A Possible Magnetar Nature for IGR J16358-4726
Kouveliotou, C.; Walter, R.; Ubertini, P.; Bazzano, A.; Del Santo, M.; Woods, P.; Göǧüş, E.; Patel, S. K.; Finger, M.; Wachter, S.; Zurita, J.; Eichler, D.; Wilson, C. A.
United States, Switzerland, Italy, Israel, Turkey
Abstract
We present detailed spectral and timing analysis of the hard X-ray transient IGR J16358-4726 using multisatellite archival observations. A study of the source flux time history over 6 yr suggests that lower luminosity transient outbursts can be occurring in intervals of at most 1 yr. Joint spectral fits of the higher luminosity outburst using simultaneous Chandra ACIS and INTEGRAL ISGRI data reveal a spectrum well described by an absorbed power-law model with a high-energy cutoff plus an Fe line. We detected the 1.6 hr pulsations initially reported using Chandra ACIS also in the INTEGRAL ISGRI light curve and in subsequent XMM-Newton observations. Using the INTEGRAL data, we identified a spin-up of 94 s (P˙=1.6×10-4), which strongly points to a neutron star nature for IGR J16358-4726. Assuming that the spin-up is due to disk accretion, we estimate that the source magnetic field ranges between 1013 and 1015 G, depending on its distance, possibly supporting a magnetar nature for IGR J16358-4726.