Related papers: Decade time-scale modulation of low mass X-ray bin…

The search for periodicity in the multi-wavelength high variable emission of blazars is a key feature to understand dynamical processes at work in this class of active galactic nuclei. The blazar PG 1553+113 is an attractive target due to…

The last comprehensive catalogue of high-mass X-ray binaries in the Small Magellanic Cloud (SMC) was published about ten years ago. Since then new such systems were discovered, mainly by X-ray observations with Chandra and XMM-Newton. For…

We have carried out a new photometric V,Rc study of 12 protoplanetary nebulae, objects in the short-lived transition between the AGB and PN phases of stellar evolution. These had been the subjects of an earlier study, using data from…

Short-term variability of X-ray continuum spectra has been reported for several Active Galactic Nuclei. Significant X-ray flux variations are observed within time scales down to 10^3-10^5 seconds. We discuss short variability time scales in…

This is a call for amateur astronomers who have the equipment and experience for producing high quality photometry to contribute to a program of finding periods in the optical light curves of high mass X-ray binaries (HMXB). HMXBs are…

Optical and near-infrared variability is a well-known property of young stellar objects. However, a growing number of recent studies claim that a considerable fraction of them also exhibit mid-infrared flux changes. With the aim of studying…

While the distribution of spin periods of High Mass X-ray Binaries (HMXBs) spans more than four orders of magnitude (69ms - 25min), the few known X-ray pulsars accreting from very low mass companions (<1 Msun) have very similar periods…

Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity. We investigate the correlation between the…

We report differential I-band and J-band photometry of S Ori 45, a cool (M8.5), young (1-8 Myr) brown dwarf of the sigma Orionis cluster with a likely mass estimated at around 20 times the mass of Jupiter. We detect variability (amplitudes…

A neutron star low-mass X-ray binary is a binary stellar system with a neutron star and a low-mass companion star rotating around each other. In this system the neutron star accretes mass from the companion, and as this matter falls into…

A significant number of X-ray binaries are now known to exhibit long-term ``superorbital'' periodicities on timescales of $\sim$ 10 - 100 days. Several physical mechanisms have been proposed that give rise to such periodicities, in…

High amplitude X-ray brightness oscillations during thermonuclear X-ray bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early 1996. Spectral and timing evidence strongly supports the conclusion that these oscillations…

Cen X-3 is a compact high mass X-ray binary likely powered by Roche lobe overflow. We present a phase-resolved X-ray spectral and timing analysis of two pointed XMM-Newton observations. The first one took place during a normal state of the…

We analyze the long-term (rest-frame 3-30 yr) X-Ray variability of eleven broad absorption line (BAL) quasars, mainly to constrain the variation properties of the X-Ray absorbing shielding gas that is thought to play a critical role in BAL…

We study photometric variability among the optical counterparts of X-ray sources in the old open cluster M67. The two puzzling binaries below the giant branch are both variables: for S1113 the photometric period is compatible with the…

One of the first massive stars detected in X-rays, Schulte 12 has remained a puzzle in several aspects. In particular, its extreme brightness both in the visible and X-ray ranges is intriguing. Thanks to Swift and XMM-Newton observations…

30$\%$--50$\%$ of the luminous pulsating red-giant stars show light variations of a longer period than the pulsation periods. Those periods are called long secondary periods (LSP). There has been debated for many years but the origin of the…

New observations are presented of four evolved objects that display long, multi-year variations in their light curves. These are interpreted as good evidence of their binary nature, with the modulation caused by the barycenter motion of the…

In the past five years observations with the Rossi X-ray Timing Explorer have revealed fast quasi-periodic oscillations in the X-ray flux of about 20 X-ray binaries. Thought to originate close to the surface of a neutron star, these…

A great portion of the cataclysmic variable population, between 40% and 70%, is predicted to be made up of period-bouncers, systems with degenerate donors that have evolved past the period minimum. However, due to their intrinsic faintness,…