constraint