Interferometric view of the circumstellar envelopes of northern FU Orionis-type stars

FU Orionis-type objects are young, low-mass stars with large outbursts in visible light that last for several years or decades. They are thought to represent an evolutionary phase during the life of every young star when accretion from the circumstellar disk is enhanced during recurring time periods. These outbursts are able to rapidly build up the star while affecting the circumstellar disk and thus the ongoing or future planet formation. In many models infall from a circumstellar envelope seems to be necessary to trigger the outbursts. We observed the J=1$-$0 rotational transition of $^{13}$CO and C$^{18}$O towards eight northern FU Orionis-type stars (V1057 Cyg, V1515 Cyg, V2492 Cyg, V2493 Cyg, V1735 Cyg, V733 Cep, RNO 1B and RNO 1C) and derive temperatures and envelope masses and discuss the morphology and kinematics of the circumstellar material. We detected extended CO emission associated with all our targets. Smaller scale CO clumps were found to be associated with five objects with radii of 2000$-$5000 AU and masses of 0.02$-$0.5 $M_{\odot}$; these are clearly heated by the central stars. Three of these envelopes are also strongly detected in the 2.7 mm continuum. No central CO clumps were detected around V733 Cep and V710 Cas but there are many other clumps in their environments. Traces of outflow activity were observed towards V1735 Cyg, V733 Cep and V710 Cas. The diversity of the observed envelopes enables us to set up an evolutionary sequence between the objects. We find their evolutionary state to range from early, embedded Class I stage to late, Class II-type objects with very low-mass circumstellar material. The results reinforce the idea of FU Orionis-type stars as representatives of a transitory stage between embedded Class I young stellar objects and classical T-Tauri stars.Comment: 17 pages, 11 figures; accepted for publication in A&

Internet as an innovative tool for the development of food products

As a result of the fast innovation activity, the so called “many to many” communication channel has become one of the most important tools for the Hungarian food industry. The number of Internet users in Hungary was 6.5 million in 2011 that represents 65.4 percent of the total population. The Internet based social media provides a strong and active platform between food producers and consumers. The online platform gives up-to-date and precise information about food companies and food products to the consumers. The information flow is two-directional as food companies receive a precise overview on consumers, their habits and latent needs by using innovative market research methods. The aim of this paper is to present an example and to evaluate the customers’ socio-demographic profile and their preferences of a dominant food company and its product. We used data mining techniques to get more precise and the latest information about Hungarian food consumers. This survey supports more efficient marketing communication and strategies for the innovation of the food products

Mass transport from the envelope to the disk of V346 Nor: a case study for the luminosity problem in an FUor-type young eruptive star

A long-standing open issue of the paradigm of low-mass star formation is the luminosity problem: most protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Ori-type stars (FUors) are thought to be the visible examples for objects in the high accretion state. FUors are often surrounded by massive envelopes, which replenish the disk material and enable the disk to produce accretion outbursts. However, we have insufficient information on the envelope dynamics in FUors, about where and how mass transfer from the envelope to the disk happens. Here we present ALMA observations of the FUor-type star V346 Nor at 1.3 mm continuum and in different CO rotational lines. We mapped the density and velocity structure of its envelope and analyze the results using channel maps, position-velocity diagrams, and spectro-astrometric methods. We found that V346 Nor is surrounded by gaseous material on 10000 au scale in which a prominent outflow cavity is carved. Within the central $\sim$700 au, the circumstellar matter forms a flattened pseudo-disk where material is infalling with conserved angular momentum. Within $\sim$350 au, the velocity profile is more consistent with a disk in Keplerian rotation around a central star of 0.1 $M_{\odot}$. We determined an infall rate from the envelope onto the disk of 6$\times$10$^{-6}\,M_{\odot}$yr$^{-1}$, a factor of few higher than the quiescent accretion rate from the disk onto the star, hinting for a mismatch between the infall and accretion rates as the cause of the eruption.Comment: 16 pages, 8 figures, published in Ap

Magnetic resonance in the antiferromagnetic and normal state of NH_3K_3C_60

We report on the magnetic resonance of NH_3K_3C_60 powders in the frequency range of 9 to 225 GHz. The observation of an antiferromagnetic resonance below the phase transition at 40 K is evidence for an antiferromagnetically ordered ground state. In the normal state, above 40 K, the temperature dependence of the spin-susceptibilty measured by ESR agrees with previous static measurements and is too weak to be explained by interacting localized spins in an insulator. The magnetic resonance line width has an unusual magnetic-field dependence which is large and temperature independent in the magnetically ordered state and decreases rapidly above the transition. These observations agree with the suggestion that NH_3K_3C_60 is a metal in the normal state and undergoes a Mott-Hubbard metal to insulator transition at 40 K.Comment: 4 pages, 5 figures. Submitted to Phys. Rev.

