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Register a new userHigh spatial resolution X-ray spectroscopy of SNR Cassiopeia A with {sl Chandra}
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We present high spatial resolution X-ray spectroscopy of supernova remnant Cassiopeia A with the {sl Chandra} observations. The X-ray emitting region of this remnant was divided into 38 $times$ 34 pixels with a scale of 10$arcsec$ $times$ 10$arcsec$ each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. With the spectral analysis results we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances for Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obviously jet structures, while Fe doesnt follow the jet but seems to be distributed perpendicular to it. In the range of about two orders of magnitude, the abundances of Si, S and Ca show tight correlations between each other, suggesting them to be ejecta from explosive O-burning and incomplete Si-burning. Meanwhile, Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when Si abundance is lower than 3 solar abundances, but a negative correlation appears when the Si abundance is higher. We suggest that such a two phase correlation is the results of different ways in which Fe is synthesized.
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We present high spatial resolution X-ray spectroscopy of supernova remnant G292.0+1.8 with the {sl Chandra} observations. The X-ray emitting region of this remnant was divided into 25 $times$ 25 pixels with a scale of 20$arcsec$ $times$ 20$arcsec$ each. Spectra of 324 pixels were created and fitted with an absorbed one component non-equilibrium ionization model. With the spectral analysis results we obtained maps of absorbing column density, temperature, ionization age, and the abundances for O, Ne, Mg, Si, S, and Fe. The abundances of O, Ne and Mg show tight correlations between each other in the range of about two orders of magnitude, suggesting them all from explosive C/Ne burning. Meanwhile, the abundances of Si and S are also well correlated, indicating them to be the ashes of explosive explosive O-burning or incomplete Si-burbing. The Fe emission lines are not prominent among the whole remnant, and its abundance are significantly deduced, indicating that the reverse shock may have not propagated to the Fe-rich ejecta. Based on relative abundances of O, Ne, Mg, Si and Fe to Si, we suggest a progenitor mass of $25-30 M_{odot}$ for this remnant.
Results from a 60 ks Chandra HETGS observation of the nearby Seyfert 2 Circinus are presented. The spectrum shows a wealth of emission lines at both soft and hard X-rays, including lines of Ne, Mg, Si, S, Ar, Ca, and Fe, and a prominent Fe Kalpha line at 6.4 keV. We identify several of the He-like components and measure several of the Lyman lines of the H-like ions. The lines profiles are unresolved at the limited signal-to-noise ratio of the data. Our analysis of the zeroth-order image in a companion paper constrains the size of the emission region to be 20-60 pc, suggesting that emission within this volume is almost entirely due to the reprocessing of the obscured central source. Here we show that a model containing two distinct components can reproduce almost all the observed properties of this gas. The ionized component can explain the observed intensities of the ionized species, assuming twice-solar composition and an N propto r^{-1.5} density distribution. The neutral component is highly concentrated, well within the 0.8arcsec point source, and is responsible for almost all of the observed Kalpha (6.4 keV) emission. Circinus seems to be different than Mkn~3 in terms of its gas distribution.
Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were carried out. K-shell transition lines from highly ionized ions of various elements were detected, including Chromium (Cr-Kalpha at 5.61 keV). The X-ray continuum spectra were modeled in the 3.4--40 keV band, summed over the entire remnant, and were fitted with a simplest combination of the thermal bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits with this assumption indicate that the continuum emission is likely to be dominated by the non-thermal emission with a cut-off energy at > 1 keV. The thermal-to-nonthermal fraction of the continuum flux in the 4-10 keV band is best estimated as ~0.1. Non-thermal-dominated continuum images in the 4--14 keV band were made. The peak of the non-thermal X-rays appears at the western part. The peak position of the TeV gamma-rays measured with HEGRA and MAGIC is also shifted at the western part with the 1-sigma confidence. Since the location of the X-ray continuum emission was known to be presumably identified with the reverse shock region, the possible keV-TeV correlations give a hint that the accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements in the reverse shock region.
We present a preliminary analysis of the 1--10 keV spectrum of the massive X-ray binary Cyg X-3, obtained with the High Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory. The source reveals a richly detailed discrete emission spectrum, with clear signatures of photoionization-driven excitation. Among the spectroscopic novelties in the data are the first astrophysical detections of a number of He-like triplets (Si, S, Ar) with emission line ratios characteristic of photoionization equilibrium, fully resolved narrow radiative recombination continua of Mg, Si, and S, the presence of the H-like Fe Balmer series, and a clear detection of a ~ 800 km/s large scale velocity field, as well as a ~1500 km/s FWHM Doppler broadening in the source. We briefly touch on the implications of these findings for the structure of the Wolf-Rayet wind.
Context : The peculiar hot star Theta Car in the open cluster IC2602 is a blue straggler as well as a single-line binary of short period (2.2d). Aims : Its high-energy properties are not well known, though X-rays can provide useful constraints on the energetic processes at work in binaries as well as in peculiar, single objects. Methods : We present the analysis of a 50ks exposure taken with the XMM-Newton observatory. It provides medium as well as high-resolution spectroscopy. Results : Our high-resolution spectroscopy analysis reveals a very soft spectrum with multiple temperature components (1--6MK) and an X-ray flux slightly below the `canonical value (log[L_X(0.1-10.)/L_{BOL}] ~ -7). The X-ray lines appear surprisingly narrow and unshifted, reminiscent of those of beta Cru and tau Sco. Their relative intensities confirm the anomalous abundances detected in the optical domain (C strongly depleted, N strongly enriched, O slightly depleted). In addition, the X-ray data favor a slight depletion in neon and iron, but they are less conclusive for the magnesium abundance (solar-like?). While no significant changes occur during the XMM-Newton observation, variability in the X-ray domain is detected on the long-term range. The formation radius of the X-ray emission is loosely constrained to <5 R_sol, which allows for a range of models (wind-shock, corona, magnetic confinement,...) though not all of them can be reconciled with the softness of the spectrum and the narrowness of the lines.
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