2,967 research outputs found
HEALTHY COMMAND ENVIRONMENTS: DEFINITIONS, RISK FACTORS, AND PROTECTIVE FACTORS
This project aims to identify protective and risk factors that contribute to a healthy command environment and the effects of those factors on Sailor behavior. To examine which factors were most impactful for building a healthy command environment, we developed and asked our participants a series of Likert scale questions and open-ended questions. Using their answers, we analyzed any perceived effects upon Sailor behavior. We compared responses from sea vs. shore command experiences as well as responses from different communities within the Navy. Our research shows which command practices, policies, procedures, and processes (P4) contributed to healthier environments. Our research shows that trust, leadership, and communication significantly influence a command’s environment. Our findings indicate that these themes can manifest through a variety of programs, policies, practices, and procedures. As a result, we recommend expanding the current leadership curriculum to include organizational behavior to improve implementation of the P4 throughout the military. We also recommend expanding the data collection effort throughout the Navy to gain a more complete understanding of healthy environments in the fleet and to enhance readiness, foster healthier Sailor behaviors, and encourage higher retention.N17Lieutenant, United States NavyCaptain, United States Marine CorpsLieutenant, United States NavyApproved for public release. Distribution is unlimited
A Hard X-Ray Study of Ultraluminous X-ray Source NGC 5204 X-1 with NuSTAR and XMM-Newton
We present the results from coordinated X-ray observations of the
ultraluminous X-ray source NGC 5204 X-1 performed by NuSTAR and XMM-Newton in
early 2013. These observations provide the first detection of NGC 5204 X-1
above 10 keV, extending the broadband coverage to 0.3-20 keV. The observations
were carried out in two epochs separated by approximately 10 days, and showed
little spectral variation, with an observed luminosity of Lx = (4.95+/-0.11)e39
erg/s. The broadband spectrum confirms the presence of a clear spectral
downturn above 10 keV seen in some previous observations. This cutoff is
inconsistent with the standard low/hard state seen in Galactic black hole
binaries, as would be expected from an intermediate mass black hole accreting
at significantly sub-Eddington rates given the observed luminosity. The
continuum is apparently dominated by two optically thick thermal-like
components, potentially accompanied by a faint high energy tail. The broadband
spectrum is likely associated with an accretion disk that differs from a
standard Shakura & Sunyaev thin disk.Comment: 7 pages, 5 figures. Accepted for publication in Ap
A Soft X-Ray Spectral Episode for the Clocked Burster, GS 1826-24 as Measured by Swift and NuSTAR
We report on NuSTAR and Swift observations of a soft state of the neutron
star low-mass X-ray binary GS 1826-24, commonly known as the "clocked" burster.
The transition to the soft state was recorded in 2014 June through an increase
of the 2-20 keV source intensity measured by MAXI, simultaneous with a decrease
of the 15-50 keV intensity measured by Swift/BAT. The episode lasted
approximately two months, after which the source returned to its usual hard
state. We analyze the broad-band spectrum measured by Swift/XRT and NuSTAR, and
estimate the accretion rate during the soft episode to be about 13% of
Eddington, within the range of previous observations. However, the best fit
spectral model, adopting the double Comptonization used previously, exhibits
significantly softer components. We detect seven type-I X-ray bursts, all
significantly weaker (and with shorter rise and decay times) than observed
previously. The burst profiles and recurrence times vary significantly, ruling
out the regular bursts that are typical for this source. One burst exhibited
photospheric radius expansion, and we estimate the source distance at about
(5.7 / xi_b^1/2) kpc, where xi_b parameterizes the possible anisotropy of the
burst emission. Interpreting the soft state as a transition from an optically
thin inner flow to an optically thick flow passing through a boundary layer, as
is commonly observed in similar systems, is contradicted by the lower optical
depth measured for the double Comptonization model we find for this soft state.
