The intriguing nature of the high energy gamma ray source XSSJ12270-4859 - Astrophysics > High Energy Astrophysical PhenomenaReport as inadecuate

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Abstract: The nature of the hard X-ray source XSSJ12270-4859 is still unclear though itwas claimed to be a magnetic Cataclysmic Variable. We here present a broad-bandX-ray and gamma ray study based on a recent XMM-Newton observation and archivalINTEGRAL and RXTE data. From the Fermi-LAT 1-year point source catalogue, wetentatively associate XSSJ12270-4859 with 1FGLJ1227.9-4852, a source of highenergy gamma rays with emission up to 10GeV. We complement the study with UVphotometry from XMM-Newton and ground-based optical and near-IR photometry. TheX-ray emission is highly variable showing flares and intensity dips. The X-rayflares consist of flare-dip pairs. Flares are also detected in the UV range butnot the dips. Aperiodic dipping behaviour is also observed during X-rayquiescence but not in the UV. The 0.2-100keV spectrum is featureless anddescribed by a power law model with Gamma=1.7. The 100MeV-10GeV spectrum isinstead represented by a power law index of 2.45. The luminosity ratio between0.1-100GeV and 0.2-100keV is ~0.8, hence the GeV emission is a significantcomponent of the total energy output. Furthermore, the X-ray spectrum does notgreatly change during flares, quiescence and the dips seen in quiescence but ithardens during the post-flare dips. Optical photometry reveals a period of4.32hr likely related to the binary orbit. Near-IR, possibly ellipsoidal,variations are detected. Large amplitude variability on shorter tens minstimescales are found to be non-periodic. The observed variability at allwavelengths and the spectral characteristics strongly favour a low-massatypical low-luminosity X-ray binary and are against a Cataclysmic Variablenature. The association with a Fermi-LAT high energy gamma ray source furtherstrengths this interpretation.

Author: D. de Martino, M. Falanga, J.-M. Bonnet-Bidaud, T. Belloni, M. Mouchet, N. Masetti, I. Andruchow, S.A. Cellone, K. Mukai, G. Matt


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