We present a new technique for identifying stellar mass black holes in low mass X-ray binaries (LMXBs), and apply it to XMM-Newton observations of M31. We examine X-ray time series variability seeking power density spectra (PDS) typical of LMXBs accreting at a low accretion rate (which we refer to as Type A PDS); these are very similar for black hole and neutron star LMXBs. Galactic neutron sta...

We present a multiwavelength investigation of the circumnuclear environment of the Andromeda Galaxy (M31), utilizing archival Chandra, FUSE, GALEX, HST and Spitzer data as well as ground-based observations. Based on the Chandra/ACIS data, we tightly constrain the X-ray luminosity of M31, the central supermassive black hole (SMBH) of the galaxy, to be L0.3−7 keV . 1.2 × 10 36 ergs s−1, approxima...

We report new photometry for 10 globular clusters in M31, observed to a uniform depth of four orbits in F5555W(V) and F814W(I) using WFPC2 on board HST. Additionally we have reanalyzed HST archival data of comparable quality, for 2 more clusters. A special feature of our analysis is the extraordinary care taken to account for the effects of blended stellar images and required subtraction of con...

The projected structures and integrated properties of the Andromeda I, II, III, V, VI, VII and Cetus dwarf spheroidal galaxies are analysed based upon resolved counts of red giant branch stars. The observations were taken as part of the Isaac Newton Telescope Wide Field Survey of M31 and its environs. For each object, we have derived isopleth maps, surface brightness profiles, intensity-weighte...

We re-analyze the M31 microlensing event WeCAPP-GL1/Point-AGAPE-S3 taking into account that stars are not point-like but extended. We show that the finite size of stars can dramatically change the self-lensing event rate and (less dramatically) also the halo lensing event rate, if events are as bright as WeCAPP-GL1. The brightness of the brightest events mostly depends on the source sizes and f...

The aim of this thesis is to study the environmental dependence of populations of low-mass X-ray binaries (LMXBs) in early-type galaxies. The dissertation is mainly based on archival data of the Chandra observatory whose unprecedented sub-arcsec angular resolution made it possible to resolve individual compact sources in nearby galaxies. The Chandra data is complemented by the infrared data of ...