90,102 research outputs found
Spectro-astrometry of V1515 Cyg
FU Orionis objects are a class of young stars with important bursts in
luminosity and which show evidence of accretion and ejection activity. It is
generally accepted that they are surrounded by a Keplerian circumstellar disk
and an infalling envelope. The outburst would occurs because of a sudden
increase in the accretion rate. We aim at studying the regions closer to the
central star in order to observe the signs of the accretion/ejection activity.
We present optical observations of the Halpha line using the Integral Field
Spectrograph OASIS, at the William Herschel Telescope, combined with Adaptive
Optics. Since this technique gives the spectral information for both spatial
directions, we carried out a two-dimensional spectro-astrometric study of the
signal. We measured a clear spectro-astrometric signal in the North-South
direction. The cross-correlation between the spectra showed a spatial
distribution in velocity suggestive of scattering by a disk surrounding the
star. This would be one of the few spatial inferences of a disk observed in a
FU Orionis object. However, in order to fully understand the observed
structure, higher angular and spectral resolution observations are required.
V1515 Cyg appears now as an important object to be observed with a new
generation of instruments to increase our knowledge about the disk and outflows
structure in FU Orionis objects
Bounds on isocurvature perturbations from CMB and LSS data
We obtain very stringent bounds on the possible cold dark matter, baryon and
neutrino isocurvature contributions to the primordial fluctuations in the
Universe, using recent cosmic microwave background and large scale structure
data. In particular, we include the measured temperature and polarization power
spectra from WMAP and ACBAR, as well as the matter power spectrum from the 2dF
galaxy redshift survey. Neglecting the possible effects of spatial curvature,
tensor perturbations and reionization, we perform a Bayesian likelihood
analysis with nine free parameters, and find that the amplitude of the
isocurvature component cannot be larger than about 31% for the cold dark matter
mode, 91% for the baryon mode, 76% for the neutrino density mode, and 60% for
the neutrino velocity mode, at 2-sigma, for uncorrelated models. On the other
hand, for correlated adiabatic and isocurvature components, the fraction could
be slightly larger. However, the cross-correlation coefficient is strongly
constrained, and maximally correlated/anticorrelated models are disfavored.
This puts strong bounds on the curvaton model, independently of the bounds on
non-Gaussianity.Comment: 4 pages, 1 figure, some minor corrections; version accepted in PR
Magnetic behavior of lamellar mnps3 and cdps3 composites with a paramagnetic manganese(iii) macrocyclic guest
Indexación: ScieloSix new composites derived from the intercalation of the MPS3 phases (M = MnII, CdIII) with the macrocyclic manganese(III) complex [MnL(H2O)2].NO3(H2O) (LH2 = Schiff base macrocyclic ligand derived from the condensation of 2-hydroxy-5-methy1-1,3-benzene-dicarbaldehyde and 1,2-diamine-benzene) were obtained by two different synthetic procedures: a conventional and a microwave assisted method. The composites [MnL]0.25K0.15Mn0.80 PS3(H2O)~1.0 (1), and [MnL]0.25K0.15Cd 0. 80PS3(H2O)~0.5 (2) were obtained by the conventional method, after stirring a suspension of the corresponding potassium precursor and the macrocyclic complex for two weeks, while [MnL]0.35K0.15Mn0.80 PS3(H2O)~1.0 (3) and [MnL]0.25K0.15Cd 0. 80PS3(H2O)~0.5 (4) after stirring for four weeks at room temperature. Using a microwave assisted reaction permitted to obtain in a shorter period of time as compared with the conventional method, composites [MnL]0.20K0.15Mn0.80 PS3(H2O)~1.0 (5) and [MnL]0.15K0.15Cd 0. 80PS3(H2O)~0.5 (6). All the M = MnII, MnIII composites show a bulk antiferromagnetic behavior. However, the spontaneous magnetization present at low temperature in the potassium precursor K0.40Mn0.80 PS3(H2O)~1.0 is observable in composite [MnL]0.20K0.15Mn0.80 PS3(H2O)~1.0 (5), while it is completely absent in composites [MnL]0.25K0.15Mn0.80 PS3(H2O)~1.0 (1) and [MnL]0.35K0.15Mn0.80 PS3(H2O)~1.0 (3).
Keywords: Intercalation; MPS3 phases; MnIII macrocyclic complex; microwave assisted synthesis; magnetic properties
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