4,596 research outputs found
Pressure test analysis of 200-inch multicell test tank
Pressure test analysis for large multiple cell tank with sectioned ski
Self-recording portable soil penetrometer
A lightweight portable penetrometer for testing soil characteristics is described. The penetrometer is composed of a handle, data recording, and probe components detachably joined together. The data recording component has an easily removed recording drum which rotates according to the downward force applied on the handle, and a stylus means for marking the drum along its height according to the penetration depth of probe into the soil
Multi-wavelength properties of IGR J05007-7047 (LXP 38.55) and identification as a Be X-ray binary pulsar in the LMC
We report on the results of a 40 d multi-wavelength monitoring of the
Be X-ray binary system IGR J05007-7047 (LXP 38.55). During that period the
system was monitored in the X-rays using the Swift telescope and in the optical
with multiple instruments. When the X-ray luminosity exceeded erg/s
we triggered an XMM-Newton ToO observation. Timing analysis of the photon
events collected during the XMM-Newton observation reveals coherent X-ray
pulsations with a period of 38.551(3) s (1 {\sigma}), making it the 17
known high-mass X-ray binary pulsar in the LMC. During the outburst, the X-ray
spectrum is fitted best with a model composed of an absorbed power law () plus a high-temperature black-body (kT 2 keV) component. By
analysing 12 yr of available OGLE optical data we derived a 30.776(5) d
optical period, confirming the previously reported X-ray period of the system
as its orbital period. During our X-ray monitoring the system showed limited
optical variability while its IR flux varied in phase with the X-ray
luminosity, which implies the presence of a disk-like component adding cooler
light to the spectral energy distribution of the system.Comment: 11 pages, 11 figures, Accepted for publication in MNRA
Subtropical Real Root Finding
We describe a new incomplete but terminating method for real root finding for
large multivariate polynomials. We take an abstract view of the polynomial as
the set of exponent vectors associated with sign information on the
coefficients. Then we employ linear programming to heuristically find roots.
There is a specialized variant for roots with exclusively positive coordinates,
which is of considerable interest for applications in chemistry and systems
biology. An implementation of our method combining the computer algebra system
Reduce with the linear programming solver Gurobi has been successfully applied
to input data originating from established mathematical models used in these
areas. We have solved several hundred problems with up to more than 800000
monomials in up to 10 variables with degrees up to 12. Our method has failed
due to its incompleteness in less than 8 percent of the cases
Swift J053041.9-665426, a new Be/X-ray binary pulsar in the Large Magellanic Cloud
We observed the newly discovered X-ray source Swift J053041.9-665426 in the
X-ray and optical regime to confirm its proposed nature as a high mass X-ray
binary. We obtained XMM-Newton and Swift X-ray data, along with optical
observations with the ESO Faint Object Spectrograph, to investigate the
spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton
data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma).
The X-ray spectrum can be modelled by an absorbed power law with photon index
within the range 0.76 to 0.87. The addition of a black body component increases
the quality of the fit but also leads to strong dependences of the photon
index, black-body temperature and absorption column density. We identified the
only optical counterpart within the error circle of XMM-Newton at an angular
distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical
spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray
pulsations and long-term variability, as well as the properties of the optical
counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary
pulsar in the Large Magellanic Cloud.Comment: 10 pages, 8 figures, accepted for publication in A&
Discovery of SXP265, a Be/X-ray binary pulsar in the Wing of the Small Magellanic Cloud
We identify a new candidate for a Be/X-ray binary in the XMM-Newton slew
survey and archival Swift observations that is located in the transition region
of the Wing of the Small Magellanic Cloud and the Magellanic Bridge. We
investigated and classified this source with follow-up XMM-Newton and optical
observations. We model the X-ray spectra and search for periodicities and
variability in the X-ray observations and the OGLE I-band light curve. The
optical counterpart has been classified spectroscopically, with data obtained
at the SAAO 1.9 m telescope, and photometrically, with data obtained using
GROND at the MPG 2.2 m telescope. The X-ray spectrum is typical of a high-mass
X-ray binary with an accreting neutron star. We detect X-ray pulsations, which
reveal a neutron-star spin period of P = (264.516+-0.014) s. The source likely
shows a persistent X-ray luminosity of a few 10^35 erg/s and in addition type-I
outbursts that indicate an orbital period of ~146 d. A periodicity of 0.867 d,
found in the optical light curve, can be explained by non-radial pulsations of
