Speaker: Malu Sudha (Wayne State)

Abstract: Neutron Star (NS) Low Mass X-Ray Binaries (LMXBs) are phenomenologically rich systems that consist of a neutron star accreting matter from a low mass (< 1 M_⊙) companion star. NS LMXBs that trace out a characteristic Z-shaped track in their hardness-intensity diagram (HID) or in their color-color diagram (CCD) are classified as ‘Z’ sources and those that trace out a characteristic C shaped track in the HID are classified as ‘atoll’ sources. The current picture of these binaries involves an accretion disk formed via Roche lobe overflow from the secondary star, a boundary layer around the NS surface (which is the site where the disk material reaches the relatively slowly spinning NS), a compact corona/hot electron cloud close to the NS. But the exact location, structural configuration in this region or the extent of the corona and its nature is not clearly understood. Timing variability in NS LMXBs can vary from a timescale of a few seconds to a few years. These systems exhibit a multicolor disk blackbody emission from the accretion disk, a hot blackbody emission from the boundary layer, a hot Comptonized emission from the corona and a reprocessed emission from the innermost accretion disk region. Although several models have been proposed to explain the spectral and temporal nature of these binaries, a unified model that addresses the spectral and temporal nature of these systems is essential. In this talk I will be discussing the broadband spectro-temporal studies of these NS LMXBs. Results obtained from these studies will be discussed in the context of understanding the physical behavior and geometry of the inner accretion disk region of NS LMXBs.