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Register a new userCH Cyg X-ray Jet Activity and Multi-component Structures
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In this paper we report detection of multiple component structures in a Chandra X-ray image obtained in March 2001 of the nearby symbiotic interacting binary system CH Cyg. These components include a compact central source, an arc-like structure or a loop extending to 1.5 (400 AU) from the central source associated with the 1997 jet activity, and possibly a newly formed jet extending to about 150 AU from the central source. The structures are also visible in VLA and HST images obtained close in time to the Chandra observations. The emission from the loop is consistent with optically thin thermal X-ray emission originating from a shock resulting from interaction of the jet ejecta with the dense circumbinary material. The emission from the central source originates within less then 50 AU region, and is likely associated with the accretion disk around the white dwarf. CH Cyg is only the second symbiotic system with jet activity detected at X-ray wavelengths, and the Chandra high-angular resolution image, combined with the VLA and HST images, provides the closest view of the region of jet formation and interaction with the circumbinary material in a symbiotic binary.
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We have reanalysed the ASCA X-ray spectrum of the bright symbiotic star CH Cyg, which exhibits apparently distinct hard and soft X-ray components. Our analysis demonstrates that the soft X-ray emission can be interpreted as scattering of the hard X-ray component in a photo-ionised medium surrounding the white dwarf. This is in contrast to previous analyses in which the soft X-ray emission was fitted separately and assumed to arise independently of the hard X-ray component. We note the striking similarity between the X-ray spectra of CH Cyg and Seyfert 2 galaxies, which are also believed to exhibit scattering in a photo-ionised medium.
X-ray shots of Cyg X-1 in different energy bands and spectral states have been studied with PCA/RXTE observations. The detailed shot structure is obtained by superposing many shots with one millisecond time bin through aligning their peaks with an improved algorithm. In general, the shots are composed of a slow rise and fast decay. The shot structures in the different states are different. The duration of shot in the high state is shorter than that in the low and transition states. The shot profile in the high energy band is more asymmetric and narrower than that in the low energy band. The average hardness of shot is lower than that of steady emission in the transition and low states but higher than that in the high state. The time lags between the shots in higher and lower energy bands have been found in the different states. In transition states, the time lag is the largest among the different states of Cyg X-1, and it is the smallest in the low state. The implications of the observed shot features for shot models are discussed.
Here we present quasi-simultaneous observations of the flickering of the symbiotic binary star CH Cyg in U, B and V bands. We calculate the flickering source parameters and discuss the possible reason for the flickering cessation in the period 2010-2013.
We report on observations of NGC1068 with NuSTAR, which provide the best constraints to date on its $>10$~keV spectral shape. We find no strong variability over the past two decades, consistent with its Compton-thick AGN classification. The combined NuSTAR, Chandra, XMM-Newton, and Swift-BAT spectral dataset offers new insights into the complex reflected emission. The critical combination of the high signal-to-noise NuSTAR data and a spatial decomposition with Chandra allow us to break several model degeneracies and greatly aid physical interpretation. When modeled as a monolithic (i.e., a single N_H) reflector, none of the common Compton-reflection models are able to match the neutral fluorescence lines and broad spectral shape of the Compton reflection. A multi-component reflector with three distinct column densities (e.g., N_H~1.5e23, 5e24, and 1e25 cm^{-2}) provides a more reasonable fit to the spectral lines and Compton hump, with near-solar Fe abundances. In this model, the higher N_H components provide the bulk of the Compton hump flux while the lower N_H component produces much of the line emission, effectively decoupling two key features of Compton reflection. We note that ~30% of the neutral Fe Kalpha line flux arises from >2 (~140 pc), implying that a significant fraction of the <10 keV reflected component arises from regions well outside of a parsec-scale torus. These results likely have ramifications for the interpretation of poorer signal-to-noise observations and/or more distant objects [Abridged].
The photospheric abundances for the cool component of the symbiotic star CH Cyg were calculated for the first time using high-resolution near-infrared spectra and the method of of standard LTE analysis and atmospheric models. The iron abundance for CH Cyg was found to be solar, [Fe/H] = 0.0+/-0.19. The atmospheric parameters and metallicity for CH Cyg are found to be approximately equal to those for nearby field M7 giants. The calculated [C/H] = -0.15, [N/H] = +0.16, [O/H] = -0.07, and the isotopic ratios of 12C/13C and 16O/17O are close to the mean values for single M giants that have experienced the first dredge-up. A reasonable explanation for the absence of barium star-like chemical peculiarities seems to be the high metallicity of CH Cyg. The emission line technique was explored for estimating CNO ratios in the wind of the giant.
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