Search Publications
Is the soft excess in active galactic nuclei real?
Done, Chris; Gierliński, Marek
We systematically analyse all publicly available XMM-Newton spectra of radio-quiet PG quasars. The soft X-ray excess in these objects is well modelled by an additional, cool, Compton scattering region. However, the remarkably constant temperature derived for this component over the whole sample requires a puzzling fine tuning of the parameters. In…
X-ray astronomy of stellar coronae
Güdel, Manuel
X-ray emission from stars in the cool half of the Hertzsprung-Russell diagram is generally attributed to the presence of a magnetic corona that contains plasma at temperatures exceeding 1 million K. Coronae are ubiquitous among these stars, yet many fundamental mechanisms operating in their magnetic fields still elude an interpretation through a d…
Comparing the temperatures of galaxy clusters from hydrodynamical N-body simulations to Chandra and XMM-Newton observations
Rasia, E.; Mazzotta, P.; Moscardini, L. +1 more
Theoretical studies of the physical processes guiding the formation and evolution of galaxies and galaxy clusters in the X-ray region are mainly based on the results of numerical hydrodynamical N-body simulations, which in turn are often directly compared with X-ray observations. Although trivial in principle, these comparisons are not always simp…
The 2-8 keV cosmic X-ray background spectrum as observed with XMM-Newton
Molendi, S.; De Luca, A.
We have measured the spectrum of the Cosmic X-ray Background (CXB) in the 2-8 keV range with the high throughput EPIC/MOS instrument onboard XMM-Newton. A large sample of high galactic latitude observations was used, covering a total solid angle of 5.5 square degrees. Our study is based on a very careful characterization and subtraction of the ins…
Combined long and short time-scale X-ray variability of NGC 4051 with RXTE and XMM-Newton
Papadakis, I. E.; Page, M. J.; Uttley, P. +2 more
We present a comprehensive examination of the X-ray variability of the narrow-line Seyfert 1 (NLS1) galaxy NGC 4051, one of the most variable active galactic nuclei (AGN) in the sky. We combine over 6.5 years of frequent monitoring observations by RXTE with a >100-ks continuous observation by XMM-Newton and so present an overall 2-10 keV power …
Photoionization Modeling and the K Lines of Iron
Kallman, T. R.; Krolik, J. H.; Bautista, M. A. +2 more
We calculate the efficiency of iron K line emission and iron K absorption in photoionized models using a new set of atomic data. These data are more comprehensive than those previously applied to the modeling of iron K lines from photoionized gases and allow us to systematically examine the behavior of the properties of line emission and absorptio…
Probing turbulence in the Coma galaxy cluster
Finoguenov, A.; Böhringer, H.; Miniati, F. +2 more
Spatially-resolved gas pressure maps of the Coma galaxy cluster are obtained from a mosaic of XMM-Newton observations in the scale range between a resolution of 20 kpc and an extent of 2.8 Mpc. A Fourier analysis of the data reveals the presence of a scale-invariant pressure fluctuation spectrum in the range between 40 and 90 kpc and is found to b…
An Extended Scheme for Fitting X-Ray Data with Accretion Disk Spectra in the Strong Gravity Regime
Yaqoob, T.; Dovčiak, M.; Karas, V.
Accreting black holes are believed to emit X-rays, which then mediate information about strong gravity in the vicinity of the emission region. We report on a set of new routines for the XSPEC package for analyzing X-ray spectra of black-hole accretion disks. The new computational tool significantly extends the capabilities of the currently availab…
XMM-Newton Observation of Solar Wind Charge Exchange Emission
Kuntz, K. D.; Snowden, S. L.; Collier, M. R.
We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by probable C VI lines at 0.37 and 0.46 keV, an O VII line at 0.56 keV, O VIII lines at 0.65 and ~0.8 keV, Ne IX lines at ~0.92 keV, and Mg XI lines at ~1.35 keV. This spectrum is consistent with that expected from charge exchange em…
XMM-Newton EPIC observations of 21 low-redshift PG quasars
Porquet, D.; Reeves, J. N.; Brinkmann, W. +1 more
We present an X-ray spectral analysis of 21 low redshift quasars observed with XMM-Newton EPIC. All the sources are Palomar Green quasars with redshifts between 0.05 and 0.4 and have low Galactic absorption along the line-of-sight. A large majority of quasars in the sample (19/21) exhibit a significant soft excess below ∼1-1.5 keV, whilst two obje…