Aims. We report the first detailed X-ray study of the supernova remnant (SNR) G304.6+0.1, achieved with the XMM-Newton mission. Methods. The powerful imaging capability of XMM-Newton was used to study the X-ray characteristics of the remnant at different energy ranges. The X-ray morphology and spectral properties were analyzed. In addittion, radio and mid-infrared data obtained with the Molonglo Observatory Synthesis Telescope and the Spitzer Space Telescope were used to study the association with the detected X-ray emission and to understand the structure of the SNR at differents wavelengths. Results. The SNR shows an extended and arc-like internal structure in the X-ray band without a compact point-like source inside the remnant. We find a high column density of N H in the range 2.5-3.5 × 10 22 cm −2 , which supports a relatively distant location (d ≥ 9.7 kpc). The X-ray spectrum exhibits at least three emission lines, indicating that the X-ray emission has a thin thermal plasma origin, although a non-thermal contribution cannot be discarded. The spectra of three different regions (north, center and south) are well represented by a combination of a non-equilibrium ionization (PSHOCK) and a power-law (PL) model. The mid-infrared observations show a bright filamentary structure along the north-south direction coincident with the NW radio shell. This suggests that Kes 17 is propagating in a non-uniform environment with high density and that the shock front is interacting with several adjacent massive molecular clouds. The good correspondence of radio and mid-infrared emissions suggests that the filamentary features are caused by shock compression. The X-ray characteristics and well-known radio parameters indicate that G304.6+0.1 is a middle-aged SNR (2.8−6.4) × 10 4 yr old and a new member of the recently proposed group of mixed-morphology SNRs.
Aims. We report results of an X-ray study of the supernova remnant (SNR) G344.7-0.1 and the point-like X-ray source located at the geometrical center of the SNR radio structure. Methods. The morphology and spectral properties of the remnant and the central X-ray point-like source were studied using data from the XMM-Newton and Chandra satellites. Archival radio data and infrared Spitzer observations at 8 and 24 µm were used to compare and study its multi-band properties at different wavelengths.Results. The XMM-Newton and Chandra observations reveal that the overall X-ray emission of G344.7-0.1 is extended and correlates very well with regions of bright radio and infrared emission. The X-ray spectrum is dominated by prominent atomic emission lines. These characteristics suggest that the X-ray emission originated in a thin thermal plasma, whose radiation is represented well by a plane-parallel shock plasma model (PSHOCK). Our study favors the scenario in which G344.7-0.1 is a 6 × 10 3 year old SNR expanding in a medium with a high density gradient and is most likely encountering a molecular cloud on the western side. In addition, we report the discovery of a soft point-like X-ray source located at the geometrical center of the radio SNR structure. The object presents some characteristics of the so-called compact central objects (CCO). However, its neutral hydrogen absorption column (N H ) is inconsistent with that of the SNR. Coincident with the position of the source, we found infrared and optical objects with typical early-K star characteristics. The X-ray source may be a foreground star or the CCO associated with the SNR. If this latter possibility were confirmed, the point-like source would be the farthest CCO detected so far and the eighth member of the new population of isolated and weakly magnetized neutron stars.
Context. The recent detection of very high-energy (VHE) gamma-ray emission from the direction of the W43 star-forming region prompted us to investigate its stellar population in detail in an attempt to see wether or not it is possible an association. Aims. We search for the possible counterpart(s) of the gamma-ray source or any hints of them, such as non-thermal synchrotron emission as a tracer of relativistic particles often involved in plausible physical scenarios for VHE emission. Methods. We data-mined several archival databases with different degrees of success. The most significant results came from radio and near-infrared archival data. Results. The previously known Wolf-Rayet star in the W43 central cluster and another cluster member appear to be resolved into two components,suggesting a likely binary nature. In addition, extended radio emission with a clearly negative spectral index is detected in coincidence with the W43 cluster. These findings could have important implications for possible gamma-ray emitting scenarios, which we also briefly discuss.
Context. Understood to be a microquasar in the Galactic center region, GRS has not yet been unambiguously identified to have an optical/near-infrared counterpart, mainly because of the high absorption and the historic lack of suitable astrometric stars, which led to the use of secondary astrometric solutions. Although it is considered with 1E 1740.7-2942 as the prototypical microquasar in the Galactic center region, the Galactic origin of both sources has not yet been confirmed. Aims. We attempt to improve previous astrometry to identify a candidate counterpart to GRS 1758-258. We present observations with the Gran Telescopio de Canarias (GTC), in which we try to detect any powerful emission lines that would infer an extragalactic origin of this source. Methods. We use modern star catalogues to reanalyze archival images of the GRS 1758-258 field in the optical and near-infrared wavelengths, and compute a new astrometric solution. We also reanalyzed archival radio data of GRS 1758-258 to determine a new and more accurate radio position. Results. Our improved astrometric solution for the GRS 1758-258 field represents a significant advancement on previous works and allows us to identify a single optical/near-infrared source, which we propose as the counterpart of GRS 1758-258. The GTC spectrum of this source is however of low signal-to-noise ratio and does not rule out a Galactic origin. Hence, new spectral observations are required to confirm or discard a Galactic nature.
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