Young pre-low-mass X-ray binaries in the propeller phase

Nature of the 6.7-h periodic X-ray source 1E 161348-5055 in RCW 103

Department of Astronomy & Astrophysics, Tata Institute of Fundamental Research, Mumbai 400 005, India e-mail: [pranab;harshalhb]@tifr.res.in

Received: 21 May 2009
Accepted: 23 August 2009

Abstract

Context. Discovery of the 6.7-h periodicity in the X-ray source 1E 161348-5055 in RCW 103 has led to investigations of the nature of this periodicity.

Aims. To explore a model for 1E 161348-5055 wherein a fast-spinning neutron star with a magnetic field ~10¹² G in a young pre-low-mass X-ray Binary (pre-LMXB) with an eccentric orbit of period 6.7 h operates in the “propeller” phase.

Methods. The 6.7-h light curve of 1E 161348-5055 is modeled in terms of orbitally-modulated mass transfer through a viscous accretion disk and subsequent propeller emission. Formation of eccentric binaries in supernovae and their subsequent tidal evolution are studied.

Results. The light curve of 1E 161348-5055 can be quantitatively accounted for by models of propeller torques of both Illarionov-Sunyaev type and Romanova-Lovelace et al. type, and spectral and other properties are also in agreement. Formation and evolution of model systems are shown to be in accordance both with standard theories and with X-ray observations of 1E 161348-5055.

Conclusions. The pre-LMXB model for 1E 161348-5055 and similar sources agrees with observation. Distinguishing features between this model and the recently-proposed magnetar model need to be explored.