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

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China e-mail: wangwei@bao.ac.cn

Received: 28 August 2009
Accepted: 5 March 2010

Abstract

Aims. IGR J01583+6713 is a new transient source discovered by the INTEGRAL/IBIS hard X-ray surveys. Optical observations have provided evidence that it is a high mass X-ray binary, but its nature remains unclear.

Methods. We used the INTEGRAL/IBIS data to study IGR J01583+6713 during its outburst.

Results. We present the temporal profiles and spectral properties of IGR J01583+6713 around its outburst on 2005 Dec. 6. During the outburst, the mean X-ray luminosity reached around 4 × 10³⁵ erg s^-1 in the energy range of 20–100 keV. The continuum spectrum can be fitted by a bremsstrahlung model of kT ~ 35 keV or a power-law model of Γ ~ 2.1. In addition, the electron resonant cyclotron absorption lines were detected at 35 keV and possible at 67 keV, implying that a magnetic neutron star of B ~ 4 × 10¹² G is located in IGR J01583+6713. We class IGR J01583+6713 as a transient X-ray sources with a magnetic neutron star. After the outburst, the flux of IGR J01583+6713 decreased and could not be detected by IBIS after 2005 Dec. 10. During the outburst, we cannot confirm the possible pulse period at 469 s previously reported and did not detect the modulation signals in the range of 200–2000 s with the IBIS observations.

Conclusions. The transient hard X-ray source IGR J01583+6713 contains a magnetic neutron star, which would help to understand its transient nature.