Cross-calibration of the XMM-Newton EPIC pn and MOS on-axis effective areas using 2XMM sources

Aims. We aim to examine the relative cross-calibration accuracy of the on-axis effective areas of the XMM-Newton EPIC pn and MOS instruments. Methods. Spectra from a sample of 46 bright, high-count, non-piled-up, isolated on-axis point sources are stacked together, and model residuals are examined to characterize the EPIC MOS-to-pn inter-calibration. Results. The MOS1-to-pn and MOS2-to-pn results are broadly very similar. The cameras show the closest agreement below 1 keV, with MOS excesses over pn of 0–2% (MOS1/pn) and 0–3% (MOS2/pn). Above 3 keV, the MOS/pn ratio is consistent with energy-independent (or only mildly increasing) excesses of 7–8% (MOS1/pn) and 5–8% (MOS2/pn). In addition, between 1–2 keV there is a “silicon bump” − an enhancement at a level of 2–4% (MOS1/pn) and 3–5% (MOS2/pn). Tests suggest that the methods employed here are stable and robust. Conclusions. The results presented here provide the most accurate cross-calibration of the effective areas of the XMM-Newton EPIC pn and MOS instruments to date. They suggest areas of further research where causes of the MOS-to-pn differences might be found, and allow the potential for corrections and possible rectification of the EPIC cameras to be made in the future

A high charge state coronal mass ejection seen through solar wind charge exchange emission as detected by XMM-Newton

We present the analysis of an observation by XMM–Newton that exhibits strongly variable, low-energy diffuse X-ray line emission. We reason that this emission is due to localized solar wind charge exchange (SWCX), originating from a passing cloud of plasma associated with a Coronal mass ejection (CME) interacting with neutrals in the Earth's exosphere. This case of SWCX exhibits a much richer emission-line spectrum in comparison with previous examples of geocoronal SWCX or in interplanetary space. We show that emission from O viii is very prominent in the SWCX spectrum. The observed flux from oxygen ions of Graphic is consistent with SWCX resulting from a passing CME. Highly ionized silicon is also observed in the spectrum, and the presence of highly charged iron is an additional spectral indicator that we are observing emission from a CME. We argue that this is the same event detected by the solar wind monitors Advanced Composition Explorer and Wind which measured an intense increase in the solar wind flux due to a CME that had been released from the Sun 2 d previous to the XMM–Newton observation

X-ray imaging of Kelvin-Helmholtz waves at the magnetopause

This paper simulates the Kelvin-Helmholtz wave (KHW)-induced X-ray emissions at the low-latitude magnetopause based on a global MHD code. A method is proposed to extract the KHW information from the X-ray intensity measured by a hypothetical X-ray telescope onboard a satellite assumed with a low Earth orbit. Specifically, the X-ray intensity at high latitude is subtracted from the intensity map as a background to highlight the role of KHW. Using this method, global features of KHW such as the vortex velocity, perturbation degree, spatial distribution, and temporal evolution could be evaluated from the X-ray intensity map. The validity of this method during intervals of solar wind disturbances is also verified. According to the simulation results, X-ray imaging of KHW is suggested as a promising observation technique to essentially “see” the large-scale configuration and evolution of KHW for the first time

Serendipitous active galactic nuclei in the XMM–Newton fields of Markarian 205 and QSO 0130−403

The X-ray spectra of serendipitously observed active galactic nuclei (AGN) in the XMM–Newton fields of Mrk 205 and QSO 0130−403 are analysed. The sample consists of 23 objects, none of which is detected at radio frequencies, with a median X-ray luminosity of ∼4 × 10[superscript 44] erg s[superscript −1] and redshifts ranging from ∼0.1 to just over 3. The mean photon index was found to be 1.89 ± 0.04. In contrast with past ASCA and ROSAT observations of high-redshift radio-loud quasars, we find little evidence for excess intrinsic absorption in these radio-quiet objects, with only three sources requiring a column density in excess of the Galactic value. Comparing the measured spectral indices over the redshift range, we also find there is no X-ray spectral evolution of quasi-stellar objects (QSOs) with time, up to redshift of 3. Within the sample there is no evidence for evolution of the optical to X-ray spectral index, α[subscript ox], with redshift, the mean value being −1.66 ± 0.04. However, upon comparing the values from the Bright Quasar Survey at low redshift (z 4), a slight steepening of αox is noted for the more distant objects. In most of the sources there is no significant requirement for a soft excess, although a weak thermal component (⩽ 10 per cent of L[subscript X]) cannot be excluded. There is an indication of spectral flattening (by ΔΓ = 0.2) at higher energies (>3 keV, QSO rest frame) for the sample as a whole. This is consistent with the presence of a Compton reflection component in these radio-quiet AGN, with the scattering medium (such as an accretion disc or molecular torus) occupying a solid angle of 2π sr to the X-ray source

New light on the X-ray spectrum of the Crab Nebula

XMM-Newton observations of the Crab provide new information on its integrated X-ray spectrum and the variation of the spectral form across the nebula. The Crab pulsar and its surrounding torus exhibit the hardest spectra with power-law indices of $\Gamma = 1.6$ and 1.8. The jet and outer reaches of the nebula are significantly softer with $\Gamma = 2.1$ and 2.3 respectively. For the whole nebula, the huge number of recorded counts allows a detailed examination of the soft X-ray absorption due to cool gas in the foreground of the Crab. Absorption edges due to oxygen and neon are clearly identified. Oxygen and iron in the interstellar medium are underabundant by a factor of $0.63 \pm 0.01$. The average $N_{\rm H}=3.45\pm0.02 10^{21}$ cm-2 and varies by less than $\pm11\%$ on a scale equal to or larger than 20 arcsec over the face of the nebula. These observations of the Crab provide an excellent demonstration of the power of the EPIC cameras on XMM-Newton for spatial, spectral and timing studies

Wide field-of-view soft X-ray imaging for solar wind-magnetosphere interactions

Soft X-ray imagers can be used to study the mesoscale and macroscale density structures that occur whenever and wherever the solar wind encounters neutral atoms at comets, the Moon, and both magnetized and unmagnetized planets. Charge exchange between high charge state solar wind ions and exospheric neutrals results in the isotropic emission of soft X-ray photons with energies from 0.1 to 2.0 keV. At Earth, this process occurs primarily within the magnetosheath and cusps. Through providing a global view, wide field-of-view imaging can determine the significance of the various proposed solar wind-magnetosphere interaction mechanisms by evaluating their global extent and occurrence patterns. A summary of wide field-of-view (several to tens of degrees) soft X-ray imaging is provided including slumped micropore microchannel reflectors, simulated images, and recent flight results