720 research outputs found
The health and welfare of rural and urban cancer survivors in Missouri
INTRODUCTION: An estimated 2.8 million cancer survivors reside in rural areas in the United States. We compared the risk behaviors, psychosocial factors, health outcomes, quality of life, and follow-up care of rural and urban cancer survivors in Missouri. METHODS: We used 2009–2010 Missouri Behavioral Risk Factor Surveillance System data to examine various health outcomes, behaviors, and psychosocial factors among rural and urban cancer survivors and their respective rural and urban counterparts without a cancer history. Cancer survivors also were asked about receipt of survivorship care plan components. Sociodemographic factors, access to medical care, and chronic conditions were examined as potential explanatory factors for differences among the 4 groups. RESULTS: An estimated 9.4% of rural and 7.9% of urban Missourians aged 18 years or older reported a cancer history. Rural survivors reported the highest rates of poor self-reported health, physical distress, and activity limitation; however differences between rural and urban survivors were attributable largely to sociodemographic differences. Both rural and urban cancer survivors reported more fatigue than their respective counterparts without a cancer history. Rural survivors also were less likely to meet Centers for Disease Control and Prevention recommendations for physical activity than their rural controls. The prevalence of smoking among rural survivors was higher than among urban survivors. Only 62% of rural survivors versus 78% of urban survivors reported receiving advice about cancer follow-up care. CONCLUSION: Rural cancer survivors face many health challenges. Interventions to improve quality of life and health behaviors should be adapted to meet the needs of rural cancer survivors
A Persistent Disk Wind in GRS 1915+105 with NICER
The bright, erratic black hole X-ray binary GRS 1915+105 has long been a
target for studies of disk instabilities, radio/infrared jets, and accretion
disk winds, with implications that often apply to sources that do not exhibit
its exotic X-ray variability. With the launch of NICER, we have a new
opportunity to study the disk wind in GRS 1915+105 and its variability on short
and long timescales. Here we present our analysis of 39 NICER observations of
GRS 1915+105 collected during five months of the mission data validation and
verification phase, focusing on Fe XXV and Fe XXVI absorption. We report the
detection of strong Fe XXVI in 32 (>80%) of these observations, with another
four marginal detections; Fe XXV is less common, but both likely arise in the
well-known disk wind. We explore how the properties of this wind depends on
broad characteristics of the X-ray lightcurve: mean count rate, hardness ratio,
and fractional RMS variability. The trends with count rate and RMS are
consistent with an average wind column density that is fairly steady between
observations but varies rapidly with the source on timescales of seconds. The
line dependence on spectral hardness echoes known behavior of disk winds in
outbursts of Galactic black holes; these results clearly indicate that NICER is
a powerful tool for studying black hole winds.Comment: Accepted for publication in ApJL. Comments welcom
GRO J1655-40: Early Stages of the 2005 Outburst
The black-hole X-ray binary transient GRO J1655-40 underwent an outburst
beginning in early 2005. We present the results of our multi-wavelength
observational campaign to study the early outburst spectral and temporal
evolution, which combines data from X-ray (RXTE, INTEGRAL), radio (VLA) and
optical (ROTSE, SMARTS) instruments. During the reported period the source left
quiescence and went through four major accreting black hole states: low-hard,
hard intermediate, soft intermediate and high-soft. We investigated dipping
