Related papers: Quantifying Rapid Variability in Accreting Compact…
Narrow spectral features in the 5--6 keV range were recently discovered in the X-ray spectra of a few active galactic nuclei. We discuss the possibility that these features are due to localized spots which occur on the surface of an…
Simultaneous, precise measurements of the mass $M$ and radius $R$ of neutron stars can yield uniquely valuable information about the still uncertain properties of cold matter at several times the density of nuclear matter. One method that…
RXTE has been operating for nearly 2 years and is planning the third. The spacecraft performance has been good and the three instruments are operating well. Observations have been made of the range of targets suitable for RXTE, including…
Fluctuations in ultralight dark matter produce significant metric perturbations, which may be detected by monitoring the arrival times of light from millisecond pulsars. While searches using this technique are already underway, they do not…
The possibility of observationally discriminating between various types of neutron stars, described by different equations of state of the nuclear matter, as well as differentiating neutron stars from other types of exotic objects, like,…
We investigate aperiodic X-ray flux variability in accreting highly magnetized neutron stars - X-ray pulsars (XRPs). The X-ray variability is largely determined by mass accretion rate fluctuations at the NS surface, which replicate…
Millisecond and binary pulsars are the most stable astronomical standards of frequency. They can be applied to solving a number of problems in astronomy and time-keeping metrology including the search for a stochastic gravitational wave…
X-ray pulsars shine thanks to the conversion of the gravitational energy of accreted material to X-ray radiation. The accretion rate is modulated by geometrical and hydrodynamical effects in the stellar wind of the pulsar companions and/or…
Progress in astronomy comes from interpreting the signals encoded in the light received from distant objects: the distribution of light over the sky (images), over photon wavelength (spectrum), over polarization angle, and over time…
Kilohertz Quasi-Periodic Oscillations (QPOs) have been detected in many accreting X-ray binaries. It has been suggested that the highest QPO frequencies observed in the modulation of the X-ray flux reflect a non-linear resonance between two…
We analyze the currently available observations of X-ray binaries in a consistent way, to re-determine the masses of the neutron stars in these systems. In particular, our attention is focussed on a realistic and consistent assessment of…
I review the X-ray observations of Galactic accreting black holes and neutron stars, and interpretions of these in terms of solutions of the accretion flow equations.
The black hole candidates exhibit fast variability of their X-ray emission on a wide range of timescales. The short, coherent variations, with frequencies above 1 Hz, are referred to as quasi-periodic oscillations, and are generally…
A method to calculate the statistical properties of microlensing light curves is developed. The approach follows works by Deguchi & Watson, Seitz & Schneider and Neindorf, attempting to clarify the ideas involved and techniques used in the…
The Fourier frequency dependent hard X-ray lag, first discovered from the analysis of aperiodic variability of the light curves of the black hole candidate Cygnus X-1, turns out to be a property shared by several other accreting compact…
In this chapter, I present a summary of observational tests of the basic picture of disk accretion. An emphasis is placed on tests relevant to black holes, but many of the fundamental results are drawn from studies of other classes of…
Relativistic jets from Active Galactic Nuclei are known since decades, but the study of the connection between accretion and ejection in these systems is hampered by the long time scales associated to these events. The past decade has seen…
A technique of timescale analysis performed directly in the time domain has been developed recently. We have applied the technique to studying rapid variabilities of hard X-rays from neutron star and black hole binaries, gamma-ray bursts…
The regions around massive black holes can show X-ray variability on timescales from seconds to decades. Observing many black holes over different timescales can enhance our chances of detecting variability coming from (partial) tidal…
Radio astronomical observations have very poor signal to noise ratios, unlike in other disciplines. On the other hand, it is possible to observe the object of interest for long time intervals as well as using a wider bandwidth.…