Magnetic domain observation of hydrogenation disproportionation desorption recombination processed Nd－Fe－B powder with a high-resolution Kerr microscope using ultraviolet light

A Kerr microscope that uses ultraviolet (UV) light for high-resolution domain observation was built, and the domain structure and magnetization process of hydrogenation disproportionation desorption recombination (HDDR) powder were examined. The UV Kerr microscope could observe nanometer-sized domain patterns. Applying a dc field of 1.0 kOe to HDDR powder at a desorption recombination (DR) time of 12 min produced abrupt wall motion. The pinning force exerted by the grain boundaries is inadequate for producing high coercivity because the Nd-rich phase layers along these boundaries are absent at a DR time of 12 min. For HDDR powder at a DR time greater than 14 min, changing the magnetic field by up to 1.0 kOe produced no observable wall motion. It follows that the high coercivity of HDDR powder is due to domain wall pinning at the grain boundaries

A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia Event with Circumstellar Interaction

We present initial results of a 750 ks Chandra observation of the remnant of Kepler's supernova of AD 1604. The strength and prominence of iron emission, together with the absence of O-rich ejecta, demonstrate that Kepler resulted from a thermonuclear supernova, even though evidence for circumstellar interaction is also strong. We have analyzed spectra of over 100 small regions, and find that they fall into three classes. (1) The vast majority show Fe L emission between 0.7 and 1 keV and Si and S K alpha emission; we associate these with shocked ejecta. A few of these are found at or beyond the mean blast wave radius. (2) A very few regions show solar O/Fe abundance rations; these we associate with shocked circumstellar medium (CSM). Otherwise O is scarce. (3) A few regions are dominated by continuum, probably synchrotron radiation. Finally, we find no central point source, with a limit about 100 times fainter than the central object in Cas A. The evidence that the blast wave is interacting with CSM may indicate a Ia explosion in a more massive progenitor.Comment: Accepted by ApJ Letter

Supernova Remnants in the Magellanic Clouds. VI. The DEML316 Supernova Remnants

The DEML316 system contains two shells, both with the characteristic signatures of supernova remnants (SNRs). We analyze Chandra and XMM-Newton data for DEML316, investigating its spatial and spectral X-ray features. Our Chandra observations resolve the structure of the northeastern SNR (Shell A) as a bright inner ring and a set of "arcs" surrounded by fainter diffuse emission. The spectrum is well fit by a thermal plasma model with temperature ~1.4 keV; we do not find significant spectral differences for different regions of this SNR. The southwestern SNR (Shell B) exhibits an irregular X-ray outline, with a brighter interior ring of emission including a bright knot of emission. Overall the emission of the SNR is well described by a thermal plasma of temperature ~0.6 keV. The Bright Knot, however, is spectrally distinct from the rest of the SNR, requiring the addition of a high-energy spectral component consistent with a power-law spectrum of photon index 1.6--1.8. We confirm the findings of Nishiuchi et al. (2001) that the spectra of these shells are notably different, with Shell A requiring a high iron abundance for a good spectral fit, implying a Type Ia origin. We further explicitly compare abundance ratios to model predictions for Type Ia and Type II supernovae. The low ratios for Shell A (O/Fe of 1.5 and Ne/Fe of 0.2) and the high ratios for Shell B (O/Fe of 30--130 and Ne/Fe of 8--16) are consistent with Type Ia and Type II origins, respectively. The difference between the SNR progenitor types casts some doubt on the suggestion that these SNRs are interacting with one another.Comment: Accepted for ApJ v. 635 (December issue

The intriguing nature of the high energy gamma ray source XSSJ12270-4859

The nature of the hard X-ray source XSSJ12270-4859 is still unclear though it was claimed to be a magnetic Cataclysmic Variable. We here present a broad-band X-ray and gamma ray study based on a recent XMM-Newton observation and archival INTEGRAL and RXTE data. From the Fermi/LAT 1-year point source catalogue, we tentatively associate XSSJ12270-4859 with 1FGLJ1227.9-4852, a source of high energy gamma rays with emission up to 10GeV. We complement the study with UV photometry from XMM-Newton and ground-based optical and near-IR photometry. The X-ray emission is highly variable showing flares and intensity dips. The X-ray flares consist of flare-dip pairs. Flares are also detected in the UV range but not the dips. Aperiodic dipping behaviour is also observed during X-ray quiescence but not in the UV. The 0.2-100keV spectrum is featureless and described by a power law model with Gamma=1.7. The 100MeV-10GeV spectrum is instead represented by a power law index of 2.45. The luminosity ratio between 0.1-100GeV and 0.2--100keV is ~0.8, hence the GeV emission is a significant component of the total energy output. Furthermore, the X-ray spectrum does not greatly change during flares, quiescence and the dips seen in quiescence but it hardens during the post-flare dips. Optical photometry reveals a period of 4.32hr likely related to the binary orbit. Near-IR, possibly ellipsoidal, variations are detected. Large amplitude variability on shorter (tens mins) timescales are found to be non-periodic. The observed variability at all wavelengths and the spectral characteristics strongly favour a low-mass atypical low-luminosity X-ray binary and are against a Cataclysmic Variable nature. The association with a Fermi/LAT high energy gamma ray source further strengths this interpretation.Comment: 12 pages, 11 figures, 3 tables; Accepted for publication in Astronomy & Astrophysics Main Journ