The effect of a change in disk geometry on the burst behavior remains unclear.Comment: 40 pages (single-column, doubled spaced format), 9 figures, 3 tables;
submitted to Ap
A Hard Look at NGC 5347: Revealing a Nearby Compton-thick AGN
Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC 5347 (z = 0.00792, D = 35.5 Mpc ) have alternately suggested a CT and Compton-thin source. Combining archival data from Suzaku, Chandra, and—most importantly—new data from NuSTAR, ... See full text for complete abstrac
ASCA Observations of GX 354-0 and KS 1731-260
We report on ASCA observations of the low mass X-ray binaries GX 354-0 and KS
1731-260. The spectrum of GX 354-0 is best described as a power-law or a
Comptonized spectrum with tau ~ 5 and kT ~ 8 keV and a residual at ~6.5 keV.
The residual may be a disk reflection or a Compton broadened Gaussian line from
the hot inner ADAF-like coronal region. The absorption column density to the
source is 2.9e22 cm^-2. No soft thermal component was detected. The spectrum
from KS 1731-260 is softer and it is best fit with a two component model with a
column density of 1.1e22 cm^-2. The likely interpretation is emission from a
Comptonizing cloud with an optical depth tau>12 and either a neutron star or a
disk blackbody emission. We discuss the likely location of the Comptonizing
cloud for both sources within the context of several proposed emission models.Comment: Accepted for publication in the Astrophysical Journa
RXTE Studies of Long-Term X-ray Spectral Variations in 4U 1820-30
We present the results of detailed spectral studies of the ultra-compact low
mass X-ray binary (LMXB) 4U 1820-30 carried out with the Rossi X-ray Timing
Explorer (RXTE) during 1996-7. 4U 1820-30 is an ``atoll'' source X-ray burster
(XRB) located in the globular cluster NGC 6624. It is known to have an 11
minute binary period and a ~176 day modulation in its 2--12 keV flux.
Observations were made with the PCA and HEXTE instruments on RXTE at roughly
one-month intervals to sample this long-term period and study flux-related
spectral changes. There are clear correlations between our fitted spectral
parameters and both the broad-band (2--50 keV) flux and the position in the
color-color diagram, as described by the parameter S_a introduced by Mendez et
al. (1999). In addition, we find a strong correlation between the position in
the color-color diagram and the frequencies of the kilohertz quasi-periodic
oscillations (kHz QPOs) reported by Zhang et al. (1998). This lends further
support to the notion that evidence for the last stable orbit in the accretion
disk of 4U 1820-30 has been observed. For a model consisting of Comptonization
of cool photons by hot electrons plus an additional blackbody component, we
report an abrupt change in the spectral parameters at the same accretion rate
at which the kHz QPOs disappear. For a model consisting of a multicolor disk
blackbody plus a cut-off power law, we find that the inner disk radius reaches
a minimum at the same accretion rate at which the kHz QPO frequency saturates,
as expected if the disk reaches the last stable orbit. Both models face
theoretical and observational problems when interpreted physically for this
system.Comment: 39 pages, 11 figures, accepted to the Astrophysical Journa
A NuSTAR observation of the reflection spectrum of the low mass X-ray binary 4U 1728-34
We report on a simultaneous NuSTAR and Swift observation of the neutron star
low-mass X-ray binary 4U 1728-34. We identified and removed four Type I X-ray
bursts during the observation in order to study the persistent emission. The
continuum spectrum is hard and well described by a black body with 1.5
keV and a cutoff power law with 1.5 and a cutoff temperature of 25
keV. Residuals between 6 and 8 keV provide strong evidence of a broad Fe
K line. By modeling the spectrum with a relativistically blurred
reflection model, we find an upper limit for the inner disk radius of . Consequently we find that km,
assuming M=1.4{\mbox{\rm\,M_{\mathord\odot}}} and . We also find an
upper limit on the magnetic field of G.Comment: 9 pages, 8 figure
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