213 research outputs found
Broad-band X-ray spectral analysis of the Seyfert 1 galaxy GRS 1734-292
We discuss the broad-band X-ray spectrum of GRS 1734â292 obtained from non-simultaneous XMMâNewton and NuSTAR (Nuclear Spectroscopic Telescope Array) observations, performed in 2009 and 2014, respectively. GRS1734â292 is a Seyfert 1 galaxy, located near the Galactic plane at z = 0.0214. The NuSTAR spectrum (3â80 keV) is dominated by a primary power-law continuum with Î = 1.65 ± 0.05 and a high-energy cut-off Ec=53+11â8 keV, one of the lowest measured by NuSTAR in a Seyfert galaxy. Comptonization models show a temperature of the coronal plasma of kTe=11.9+1.2â0.9 keV and an optical depth, assuming a slab geometry, Ï=2.98+0.16â0.19 or a similar temperature and Ï=6.7+0.3â0.4 assuming a spherical geometry. The 2009 XMMâNewton spectrum is well described by a flatter intrinsic continuum (â Î=1.47+0.07â0.03â ) and one absorption line due to Fe XXV Kα produced by a warm absorber. Both data sets show a modest iron Kα emission line at 6.4 keV and the associated Compton reflection, due to reprocessing from neutral circumnuclear material
NuSTAR observations of Mrk 766: Distinguishing reflection from absorption
We present two new NuSTAR observations of the narrow line Seyfert 1 (NLS1) galaxy Mrk 766 and give constraints on the two scenarios previously proposed to explain its spectrum and that of other NLS1s: relativistic reflection and partial covering. The NuSTAR spectra show a strong hard (> 15 keV) X-ray excess, while simultaneous soft X-ray coverage of one of the observations provided by XMM-Newton constrains the ionised absorption in the source. The pure reflection model requires a black hole of high spin (a > 0.92) viewed at a moderate inclination (i = 46 +1 â4 ). The pure partial covering model requires extreme parameters: the cut-off of the primary continuum is very low (22 +7 â5 keV) in one observation and the intrinsic X-ray emission must provide a large fraction (75%) of the bolometric luminosity. Allowing a hybrid model with both partial covering and reflection provides more reasonable absorption parameters and relaxes the constraints on reflection parameters. The fractional variability reduces around the iron K band and at high energies including the Compton hump, suggesting that the reflected emission is less variable than the continuum
The corona of the broad-line radio galaxy 3C 390.3
We present the results from a joint Suzaku/NuSTAR broad-band spectral
analysis of 3C 390.3. The high quality data enables us to clearly separate the
primary continuum from the reprocessed components allowing us to detect a high
energy spectral cut-off ( keV), and to place
constraints on the Comptonization parameters of the primary continuum for the
first time. The hard over soft compactness is 69 and the optical
depth 4.1, this leads to an electron temperature of
keV. Expanding our study of the Comptonization spectrum to the
optical/UV by studying the simultaneous Swift-UVOT data, we find indications
that the compactness of the corona allows only a small fraction of the total
UV/optical flux to be Comptonized. Our analysis of the reprocessed emission
show that 3C 390.3 only has a small amount of reflection (R~0.3), and of that
the vast majority is from distant neutral matter. However we also discover a
soft X-ray excess in the source, which can be described by a weak ionized
reflection component from the inner parts of the accretion disk. In addition to
the backscattered emission, we also detect the highly ionized iron emission
lines Fe XXV and Fe XXVI
NuSTAR and XMM-Newton observations of NGC 1365: Extreme absorption variability and a constant inner accretion disk
We present a spectral analysis of four coordinated NuSTAR+XMM-Newton
observations of the Seyfert galaxy NGC 1365. These exhibit an extreme level of
spectral variability, which is primarily due to variable line-of-sight
absorption, revealing relatively unobscured states in this source for the first
time. Despite the diverse range of absorption states, each of the observations
displays the same characteristic signatures of relativistic reflection from the
inner accretion disk. Through time-resolved spectroscopy we find that the
strength of the relativistic iron line and the Compton reflection hump relative
to the intrinsic continuum are well correlated, as expected if they are two
aspects of the same broadband reflection spectrum. We apply self-consistent
disk reflection models to these time-resolved spectra in order to constrain the
inner disk parameters, allowing for variable, partially covering absorption to
account for the vastly different absorption states observed. Each of the four
observations is treated independently to test the consistency of the results
obtained for the black hole spin and the disk inclination, which should not
vary on observable timescales. We find both the spin and the inclination
determined from the reflection spectrum to be consistent, confirming NGC 1365
hosts a rapidly rotating black hole; in all cases the dimensionless spin
parameter is constrained to be a* > 0.97 (at 90% statistical confidence or
better)
Development and quantitative analyses of a universal rRNA-subtraction protocol for microbial metatranscriptomics
Metatranscriptomes generated by pyrosequencing hold significant potential for describing functional processes in complex microbial communities. Meeting this potential requires protocols that maximize mRNA recovery by reducing the relative abundance of ribosomal RNA, as well as systematic comparisons to identify methodological artifacts and test for reproducibility across data sets. Here, we implement a protocol for subtractive hybridization of bacterial rRNA (16S and 23S) that uses sample-specific probes and is applicable across diverse environmental samples. To test this method, rRNA-subtracted and unsubtracted transcriptomes were sequenced (454 FLX technology) from bacterioplankton communities at two depths in the oligotrophic open ocean, yielding 10 data sets representing ~350âMbp. Subtractive hybridization reduced bacterial rRNA transcript abundance by 40â58%, increasing recovery of non-rRNA sequences up to fourfold (from 12% to 20% of total sequences to 40â49%). In testing this method, we established criteria for detecting sequences replicated artificially via pyrosequencing errors and identified such replicates as a significant component (6â39%) of total pyrosequencing reads. Following replicate removal, statistical comparisons of reference genes (identified via BLASTX to NCBI-nr) between technical replicates and between rRNA-subtracted and unsubtracted samples showed low levels of differential transcript abundance (<0.2% of reference genes). However, gene overlap between data sets was remarkably low, with no two data sets (including duplicate runs from the same pyrosequencing library template) sharing greater than 17% of unique reference genes. These results indicate that pyrosequencing captures a small subset of total mRNA diversity and underscores the importance of reliable rRNA subtraction procedures to enhance sequencing coverage across the functional transcript pool.Agouron InstituteGordon and Betty Moore FoundationUnited States. Dept. of Energy. Office of ScienceNational Science Foundation (U.S.) (NSF Science and Technology Center Award EF0424599
