360 research outputs found
Manufacturing development of DC-10 advanced rudder
The design, manufacture, and ground test activities during development of production methods for an advanced composite rudder for the DC-10 transport aircraft are described. The advanced composite aft rudder is satisfactory for airline service and a cost saving in a full production manufacturing mode is anticipated
Study of aircraft crashworthiness for fire protection
Impact-survivable postcrash fire accidents were surveyed. The data base developed includes foreign and domestic accidents involving airlines and jet aircraft. The emphasis was placed on domestic accidents, airlines, and jet aircraft due principally to availability of information. Only transport category aircraft in commercial service designed under FAR Part 25 were considered. A matrix was prepared to show the relationships between the accident characteristics and the fire fatalities. Typical postcrash fire scenaries were identified. Safety concepts were developed for three engineering categories: cabin interiors - cabin subsystems; power plant - engines and fuel systems; and structural mechanics - primary and secondary structures. The parameters identified for concept evaluation are cost, effectiveness, and societal concerns. Three concepts were selected for design definition and cost and effectiveness analysis: improved fire-resistant seat materials; anti-misting kerosene; and additional cabin emergency exits
Complex outburst behaviour from the black-hole candidate 4U 1630-47
We present data from different epochs in 1978, 1987-1991 and 1996 from the
black-hole candidate 4U1630-47. For the first time we present almost complete
coverage of the outbursts which started in 1987, 1988 and 1996. We find that
the outburst behaviour of 4U1630-47 is more complex than previously realized.
The source shows outbursts with durations on the order of ~100-200 days and
sometimes intervals of long-term X-ray activity.
The relatively short outbursts which occurred in 1987 and 1996 exhibited
different colour behaviour: the outburst in 1987 showed softening of the X-ray
spectrum, whereas the outburst in 1996 showed hardening of the X-ray spectrum,
as the outbursts proceeded.
The outburst which started in 1977 may have lasted for up to ~10 months,
whereas the outburst which started in 1988 showed activity for up to ~2.4
years. Such long-term activity is reminiscent of that seen in GRS1716-249 and
in the galactic superluminal sources GRS1915+105 and GROJ1655-40.
We refine the outburst ephemeris of 4U\1630-47 and find that the outburst
recurrence time scale may have changed from ~600 days to ~690 days between the
1984 and 1987 outbursts. If the recurrence interval of ~690 days continues, the
next outburst of 4U1630-47 is predicted to occur in 1998 January.Comment: 30 pages including 9 figures accepted for publication in MNRA
BeppoSAX observation of the eclipsing dipping X-ray binary X1658-298
Results of a 2000 August 12-13 BeppoSAX observation of the 7.1 hr eclipsing,
dipping, bursting, transient, low-mass X-ray binary (LMXRB) X1658-298 are
presented. The spectrum outside of eclipses, dips and bursts can be modeled by
the combination of a soft disk-blackbody and a harder Comptonized component
with a small amount (1.3 10E21 atom/cm2) of low-energy absorption. In contrast,
an RXTE observation 18 months earlier during the same outburst, measured an
absorption of 5.0 10E22 atom/cm2. Such a change is consistent with a thinning
of the accretion disk as the outburst progresses. Structured residuals from the
best-fit spectral model are present which are tentatively identified with
Ne-K/Fe-L and Fe-K shell emission. The spectral changes during dips are complex
and may be modeled by a strong (~3 10E23 atom/cm2) increase in absorption of
the Comptonized component only, together with reductions in normalizations of
both spectral components. This behavior is in contrast to the ``complex
continuum'' model for X-ray dip sources, where the softer blackbody component
rapidly suffers strong absorption. It is however, similar to that found during
recent XMM-Newton observations of the eclipsing, dipping, LMXRB EXO0748-676.Comment: 11 pages. Accepted for publication in A&A
4U 0115+63 from RXTE and INTEGRAL Data: Pulse Profile and Cyclotron Line Energy
We analyze the observations of the transient X-ray pulsar 4U 0115+63 with the
RXTE and INTEGRAL observatories in a wide X-ray (3-100 keV) energy band during
its intense outbursts in 1999 and 2004. The energy of the fundamental harmonic
of the cyclotron resonance absorption line near the maximum of the X-ray flux
from the source (luminosity range 5x10^{37} - 2x10^{38} erg/s) is ~11 keV. When