NEATH II: N2_2H+^+ as a tracer of imminent star formation in quiescent high-density gas

Star formation activity in molecular clouds is often found to be correlated with the amount of material above a column density threshold of $\sim 10^{22} \, {\rm cm^{-2}}$. Attempts to connect this column density threshold to a ${\it volume}$ density above which star formation can occur are limited by the fact that the volume density of gas is difficult to reliably measure from observations. We post-process hydrodynamical simulations of molecular clouds with a time-dependent chemical network, and investigate the connection between commonly-observed molecular species and star formation activity. We find that many molecules widely assumed to specifically trace the dense, star-forming component of molecular clouds (e.g. HCN, HCO$^+$, CS) actually also exist in substantial quantities in material only transiently enhanced in density, which will eventually return to a more diffuse state without forming any stars. By contrast, N$_2$H$^+$ only exists in detectable quantities above a volume density of $10^4 \, {\rm cm^{-3}}$, the point at which CO, which reacts destructively with N$_2$H$^+$, begins to deplete out of the gas phase onto grain surfaces. This density threshold for detectable quantities of N$_2$H$^+$ corresponds very closely to the volume density at which gas becomes irreversibly gravitationally bound in the simulations: the material traced by N$_2$H$^+$ never reverts to lower densities, and quiescent regions of molecular clouds with visible N$_2$H$^+$ emission are destined to eventually form stars. The N$_2$H$^+$ line intensity is likely to directly correlate with the star formation rate averaged over timescales of around a Myr.Comment: 10 pages, 10 figures. MNRAS accepte

Non-Equilibrium Abundances Treated Holistically (NEATH): the molecular composition of star-forming clouds

Much of what we know about molecular clouds, and by extension star formation, comes from molecular line observations. Interpreting these correctly requires knowledge of the underlying molecular abundances. Simulations of molecular clouds typically only model species that are important for the gas thermodynamics, which tend to be poor tracers of the denser material where stars form. We construct a framework for post-processing these simulations with a full time-dependent chemical network, allowing us to model the behaviour of observationally-important species not present in the reduced network used for the thermodynamics. We use this to investigate the chemical evolution of molecular gas under realistic physical conditions. We find that molecules can be divided into those which reach peak abundances at moderate densities ($10^3 \, {\rm cm^{-3}}$) and decline sharply thereafter (such as CO and HCN), and those which peak at higher densities and then remain roughly constant (e.g. NH$_3$, N$_2$H$^+$). Evolving the chemistry with physical properties held constant at their final values results in a significant overestimation of gas-phase abundances for all molecules, and does not capture the drastic variations in abundance caused by different evolutionary histories. The dynamical evolution of molecular gas cannot be neglected when modelling its chemistry.Comment: 14 pages, 13 figures. MNRAS accepte

Classical Wakimoto Realizations of Chiral WZNW Bloch Waves

It is well-known that the chiral WZNW Bloch waves satisfy a quadratic classical exchange algebra which implies the affine Kac-Moody algebra for the corresponding currents. We here obtain a direct derivation of the exchange algebra by inverting the symplectic form on the space of Bloch waves, and give a completely algorithmic construction of its generalized free field realizations that extend the classical Wakimoto realizations of the current algebra.Comment: 13 pages, LaTe

Generalized Drinfeld-Sokolov Reductions and KdV Type Hierarchies

Generalized Drinfeld-Sokolov (DS) hierarchies are constructed through local reductions of Hamiltonian flows generated by monodromy invariants on the dual of a loop algebra. Following earlier work of De Groot et al, reductions based upon graded regular elements of arbitrary Heisenberg subalgebras are considered. We show that, in the case of the nontwisted loop algebra $\ell(gl_n)$, graded regular elements exist only in those Heisenberg subalgebras which correspond either to the partitions of $n$ into the sum of equal numbers $n=pr$ or to equal numbers plus one $n=pr+1$. We prove that the reduction belonging to the grade $1$ regular elements in the case $n=pr$ yields the $p\times p$ matrix version of the Gelfand-Dickey $r$-KdV hierarchy, generalizing the scalar case $p=1$ considered by DS. The methods of DS are utilized throughout the analysis, but formulating the reduction entirely within the Hamiltonian framework provided by the classical r-matrix approach leads to some simplifications even for $p=1$.Comment: 43 page

Chemical Traits of Fermented Alfalfa Brown Juice: Its Implications on Physiological, Biochemical, Anatomical, and Growth Parameters of Celosia

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