Discovery of a magnetic neutron star in X-ray transient IGR J01583+6713

Abstract

IGR J01583+6713 is a new transient source discovered by the INTEGRAL/IBIS hard X-ray surveys. Optical observations suggested that it should be a high mass X-ray binary, but its nature is still unclear. We used the INTEGRAL/IBIS data to study the nature of the transient hard X-ray source IGR J01583+6713 during its outburst. Temporal profiles and spectral properties of IGR J01583+6713 around its outburst on 2005 Dec 6 were obtained. During the outburst, the mean X-ray luminosity reached around $4\times 10^{35}$ erg s$^{-1}$ in the energy range of 20 -- 100 keV. The continuum spectrum can be fitted by a bremsstrahlung model of $kT\sim 35$ keV or a power-law model of $\Gamma\sim 2.1$, and the electron resonant cyclotron absorption lines at $\sim 35$ keV and possible at $\sim 67$ keV were detected, suggesting that a magnetic neutron star of $B\sim 4\times 10^{12}$ G is located in IGR J01583+6713. Then we identify IGR J01583+6713 as a transient X-ray sources with a magnetic neutron star. After the outburst, the flux of IGR J01583+6713 was decreasing and it could not be detected by IBIS after 2005 Dec 10. During the outburst, we cannot conform the possible pulse period at 469 s reported before and have not detected the modulation signals in the range of 200 -- 2000 s with the IBIS observations. The transient hard X-ray source IGR J01583+6713 contain a magnetic neutron star, which would help to understand its transient nature.