Observational Constraints on Superbubble X-ray Energy Budgets

The hot, X-ray-emitting gas in superbubbles imparts energy and enriched material to the interstellar medium (ISM) and generates the hot ionized medium, the ISM's high-temperature component. The evolution of superbubble energy budgets is not well understood, however, and the processes responsible for enhanced X-ray emission in superbubbles remain a matter of debate. We present Chandra ACIS-S observations of two X-ray-bright superbubbles in the Large Magellanic Cloud (LMC), DEM L50 (N186) and DEM L152 (N44), with an emphasis on disentangling the true superbubble X-ray emission from non-related diffuse emission and determining the spatial origin and spectral variation of the X-ray emission. An examination of the superbubble energy budgets shows that on the order of 50% of the X-ray emission comes from regions associated with supernova remnant (SNR) impacts. We find some evidence of mass-loading due to swept-up clouds and metallicity enrichment, but neither mechanism provides a significant contribution to the X-ray luminosities. We also find that one of the superbubbles, DEM L50, is likely not in collisional ionization equilibrium. We compare our observations to the predictions of the standard Weaver et al. model and to 1-D hydrodynamic simulations including cavity supernova impacts on the shell walls. Our observations show that mass-loading due to thermal evaporation from the shell walls and SNR impacts are the dominant source of enhanced X-ray luminosities in superbubbles. These two processes should affect most superbubbles, and their contribution to the X-ray luminosity must be considered when determining the energy available for transport to the ISM.Comment: 25 pages, 11 figures, accepted for publication in Ap

Local Probe Isomerization in a One-Dimensional Molecular Array

Synthesis of one-dimensional molecular arrays with tailored stereoisomers is challenging yet has a great potential for application in molecular opto-, electronic- and magnetic-devices, where the local array structure plays a decisive role in the functional properties. Here, we demonstrate construction and characterization of dehydroazulene isomer and diradical units in three-dimensional organometallic compounds on Ag(111) with a combination of low-temperature scanning tunneling microscopy and density functional theory calculations. Tip-induced voltage pulses firstly result in the formation of a diradical species via successive homolytic fission of two C-Br bonds in the naphthyl groups, which are subsequently transformed into chiral dehydroazulene moieties. The delicate balance of the reaction rates among the diradical and two stereoisomers, arising from an in-line configuration of tip and molecular unit, allows directional azulene-to-azulene and azulene-to-diradical local probe isomerization in a controlled manner. Furthermore, we found that the diradical moiety hosts an open-shell singlet with antiferromagnetic coupling between the unpaired electrons, which can undergo an inelastic spin transition of 91 meV to the ferromagnetically coupled triplet state

A Study of the Populations of X-ray Sources in the Small Magellanic Cloud with ASCA

The Advanced Satellite for Cosmology and Astrophysics (ASCA) has made multiple observations of the Small Magellanic Cloud (SMC). X-ray mosaic images in the soft (0.7--2.0 keV) and hard (2.0--7.0 keV) bands are separately constructed, and the latter provides the first hard X-ray view of the SMC. We extract 39 sources from the two-band images with a criterion of S/N>5, and conduct timing and spectral analyses for all of these sources. Coherent pulsations are detected from 12 X-ray sources; five of which are new discoveries. Most of the 12 X-ray pulsars are found to exhibit long-term flux variabilities, hence they are likely to be X-ray binary pulsars (XBPs). On the other hand, we classify four supernova remnants (SNRs) as thermal SNRs, because their spectra exhibit emission lines from highly ionized atoms. We find that XBPs and thermal SNRs in the SMC can be clearly separated by their hardness ratio (the ratio of the count rate between the hard and soft bands). Using this empirical grouping, we find many XBP candidates in the SMC, although no pulsations have yet been detected from these sources. Possible implications on the star-formation history and evolution of the SMC are presented by a comparison of the source populations in the SMC and our Galaxy.Comment: 11 pages, 39 Figures, to be published in ApJ Supplement. Tables (body and figures also) are available at http://www-cr.scphys.kyoto-u.ac.jp/member/jun/job

X-ray emission from stainless steel foils irradiated by femtosecond petawatt laser pulses

We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases as ∼ I 4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7-2.1 Å, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.21021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target

Xanthogranuloma of the intrasellar region presenting in pituitary dysfunction: a case report

<p>Abstract</p> <p>Introduction</p> <p>Differentiation of cystic mass lesions of the sellar and parasellar regions may pose a diagnostic dilemma for physicians, neurosurgeons, radiologists and pathologists involved in treating patients with these entities. A considerable number of tumors previously identified as craniopharyngiomas may, in fact, have been xanthogranulomas. We report a case of pituitary dysfunction caused by xanthogranuloma of the intrasellar region.</p> <p>Case presentation</p> <p>A 47-year-old man of Japanese descent presented to our institution with a tumor located exclusively in the intrasellar region which manifested as severe hypopituitarism. MRI revealed a clearly defined intrasellar mass that was heterogeneously hyperintense on T1-weighted images and markedly hypointense on T2-weighted images. We preoperatively diagnosed the patient with Rathke's cleft cyst or non-functioning pituitary adenoma. Although the tumor was completely removed using a transsphenoidal approach, the improvement of the patient's endocrine function was marginal, and continued endocrine replacement therapy was needed. Postoperatively, a histological examination revealed the tumor to be a xanthogranuloma of the intrasellar region. His visual field defects and headache improved.</p> <p>Conclusion</p> <p>Because diagnosis depends on surgical intervention and xanthogranulomas of the intrasellar region are very rare, the natural history of xanthogranuloma is still unknown. Therefore, this entity is difficult to diagnose preoperatively. We suggest that xanthogranuloma should be included in the differential diagnosis, even in the case of sellar lesions, to formulate appropriate postoperative management and improve endocrine outcomes.</p