Related papers: Variable Stars: A Net of Complementary Methods for…

We analyze X-ray light curves of the blazars Mrk 421, PKS 2155-304, and 3C 273 using observations by the Soft X-ray Telescope on board AstroSat and archival XMM-Newton data. We use light curves of length 30-90 ks each from 3-4 epochs for…

The Allan variance is a standard technique to characterise the stability of spectroscopic instruments used in astronomical observations. The period for switching between source and reference measurement is often derived from the Allan…

RR Lyr is one of the most studied variable stars. Its light curve has been regularly monitored since the discovery of the periodic variability in 1899. Analysis of all observed maxima allows us to identify two primary pulsation states…

The B0.5IVe star gam Cas is of great interest because it is the prototype of a small group of classical Be stars having hard X-ray emission of unknown origin. We discuss results from ongoing B and V observations of the gam Cas star-disk…

The lower part of the classical instability strip and the surrounding main sequence are populated by a large variety of pulsating variable stars. In the past years a great effort was made by the stellar group of Brera Observatory to collect…

CCD photometry in the V band is presented for 7 field RR Lyrae stars selected from a sample of eight variables which, according to data collected in the literature, are expected to be {\it ab}-type pulsators, to have short periods and hence…

We have used many decades of visual observations from the AAVSO International Database, and the AAVSO time-series analysis package VSTAR, to study the long-term changes in period, amplitude, and mean magnitude in about 30 normal pulsating…

The nature of period and amplitude changes in nonradial pulsators is presently unknown. It is therefore important to examine the correlations between these changes in stars with a large number of simultaneously excited pulsation modes.…

The Wolf-Rayet star WR 46 is known to exhibit a very complex variability pattern on relatively short time scales of a few hours. Periodic but intermittent radial velocity shifts of optical lines as well as multiple photometric periods have…

We report the discovery of a new catacysmic variable system, RXJ051541+0104.6. The optical spectrum has a blue continuum with superposed H~I and He~I and II emission lines. The soft X-ray spectrum is well fit with a 50~eV black body. The…

The VIIRS Day Night Band sensor on the Suomi NPP satellite provides almost a decade of observations of night light. The daily frequency of sampling, without the temporal averaging of annual composites, requires the distinction between…

The paper addresses a sequential changepoint detection problem, assuming that the duration of change may be finite and unknown. This problem is of importance for many applications, e.g., for signal and image processing where signals appear…

The quasi-periodic feature of 1-10 years exhibited in pulsar timing noise has not been well understood since 1980. The recently demonstrated correlation between timing noise and variation of pulse profile motivates us to further investigate…

We investigate the question whether there is a real difference in the light change between stars classified as semiregular (SRV) or irregular (Lb) variables by analysing photometric light curves of 12 representatives of each class. Using…

This paper describes the first part of the photometric data from the 9x9 deg ASAS cameras monitoring the whole southern hemisphere in V-band. Data acquisition and reduction pipeline is described and preliminary list of variable stars is…

DM Cyg, a fundamental mode RRab star was observed in the 2007 and 2008 seasons in the frame of the Konkoly Blazhko Survey. Very small amplitude light curve modulation was detected with 10.57 d modulation period. The maximum brightness and…

The star CoRoT102781750 reveals a puzzle, showing a very complex and altering variation in different `CoRoT colours'. We established without doubt that more than a single star was situated within the CoRoT mask. Using a search for…

A significant amount of data on the historical and current behaviour of variable stars is derived from visual estimates of brightness using a set of comparison stars. To make optimum use of this invaluable collection one must understand the…

We present the analysis of time-resolved spectroscopy of the pulsating sdB star PG1605+072. From our main observing run of 16 nights we have detected velocity variations at 5 frequencies that correspond to those found in photometry. Based…

Archival observations from the Very Large Array (VLA) at frequencies between 1.4 GHz and 43 GHz of the 6.6-day O6.5-7+O5.5-6 binary Cyg OB2 #5 over 20 years are re-examined. The aim is to determine the location and character of its known…