the pulsar luminosity falls below ~5x10^{37} erg/s, the energy of the
fundamental harmonic is displaced sharply toward the high energies, up to ~16
keV. Under the assumption of a dipole magnetic field configuration, this change
in cyclotron harmonic energy corresponds to a decrease in the height of the
emitting region by ~2 km, while other spectral parameters, in particular, the
cutoff energy, remain essentially constant. At a luminosity ~7x10^{37} erg/s,
four almost equidistant cyclotron line harmonics are clearly seen in the
spectrum. This suggests that either the region where the emission originates is
compact or the emergent spectrum from different (in height) segments of the
accretion column is uniform. We have found significant pulse profile variations
with energy, luminosity, and time. In particular, we show that the profile
variations from pulse to pulse are not reduced to a simple modulation of the
accretion rate specified by external conditions.Comment: 30 pages, 13 figures, Astronomy Letters, 33, 368 (2007
Anisotropic inverse Compton scattering of photons from the circumstellar disc in PSR B1259-63
The gamma-ray binary system PSR B1259-63 consists of a 48 ms pulsar orbiting
a Be star. The system is particularly interesting because it is the only
gamma-ray binary system where the nature of the compact object is known. The
non-thermal radiation from the system is powered by the spin-down luminosity of
the pulsar and the unpulsed radiation originates from the stand-off shock front
which forms between the pulsar and stellar wind. The Be star/optical companion
in the system produces an excess infrared flux from the associated
circumstellar disc. This infrared excess provides an additional photon source
for inverse Compton scattering. We discuss the effects of the IR excess near
periastron, for anisotropic inverse Compton scattering and associated gamma-ray
production. We determine the infrared excess from the circumstellar disc using
a modified version of a curve of growth method, which takes into account the
changing optical depth through the circumstellar disc during the orbit. The
model is constrained using archive data and additional mid-IR observations
obtained with the VLT during January 2011. The inverse Compton scattering rate
was calculated for three orientations of the circumstellar disc. The predicted
gamma-ray light curves show that the disc contribution is a maximum around
periastron and not around the disc crossing epoch. This is a result of the disc
being brightest near the stellar surface. Additional spectroscopic and
near-infrared observations were obtained of the system and these are discussed
in relation to the possibility of shock heating during the disc crossing epoch.Comment: 15 pages, 14 figures and 4 tables. MNRAS in press. Updated
references, correction of typos in a few of the equations in sec. 5.2 and
appendix, and other minor typo correction
The Nuclear Spectroscopic Telescope Array (NuSTAR)
The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer
mission that will carry the first focusing hard X-ray (5 -- 80 keV) telescope
to orbit. NuSTAR will offer a factor 50 -- 100 sensitivity improvement compared
to previous collimated or coded mask imagers that have operated in this energy
band. In addition, NuSTAR provides sub-arcminute imaging with good spectral
resolution over a 12-arcminute field of view. After launch, NuSTAR will carry
out a two-year primary science mission that focuses on four key programs:
studying the evolution of massive black holes through surveys carried out in
fields with excellent multiwavelength coverage, understanding the population of
compact objects and the nature of the massive black hole in the center of the
Milky Way, constraining explosion dynamics and nucleosynthesis in supernovae,
and probing the nature of particle acceleration in relativistic jets in active
galactic nuclei. A number of additional observations will be included in the
primary mission, and a guest observer program will be proposed for an extended
mission to expand the range of scientific targets. The payload consists of two
co-aligned depth-graded multilayer coated grazing incidence optics focused onto
solid state CdZnTe pixel detectors. To be launched in early 2012 on a Pegasus
rocket into a low-inclination Earth orbit. Data will be publicly available at
GSFC's High Energy Astrophysics Science Archive Research Center (HEASARC)
following validation at the science operations center located at Caltech.Comment: 9 pages, 5 figures, to appear in Proceedings of the SPIE, Space
Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ra
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