the Be star. We identify the optical counterpart and classify it as a
B1-2II-IVe star. This confirms SXP 265 as a new Be/X-ray binary pulsar
originating in the tidal structure between the Magellanic Clouds.Comment: 11 pages, 12 figures, accepted for publication in MNRA
The XMM-Newton view of the central degrees of the Milky Way
The deepest XMM-Newton mosaic map of the central 1.5 deg of the Galaxy is
presented, including a total of about 1.5 Ms of EPIC-pn cleaned exposures in
the central 15" and about 200 ks outside. This compendium presents broad-band
X-ray continuum maps, soft X-ray intensity maps, a decomposition into spectral
components and a comparison of the X-ray maps with emission at other
wavelengths. Newly-discovered extended features, such as supernova remnants
(SNRs), superbubbles and X-ray filaments are reported. We provide an atlas of
extended features within +-1 degree of Sgr A*. We discover the presence of a
coherent X-ray emitting region peaking around G0.1-0.1 and surrounded by the
ring of cold, mid-IR-emitting material known from previous work as the "Radio
Arc Bubble" and with the addition of the X-ray data now appears to be a
candidate superbubble. Sgr A's bipolar lobes show sharp edges, suggesting that
they could be the remnant, collimated by the circumnuclear disc, of a SN
explosion that created the recently discovered magnetar, SGR J1745-2900. Soft
X-ray features, most probably from SNRs, are observed to fill holes in the dust
distribution, and to indicate a direct interaction between SN explosions and
Galactic center (GC) molecular clouds. We also discover warm plasma at high
Galactic latitude, showing a sharp edge to its distribution that correlates
with the location of known radio/mid-IR features such as the "GC Lobe". These
features might be associated with an inhomogeneous hot "atmosphere" over the
GC, perhaps fed by continuous or episodic outflows of mass and energy from the
GC region.Comment: MNRAS published online. See www.mpe.mpg.de/heg/gc/ for a higher
resolution version of the figure
Spitzer Power-law AGN Candidates in the Chandra Deep Field-North
We define a sample of 62 galaxies in the Chandra Deep Field-North whose
Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of
luminous AGN. We study the multiwavelength properties of this sample, and
compare the AGN selected in this way to those selected via other Spitzer
color-color criteria. Only 55% of the power-law galaxies are detected in the
X-ray catalog at exposures of >0.5 Ms, although a search for faint emission
results in the detection of 85% of the power-law galaxies at the > 2.5 sigma
detection level. Most of the remaining galaxies are likely to host AGN that are
heavily obscured in the X-ray. Because the power-law selection requires the AGN
to be energetically dominant in the near- and mid-infrared, the power-law
galaxies comprise a significant fraction of the Spitzer-detected AGN population
at high luminosities and redshifts. The high 24 micron detection fraction also
points to a luminous population. The power-law galaxies comprise a subset of
color-selected AGN candidates. A comparison with various mid-infrared color
selection criteria demonstrates that while the color-selected samples contain a
larger fraction of the X-ray luminous AGN, there is evidence that these
selection techniques also suffer from a higher degree of contamination by
star-forming galaxies in the deepest exposures. Considering only those
power-law galaxies detected in the X-ray catalog, we derive an obscured
fraction of 68% (2:1). Including all of the power-law galaxies suggests an
obscured fraction of < 81% (4:1).Comment: Accepted for publication in the Astrophysical Journal, 27 pages, 20
figures, 5 tables, version with high-resolution figures and online-only
tables available at: http://frodo.as.arizona.edu/~jdonley/powerlaw
High Resolution X-Ray Spectroscopy of SN 1987A: Monitoring with XMM-Newton
We report the results of our XMM-Newton monitoring of SN 1987A. The ongoing
propagation of the supernova blast wave through the inner circumstellar ring
caused a drastic increase in X-ray luminosity during the last years, enabling
detailed high resolution X-ray spectroscopy with the Reflection Grating
Spectrometer. The observations can be used to follow the detailed evolution of
the arising supernova remnant. The fluxes and broadening of the numerous
emission lines seen in the dispersed spectra provide information on the
evolution of the X-ray emitting plasma and its dynamics. These were analyzed in
combination with the EPIC-pn spectra, which allow a precise determination of
the higher temperature plasma. We modeled individual emission lines and fitted
plasma emission models. Especially from the observations between 2003 and 2007
we can see a significant evolution of the plasma parameters and a deceleration
of the radial velocity of the lower temperature plasma regions. We found an
indication (3-sigma-level) of an iron K feature in the co-added EPIC-pn
spectra. The comparison with Chandra grating observations in 2004 yields a
clear temporal coherence of the spectral evolution and the sudden deceleration
of the expansion velocity seen in X-ray images ~6100 days after the explosion.Comment: 10 pages, 8 Figures; accepted by A&
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