behavior in the RXTE band and compare our results to the 1996-1997 case, when
the source was predominantly in the high-soft state, finding significant
differences. We consider the evolution of the low frequency quasi-periodic
oscillations and find that the frequency strongly correlates with the spectral
characteristics, before shutting off prior to the transition to the high-soft
state. We model the broad-band high-energy spectrum in the context of empirical
models, as well as more physically motivated thermal and bulk-motion
Comptonization and Compton reflection models. RXTE and INTEGRAL data together
support a statistically significant high energy cut-off in the energy spectrum
at 100~200 keV during the low-hard state. The RXTE data alone also show it very
significantly during the transition, but cannot see one in the high-soft state
spectra. We consider radio, optical and X-ray connections in the context of
possible synchrotron and synchrotron self-Compton origins of X-ray emission in
low-hard and intermediate states. In this outburst of GRO J1655-40, the radio
flux does not rise strongly with the X-ray flux.Comment: 23 pages, 16 figures, accepted for publication in Ap
A transient relativistic radio jet from Cygnus X-1
We report the first observation of a transient relativistic jet from the
canonical black hole candidate, Cygnus X-1, obtained with the Multi-Element
Radio-Linked Interferometer Network (MERLIN). The jet was observed in only one
of six epochs of MERLIN imaging of the source during a phase of repeated X-ray
spectral transitions in 2004 Jan--Feb, and this epoch corresponded to the
softest 1.5-12 keV X-ray spectrum. With only a single epoch revealing the jet,
we cannot formally constrain its velocity. Nevertheless, several lines of
reasoning suggest that the jet was probably launched 0.5-4.0 days before this
brightening, corresponding to projected velocities of 0.2c < v_app < 1.6c, and
an intrinsic velocity of > 0.3c. We also report the occurrence of a major radio
flare from Cyg X-1, reaching a flux density of ~120 mJy at 15 GHz, and yet not
associated with any resolvable radio emission, despite a concerted effort with
MERLIN. We discuss the resolved jet in terms of the recently proposed 'unified
model' for the disc-jet coupling in black hole X-ray binaries, and tentatively
identify the 'jet line' for Cyg X-1. The source is consistent with the model in
the sense that a steady jet appears to persist initially when the X-ray
spectrum starts softening, and that once the spectral softening is complete the
core radio emission is suppressed and transient ejecta / shock observed.
However, there are some anomalies, and Cyg X-1 clearly does not behave like a
normal black hole transient in progressing to the canonical soft / thermal
state once the ejection event has happened.Comment: Accepted for publication in MNRA
Faraday rotation in the MOJAVE blazars: 3C 273 a case study
Radio polarimetric observations of Active Galactic Nuclei can reveal the
magnetic field structure in the parsec-scale jets of these sources. We have
observed the gamma-ray blazar 3C 273 as part of our multi-frequency survey with
the Very Long Baseline Array to study Faraday rotation in a large sample of
jets. Our observations re-confirm the transverse rotation measure gradient in
3C 273. For the first time the gradient is seen to cross zero which is further
indication for a helical magnetic field and spine-sheath structure in the jet.
We believe the difference to previous epochs is due to a different part of the
jet being illuminated in our observations.Comment: 6 pages, 3 figures. To appear in the proceedings of "Beamed and
Unbeamed Gamma-rays from Galaxies", held in Muonio, Finland, April 11-15,
2011. Journal of Physics: Conference Serie
Millisecond Oscillations in X-Ray Binaries
The first millisecond X-ray variability phenomena from accreting compact
objects have recently been discovered with the Rossi X-ray Timing Explorer.
