X-ray Development of the Classical Nova V2672 Ophiuchi with Suzaku

We report the Suzaku detection of a rapid flare-like X-ray flux amplification early in the development of the classical nova V2672 Ophiuchi. Two target-of-opportunity ~25 ks X-ray observations were made 12 and 22 days after the outburst. The flux amplification was found in the latter half of day 12. Time-sliced spectra are characterized by a growing supersoft excess with edge-like structures and a relatively stable optically-thin thermal component with Ka emission lines from highly ionized Si. The observed spectral evolution is consistent with a model that has a time development of circumstellar absorption, for which we obtain the decline rate of ~10-40 % in a time scale of 0.2 d on day 12. Such a rapid drop of absorption and short-term flux variability on day 12 suggest inhomogeneous ejecta with dense blobs/holes in the line of sight. Then on day 22 the fluxes of both supersoft and thin-thermal plasma components become significantly fainter. Based on the serendipitous results we discuss the nature of this source in the context of both short- and long-term X-ray behavior.Comment: To appear in PASJ; 9 pages, 5 figures, 2 table

Time domain Einstein-Podolsky-Rosen correlation

We experimentally demonstrate creation and characterization of Einstein-Podolsky-Rosen (EPR) correlation between optical beams in the time domain. The correlated beams are created with two independent continuous-wave optical parametric oscillators and a half beam splitter. We define temporal modes using a square temporal filter with duration $T$ and make time-resolved measurement on the generated state. We observe the correlations between the relevant conjugate variables in time domain which correspond to the EPR correlation. Our scheme is extendable to continuous variable quantum teleportation of a non-Gaussian state defined in the time domain such as a Schr\"odinger cat-like state.Comment: 4 pages, 4 figure

Molecular transistor coupled to phonons and Luttinger-liquid leads

We study the effects of electron-phonon interactions on the transport properties of a molecular quantum dot coupled to two Luttinger-liquid leads. In particular, we investigate the effects on the steady state current and DC noise characteristics. We consider both equilibrated and unequilibrated on-dot phonons. The density matrix formalism is applied in the high temperature approximation and the resulting semi-classical rate equation is numerically solved for various strengths of electron-electron interactions in the leads and electron-phonon coupling. The current and the noise are in general smeared out and suppressed due to intralead electron interaction. On the other hand, the Fano factor, which measures the noise normalized by the current, is more enhanced as the intralead interaction becomes stronger. As the electron-phonon coupling becomes greater than order one, the Fano factor exhibits super-Poissonian behaviour.Comment: 11 pages, 11 figure

Long period polytype boundaries in silicon carbide

A significant gap in our understanding of polytypism exists, caused partly by the lack of experimental data on the spatial distribution of polytype coalescence and knowledge of the regions between adjoining polytypes. Few observations, Takei & Francombe (1967) apart, of the relative location of different polytypes have been reported. A phenomenological description of the boundaries, exact position of one-dimensional disorder (1DD) and long period polytypes (LPP’s) has been made possible by synchrotron X-ray diffraction topography (XRDT)

Anti-damping spin transfer torque through epitaxial Nickel oxide

We prepare the high quality epitaxial MgO(001)[100]/Pt(001)[100]/NiO(001)[100]/FeNi/SiO2 films to investigate the spin transport in the NiO antiferromagnetic insulator. The ferromagnetic resonance measurements of the FeNi under a spin current injection from the Pt by the spin Hall effect revealed the change of the ferromagnetic resonance linewidth depending on the amount of the spin current injection. The results can be interpreted that there is an angular momentum transfer through the NiO. A high efficient angular momentum transfer we observed in the epitaxial NiO can be attributed to the well-defined orientation of the antiferromagnetic moments and the spin quantization axis of the injected spin current

