XMM-Newton and Chandra observations of G272.2-3.2. Evidence of stellar ejecta in the central region

We aim to study the spatial distribution of the physical and chemical properties of the X-ray emitting plasma of the supernova remnant G272.2-3.2, in order to get important constraints on its ionization stage, on the progenitor supernova explosion, and the age of the remnant. We report combined XMM-Newton and Chandra images, median photon energy map, silicon and sulfur equivalent width maps, and a spatially resolved spectral analysis for a set of regions of the remnant. Complementary radio and H{\alpha} observations, available in the literature, are also used to study the multi-wavelength connection of all detected emissions. The X-ray morphology of the remnant displays an overall structure with an almost circular appearance, a centrally brightened hard region, with a peculiar elongated hard structure oriented along the northwest-southeast direction of the central part. The X-ray spectral study of the regions shows distinct K{\alpha} emission-line features of metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by an absorbed VNEI thermal plasma model, which produces elevated abundances of Si, S, and Fe in the circular central region, typical of ejecta material. The values of abundances found in the central region of the SNR favor a Type Ia progenitor for this remnant. The outer region shows abundances below the solar value, as expected if the emission arises from the shocked ISM. The relatively low ionization timescales suggests non-equilibrium ionization. We identify the location of the contact discontinuity. Its distance to the outer shock is higher than expected for expansion in a uniform media, what suggests that the remnant spent most of its time in a more dense medium.Comment: 9 pages, 7 figures. Accepted for publication in A&

Counterpart candidates to the unidentified Fermi source 0FGL J1848.6-0138

Aims: We aim to contribute to the identification of the counterpart for one of the bright sources of gamma-rays in the catalogue obtained and released by the Fermi collaboration. Methods: Our work is based on a extensive identification of sources from different wavelength catalogues and databases. Results: As a first result, we report the finding of a few counterpart candidates inside the 95% confidence error box of the Fermi LAT unidentified gamma-ray source 0FGL J1848.6-0138. The globular cluster GLIMPSE-C01 is remarkably distinctive being among the most peculiar objects consistent with both the position uncertainty in the gamma-ray source and a conceivable physical scenario for gamma-ray production. The Fermi-observed spectrum is compared with theoretical predictions in the literature and the association is found to be plausible but not yet certain because of its low X-ray to gamma-ray luminosity ratio. Other competing counterparts are also discussed. In particular, we pay special attention to a possible Pulsar Wind Nebula inside the Fermi error box, whose nature is yet to be confirmed. Conclusions: Both a globular cluster and an infrared source resembling a Pulsar Wind Nebula were found to be in positional agreement with 0FGL J1848.6-0138. In addition, other interesting objects in the field are also reported. Future gamma-ray observations will reduce the position uncertainty and we hope eventually confirm one of the counterpart candidates reported here. If GLIMPSE-C01 is confirmed together with the possible Fermi detection of the well known globular cluster 47 Tuc, then this would provide strong support to theoretical predictions that globular clusters are possible gamma-ray sources.Facultad de Ciencias Astronómicas y Geofísica

XMM-Newton and Chandra observations of G272.2-3.2. Evidence of stellar ejecta in the central region

Aims. We aim to study the spatial distribution of the physical and chemical properties of the X-ray emitting plasma of the supernova remnant G272.2−3.2 in order to obtain important constraints on its ionization stage, the progenitor supernova explosion, and the age of the remnant. Methods. We report on combined XMM-Newton and Chandra images, median photon energy maps, silicon and sulfur equivalent width maps, and a spatially resolved spectral analysis for a set of regions of the remnant. Complementary radio and Hα observations, available in the literature, are also used to study the multi-wavelength connection of all detected emissions. Results. The X-ray morphology of the remnant displays an overall structure with an almost circular appearance and a centrally brightened hard region with a peculiar elongated hard structure oriented along the northwest-southeast direction of the central part. The X-ray spectral study of the regions shows distinct Kα emission-line features of metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by an absorbed variable abundance non-equilibrium ionization thermal plasma model, which produces elevated abundances of Si, S, and Fe in the circular central region, typical of ejecta material. The values of abundances found in the central region of the supernova remnant favor a Type Ia progenitor for this remnant. The outer region shows abundances below the solar value, to be expected if the emission arises from the shocked interstellar medium. The relatively low ionization timescales suggest non-equilibrium ionization. We identify the location of the contact discontinuity. Its distance to the outer shock is higher than expected for expansion in a uniform media, which suggests that the remnant spent most of its time in more dense medium.Fil: Sánchez Ayaso, E.. Universidad de Jaén; EspañaFil: Combi, Jorge Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto Argentino de Radioastronomia (i); ArgentinaFil: Bocchino, F.. Istituto Nazionale Di Astrofisica; ItaliaFil: Albacete Colombo, Juan Facundo. Universidad Nacional del Comahue; ArgentinaFil: López-santiago, J.. Universidad Complutense de Madrid; EspañaFil: Martí, J.. Universidad de Jaén; EspañaFil: Castro, E.. Universidad de Jaén; Españ

XMM-Newton and Chandra observations of G272.2-3.2. Evidence of stellar ejecta in the central region

