Chandra X-ray counterpart of KS 1741-293

We aim to investigate the nature of the high energy source KS 1741-293 by revisiting the radio and infrared associations proposed in the early 1990s. Our work is mostly based on the analysis of modern survey and archive data, including the NRAO, MSX, 2MASS and Chandra archives, and catalogues. We also have obtained deep CCD optical observations by ourselves. The coincidence of KS 1741-293 with an extended radio and far-infrared source, tentatively suggested in 1994, is no longer supported by modern observational data. Instead, a Chandra source is the only peculiar object found to be consistent with all high-energy error circles of KS 1741-293 and we propose it to be its most likely X-ray counterpart. We also report the existence of a non-thermal radio nebula in the vicinity of the KS 1741-293 position with the appearance of a supernova remnant. The possibility of being associated to this X-ray binary is discussed.Comment: 5 pages, 4 figures, 2 tables. Accepted for publication in Astronomy & Astrophysic

A radio and infrared exploration of the Cygnus X-3 environments

To confirm, or rule out, the possible hot spot nature of two previously detected radio sources in the vicinity of the Cygnus X-3 microquasar. We present the results of a radio and near infrared exploration of the several arc-minute field around the well known galactic relativistic jet source Cygnus X-3 using the Very Large Array and the Calar Alto 3.5~m telescope. The data this paper is based on do not presently support the hot spot hypothesis. Instead, our new observations suggest that these sources are most likely background or foreground objects. Actually, none of them appears to be even barely extended as would be expected if they were part of a bow shock structure. Our near infrared observations also include a search for extended emission in the Bracket $\gamma$ (2.166 $\mu$m) and $H_{2}$ (2.122 $\mu$m) lines as possible tracers of shocked gas in the Cygnus X-3 surroundings. The results were similarly negative and the corresponding upper limits are reported.Comment: Accepted for publication in A&A; 5 pages, 4 figure

An X-ray study of the SNR G344.7-0.1 and the central object CXOU J170357.8-414302

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 $\mu$m 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 x 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.Comment: 9 pages, 8 figures, accepted for publication in Astronomy and Astrophysics. Higher resolution figures can be seen on A&