NuStar observations of WISE J1036+0449, a galaxy at z ⌠1 obscured by hot dust
Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorerâs all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z> 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at zË 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 ({L}{Bol}â 8Ă {10}46 {erg} {{{s}}}-1). We find evidence of a broadened component in Mg II, which would imply a black hole mass of {M}{BH}â 2Ă {10}8 {M}â and an Eddington ratio of {λ }{Edd}â 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of {N}{{H}}â (2{--}15)Ă {10}23 {{cm}}-2. The source has an intrinsic 2-10 keV luminosity of Ë 6Ă {10}44 {erg} {{{s}}}-1, a value significantly lower than that expected from the mid-infrared/X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at zâČ 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio
Pain, psychological distress and health-related quality of life at baseline and 3 months after radical prostatectomy
BACKGROUND: Inadequate management of postoperative pain is common, and postoperative pain is a risk factor for prolonged pain. In addition to medical and technical factors, psychological factors may also influence the experience of postoperative pain. METHODS: Pain was measured postoperatively at 24, 48, and 72 hr in hospital and after 3 months at home in 140 patients undergoing radical prostatectomy (RP). Patients answered questionnaires about anxiety and depression (HAD scale) and health-related quality of life (SF-36) at baseline and 3 months after surgery. RESULTS: In the first 3 postoperative days, mild pain was reported by 45 patients (32%), moderate pain by 64 (45%), and severe pain by 31 (22%) on one or more days. High postoperative pain scores were correlated with length of hospital stay and with high pain scores at home. Forty patients (29%) reported moderate (n = 35) or severe (n = 5) pain after discharge from hospital. Patients who experienced anxiety and depression preoperatively had higher postoperative pain scores and remained anxious and depressed 3 months after surgery. The scores for the physical domains in the SF-36 were decreased, while the mental health scores were increased at 3 months. Anxiety and depression were negatively correlated with all domains of the SF-36. CONCLUSION: There is a need for nurses to be aware of the psychological status of RP patients and its impact upon patients' experience of postoperative pain and recovery. The ability to identify patients with psychological distress and to target interventions is an important goal for future research
X-ray Absorption and Reflection in Active Galactic Nuclei
X-ray spectroscopy offers an opportunity to study the complex mixture of
emitting and absorbing components in the circumnuclear regions of active
galactic nuclei, and to learn about the accretion process that fuels AGN and
the feedback of material to their host galaxies. We describe the spectral
signatures that may be studied and review the X-ray spectra and spectral
variability of active galaxies, concentrating on progress from recent Chandra,
XMM-Newton and Suzaku data for local type 1 AGN. We describe the evidence for
absorption covering a wide range of column densities, ionization and dynamics,
and discuss the growing evidence for partial-covering absorption from data at
energies > 10 keV. Such absorption can also explain the observed X-ray spectral
curvature and variability in AGN at lower energies and is likely an important
factor in shaping the observed properties of this class of source.
Consideration of self-consistent models for local AGN indicates that X-ray
spectra likely comprise a combination of absorption and reflection effects from
material originating within a few light days of the black hole as well as on
larger scales. It is likely that AGN X-ray spectra may be strongly affected by
the presence of disk-wind outflows that are expected in systems with high
accretion rates, and we describe models that attempt to predict the effects of
radiative transfer through such winds, and discuss the prospects for new data
to test and address these ideas.Comment: Accepted for publication in the Astronomy and Astrophysics Review. 58
pages, 9 figures. V2 has fixed an error in footnote
X-Ray Spectroscopy of Stars
(abridged) Non-degenerate stars of essentially all spectral classes are soft
X-ray sources. Low-mass stars on the cooler part of the main sequence and their
pre-main sequence predecessors define the dominant stellar population in the
galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense,
of X-ray spectra from the solar corona. X-ray emission from cool stars is
indeed ascribed to magnetically trapped hot gas analogous to the solar coronal
plasma. Coronal structure, its thermal stratification and geometric extent can
be interpreted based on various spectral diagnostics. New features have been
identified in pre-main sequence stars; some of these may be related to
accretion shocks on the stellar surface, fluorescence on circumstellar disks
due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot
stars clearly dominate the interaction with the galactic interstellar medium:
they are the main sources of ionizing radiation, mechanical energy and chemical
enrichment in galaxies. High-energy emission permits to probe some of the most
important processes at work in these stars, and put constraints on their most
peculiar feature: the stellar wind. Here, we review recent advances in our
understanding of cool and hot stars through the study of X-ray spectra, in
particular high-resolution spectra now available from XMM-Newton and Chandra.
We address issues related to coronal structure, flares, the composition of
coronal plasma, X-ray production in accretion streams and outflows, X-rays from
single OB-type stars, massive binaries, magnetic hot objects and evolved WR
stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures
(partly multiple); some corrections made after proof stag
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