Aims. We aim to study the spatial distribution of the physical and chemical properties of the X-ray emitting plasma of the supernova remnant G272.2-3.2 in order to obtain important constraints on its ionization stage, the progenitor supernova explosion, and the age of the remnant. Methods. We report on combined XMM-Newton and Chandra images, median photon energy maps, silicon and sulfur equivalent width maps, and a spatially resolved spectral analysis for a set of regions of the remnant. Complementary radio and Hα observations, available in the literature, are also used to study the multi-wavelength connection of all detected emissions. Results. The X-ray morphology of the remnant displays an overall structure with an almost circular appearance and a centrally brightened hard region with a peculiar elongated hard structure oriented along the northwest-southeast direction of the central part. The X-ray spectral study of the regions shows distinct Kα emission-line features of metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by an absorbed variable abundance non-equilibrium ionization thermal plasma model, which produces elevated abundances of Si, S, and Fe in the circular central region, typical of ejecta material. The values of abundances found in the central region of the supernova remnant favor a Type Ia progenitor for this remnant. The outer region shows abundances below the solar value, to be expected if the emission arises from the shocked interstellar medium. The relatively low ionization timescales suggest non-equilibrium ionization. We identify the location of the contact discontinuity. Its distance to the outer shock is higher than expected for expansion in a uniform media, which suggests that the remnant spent most of its time in more dense medium.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Identification of the optical and near-infrared counterpart of GRS 1758-258

Context. Understood to be a microquasar in the Galactic center region, GRS 1758-258 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.Comment: 4 pages, 3 figures, accepted by Astronomy and Astrophysic

Counterpart candidates to the unidentified Fermi source 0FGL J1848.6-0138

Aims. We aim here to contribute to the identification of unassociated bright sources of gamma-rays in the recently released catalogue obtained by the Fermi collaboration. Methods. Our work is based on a extensive cross-identification of sources from different wavelength catalogues and databases. Results. As a first result, we report the finding of a few counterpart candidates inside the 95% confidence error box of the Fermi LAT unidentified gamma-ray source 0FGL J1848.6$-$0138. The globular cluster GLIMPSE-C01 remarkably stands out among the most peculiar objects consistent with the position uncertainty of the gamma-ray source and with a conceivable physical scenario for gamma-ray production. The Fermi observed spectrum is compared against theoretical predictions in the literature making the association plausible but not yet certain due to its low X-ray to gamma-ray luminosity ratio. Other competing counterparts are also discussed. In particular, we pay a special attention to a possible Pulsar Wind Nebula inside the Fermi error box whose nature is yet to be confirmed. Conclusions.Both a globular cluster and an infrared source resembling a Pulsar Wind Nebula have been found in positional agreement with 0FGL J1848.6$-$0138. In addition, other interesting objects in the field are also reported. Future gamma-ray observations will narrow the position uncertainty and we hope to eventually confirm one of the counterpart candidates reported here. If GLIMPSE-C01 is confirmed, together with the Fermi possible detection of the well known globular cluster 47 Tuc, then it would provide strong support to theoretical predictions of globular clusters as gamma-ray sources.Comment: 5 pages, 2 figures and 1 table. Accepted for publication in Astronomy and Astrophysic

The star forming region Monoceros R2 as a gamma-ray source

Context. After the release of the gamma-ray source catalog produced by the Fermi satellite during its first two years of operation, a significant fraction of sources still remain unassociated at lower energies. In addition to well-known high-energy emitters (pulsars, blazars, supernova remnants, etc.), theoretical expectations predict new classes of gamma-ray sources. In particular, gamma-ray emission could be associated with some of the early phases of stellar evolution, but this interesting possibility is still poorly understood. Aims. The aim of this paper is to assess the possibility of the Fermi gamma-ray source 2FGL J0607.5-0618c being associated with the massive star forming region Monoceros R2. Methods. A multi-wavelength analysis of the Monoceros R2 region is carried out using archival data at radio, infrared, X-ray, and gamma-ray wavelengths. The resulting observational properties are used to estimate the physical parameters needed to test the different physical scenarios. Results. We confirm the 2FGL J0607.5-0618c detection with improved confidence over the Fermi two-year catalog. We find that a combined effect of the multiple young stellar objects in Monoceros R2 is a viable picture for the nature of the source.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

The star forming region Monoceros R2 as a gamma-ray source

Context. After the release of the gamma-ray source catalog produced by the Fermi satellite during its first two years of operation, a significant fraction of sources still remain unassociated at lower energies. In addition to well-known high-energy emitters (pulsars, blazars, supernova remnants, etc.), theoretical expectations predict new classes of gamma-ray sources. In particular, gamma-ray emission could be associated with some of the early phases of stellar evolution, but this interesting possibility is still poorly understood. Aims. The aim of this paper is to assess the possibility of the Fermi gamma-ray source 2FGL J0607.5-0618c being associated with the massive star forming region Monoceros R2. Methods. A multi-wavelength analysis of the Monoceros R2 region is carried out using archival data at radio, infrared, X-ray, and gamma-ray wavelengths. The resulting observational properties are used to estimate the physical parameters needed to test the different physical scenarios. Results. We confirm the 2FGL J0607.5-0618c detection with improved confidence over the Fermi two-year catalog. We find that a combined effect of the multiple young stellar objects in Monoceros R2 is a viable picture for the nature of the source.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Sub-arcsecond radio and optical observations of the likely counterpart to the gamma-ray source 2FGL J2056.7+4939

We have searched and reviewed all multi- wavelength data available for the region towards the gamma-ray source 2FGL J2056.7+4939 in order to con- strain its possible counterpart at lower energies. As a result, only a point-like optical/infrared source with flat-spectrum radio emission is found to be consistent with all X-ray and gamma-ray error circles. Its struc- ture is marginally resolved at radio wavelengths at the sub-arcsecond level. An extragalactic scenario appears to be the most likely interpretation for this object.Comment: 5 pages, 3 figures, 1 tabl