Three new phenomena are observed from low-mass X-ray binaries containing
low-magnetic-field neutron stars: millisecond pulsations, burst oscillations
and kiloHertz quasi-periodic oscillations. Models for these new phenomena
involve the neutron star spin, and orbital motion closely around the neutron
star and rely explicitly on our understanding of strong gravity and dense
matter. I review the observations of these new neutron-star phenomena and
possibly related ones in black-hole candidates, and describe the attempts to
use them to perform measurements of fundamental physical interest in these
systems.Comment: 40 pages, 17 figures, 4 tables - submitted to the Annual Review of
Astronomy and Astrophysics; to appear September 200
Relations Between Timing Features and Colors in the X-Ray Binary 4U 0614+09
We study the correlations between timing and X-ray spectral properties in the
low mass X-ray binary 4U 0614+09 using a large (265-ks) data set obtained with
the Rossi X-ray Timing Explorer. We find strong quasi-periodic oscillations
(QPOs) of the X-ray flux, like the kilohertz QPOs in many other X-ray binaries
with accreting neutron stars, with frequencies ranging from 1329 Hz down to 418
Hz and, perhaps, as low as 153 Hz. We report the highest frequency QPO yet from
any low mass X-ray binary at 1329+-4 Hz, which has implications for neutron
star structure. This QPO has a 3.5-sigma single-trial significance, for an
estimated 40 trials the significance is 2.4-sigma. Besides the kilohertz QPOs,
the Fourier power spectra show four additional components: high frequency noise
(HFN), described by a broken power-law with a break frequency between 0.7 and
45 Hz, very low frequency noise (VLFN), which is fitted as a power-law below 1
Hz, and two broad Lorentzians with centroid frequencies varying from 6 to 38 Hz
and 97 to 158 Hz, respectively. We find strong correlations between the
frequencies of the kilohertz QPOs, the frequency of the 6 to 38 Hz broad
Lorentzian, the break frequency of the HFN, the strength of both the HFN and
the VLFN and the position of the source in the hard X-ray color vs. intensity
diagram. The frequency of the 97 to 158 Hz Lorentzian does not correlate with
these parameters. We also find that the relation between power density and
break frequency of the HFN is similar to that established for black hole
candidates in the low state. We suggest that the changing mass accretion rate
is responsible for the correlated changes in all these parameters.Comment: ApJ, referee
High- and low-frequency quasi-periodic oscillations in the X-ray light curves of the black hole transient H1743-322
We present a variability study of the black hole candidate and X-ray
transient H1743-322 during its 2003/2004 outburst. We analyzed five Rossi X-ray
Timing Explorer observations that were performed as part of a multi-wavelength
campaign, as well as six observations from the early rise of the outburst. The
source was observed in several black hole states and showed various types of
X-ray variability, including high frequency quasi-periodic oscillations (QPOs)
at 240 Hz and 160 Hz (i.e. with a 3:2 frequency ratio), several types of low
frequency QPOs, and strong variations on a time scale of a few hundred seconds.
The discovery of high frequency QPOs in H1743-322 supports predictions that
these QPOs should be more easily observed in high inclination systems. In one
of our observations we observed a transition in count rate and color, during
which we were able to follow the smooth evolution of the low-frequency QPOs
from type-B to type-A. We classify the X-ray observations and QPOs, and briefly
discuss the QPOs in terms of recently proposed models.Comment: Submitted to Ap
Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV. Fine Scale Structure
We have used VLBA fringe visibility data obtained at 15 GHz to examine the
compact structure in 250 extragalactic radio sources. For 171 sources in our
sample, more than half of the total flux density seen by the VLBA remains
unresolved on the longest baselines. There are 163 sources in our list with a
median correlated flux density at 15 GHz in excess of 0.5 Jy on the longest
baselines. For about 60% of the sources, we have at least one observation in
which the core component appears unresolved (generally smaller than 0.05 mas)
in one direction, usually transverse to the direction into which the jet
extends. BL Lacs are on average more compact than quasars, while active
galaxies are on average less compact. Also, in an active galaxy the
sub-milliarcsecond core component tends to be less dominant. IDV sources
typically have a more compact, more core-dominated structure on
sub-milliarcsecond scales than non-IDV sources, and sources with a greater
amplitude of intra-day variations tend to have a greater unresolved VLBA flux
density. The objects known to be GeV gamma-ray loud appear to have a more
compact VLBA structure than the other sources in our sample. This suggests that
the mechanisms for the production of gamma-ray emission and for the generation
of compact radio synchrotron emitting features are related. The brightness
temperature estimates and lower limits for the cores in our sample typically
range between 10^11 and 10^13 K, but they extend up to 5x10^13 K, apparently in
excess of the equipartition brightness temperature, or the inverse Compton
limit for stationary synchrotron sources. The largest component speeds are
observed in radio sources with high observed brightness temperatures, as would
be expected from relativistic beaming (abridged).Comment: 31 pages, 13 figures, 4 tables, accepted for publication in the
Astronomical Journal; minor changes to the text are mad
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