ABSTRACT
NGC 5548 is a very well-studied Seyfert 1 galaxy in broad wavelengths. Previous multiwavelength observation campaigns have indicated that its multiple absorbers are highly variable and ...complex. A previous study applied a two-zone partial covering model with different covering fractions to explain the complex X-ray spectral variation and reported a correlation between one of the covering fractions and the photon index of the power-law continuum. However, it is not straightforward to physically understand such a correlation. In this paper, we propose a model to avoid this unphysical situation; the central X-ray emission region is partially covered by clumpy absorbers composed of double layers. These ‘double partial coverings’ have precisely the same covering fraction. Based on our model, we have conducted an extensive spectral study using the data taken by XMM–Newton, Suzaku, and NuSTAR in the range of 0.3–78 keV for 16 yr. Consequently, we have found that the X-ray spectral variations are mainly explained by independent changes of the following three components; (1) the soft excess spectral component below ∼1 keV, (2) the cut-off power-law normalization, and (3) the partial covering fraction of the clumpy absorbers. In particular, spectral variations above ∼1 keV are mostly explained only by the changes of the partial covering fraction and the power-law normalization. In contrast, the photon index and all the other spectral parameters are not significantly variable.
We report the first half-year monitoring of the new Galactic black hole candidate MAXI J1348-630, discovered on 2019 January 26 with the Gas Slit Camera on board the Monitor of All-sky X-ray Image ...(MAXI). During the monitoring period, the source exhibited two outburst peaks, where the first peak flux (at T = 14 days from the discovery of T = 0) was ∼4 Crab (2-20 keV) and the second one (at T = 132 days) was ∼0.4 Crab (2-20 keV). The source exhibited distinct spectral transitions between the high/soft and low/hard states and an apparent "q"-shape curve on the hardness-intensity diagram, both of which are well-known characteristics of black hole binaries (BHBs). Compared to other bright black hole transients, MAXI J1348-630 is characterized by its low disk temperature (∼0.75 keV at the maximum) and high peak flux in the high/soft state. The low peak temperature leads to a large innermost radius that is identified as the innermost stable circular orbit, determined by the black hole mass and spin. Assuming the empirical relation between the soft-to-hard transition luminosity (Ltrans) and the Eddington luminosity (LEdd), Ltrans/LEdd 0.02, and a face-on disk around a non-spinning black hole, the source distance and the black hole mass are estimated to be D 4 kpc and , respectively. The black hole is more massive if the disk is inclined and the black hole is spinning. These results suggest that MAXI J1348-630 may host a relatively massive black hole among the known BHBs in our Galaxy.
ABSTRACT
We analyse a series of XMM–Newton RGS data of the binary Wolf–Rayet star WR140 that encompasses one entire orbit. We find that the RGS detects X-rays from optically thin thermal plasma only ...during orbital phases when the companion O star is on the near side of the WR star. Although such X-rays are believed to be emitted from the shock cone formed through collision of the stellar winds, temperature and density profiles of the plasma along the cone have not been measured observationally. We find that the temperature of the plasma producing Ne emission lines is 0.4–0.8 keV, using the intensity ratio of Kα lines from He-like and H-like Ne. We also find, at orbital phases 0.816 and 0.912, that the electron number density in the Ne line-emission site is approximately 1012 cm−3 from the observed intensity ratios f/r and i/r of the He-like triplet. We calculated the shock cone shape analytically, and identify the distance of the Ne line-emission site from the shock stagnation point to be 0.9–8.9 × 1013 cm using the observed ratio of the line-of-sight velocity and its dispersion. This means that we will be able to obtain the temperature and density profiles along the shock cone with emission lines from other elements. We find that the photoexcitation rate by the O star is only 1.3–16.4 per cent of that of the collisional excitation at orbital phase 0.816. This implies that our assumption that the plasma is collisionally excited is reasonable, at least at this orbital phase.
ABSTRACT We present multi-epoch X-ray spectral observations of three Type IIn supernovae (SNe), SN 2005kd, SN 2006jd, and SN 2010jl, acquired with Chandra, XMM-Newton, Suzaku, and Swift. Previous ...extensive X-ray studies of SN 2010jl have revealed that X-ray spectra are dominated by thermal emission, which likely arises from a hot plasma heated by a forward shock propagating into a massive circumstellar medium (CSM). Interestingly, an additional soft X-ray component was required to reproduce the spectra at a period of ∼1-2 years after the SN explosion. Although this component is likely associated with the SN, its origin remained an open question. We find a similar, additional soft X-ray component from the other two SNe IIn as well. Given this finding, we present a new interpretation for the origin of this component; it is thermal emission from a forward shock essentially identical to the hard X-ray component, but directly reaches us from a void of the dense CSM. Namely, the hard and soft components are responsible for the heavily and moderately absorbed components, respectively. The co-existence of the two components with distinct absorptions as well as the delayed emergence of the moderately absorbed X-ray component could be evidence for asphericity of the CSM. We show that the X-ray spectral evolution can be qualitatively explained by considering a torus-like geometry for the dense CSM. Based on our X-ray spectral analyses, we estimate the radius of the torus-like CSM to be on the order of ∼5 × 1016 cm.