O and Ne K absorption edge structures and interstellar abundance towards Cyg X-2

We have studied the O and Ne absorption features in the X-ray spectrum of Cyg X-2 observed with the Chandra LETG. The O absorption edge is represented by the sum of three absorption-edge components within the limit of the energy resolution and the photon counting statistics. Two of them are due to the atomic O; their energies correspond to two distinct spin states of photo-ionized O atoms. The remaining edge component is considered to represent compound forms of oxide dust grains. Since Cyg X-2 is about 1.4 kpc above the galactic disk, the H column densities can be determined by radio (21 cm and CO emission line) and H alpha observations with relatively small uncertainties. Thus the O abundance relative to H can be determined from the absorption edges. We found that the dust scattering can affect the apparent depth of the edge of the compound forms. We determined the amplitude of the effect, which we consider is the largest possible correction factor. The ratio of column densities of O in atomic to compound forms and the O total abundance were respectively determined to be in the range 1.7^{+3.0}_{-0.9} to 2.8^{+5.1}_{-1.5} (ratio), and 0.63 +/- 0.12 solar to 0.74 +/- 0.14 solar (total), taking into account the uncertainties in the dust-scattering correction and in the ionized H column density. We also determined the Ne abundance from the absorption edge to be 0.75 +/- 0.20 solar. These abundance values are smaller than the widely-used solar values but consistent with the latest estimates of solar abundance.Comment: 20 pages, 3 figures, AASTeX format. Accepted for publication in Ap

Nonequilibrium quantum criticality in open electronic systems

A theory is presented of quantum criticality in open (coupled to reservoirs) itinerant electron magnets, with nonequilibrium drive provided by current flow across the system. Both departures from equilibrium at conventional (equilibrium) quantum critical points and the physics of phase transitions induced by the nonequilibrium drive are treated. Nonequilibrium-induced phase transitions are found to have the same leading critical behavior as conventional thermal phase transitions.Comment: 5 pages, 1 figur

Suzaku Detection of Super-hard X-ray Emission from the Classical Nova V2491 Cygni

We report the detection of super-hard (>10 keV) X-ray emission extending up to 70 keV from the classical nova V2491 Cygni using the Suzaku observatory. We conducted two ~20 ks target-of-opportunity observations 9 and 29 days after the outburst on 2008 April 11, yielding wide energy range spectra by combining the X-ray Imaging Spectrometer and the Hard X-ray Detector. On day 9, a spectrum was obtained at 1.0-70 keV with the Fe XXV K\alpha line feature and a very flat continuum, which is explained by thermal plasma with a 3 keV temperature and power-law emission with a photon index of 0.1 attenuated by a heavy extinction of 1.4x10^{23} cm^{-2}. The 15-70 keV luminosity at 10.5 kpc is 6x10^{35} ergs s^{-1}. The super-hard emission was not present on day 29. This is the highest energy at which X-rays have been detected from a classical nova. We argue a non-thermal origin for the emission, which suggests the presence of accelerated charged particles in the nova explosion.Comment: Accepted for publication in ApJL (4 pages, 3 figures

Confirming the Detection of an Intergalactic X-ray Absorber Toward PKS 2155-304

We present new observations on PKS 2155-304 with the Chandra Low Energy Transmission Grating Spectrometer (LETG), using the Advanced CCD Imaging Spectrometer (ACIS). We confirm the detection of an absorption line plausibly identified as OVIII Ly-alpha from the warm-hot intergalactic medium associated with a small group of galaxies along the line of sight, as originally reported by Fang et al. 2002 (here after FANG02). Combining the previous observations in FANG02 and five new, long observations on the same target, we increase the total exposure time by a factor of three, and the total counts per resolution element by a factor of five. The measured line equivalent width is smaller than that observed in FANG02, but still consistent at 90% confidence. We also analyze the XMM-Newton observations on the same target, as well as observations using the Chandra LETG and the High Resolution Camera (HRC) combination. These observations have been used to challenge our reported detection. While no line is seen in either the XMM-Newton and the Chandra LETG+HRC data, we find that our result is consistent with the upper limits from both data sets. We attribute the non-detection to (1) higher quality of the Chandra LETG+ACIS spectrum, and (2) the rather extended wings of the line spread functions of both the XMM RGS and the Chandra LETG+HRC. We discuss the implication of our observation on the temperature and density of the absorber. We also confirm the detection of z ~ 0 OVII absorption and, comparing with previous Chandra analysis, we obtain much tighter constraints on the line properties.Comment: 10 pages, 8 figures, accepted for publication in Ap