17 research outputs found
Spectral State Transitions of the Ultraluminous X-ray Source IC 342 X-1
We observed the Ultraluminous X-ray Source IC 342 X-1 simultaneously in X-ray
and radio with Chandra and the JVLA to investigate previously reported
unresolved radio emission coincident with the ULX. The Chandra data reveal a
spectrum that is much softer than observed previously and is well modelled by a
thermal accretion disc spectrum. No significant radio emission above the rms
noise level was observed within the region of the ULX, consistent with the
interpretation as a thermal state though other states cannot be entirely ruled
out with the current data. We estimate the mass of the black hole using the
modelled inner disc temperature to be based on a Shakura-Sunyaev
disc model. Through a study of the hardness and high-energy curvature of
available X-ray observations, we find that the accretion state of X-1 is not
determined by luminosity alone.Comment: 10 pages, 5 Figures. MNRAS: Accepted 2014 July 2
Performance Testing of a Novel Off-plane Reflection Grating and Silicon Pore Optic Spectrograph at PANTER
An X-ray spectrograph consisting of radially ruled off-plane reflection
gratings and silicon pore optics was tested at the Max Planck Institute for
extraterrestrial Physics PANTER X-ray test facility. The silicon pore optic
(SPO) stack used is a test module for the Arcus small explorer mission, which
will also feature aligned off-plane reflection gratings. This test is the first
time two off-plane gratings were actively aligned to each other and with a SPO
to produce an overlapped spectrum. The gratings were aligned using an active
alignment module which allows for the independent manipulation of subsequent
gratings to a reference grating in three degrees of freedom using picomotor
actuators which are controllable external to the test chamber. We report the
line spread functions of the spectrograph and the actively aligned gratings,
and plans for future development.Comment: Draft Version March 19, 201
A Search for the Transit of HD 168443b: Improved Orbital Parameters and Photometry
The discovery of transiting planets around bright stars holds the potential
to greatly enhance our understanding of planetary atmospheres. In this work we
present the search for transits of HD 168443b, a massive planet orbiting the
bright star HD 168443 V=6.92 with a period of 58.11 days. The high eccentricity
of the planetary orbit e=0.53 significantly enhances the a-priori transit
probability beyond that expected for a circular orbit, making HD 168443 a
candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey
(TERMS). Using additional radial velocities from Keck-HIRES, we refined the
orbital parameters of this multi-planet system and derived a new transit
ephemeris for HD 168443b. The reduced uncertainties in the transit window make
a photometric transit search practicable. Photometric observations acquired
during predicted transit windows were obtained on three nights. CTIO 1.0 m
photometry acquired on 2010 September 7 had the required precision to detect a
transit but fell just outside of our final transit window. Nightly photometry
from the T8 0.8 m Automated Photometric Telescope (APT) at Fairborn
Observatory, acquired over a span of 109 nights, demonstrates that HD 168443 is
constant on a time scale of weeks. Higher-cadence photometry on 2011 April 28
and June 25 shows no evidence of a transit. We are able to rule out a
non-grazing transit of HD 168443b.Comment: Accepted in ApJ. 25 pages. 8 Figure
Sex-Specific Skeletal Muscle Fatigability and Decreased Mitochondrial Oxidative Capacity in Adult Rats Exposed to Postnatal Hyperoxia
Premature birth affects more than 10% of live births, and is characterized by relative hyperoxia exposure in an immature host. Long-term consequences of preterm birth include decreased aerobic capacity, decreased muscular strength and endurance, and increased prevalence of metabolic diseases such as type 2 diabetes mellitus. Postnatal hyperoxia exposure in rodents is a well-established model of chronic lung disease of prematurity, and also recapitulates the pulmonary vascular, cardiovascular, and renal phenotype of premature birth. The objective of this study was to evaluate whether postnatal hyperoxia exposure in rats could recapitulate the skeletal and metabolic phenotype of premature birth, and to characterize the subcellular metabolic changes associated with postnatal hyperoxia exposure, with a secondary aim to evaluate sex differences in this model. Compared to control rats, male rats exposed to 14 days of postnatal hyperoxia then aged to 1 year demonstrated higher skeletal muscle fatigability, lower muscle mitochondrial oxidative capacity, more mitochondrial damage, and higher glycolytic enzyme expression. These differences were not present in female rats with the same postnatal hyperoxia exposure. This study demonstrates detrimental mitochondrial and muscular outcomes in the adult male rat exposed to postnatal hyperoxia. Given that young adults born premature also demonstrate skeletal muscle dysfunction, future studies are merited to determine whether this dysfunction as well as reduced aerobic capacity is due to reduced mitochondrial oxidative capacity and metabolic dysfunction
Sex-Specific Skeletal Muscle Fatigability and Decreased Mitochondrial Oxidative Capacity in Adult Rats Exposed to Postnatal Hyperoxia
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<p>Premature birth affects more than 10% of live births, and is characterized by relative hyperoxia exposure in an immature host. Long-term consequences of preterm birth include decreased aerobic capacity, decreased muscular strength and endurance, and increased prevalence of metabolic diseases such as type 2 diabetes mellitus. Postnatal hyperoxia exposure in rodents is a well-established model of chronic lung disease of prematurity, and also recapitulates the pulmonary vascular, cardiovascular, and renal phenotype of premature birth. The objective of this study was to evaluate whether postnatal hyperoxia exposure in rats could recapitulate the skeletal and metabolic phenotype of premature birth, and to characterize the subcellular metabolic changes associated with postnatal hyperoxia exposure, with a secondary aim to evaluate sex differences in this model. Compared to control rats, male rats exposed to 14 days of postnatal hyperoxia then aged to 1 year demonstrated higher skeletal muscle fatigability, lower muscle mitochondrial oxidative capacity, more mitochondrial damage, and higher glycolytic enzyme expression. These differences were not present in female rats with the same postnatal hyperoxia exposure. This study demonstrates detrimental mitochondrial and muscular outcomes in the adult male rat exposed to postnatal hyperoxia. Given that young adults born premature also demonstrate skeletal muscle dysfunction, future studies are merited to determine whether this dysfunction as well as reduced aerobic capacity is due to reduced mitochondrial oxidative capacity and metabolic dysfunction.</p