Suzaku observations of the Wolf–Rayet (W–R) binary WR 140 (WC7pd+O5.5fc) were made at four different times around periastron passage in 2009 January. The spectra changed in shape and flux with the ...phase. As periastron approached, the column density of the low-energy absorption increased, which indicates that the emission from the wind–wind collision plasma was absorbed by the dense W–R wind. The spectra can be mostly fitted with two different components: a warm component with k
B
T = 0.3–0.6 keV and a dominant hot component with k
B
T ∼ 3 keV. The emission measure of the dominant, hot component is not inversely proportional to the distance between the two stars. This can be explained by the O star wind colliding before it has reached its terminal velocity, leading to a reduction in its wind momentum flux. At phases closer to periastron, we discovered a cool plasma component in a recombining phase, which is less absorbed. This component may be a relic of the wind–wind collision plasma, which was cooled down by radiation, and may represent a transitional stage in dust formation.
•We developed a dynamic deformable thorax phantom for DIR commissioning and QA.•Our phantom can create various deformation patterns with various marker patterns.•DIR results with different marker ...settings and DIR parameters were obtained using this phantom.
The purpose of this study was to develop a novel dynamic deformable thorax phantom for deformable image registration (DIR) quality assurance (QA) and to verify as a tool for commissioning and DIR QA.
The phantom consists of a base phantom, an inner phantom, and a motor-derived piston. The base phantom is an acrylic cylinder phantom with a diameter of 180 mm. The inner phantom consists of deformable, 20 mm thick disk-shaped sponges. To evaluate the physical characteristics of the phantom, we evaluated its image quality and deformation. DIR accuracies were evaluated using the three types of commercially DIR software (MIM, RayStation, and Velocity AI) to test the feasibility of this phantom. We used different DIR parameters to test the impact of parameters on DIR accuracy in various phantom settings. To evaluate DIR accuracy, a target registration error (TRE) was calculated using the anatomical landmark points.
The three locations (i.e., distal, middle, and proximal positions) had different displacement amounts. This result indicated that the inner phantom was not moved but deformed. In cases with different phantom settings and marker settings, the ranges of the average TRE were 0.63–15.60 mm (MIM). In cases with different DIR parameters settings, the ranges of the average TRE were as follows: 0.73–7.10 mm (MIM), 8.25–8.66 mm (RayStation), and 8.26–8.43 mm (Velocity). These results suggest that our phantom could evaluate the detailed DIR behaviors with TRE. Therefore, this is indicative of the potential usefulness of our phantom in DIR commissioning and QA.
We report the results of the stellar wind measurement for two colliding wind binaries. The X-ray spectrum is the best measurement tool for the hot postshock gas. By monitoring the changing of the the ...X-ray luminosity and column density along with the orbital phases, we derive the mass-loss rates of these stars.
•This is the first multicenter study of independent dose calculation for IMRT/VMAT.•477 clinically approved IMRT/VMAT prostate and head and neck plans were assessed.•This study will help each ...institution to establish action levels.•Feasible action levels can be set within ±5% for IMRT/VMAT.•Care is needed for MLC modeling for leaf gap and transmission factors.
No multi-institutional studies of computer-based independent dose calculation have addressed the discrepancies among radiotherapy treatment planning systems (TPSs) and the verification programs for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). We conducted a multi-institutional study to investigate whether ±5% is a reasonable action level for independent dose calculation for IMRT/VMAT.
In total, 477 IMRT/VMAT plans for prostate or head and neck (H&N) malignancies were retrospectively analyzed using a modified Clarkson-based commercial verification program. The doses from the TPSs and verification programs were compared using the mean ±1 standard deviation (SD).
In the TPS-calculated dose comparisons for prostate and H&N malignancies, the sliding window (SW) technique (−2.5 ± 1.8% and −5.3 ± 2.6%) showed greater negative systematic differences than the step-and-shoot (S&S) technique (−0.3 ± 2.2% and −0.8 ± 2.2%). The VMAT dose differences for prostate and H&N malignancies were 0.9 ± 1.8% and 1.1 ± 3.3%, respectively. The SDs were larger for the H&N plans than for the prostate plans in both IMRT and VMAT. Such plans including more out-of-field control points showed greater systematic differences and SDs.
This study will help individual institutions to establish an action level for agreement between primary calculations and verification for IMRT/VMAT. A local dose difference of ±5% at a point within the planning target volume (above −350 HU) may be a reasonable action level.
ABSTRACT
WR 102-1 was detected by Suzaku as a conspicuous point source in the 6.7 keV intensity map of the central region of the Milky Way. The source was suggested as a possible Wolf–Rayet binary ...based on its X-ray and infrared spectral characteristics. The iron line emission is expected to originate in the Wolf–Rayet star’s dynamic stellar wind when colliding the companion’s mild stellar wind. Here, we report the result of a long-term X-ray monitoring of WR 102-1 since 1998 using archival data of ASCA, XMM–Newton, Chandra, Suzaku, and Swift to reveal variations of the iron K-emission line and the circumstellar absorption. Consequently, we have detected significant redshifts of the iron K-emission line from the XMM–Newton observation in 2003 March and the Suzaku observation in 2006 September. Furthermore, when the redshift was observed, which suggests that the Wolf–Rayet star was in front of the companion star, the circumstellar absorption values were smaller than other periods. These results appear contrary to the expectation if the Wolf–Rayet’s stellar wind is spherically symmetric, but may be understood if the Wolf–Rayet star’s stellar wind is significantly distorted due to the rapid orbital motion near the periastron.
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