Probing the nature of IGR J16493-4348: Spectral and temporal analysis of the 1-100 keV emission

Abstract

IGR J16493-4348 was one of the first new sources to be detected by the INTEGRAL gamma-ray telescope in the 18-100 keV energy band. Based upon spatial coincidence the source was originally associated with the free radio pulsar PSR J1649-4349. Presented here are the results of 2.8 Ms of observations made by the INTEGRAL mission and a 5.6 ks observation with the Swift X-ray Telescope. Spectral analysis indicates that the source is best modeled by an absorbed power law with a high energy cut-off at E$_{cut}$~15 keV and a hydrogen absorbing column of NH=5.4$^{+1.3}_{-1}$ x 10$^{22}$ cm$^{-2}$. Analysis of the light curves indicates that the source is a weak, persistent gamma-ray emitter showing indications of variability in the 2-9 and 22-100 keV bands. The average source flux is ~1.1 x 10^{-10} erg cm$^{-2}$ s$^{-1}$ in the 1-100 keV energy band. No coherent timing signal is identified at any timescale in the INTEGRAL or Swift data. The refined source location and positional uncertainty of IGR J16493-4348 places PSR J1649-4349 outside of the 90% error circle. We conclude that IGR J16493-4348 is not associated with PSR J1649-4349. Combining the INTEGRAL observations with Swift/XRT data and information gathered by RXTE and Chandra we suggest that IGR J16493-4348 is an X-ray binary; and that the source characteristics favour a high mass X-ray binary although an LMXB nature cannot be ruled out.

Accepted for publication in MNRAS. 7 pages, 5 figures (Note the resolution of figure 5 has been reduced)