Related papers: Short time-scale X-ray variability of Active Galac…
We present a spectral-timing analysis of two NICER observations of the weakly magnetized neutron star low-mass X-ray binary Cygnus X-2. During these observations, we detect a rapid transition from a narrow 50-Hz horizontal-branch…
We report on the results of X-ray observations of 4XMM J111816.0-324910, a transient ultra-luminous X-ray source located in the galaxy NGC 3621. This system is characterised by a transient nature and marked variability with characteristic…
The results of a 0.4-10.0 keV ASCA spectral analysis of a sample of low-luminosity AGN (LLAGN; M51, NGC 3147, NGC 4258), low-ionization nuclear emission line regions (LINERs; NGC 3079, NGC 3310, NGC 3998, NGC 4579, NGC 4594) and starburst…
We studied the aperiodic X-ray timing behaviour of the accreting millisecond pulsar SAX J1808.4-3658. The source was recently found to be the first accreting millisecond pulsar that shows the kilohertz quasi-periodic oscillations (kilohertz…
We study the timing properties of XTE J1858+034 using the Nuclear Spectroscopic Telescope Array (NuSTAR) and Burst Alert Telescope onboard Swift during the outburst in October--November 2019. We have investigated for Quasi-Periodic…
We report on a study of the narrow Fe K$\alpha$ line and reflection spectrum in the well-known Seyfert-2 AGN, NGC 4388. X-ray spectra summed from two extensive NICER monitoring campaigns, separated by years, show strong evidence of…
We used the Gemini Multi-Object Spectrograph Integral Field Unit to map the gas distribution, excitation and kinematics within the inner kiloparsec of four nearby low-luminosity active galaxies: NGC3982, NGC4501, NGC2787 and NGC4450. The…
We present a flux variability study of simultaneous RXTE and EUVE observations of the highly variable Seyfert galaxy NGC4051. We find a strong correlation between variability in the EUV and medium energy X-ray bands,indicating that both are…
We present our latest results about the short-term variability of trans-Neptunian objects (TNOs). We performed broad-band CCD photometric observations using several telescopes in Spain and Chile. We present results based on three years of…
We report the first results of quasi-simultaneous two passband optical monitoring of six quasi-stellar objects to search for micro-variability. We carried out photometric monitoring of these sources in an alternating sequence of R and V…
In this work I report on the stochastic X-ray variability of the 340 Hz accreting millisecond pulsar MAXI J0911-655. Analyzing pointed observations of the XMM-Newton and NuSTAR observatories I find that the source shows broad band-limited…
We present the results of an extensive timing analysis of the 1999 outburst of the soft X-ray transient and black hole candidate XTE J1859+226 as observed with the Rossi X-Ray Timing Explorer. Three main different types of low frequency…
Time variability is a strong probe of energetic phenomena which occur at small spatial scales, like Active Galactic Nuclei (AGN). We use ALMA observations at 100 GHz executed over a period of 2.5 months to look for time variability in the…
Long-standing optical quasi-periodic oscillations (QPOs) with periodicity of hundreds to thousands of days have been accepted as indicators for central sub-pc binary black hole systems (BBHs) in broad line active galactic nuclei (BLAGN).…
The Narrow-line Seyfert 1 galaxy NGC 4051 is known to exhibit significant X-ray spectral/flux variations and have a number of emission/absorption features. X-ray observations have revealed that these absorption features are blueshifted,…
We report the detection of an absorbed central X-ray source and its strong, rapid variability in NGC4395, the least luminous Seyfert nucleus known. The X-ray source exhibits a number of flares with factors of 3-4 flux changes during a half…
We use a model-independent technique to investigate the nature of the 2-15 keV X-ray spectral variability in four Seyfert galaxies and distinguish between spectral pivoting and the two-component model for spectral variability. Our analysis…
We report the detection of mHz quasi-periodic oscillations (QPOs) in four NuSTAR observations of 4U 1626-67 during its recent spin-down episode. By using a novel method based on the Hilbert-Huang Transform (HHT), we present the first…
We showcase a tool suite that enables the fitting of soft X-ray spectra in active galactic nuclei (AGN), without the need for specialist software, allowing access to AGN physics for school students. While these standardised Python tools…
We present a study of variability time scales in a large sample of Active Galactic Nuclei at several frequencies between 4.8 and 230 GHz. We investigate the differences of various AGN types and frequencies and correlate the measured time…