11,277 research outputs found
Morphology of the 12-micron Seyfert Galaxies: II. Optical and Near-Infrared Image Atlas
We present 263 optical and near-infrared (NIR) images for 42 Seyfert 1s and
48 Seyfert 2s, selected from the Extended 12-micron Galaxy Sample.
Elliptically-averaged profiles are derived from the images, and isophotal radii
and magnitudes are calculated from these. We also report virtual aperture
photometry, that judging from comparison with previous work, is accurate to
roughly 0.05mag in the optical, and 0.07mag in the NIR. Our B-band isophotal
magnitude and radii, obtained from ellipse fitting, are in good agreement with
those of RC3. When compared with the B band, V, I, J, and K isophotal diameters
show that the colors in the outer regions of Seyferts are consistent with the
colors of normal spirals. Differences in the integrated isophotal colors and
comparison with a simple model show that the active nucleus+bulge is stronger
and redder in the NIR than in the optical. Finally, roughly estimated Seyfert
disk surface brightnesses are significantly brighter in B and K than those in
normal spirals of similar morphological type.Comment: 17 pgs including figures; Table 2 is a separate file. Complete Figure
1 is available by contacting the authors. Accepted for publication in ApJ
Glycyl-L-proline hemihydrate at 298 K
The crystal structure of glycyl-L-proline (GLY-PRO) hemihydrate, C(7)H(12)N(2)O(3)(.)0.5H(2)O, has two molecules of GLY-PRO in the asymmetric unit; one molecule adopts the cis configuration at the peptide bond and the other adopts the trans configuration.</p
On the accuracy of retrieved wind information from Doppler lidar observations
A single pulsed Doppler lidar was successfully deployed to measure air flow and turbulence over the Malvern hills, Worcester, UK. The DERA Malvern lidar used was a CO2 µm pulsed Doppler lidar. The lidar pulse repetition rate was 120 Hz and had a pulse duration of 0.6 µs The system was set up to have 41 range gates with range resolution of 112 m. This gave a theoretical maximum range of approximately 4.6 km. The lidar site was 2 km east of the Malvern hill ridge which runs in a north-south direction and is approximately 6 km long. The maximum height of the ridge is 430 m. Two elevation scans (Range-Height Indicators) were carried out parallel and perpendicular to the mean surface flow. Since the surface wind was primarily westerly the scans were carried out perpendicular and parallel to the ridge of the Malvern hills.
The data were analysed and horizontal winds, vertical winds and turbulent fluxes were calculated for profiles throughout the boundary layer. As an aid to evaluating the errors associated with the derivation of velocity and turbulence profiles, data from a simple idealized profile was also analysed using the same method. The error analysis shows that wind velocity profiles can be derived to an accuracy of 0.24 m s-1 in the horizontal and 0.3 m s-1 in the vertical up to a height of 2500 m. The potential for lidars to make turbulence measurements, over a wide area, through the whole depth of the planetary boundary layer and over durations from seconds to hours is discussed
Mg I emission lines at 12 and 18 micrometer in K giants
The solar Mg I emission lines at 12 micrometer have already been observed and
analyzed well. Previous modeling attempts for other stars have, however, been
made only for Procyon and two cool evolved stars, with unsatisfactory results
for the latter. We present high-resolution observational spectra for the K
giants Pollux, Arcturus, and Aldebaran, which show strong Mg I emission lines
at 12 micrometer as compared to the Sun. We also present the first observed
stellar emission lines from Mg I at 18 micrometer and from Al I, Si I, and
presumably Ca I at 12 micrometer. To produce synthetic line spectra, we employ
standard non-LTE modeling for trace elements in cool stellar photospheres. We
compute model atmospheres with the MARCS code, apply a comprehensive magnesium
model atom, and use the radiative transfer code MULTI to solve for the
magnesium occupation numbers in statistical equilibrium. We successfully
reproduce the observed Mg I emission lines simultaneously in the giants and in
the Sun, but show how the computed line profiles depend critically on atomic
input data and how the inclusion of energy levels with n > 9 and collisions
with neutral hydrogen are necessary to obtain reasonable fits.Comment: 9 pages, 6 figures, accepted for publication in Astronomy &
Astrophysic
VOLUNTARY REVELATION OF THE DEMAND FOR PUBLIC GOODS USING A PROVISION POINT MECHANISM
public goods, voluntary contributions, provision point, experiments, information, group size, Resource /Energy Economics and Policy, H41, C92,
Ten possible experiments on communication and deception
I describe ten situations in which experimental data may provide useful guidance to the study of cheap-talk games. Journal of Economic Literature Classification Numbers: C92, D8. © 2013 Elsevier B.V
A Model for the X-Ray and UV Emission from Seyfert Galaxies and Galactic Black Holes
We propose that the X--ray emission from radio quiet AGN and galactic black
holes is due to Comptonization of soft thermal photons emitted by the
underlying accretion disk in localized structures (blobs). The power per unit
area produced by the blobs, impinging on the disk, can easily dominate the
radiation internally produced by the disk. In this case the electron
temperature and the high energy spectrum can be determined in a similar way as
in the previously studied homogeneous model (Haardt \& Maraschi 1991). However
in the present model: a) the emitted spectrum is largely independent of the
{\it fraction} of gravitational power dissipated in the blobs; b) the X--ray
spectrum can be harder depending on a form factor of the blobs; c) the UV (or
soft X--ray for galactic objects) luminosity that is not intercepted by the
blobs can be larger than the X--ray luminosity. In the framework of a
simplified accretion disk dynamo model, we make order of
magnitude estimates of the number of active blobs, their size, luminosity and
hence their compactness, finding values in agreement with what is observed. The
expected UV to X--ray spectra and correlations of X--ray and UV light curves
are discussed.Comment: 10 pages. Plain Tex. Accepted in ApJ Letter
Short sale constraints, divergence of opinion and asset values: evidence from the laboratory
The overvaluation hypothesis (Miller 1977) predicts that a) stocks are overvalued in the presence of short selling restrictions and that b) the overvaluation increases in the degree of divergence of opinion. We design an experiment that allows us to test these predictions in the laboratory. The results indicate that prices are higher with short selling constraints, but the overvaluation does not increase in the degree of divergence of opinion. We further find that trading volume is lower and bid-ask spreads are higher when short sale restrictions are imposed. JEL Classification: C92, G14 Keywords: Overvaluation Hypothesis , Short Selling Constraints , Divergence of Opinio
Kinetics of electron-positron pair plasmas using an adaptive Monte Carlo method
A new algorithm for implementing the adaptive Monte Carlo method is given. It
is used to solve the relativistic Boltzmann equations that describe the time
evolution of a nonequilibrium electron-positron pair plasma containing
high-energy photons and pairs. The collision kernels for the photons as well as
pairs are constructed for Compton scattering, pair annihilation and creation,
bremsstrahlung, and Bhabha & Moller scattering. For a homogeneous and isotropic
plasma, analytical equilibrium solutions are obtained in terms of the initial
conditions. For two non-equilibrium models, the time evolution of the photon
and pair spectra is determined using the new method. The asymptotic numerical
solutions are found to be in a good agreement with the analytical equilibrium
states. Astrophysical applications of this scheme are discussed.Comment: 43 pages, 7 postscript figures, to appear in the Astrophysical
Journa
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