10,276 research outputs found
NASA/ESA CV-990 Spacelab Simulation (ASSESS 2)
To test the validity of the ARC approach to Spacelab, several missions simulating aspects of Spacelab operations have been conducted as part of the ASSESS Program. Each mission was designed to evaluate potential Shuttle/Spacelab concepts in increasing detail. For this mission, emphasis was placed on development and exercise of management techniques planned for Spacelab using management participants from NASA and ESA who have responsibilities for Spacelab 1 which will be launched in 1980
Discovery of ultra-fast outflows in a sample of Broad Line Radio Galaxies observed with Suzaku
We present the results of a uniform and systematic search for blue-shifted Fe
K absorption lines in the X-ray spectra of five bright Broad-Line Radio
Galaxies (BLRGs) observed with Suzaku. We detect, for the first time at X-rays
in radio-loud AGN, several absorption lines at energies greater than 7 keV in
three out of five sources, namely 3C 111, 3C 120 and 3C 390.3. The lines are
detected with high significance according to both the F-test and extensive
Monte Carlo simulations. Their likely interpretation as blue-shifted Fe XXV and
Fe XXVI K-shell resonance lines implies an origin from highly ionized gas
outflowing with mildly relativistic velocities, in the range 0.04-0.15c. A fit
with specific photo-ionization models gives ionization parameters in the range
log_xi~4-5.6 and column densities of N_H~10^22-10^23 cm^-2. These
characteristics are very similar to those of the Ultra-Fast Outflows (UFOs)
previously observed in radio-quiet AGN. Their estimated location within
~0.01-0.3pc from the central super-massive black hole suggests a likely origin
related with accretion disk winds/outflows. Depending on the absorber covering
fraction, the mass outflow rate of these UFOs can be comparable to the
accretion rate and their kinetic power can correspond to a significant fraction
of the bolometric luminosity and is comparable to their typical jet power.
Therefore, these UFOs can play a significant role in the expected feedback from
the AGN on the surrounding environment and can give us further clues on the
relation between the accretion disk and the formation of winds/jets in both
radio-quiet and radio-loud AGN.Comment: Accepted for publication in The Astrophysical Journal; corrected
reference
Unsupervised classification and areal measurement of land and water coastal features on the Texas coast
Multispectral scanner (MSS) digital data from ERTS-1 was used to delineate coastal land, vegetative, and water features in two portions of the Texas Coastal Zone. Data (Scene ID's 1037-16244 and 1037-16251) acquired on August 29, 1972, were analyzed on NASA Johnson Space Center systems through the use of two clustering algorithms. Seventeen to 30 spectrally homogeneous classes were so defined. Many classes were identified as being pure features such as water masses, salt marsh, beaches, pine, hardwoods, and exposed soil or construction materials. Most classes were identified to be mixtures of the pure class types. Using an objective technique for measuring the percentage of wetland along salt marsh boundaries, an analysis was made of the accuracy of areal measurement of salt marshes. Accuracies ranged from 89 to 99 percent. Aircraft photography was used as the basis for determining the true areal size of salt marshes in the study sites
Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers
The existence of ionized X-ray absorbing layers of gas along the line of
sight to the nuclei of Seyfert galaxies is a well established observational
fact. This material is systematically outflowing and shows a large range in
parameters. However, its actual nature and dynamics are still not clear. In
order to gain insights into these important issues we performed a literature
search for papers reporting the parameters of the soft X-ray warm absorbers
(WAs) in 35 type 1 Seyferts and compared their properties to those of the
ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources
with WAs is >60%, consistent with previous studies. The fraction of sources
with UFOs is >34%, >67% of which also show WAs. The large dynamic range
obtained when considering all the absorbers together allows us, for the first
time, to investigate general relations among them. In particular, we find
significant correlations indicating that the closer the absorber is to the
central black hole, the higher the ionization, column, outflow velocity and
consequently the mechanical power. The absorbers continuously populate the
whole parameter space, with the WAs and the UFOs lying always at the two ends
of the distribution. This strongly suggest that these absorbers, often
considered of different types, could actually represent parts of a single
large-scale stratified outflow observed at different locations from the black
hole. The observed parameters and correlations are consistent with both
radiation pressure through Compton scattering and MHD processes contributing to
the outflow acceleration, the latter playing a major role. Most of the
absorbers, especially the UFOs, have a sufficiently high mechanical power to
significantly contribute to AGN feedback.Comment: Manuscript updated to match the MNRAS published version. Link to the
related INAF news: http://www.media.inaf.it/2013/02/05/warm-absorbers
Simultaneously imaging of dielectric properties and topography in a PbTiO_3 crystal by near-field scanning microwave microscopy
We use a near-field scanning microwave microscope to simultaneously image the
dielectric constant, loss tangent, and topography in a PbTiO_3 crystal. By this
method, we study the effects of the local dielectric constant and loss tangent
in the geometry of periodic domains on the measured resonant frequency, and
quality factor. We also carry out theoretical calculations and the results
agree well with the experimental data and reveal the anisotropic nature of
dielectric constant
The Suzaku view of 3C 382
We present a long Suzaku observation of 3C 382. A Swift BAT spectrum from the
58-month survey is also analyzed, together with an archival XMM-Newton EPIC
exposure. Our main result is the finding with Suzaku of a broad FeK line with a
relativistic profile consistent with emission from an accretion disk at tens of
gravitational radii from the central black hole. The XIS data indicate emission
from highly ionized iron and allow us to set tight, albeit model-dependent,
constraints on the inner and outer radii of the disk reflecting region,
r_in~10r_g and r_out~20r_g, respectively, and on the disk inclination, i~30deg.
