RXTE Observations of 1A 1744–361: Correlated Spectral and Timing Behavior

We analyze Rossi X–ray Timing Explorer (RXTE) Proportional Counter Array (PCA) data of the transient low mass X–ray binary (LMXB) system 1A 1744–361. We explore the X–ray intensity and spectral evolution of the source, perform timing analysis, and find that 1A 1744–361 shows ‘atoll’ behavior during the outbursts. The color-color diagram indicates that this LMXB was observed in a low intensity spectrally hard (low-hard) state and in a high intensity ‘banana’ state. The low-hard state shows a horizontal pattern in the color-color diagram, and the previously reported ‘dipper QPO’ appears only during this state. We also perform energy spectral analyses, and report the first detection of broad iron emission line and iron absorption edge from 1A 1744–361. Subject headings: methods: data analysis — stars: neutron — techniques: miscellaneous — techniques: spectroscopic — X-rays: binaries — X-rays: individual (1A 1744–361)