Discovery Of Extended X-ray Emission Research Articles

Discovery of Extended X-Ray Emission from an Unidentified TeV Source, HESS J1614$-$518, Using the Suzaku Satellite

Abstract We report Suzaku results concerning HESS J1614$-$518, which is the brightest extended TeV gamma-ray source discovered in the Galactic plane survey conducted using the H.E.S.S. telescope. We discovered three X-ray objects in the field of view of the X-ray Imaging Spectrometer, which were designated as Suzaku J1614$-$5141 (src A), Suzaku J1614$-$5152 (src B), and Suzaku J1614$-$5148 (src C). Src A is an extended source located at the peak position of HESS J1614$-$518, and is therefore a plausible counterpart to HESS J1614$-$518. The X-ray flux in the 2-10keV band is 5$\times 10^{-13}$ergs$^{-1}$cm$^{-2}$, which is an order of magnitude smaller than the TeV flux. The photon index is 1.7, which is smaller than the canonical value of synchrotron emissions from high-energy electrons found in some supernova remnants. These findings present a challenge to models in which the origin of TeV emission is inverse Compton scattering of the cosmic microwave background by accelerated electrons that emit X-rays via synchrotron emission. Src B is located at a relatively dim region in the TeV band image; however, its hydrogen column density is the same as that of src A. Therefore, src B may also be physically related to HESS J1614$-$518. Src C is a foreground late-type B star. We also discovered soft extended X-ray emission near HESS J1614$-$518.

Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the [ITAL]Chandra X-Ray Observatory[/ITAL

We report the discovery of X-ray emission from NGC 7027, a prototypical object for the study of the formation and evolution of planetary nebulae. Observations with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-Ray Observatory show that the X-ray emission from NGC 7027 is extended and is bipolar in morphology. The ACIS spectrum displays strong emission from highly ionized Ne and weaker emission features, which we attribute to O, Mg, and Si. Model fits to this spectrum suggest a characteristic temperature TX ~ 3 × 106 K and an intrinsic (unabsorbed) X-ray luminosity of LX ~ 1.3 × 1032 ergs s-1. The intranebular absorption of X-ray emission is highly nonuniform, but the modeling indicates an average column density NH ~ 6 × 1021 cm-2, consistent with previous measurements of relatively large visual extinction within the nebula. We suggest that the X-ray emission from NGC 7027 is or was generated by a hitherto undetected fast wind from the central star of NGC 7027 or from a companion to this star. Chandra's detection of extended, high-temperature X-ray emission from BD +30°3639, NGC 6543, and now NGC 7027 suggests that such emission is a common feature of young planetary nebulae.