Related papers: Amplitude variability and multiple frequencies in …

Ongoing and future surveys with repeat imaging in multiple bands are producing (or will produce) time-spaced measurements of brightness, resulting in the identification of large numbers of variable sources in the sky. A large fraction of…

We present an analysis of multifrequency light curves of the sources 2223-052 (3C 446), 2230+114 (CTA 102), and 2251+158 (3C 454.3), which had shown evidence of quasi-periodic activity. The analysis made use of data from the University of…

Solar gravity modes are considered as the {\it Rosetta Stone} for probing and subsequently deciphering the physical properties of the solar inner-most layers. Recent claims of positive detection therefore shed some new light on the…

MOST (Microvariability & Oscillations of STars) and ASAS (All Sky Automated Survey) observations have been used to characterize photometric variability of TW Hya on time scales from a fraction of a day to 7.5 weeks and from a few days to 8…

Here we present the first optical photometric monitoring results of a sample of twelve newly discovered blazars from the ICRF - Gaia CRF astrometric link. The observations were performed from April 2013 until August 2019 using eight…

Using the United Kingdom Infrared Telescope on Mauna Kea, we have carried out a new near-infrared J, H, K monitoring survey of almost a square degree of the star-forming Orion Nebula Cluster with observations on 120 nights over three…

The variability of the high-frequency peaked BL Lac object PKS 2155-304 is studied using almost 10 years of optical, X-ray and gamma-rays data. Publicly available data have been gathered and analyzed with the aim to characterize the…

We report a time-series analysis of satellite photometry of the non-radially pulsating Oe star zeta Oph, principally using data from SMEI obtained 2003--2008, but augmented with MOST and WIRE results. Amplitudes of the strongest photometric…

Previously, the X-ray emission of zeta Puppis was found to be variable with light curves harbouring "trends" with a typical timescale longer than the exposure length. The origin of these changes was proposed to be linked to large-scale…

While long period variables (LPVs) have been extensively investigated, especially with MACHO and OGLE data for the Magellanic Clouds, there still exist open questions in their pulsations regarding the excitation mechanisms, radial order and…

Pulsation frequencies of acoustic modes are calculated for realistic rotating stellar models using both a perturbative and a two-dimensional approach. A comparison between the two yields validity domains which are similar to those…

We present an analysis of the pulsation behaviour of the Delta Scuti stars 7 Aql (HD 174532) and 8 Aql (HD 174589) -- a new variable star -- observed in the framework of STEPHI XII campaign during 2003 June--July. 183 hours of high…

We present a detailed period analysis for 93 red semiregular variables by means of Fourier and wavelet analyses of long-term visual observations carried out by amateur astronomers. The results of this analysis yield insights into the mode…

The blazar 3C 454.3 was revealed by the Fermi Gamma-ray Space Telescope to be in an exceptionally high flux state in July 2008. Accordingly, we performed a multi-wavelength monitoring campaign on this blazar using IR and optical…

Observations of 25 Ori much expand the picture derived of other early-type Be stars with BRITE and SMEI. Two instead of one difference frequencies rule the variability: (a) The lower one, 0.0129 c/d, is the frequency of events with full…

A large number of AGN have been monitored for nearly 30 years at 22, 37 and 87 GHz in Mets\"ahovi Radio Observatory. These data were combined with lower frequency 4.8, 8.0 and 14.5 GHz data from the University of Michigan Radio Astronomy…

This study presents an analysis of the optical variability of the blazar 1E 1458.8+2249 on diverse timescales using multi-band observations, including observations in the optical BVRI bands carried out with the T60 and T100 telescopes from…

Searching for combinations in the frequency spectra of variable stars is a commonly used method within the asteroseismological community, as harmonics and linear combinations of individual frequencies are expected to appear not only by…

Alternative theories of gravity predict the presence of massive scalar, vector, and tensor gravitational wave modes in addition to the standard massless spin~2 graviton of general relativity. The deflection and frequency shift effects on…

We have undertaken a nearly simultaneous optical/UV and X-ray variability study of the flat spectrum radio quasar, 3C 273 using data available from the XMM$-$Newton satellite mission from June 2000 to July 2012. Here we focus on the…