2,044 research outputs found
Detection techniques for tenuous planetary atmospheres Semiannual report, 1 Jul. - 31 Dec. 1968
Absorption and desorption of oxygen by zinc oxide film irradiated by ultraviolet ligh
Detection techniques for tenuous planetary atmospheres Semiannual report, 1 Jan. - 30 Jun. 1970
Developing techniques and detectors for analysis of planetary atmosphere
Detection techniques for tenuous planetary atmospheres
The application of detectors developed for analysis of planetary atmospheres under partial vacuum conditions, and data obtained during dust charging studies to various industrial problems is summarized. A specialized apparatus for dust measurements on a planetary lander was designed with the capability of measuring ambient dust density as a function of particle size, as well as for observing the charge of the collected dust. the optical system operates on an intermittent basis and requires only low power. No radioactive source or delicate detection equipment is required. Advances in monitoring catalyst operation by means of exoelection emission are also reported
A multipoint field ionization source Final report, 11 Nov. 1966 - 12 Apr. 1968
Experimental study on use of field ionization and electron emission as ion sources for mass spectrometer
Detection techniques for tenuous planetary atmospheres Fifth six-month report, 1 Jul. - 30 Dec. 1965
Physical methods description for detection and analysis of tenuous planetary atmospheric component gases, especially water vapo
Radiative Transfer Modeling of Three-Dimensional Clumpy AGN Tori and its Application to NGC 1068
Recent observations of NGC 1068 and other AGN support the idea of a
geometrically and optically thick dust torus surrounding the central
supermassive black hole and accretion disk of AGN. In type 2 AGN, the torus is
seen roughly edge-on, leading to obscuration of the central radiation source
and a silicate absorption feature near 10 micron. While most of the current
torus models distribute the dust smoothly, there is growing evidence that the
dust must be arranged in clouds. We describe a new method for modeling near-
and mid-infrared emission of 3-dimensional clumpy tori using Monte Carlo
simulations. We calculate the radiation fields of individual clouds at various
distances from the AGN and distribute these clouds within the torus region. The
properties of the individual clouds and their distribution within the torus are
determined from a theoretical approach of self-gravitating clouds close to the
shear limit in a gravitational potential. We demonstrate that clumpiness in AGN
tori can overcome the problem of over-pronounced silicate features. Finally, we
present model calculations for the prototypical Seyfert 2 galaxy NGC 1068 and
compare them to recent high-resolution measurements. Our model is able to
reproduce both the SED and the interferometric observations of NGC 1068 in the
near- and mid-infrared.Comment: 16 pages, 16 figures, 6 tables (figures reduced due to astro-ph
limitations); accepted by A&
WISE view of Narrow-Line Seyfert 1 galaxies: mid-infrared color and variability
We present the color and flux variability analysis at 3.4 {\mu}m (W1-band)
and 4.6 {\mu}m (W 2-band) of 492 narrow-line Seyfert 1 (NLSy1) galaxies using
archival data from the Wide-field Infrared Survey Explorer (WISE). In the WISE
color-color, (W1 - W2) versus (W2 - W3) diagram, ~58% of the NLSy1 galaxies of
our sample lie in the region occupied by the blazar category of active galactic
nuclei (AGN). The mean W1 - W2 color of candidate variable NLSy1 galaxies is
mag. The average amplitude of variability is
mag in long-term (multi-year) with no difference in variability between W1 and
W2-bands. The W1 - W2 color of NLSy1 galaxies is anti-correlated with the
relative strength of [O III] to H{\beta}, strongly correlated with continuum
luminosity, black hole mass, and Eddington ratio. The long-term amplitude of
variability shows weak anti-correlation with the Fe II strength, continuum
luminosity and Eddington ratio. A positive correlation between color as well as
the amplitude of variability with the radio power at 1.4 GHz was found for the
radio-detected NLSy1 galaxies. This suggests non-thermal synchrotron
contribution to the mid-infrared color and flux variability in radio-detected
NLSy1 galaxies.Comment: 10 pages; Accepted for publication in MNRA
The subarcsecond mid-infrared view of local active galactic nuclei: II. The mid-infrared--X-ray correlation
We present an updated mid-infrared (MIR) versus X-ray correlation for the
local active galactic nuclei (AGN) population based on the high angular
resolution 12 and 18um continuum fluxes from the AGN subarcsecond MIR atlas and
2-10 keV and 14-195 keV data collected from the literature. We isolate a sample
of 152 objects with reliable AGN nature and multi-epoch X-ray data and minimal
MIR contribution from star formation. Although the sample is not homogeneous or
complete, we show that our results are unlikely to be affected by biases. The
MIR--X-ray correlation is nearly linear and within a factor of two independent
of the AGN type and the wavebands used. The observed scatter is <0.4 dex. A
possible flattening of the correlation slope at the highest luminosities probed
(~ 10^45 erg/s) is indicated but not significant. Unobscured objects have, on
average, an MIR--X-ray ratio that is only <= 0.15 dex higher than that of
obscured objects. Objects with intermediate X-ray column densities (22 < log
N_H < 23) actually show the highest MIR--X-ray ratio on average. Radio-loud
objects show a higher mean MIR--X-ray ratio at low luminosities, while the
ratio is lower than average at high luminosities. This may be explained by
synchrotron emission from the jet contributing to the MIR at low-luminosities
and additional X-ray emission at high luminosities. True Seyfert 2 candidates
and double AGN do not show any deviation from the general behaviour. Finally,
we show that the MIR--X-ray correlation can be used to verify the AGN nature of
uncertain objects. Specifically, we give equations that allow to determine the
intrinsic 2-10 keV luminosities and column densities for objects with complex
X-ray properties to within 0.34 dex. These techniques are applied to the
uncertain objects of the remaining AGN MIR atlas, demonstrating the usefulness
of the MIR--X-ray correlation as an empirical tool.Comment: Accepted for publication in MNRAS, 40 pages, 25 figure
Detection techniques for tenuous planetary atmospheres
Electrostatic charging of dust and its effect on planetary atmospheres is discussed, along with its applications to Martian atmosphere. Laboratory and field experiments in dust storms indicate that the major atmospheric parameters on Mars include: (1) pressure, temperature, and relative humidity; (2) wind velocity and direction; (3) particulate size and composition; and (4) electrostatic charge and field gradient. Various instrumentation techniques adapted for a Mars Lander are briefly reviewed. The effect of exoelectron emission on surface catalysis is studied
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