789 research outputs found
Technology and Economics, Inc. Technology Application Team
Technology + Economics, Inc. (T+E), under contract to the NASA Headquarters Technology Transfer Division, operates a Technology Applications Team (TATeam) to assist in the transfer of NASA-developed aerospace technology. T+E's specific areas of interest are selected urban needs at the local, county, and state levels. T+E contacts users and user agencies at the local, state, and county levels to assist in identifying significant urban needs amenable to potential applications of aerospace technology. Once viable urban needs have been identified in this manner, or through independent research, T+E searches the NASA technology database for technology and/or expertise applicable to the problem. Activities currently under way concerning potential aerospace applications are discussed
Goddard Robotic Telescope - Optical Follow-up of GRBs and Coordinated Observations of AGNs -
Since it is not possible to predict when a Gamma-Ray Burst (GRB) will occur
or when Active Galactic Nucleus (AGN) flaring activity starts,
follow-up/monitoring ground telescopes must be located as uniformly as possible
all over the world in order to collect data simultaneously with Fermi and Swift
detections. However, there is a distinct gap in follow-up coverage of
telescopes in the eastern U.S. region based on the operations of Swift.
Motivated by this fact, we have constructed a 14" fully automated optical
robotic telescope, Goddard Robotic Telescope (GRT), at the Goddard Geophysical
and Astronomical Observatory. The aims of our robotic telescope are 1) to
follow-up Swift/Fermi GRBs and 2) to perform the coordinated optical
observations of Fermi Large Area Telescope (LAT) AGN. Our telescope system
consists of off-the-shelf hardware. With the focal reducer, we are able to
match the field of view of Swift narrow instruments (20' x 20'). We started
scientific observations in mid-November 2008 and GRT has been fully remotely
operated since August 2009. The 3 sigma upper limit in a 30-second exposure in
the R filter is ~15.4 mag; however, we can reach to ~18 mag in a 600-second
exposures. Due to the weather condition at the telescope site, our observing
efficiency is 30-40% on average.Comment: 14 pages, 14 figures, accepted for publication in ASR special issue
on Neutron Stars and Gamma Ray Burst
Using Technology to Encourage Self-Directed Learning: The Collaborative Lecture Annotation System
The rapidly-developing 21st century world of work and knowledge calls for self-directed lifelong (SDL) learners. While higher education must embrace the types of pedagogies that foster SDL skills in graduates, the pace of change in education can be glacial. This paper describes a social annotation technology, the Collaborative Lecture Annotation System (CLAS), that can be used to leverage existing teaching and learning practices for acquisition of 21st Century SDL skills. CLAS was designed to build upon the artifacts of traditional didactic modes of teaching, create enriched opportunities for student engagement with peers and learning materials, and offer learners greater control and ownership of their individual learning strategies. Adoption of CLAS creates educational experiences that promote and foster SDL skills: motivation, self-management and self-monitoring. In addition, CLAS incorporates a suite of learning analytics for learners to evaluate their progress, and allow instructors to monitor the development of SDL skills and identify the need for learning support and guidance. CLAS stands as an example of a simple tool that can bridge the gap between traditional transmissive pedagogy and the creation of authentic and collaborative learning spaces
Tools for Dissecting Supernova Remnants Observed with Chandra: Methods and Application to the Galactic Remnant W49B
We introduce methods to quantify the X-ray morphologies of supernova remnants
observed with the Chandra X-ray Telescope. These include a power-ratio
technique to measure morphological asymmetries, correlation-length analysis to
probe chemical segregation and distribution, and wavelet-transform analysis to
quantify X-ray substructure. We demonstrate the utility and accuracy of these
techniques on relevant synthetic data. Additionally, we show the methods'
capabilities by applying them to the 55-ks Chandra ACIS observation of the
galactic supernova remnant W49B. We analyze the images of prominent emission
lines in W49B and use the results to discern physical properties. We find that
the iron morphology is very distinct from the other elements: it is
statistically more asymmetric, more segregated, and has 25% larger emitting
substructures than the lighter ions. Comparatively, the silicon, sulfur, argon,
and calcium are well-mixed, more isotropic, and have smaller, equally-sized
emitting substructures. Based on fits of XMM-Newton spectra in regions
identified as iron rich and iron poor, we determine that the iron in W49B must
have been anisotropically ejected. We measure the abundance ratios in many
regions, and we find that large, local variations are persistent throughout the
remnant. We compare the mean, global abundance ratios to those predicted by
spherical and bipolar core-collapse explosions; the results are consistent with
a bipolar origin from a 25 solar mass progenitor. We calculate the filling
factor of iron from the volume of its emitting substructures, enabling more
precise mass estimates than previous studies. Overall, this work is a first
step toward rigorously describing the physical properties of supernova remnants
for comparison within and between sources.Comment: 51 pages, 24 figures, accepted by ApJ. For full resolution figures,
see http://www.astro.ucsc.edu/~lopez/paper.html Fixed typo in URL; no other
change
A new approach for probing circumbinary disks
Circumbinary disks are considered to exist in a wide variety of astrophysical
objects, e.g., young binary stars, protoplanetary systems, and massive binary
black hole systems in active galactic nuclei (AGNs). However, there is no
definite evidence for the circumbinary disk except for some in a few young
binary star systems. In this Letter, we study possible oscillation modes in
circumbinary disks around eccentric and circular binaries. We find that