Two ionized reflection components are possibly observed, with similar
contributions of ~10% to the total continuum. A highly ionized one, with
log_xi~3, which successfully models the relativistic line and a mildly ionized
one, with log_xi~1.5, which models the narrow Fe K line and high energy hump.
When both these components are included, there is no further requirement for an
additional black body soft excess below 2keV. The Suzaku data confirm the
presence of a warm absorber previously known from grating studies. After
accounting for all the spectral features, the intrinsic photon index of the
X-ray continuum is ~1.8 with a cutoff energy at ~200keV, consistent with
Comptonization models and excluding jet-related emission up to these energies.
Comparison of the X-ray properties of 3C 382 and other BLRGs to Seyferts
confirms the idea that the distinction between radio-loud and radio-quiet AGN
at X-rays is blurred.Comment: Accepted for publication in Ap
First energetic neutral atom images from Polar
Energetic neutral atoms are created when energetic magnetospheric ions undergo charge exchange with cold neutral atoms in the Earth\u27s tenuous extended atmosphere (the geocorona). Since they are unaffected by the Earth\u27s magnetic field, these energetic neutrals travel away in straight line trajectories from the points of charge exchange. The remote detection of these particles provides a powerful means through which the global distribution and properties of the geocorona and ring current can be inferred. Due to its 2 × 9 RE polar orbit, the Polar spacecraft provides an excellent platform from which to observe ENAs because it spends much of its time in the polar caps which are usually free from the contaminating energetic charged particles that make observations of ENAs more difficult. In this brief report, we present the first ENA imaging results from Polar. Storm-time ENA images are presented for a northern polar cap apogee pass on August 29, 1996 and for a southern polar cap perigee pass on October 23, 1996. As well, we show with a third event (July 31, 1996) that ENA emissions can also be detected in association with individual substorm
Simulations of inner magnetosphere dynamics with an expanded RAM-SCB model and comparisons with Van Allen Probes observations
Abstract Simulations from our newly expanded ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB), now valid out to 9 R E, are compared for the first time with Van Allen Probes observations. The expanded model reproduces the storm time ring current buildup due to the increased convection and inflow of plasma from the magnetotail. It matches Magnetic Electron Ion Spectrometer (MagEIS) observations of the trapped high-energy (\u3e50 keV) ion flux; however, it underestimates the low-energy (\u3c10 keV) Helium, Oxygen, Proton, and Electron (HOPE) observations. The dispersed injections of ring current ions observed with the Energetic particle, Composition, and Thermal plasma (ECT) suite at high (\u3e20 keV) energy are better reproduced using a high-resolution convection model. In agreement with Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) observations, RAM-SCB indicates that the large-scale magnetic field is depressed as close as ∼4.5 RE during even a moderate storm. Regions of electromagnetic ion cyclotron instability are predicted on the duskside from ∼6 to ∼9 RE, indicating that previous studies confined to geosynchronous orbit may have underestimated their scattering effect on the energetic particles. Key Points Expanded RAM-SCB model reproduces well high-energy (\u3e50 keV) MagEIS observations The magnetic field is depressed as close as ∼4.5 RE during even a moderate storm EMIC wave growth extends on duskside from ∼6 to ∼9 RE during storm main phase
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