Probing the nature of IGR J16493-4348: spectral and temporal analysis of the 1-100 keV emission
de Rosa, A.; Hill, A. B.; Bird, A. J.; McBride, V. A.; Landi, R.; Bazzano, A.; Dean, A. J.; Sguera, V.
United Kingdom, Italy
Abstract
IGR J16493-4348 was one of the first new sources to be detected by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) γ-ray telescope in the 18-100 keV energy band. Based on 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 (XRT). Spectral analysis indicates that the source is best modelled by an absorbed power law with a high energy cut-off at Ecut ~ 15 keV and a hydrogen absorbing column of NH = 5.4+1.3-1 × 1022cm-2. Analysis of the light curves indicates that the source is a weak, persistent γ-ray emitter showing indications of variability in the 2-9 and 22-100 keV bands. The average source flux is ~1.1 × 10-10ergcm-2s-1 in the 1-100 keV energy band. No coherent timing signal is identified at any time-scale in the INTEGRAL or Swift data.
The refined source location and positional uncertainty of IGR J16493-4348 places PSR J1649-4349 outside the 90 per cent 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 a low-mass X-ray binary nature cannot be ruled out.