progarde, nonaxisymmetric waves are induced in the inner part of the
circumbinary disk by the tidal potential of the binary. Such waves would cause
variabilities in emission line profiles from circumbinary disks. Because of
prograde precession of the waves, the distance between each component of the
binary and the inner edge of the circumbinary disk varies with the beat period
between the precession period of the wave and the binary orbital period. As a
result, light curves from the circumbinary disks are also expected to vary with
the same period. The current study thus provides a new method to detect
circumbinary disks in various astrophysical systems.Comment: Accepted for publication in ApJ Letters (3/Dec/2008), 4pages, 1figur
Infrared afterglow of GRB041219 as a result of reradiation on dust in a circumstellar cloud
Observations of gamma ray bursts (GRB) afterglows in different spectral bands
provide a most valuable information about their nature, as well as about
properties of surrounding medium. Powerful infrared afterglow was observed from
the strong GRB041219. Here we explain the observed IR afterglow in the model of
a dust reradiation of the main GRB signal in the envelope surrounding the GRB
source. In this model we do not expect appearance of the prompt optical
emission which should be absorbed in the dust envelope. We estimate the
collimation angle of the gamma ray emission, and obtain restrictions on the
redshift (distance to GRB source), by fitting the model parameters to the
observational data.Comment: 6 pages, 2 figures, Submited to Astrofizik
HI Observations of the Supermassive Binary Black Hole System in 0402+379
We have recently discovered a supermassive binary black hole system with a
projected separation between the two black holes of 7.3 parsecs in the radio
galaxy 0402+379. This is the most compact supermassive binary black hole pair
yet imaged by more than two orders of magnitude. We present Global VLBI
observations at 1.3464 GHz of this radio galaxy, taken to improve the quality
of the HI data. Two absorption lines are found toward the southern jet of the
source, one redshifted by 370 +/- 10 km/s and the other blueshifted by 700 +/-
10 km/s with respect to the systemic velocity of the source, which, along with
the results obtained for the opacity distribution over the source, suggests the
presence of two mass clumps rotating around the central region of the source.
We propose a model consisting of a geometrically thick disk, of which we only
see a couple of clumps, that reproduces the velocities measured from the HI
absorption profiles. These clumps rotate in circular Keplerian orbits around an
axis that crosses one of the supermassive black holes of the binary system in
0402+379. We find an upper limit for the inclination angle of the twin jets of
the source to the line of sight of 66 degrees, which, according to the proposed
model, implies a lower limit on the central mass of ~7 x 10^8 Msun and a lower
limit for the scale height of the thick disk of ~12 pc .Comment: 20 pages, 7 figures. Accepted on the Astrophysical Journa
Effects of interleukin-1β Inhibition on blood pressure, incident hypertension, and residual inflammatory risk
While hypertension and inflammation are physiologically inter-related, the effect of therapies that specifically target inflammation on blood pressure is uncertain. The recent CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcomes Study) afforded the opportunity to test whether IL (interleukin)-1β inhibition would reduce blood pressure, prevent incident hypertension, and modify relationships between hypertension and cardiovascular events. CANTOS randomized 10 061 patients with prior myocardial infarction and hsCRP (high sensitivity C-reactive protein) ≥2 mg/L to canakinumab 50 mg, 150 mg, 300 mg, or placebo. A total of 9549 trial participants had blood pressure recordings during follow-up; of these, 80% had a preexisting diagnosis of hypertension. In patients without baseline hypertension, rates of incident hypertension were 23.4, 26.6, and 28.1 per 100-person years for the lowest to highest baseline tertiles of hsCRP (P>0.2). In all participants random allocation to canakinumab did not reduce blood pressure (P>0.2) or incident hypertension during the follow-up period (hazard ratio, 0.96 [0.85–1.08], P>0.2). IL-1β inhibition with canakinumab reduces major adverse cardiovascular event rates. These analyses suggest that the mechanisms underlying this benefit are not related to changes in blood pressure or incident hypertension
Neutrino transport in accretion disks
We test approximate approaches to solving a neutrino transport problem that
presents itself in the analysis of some accretion-disk models. Approximation #1
consists of replacing the full, angular- dependent, distribution function by a
two-stream simulation, where the streams are respectively outwardly and
inwardly directed, with angles to the vertical. In
this approximation the full energy dependence of the distribution function is
retained, as are the energy and temperature dependences of the scattering
rates. Approximation #2, used in recent works on the subject, replaces the
distribution function by an intensity function and the scattering rates by
temperature-energy-averaged quantities. We compare the approximations to the
results of solving the full Boltzmann equation. Under some interesting
conditions, approximation #1 passes the test; approximation #2 does not. We
utilize the results of our analysis to construct a toy model of a disc at a
temperature and density such that relativistic particles are more abundant than
nucleons, and dominate both the opacity and pressure. The nucleons will still
provide most of the energy density. In the toy model we take the rate of heat
generation (which drives the radiative transfer problem) to be proportional to
the nucleon density. The model allows the simultaneous solution of the neutrino
transport and hydrostatic equilibrium problems in a disk in which the nucleon
density decreases approximately linearly as one moves from the median plane of
the disk upwards, reaching zero on the upper boundary.Comment: 8 pages, 5 figures Parentheses added in eqs. 10-1
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