Aims. We present a comprehensive X-ray study of the population of supernova remnants (SNRs) in the Large Magellanic Cloud (LMC). Using primarily XMM-Newton observations, we conduct a systematic spectral analysis of LMC SNRs to gain new insight into their evolution and the interplay with their host galaxy. Methods. We combined all the archival XMM-Newton observations of the LMC with those of our Very Large Programme LMC survey. We produced X-ray images and spectra of 51 SNRs, out of a list of 59 objects compiled from the literature and augmented with newly found objects. Using a careful modelling of the background, we consistently analysed all the X-ray spectra and measure temperatures, luminosities, and chemical compositions. The locations of SNRs are compared to the distributions of stars, cold gas, and warm gas in the LMC, and we investigated the connection between the SNRs and their local environment, characterised by various star formation histories. We tentatively typed all LMC SNRs, in order to constrain the ratio of core-collapse to type Ia SN rates in the LMC. We also compared the column densities derived from X-ray spectra to H i maps, thus probing the three-dimensional structure of the LMC. Results. This work provides the first homogeneous catalogue of the X-ray spectral properties of SNRs in the LMC. It offers a complete census of LMC remnants whose X-ray emission exhibits Fe K lines (13% of the sample), or reveals the contribution from hot supernova ejecta (39%), which both give clues to the progenitor types. The abundances of O, Ne, Mg, Si, and Fe in the hot phase of the LMC interstellar medium are found to be between 0.2 and 0.5 times the solar values with a lower abundance ratio [α/Fe] than in the Milky Way. The current ratio of core-collapse to type Ia SN rates in the LMC is constrained to N CC /N Ia = 1.35( +0.11 −0.24 ), which is lower than in local SN surveys and galaxy clusters. Our comparison of the X-ray luminosity functions of SNRs in Local Group galaxies (LMC, SMC, M31, and M33) reveals an intriguing excess of bright objects in the LMC. Finally, we confirm that 30 Doradus and the LMC Bar are offset from the main disc of the LMC to the far and near sides, respectively.

We have obtained Chandra ACIS-S observations of NGC 6543, the Cat's Eye Nebula. The X-ray emission from NGC 6543 is clearly resolved into a point source at the central star and diffuse emission confined within the central elliptical shell and two extensions along the major axis. Spectral analysis of the diffuse component shows that the abundances of the X-ray-emitting gas are similar to those of the fast (1,750 km s −1 ) stellar wind but not those of the nebula. Furthermore, the temperature of this gas is ∼1.7×10 6 K, which is 100 times lower than the expected post-shock temperature of the fast stellar wind. The combination of low temperature and wind abundances is puzzling. The thermal pressure of this hot gas is about twice the pressure in the cool nebular shell; thus, the hot gas plays an essential role in the ongoing evolution of the nebula. Subject headings: planetary nebulae: general -planetary nebulae: individual (NGC 6543) -X-rays: ISM -stars: winds 1. Introduction Optical emission-line images of planetary nebulae (PNs) reveal a fascinating range of morphologies (e.g., the Hubble Space Telescope gallery of PNs 4 ), indicating complex internal structures in the nebulae. Among these PNs, NGC 6543, also known as the Cat's Eye Nebula, has perhaps the most interesting morphology. As reported by Reed et al. (1999), the Hα and [O III] λ5007 line images of NGC 6543 are similar, showing an inner shell surrounded by an envelope with multiple, interlocking, semi-circular features. The [N II] 4

We have studied the stellar and interstellar environments of two luminous X-ray sources and five ultraluminous X-ray sources (ULXs) in order to gain insight into their nature. Archival Hubble Space Telescope images were used to identify the optical counterparts of the ULXs Ho IX X-1 and NGC 1313 X-2, and to make photometric measurements of the local stellar populations of these and the luminous source IC 10 X-1. We obtained high-dispersion spectroscopic observations of the nebulae around these seven sources to search for He ii k4686 emission and to estimate the expansion velocities and kinetic energies of these nebulae. Our observations did not detect nebular He ii emission from any source, with the exception of LMC X-1; this is either because we missed the He iii regions or because the nebulae are too diffuse to produce He ii surface brightnesses that lie within our detection limit. We compare the observed ionization and kinematics of the supershells around the ULXs Ho IX X-1 and NGC 1313 X-2 with the energy feedback expected from the underlying stellar population to assess whether additional energy contributions from the ULXs are needed. In both cases, we find insufficient UV fluxes or mechanical energies from the stellar population; thus these ULXs may be partially responsible for the ionization and energetics of their supershells. All seven sources that we studied are in young stellar environments, and six of them have optical counterparts with masses k7 M ; thus, these sources are most likely high-mass X-ray binaries.

