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Register a new userA deep X-ray observation of M82 with XMM-Newton
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We report on the analysis of a deep (100 ks) observation of the starburst galaxy M82 with the EPIC and RGS instruments on board the X-ray telescope XMM-Newton. The broad-band (0.5-10 keV) emission is due to at least three spectral components: i) continuum emission from point sources; ii) thermal plasma emission from hot gas; iii) charge exchange emission from neutral metals (Mg and Si). The plasma emission has a double-peaked differential emission measure, with the peaks at ~0.5 keV and ~7 keV. Spatially resolved spectroscopy has shown that the chemical absolute abundances are not uniformly distributed in the outflow, but are larger in the outskirts and smaller close to the galaxy centre. The abundance ratios also show spatial variations. The X-ray derived Oxygen abundance is lower than that measured in the atmospheres of red supergiant stars, leading to the hypothesis that a significant fraction of Oxygen ions have already cooled off and no longer emit at energies > ~0.5 keV.
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We searched for X-ray flashes (XRFs) -- which we defined as ~10s duration transient X-ray events observable in the 0.4-15 keV passband -- in fields observed using XMM-Newton with the EPIC/pn detector. While we find two non-Poissonian events, the astrophysical nature of the events is not confirmed in fully simultaneous observations with the EPIC/MOS detectors, and we conclude that the events are anomalous to the EPIC/pn detector. We find a 90% upper limit on the number of flashes per sky per year at two different incoming flash fluxes: 4.0x10^9 events / sky / year for a flux of 7.1x10^-13 erg / cm^2 / s and 6.8x10^7 events / sky / year for 1.4x10^-11 erg / cm^2 / s. These limits are consistent with an extrapolation from the BeppoSAX/WFC XRF rate at much higher fluxes (about a factor of 10^5), assuming an homogenous population, and with a previous, more stringent limit derived from ROSAT pointed observations.
We report on an XMM-Newton observation of the z=1.055 quasar and Giga-hertz Peaked Spectrum (GPS) source 3C 287. Our 62.3 ksec observation provides an exceptional X-ray view of a prominent member of this important subclass of active galactic nuclei (AGN). The X-ray spectra of 3C 287 are consistent with a simple absorbed power-law with a spectral index of Gamma = 1.72 +/- 0.02. Our fits imply a bolometric luminosity of L = 5.8 +/- 0.2 E+45 erg/s over the 0.3-10.0 keV band; this gives a mass lower limit of M > 4.6 E+7 Msun, assuming X-rays contribute 10% of the bolometric luminosity and radiation at the Eddington limit. Iron emission lines are common in the X-ray spectra of many AGN, but the observed spectra appear to rule out strong emission lines in 3C 287. The simple power-law spectrum and absence of strong emission lines may support a picture where our line of sight intersects a relativistic jet. Milliarcsecond radio imaging of 3C 287 appears to support this interpretation. We discuss our results in the context of different AGN sub-classes and the possibility that GPS sources harbor newly-formed black hole jets.
We report on the first deep X-ray survey with the XMM-Newton observatory during the performance verification phase. The field of the Lockman Hole, one of the best studied sky areas over a very wide range of wavelengths, has been observed. A total of ~100 ksec good exposure time has been accumulated. Combining the images of the European Photon Imaging Camera (EPIC) detectors we reach a flux limit of 0.31, 1.4 and 2.4 X 10^{-15} erg cm^{-2} s^{-1}, respectively in the 0.5-2, 2-10, and 5-10 keV band. Within an off-axis angle of 10 arcmin we detect 148, 112 and 61 sources, respectively. The log(N)-log(S) relation in the three bands is compared with previous results. In particular in the 5-10 keV band these observations present the deepest X-ray survey ever, about a factor 20 more sensitive than the previous BeppoSAX observations. Using X-ray spectral diagnostics and the set of previously known, spectroscopically identified ROSAT sources in the field, the new sources can be classified. XMM-Newton detects a significant number (~40%) of X-ray sources with hard, probably intrinsically absorbed X-ray spectra, confirming a prediction of the population synthesis models for the X-ray background.
We report on the follow-up $XMM-Newton$ observation of the persistent X-ray pulsar CXOU J225355.1+624336, discovered with the CATS@BAR project on archival $Chandra$ data. The source was detected at $f_{rm X}$(0.5-10 keV) = 3.4$times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$, a flux level which is fully consistent with the previous observations performed with $ROSAT$, $Swift$, and $Chandra$. The measured pulse period $P$ = 46.753(3) s, compared with the previous measurements, implies a constant spin down at an average rate $dot P = 5.3times 10^{-10}$ s s$^{-1}$. The pulse profile is energy dependent, showing three peaks at low energy and a less structured profile above about 3.5 keV. The pulsed fraction slightly increases with energy. We described the time-averaged EPIC spectrum with four different emission models: a partially covered power law, a cut-off power law, and a power law with an additional thermal component (either a black body or a collisionally ionized gas). In all cases we obtained equally good fits, so it was not possible to prefer or reject any emission model on the statistical basis. However, we disfavour the presence of the thermal components, since their modeled X-ray flux, resulting from a region larger than the neutron star surface, would largely dominate the X-ray emission from the pulsar. The phase-resolved spectral analysis showed that a simple flux variation cannot explain the source variability and proved that it is characterized by a spectral variability along the pulse phase. The results of the $XMM-Newton$ observation confirmed that CXOU J225355.1+624336 is a BeXB with a low-luminosity ($L_{rm X} sim 10^{34-35}$ erg s$^{-1}$), a limited variability, and a constant spin down. Therefore, they reinforce the source classification as a persistent BeXB.
We present the X-ray source catalog in the Subaru/XMM-Newton deep survey. A continuous area of 1.14 deg^2 centered at R.A. = 02h18m and Dec. = -05d is mapped by seven pointings with XMM-Newton covering the 0.2-10 keV band. From the combined images of the EPIC pn and MOS cameras, we detect 866, 1114, 645, and 136 sources with sensitivity limits of 6x10^{-16}, 8x10^{-16}, 3x10^{-15}, and 5x10^{-15} erg cm^{-2} s^{-1} in the 0.5-2, 0.5-4.5, 2-10, and 4.5-10 keV bands, respectively, with detection likelihood >= 7 (corresponding to a confidence level of 99.91%). The catalog consists of 1245 sources in total including 32 extended-source candidates. The averaged log N-log S relations are in good agreement with previous results, bridging the flux range between Chandra deep surveys and brighter surveys. The log N-log S relations show significant spatial variation among pointings on a scale of 0.2 deg^2. Analyzing the auto correlation function, we detect significant clustering signals from the 0.5-2 keV band sample, which can be fit with a power law form (theta/theta_c)^{-0.8} with a correlation length of theta_c=5.9^{+1.0}_{-0.9} arcsec when the integral constraint term is included. In the 2-10 keV band, however, the clustering is not significant with a 90% upper limit of theta_c < 1.5 arcsec.
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