Anomalous orbital expansion of low-mass X-ray binary 2A 1822-371: the existence of a circumbinary disk?

Na Wei, Long Jiang, Wen-Cong Chen

The source 2A 1822-371 is an eclipsing low-mass X-ray binary (LMXB) consisting of a neutron star (NS) and a $\sim 0.5M_{\odot }$ donor star in an orbit of 5.57 hr. Based on timing o…