The supernova remnant (SNR) N49 in the Large Magellanic Cloud has been observed with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. The superb angular resolution of the Chandra/ACIS images resolves a point source, the likely X-ray counterpart of soft gammaray repeater SGR 0526À66, and the diffuse filaments and knots across the SNR. These filamentary features represent the blast wave sweeping through the ambient interstellar medium and nearby dense molecular clouds. We detect metal-rich ejecta beyond the main blast wave shock boundary in the southwest of the SNR, which appear to be explosion fragments, or '' bullets,'' ejected from the progenitor star. The detection of strong H-like Si line emission in the eastern side of the SNR requires multiphase shocks in order to describe the observed X-ray spectrum, whereas such a multiphase plasma is not evident in the western side. This complex spectral structure of N49 suggests that the postshock regions toward the east of the SNR might have been reheated by the reverse shock off the dense molecular clouds while the blast wave shock front has decelerated as it propagates into the dense clouds. The X-ray spectrum of the detected pointlike source is continuum-dominated and can be described with a power law of À $ 3. This provides a confirmation that this pointlike X-ray source is the counterpart of SGR 0526À66 in the quiescent state.

Recent Chandra ACIS-S observations have detected a point source at the central star of NGC 6543 and confirmed the point source nature of the hard X-ray emission from NGC 7293. The X-ray spectra of both sources peak between 0.5 keV and 1.0 keV and show line features indicating a thin plasma at temperatures of a few times 10 6 K. Their X-ray luminosities are 10 30 erg s −1 and 3 × 10 29 erg s −1 , respectively. We have considered four different mechanisms to explain the nature of these sources. The X-ray emission from the central star of NGC 6543 may originate from the coronal activity of an undetected companion star or from shocks in its fast stellar wind, while the hard X-ray emission from NGC 7293 might be ascribed to an undetected dMe companion. Follow-up observations are needed to determine the existence and natures of these stellar companions.Subject headings: planetary nebulae: general -planetary nebulae: individual (NGC 6543, NGC 7293)stars: AGB and post-AGB -X-rays: stars

No abstract

No abstract

We present an X‐ray study of our nearest starburst galaxy IC 10, based on XMM–Newton and Chandra observations. A list of 73 XMM–Newton and 28 Chandra detections of point‐like X‐ray sources in the field is provided; a substantial fraction of them are likely stellar objects in the Milky Way due to the low Galactic latitude location of IC 10. The brightest source in the IC 10 field, X‐1, has a mean 0.3–8.0 keV luminosity of ∼1.2 × 1038 erg s−1 and shows a large variation by a factor of up to ∼6 on time‐scales of ∼104 s during the XMM–Newton observation. The X‐ray spectra of the source indicate the presence of a multicolour blackbody accretion disc with an inner disc temperature Tin≈ 1.1 keV. These results are consistent with the interpretation of the source as a stellar mass black hole (BH), probably accreting from a Wolf–Rayet (W–R) star companion. We infer the mass of this BH to be ∼4 M⊙ if it is not spinning, or a factor of up to ∼6 higher if there is significant spinning. We also detect an apparent diffuse soft X‐ray emission component of IC 10. An effective method is devised to remove the X‐ray CCD‐readout streaks of X‐1 that strongly affect the study of the diffuse component in the XMM–Newton and Chandra observations. We find that the diffuse X‐ray morphology is oriented along the optical body of the galaxy and is chiefly associated with starburst regions. The diffuse component can be characterized by an optically thin thermal plasma with a mean temperature of ∼4 × 106 K and a 0.5–2 keV luminosity of ∼8 × 1037 erg s−1, representing only a small fraction of the expected mechanical energy inputs from massive stars in the galaxy. There is evidence that the hot gas is driving outflows from the starburst regions; therefore, the bulk of the energy inputs may be released in a galactic wind.