Related papers: Pulsations in the atmosphere of the rapidly oscill…
Seismology of stars provides insight into the physical mechanisms taking place in their interior, with modes of oscillation probing different layers. Low-amplitude acoustic oscillations excited by turbulent convection were detected four…
Phase-resolved high resolution optical spectroscopy has revealed narrow N III and He II emission lines from the soft X-ray transient Aquila X-1 during its 2004 outburst that move as a function of the orbit consistent with the phasing of the…
We have measured the times of onset of recent fadings in four R CrB stars -- V854 Cen, RY Sgr, R CrB, and S Aps. These times continue to be locked to the stars' pulsation periods, though with some scatter. In RY Sgr, the onsets of fading…
The pulsating white dwarf star PY Vul (G~185-32) exhibits pulsation modes with peculiar properties that set it apart from other variable stars in the ZZ Ceti (DAV) class. These peculiarities include a low total pulsation amplitude, a mode…
Asteroseismology has the potential to provide new insights into the physics of stellar interiors. We have obtained UVES high time resolution observations of the delta Scuti star HD21190 and of the Ap Sr star HD218994 to search for…
Pulsation period changes in Mira type variables are investigated using the stellar evolution and nonlinear stellar pulsation calculations. We considered the evolutionary sequence of stellar models with initial mass 3 Msol and population I…
Quasi-periodic pulsations (QPPs) of Sun and stars are challenging for stellar flare models. The white light stellar QPPs in the periodicity region of tens of second are unexplored yet. On the basis of observations with the 6-m telescope BTA…
The Anomalous X-ray Pulsars (AXPs) are a small class of pulsars with spin periods in the 6-12 s range, very soft X-ray spectra, secular spin down on time scales of ~10^3-10^5 years, and lack of bright optical counterparts. Two, possibly…
Associated absorption lines (AALs) are valuable probes of the gaseous environments near quasars. Here we discuss high-resolution (6.7 km/s) spectra of the AALs in the radio-loud quasar 3C 191 (redshift z=1.956). The measured AALs have…
Context: Rapid rotation is a common feature of early-type stars but which remains a challenge for the models. The understanding of its effect on stellar evolution is however imperative to interpret the observed properties of numerous stars.…
This paper presents the multi-wavelength analysis of a 13 s quasi-periodic pulsation (QPP) observed in hard X-ray (12-300 keV) and microwave (4.9-34 GHz) emissions during a C-class flare occurred on 21 September 2015. AIA 304 and 171 \AA~…
High-energy photons may oscillate with axion-like particles (ALPs) when they propagate through the Milky Way's magnetic field, resulting in an alteration in the observed photon energy spectrum. The ultra-high energy gamma-ray spectra,…
A search was carried out for pulsars with periods (P) from 2 to 90 s in daily observations carried out over an interval of 5 years in a area measuring 6300 sq.deg. The data was obtained on a Large Phased Array (LPA) at a frequency of 111…
It has been proposed that radio pulsars can be distinguished from other point-like radio sources in continuum images by their unique interstellar scintillation signatures. Using data from the Australian Square Kilometre Array Pathfinder…
We have obtained I-band photometry of the neutron star X-ray transient Aql X--1 during quiescence. We find a periodicity at 2.487 cd-1, which we interpret as twice the orbital frequency (19.30+/-0.05 h). Folding the data on the orbital…
A search has been carried out for the pulsar J0311+1402, which has a period of $P = 40.9$ s, in the data archive of the Large Phased Array (LPA) radio telescope. When searching using fast folding algorithm (FFA), periodic pulsar radiation…
A number of studies have revealed variability from neutron star low-mass X-ray binaries during quiescence. Such variability is not well characterised, or understood, but may be a common property that has been missed due to lack of multiple…
We are using the LOw-Frequency ARray (LOFAR) to perform the LOFAR Tied-Array All-Sky (LOTAAS) survey for pulsars and fast transients. Here we present the astrometric and rotational parameters of 20 pulsars discovered as part of LOTAAS.…
Statistically analyzing Johnson UBVR observations of V1285 Aql during the three observing seasons, both activity level and behavior of the star are discussed in respect to obtained results. We also discuss the out-of-flare variation due to…
We derive expressions and develop a numerical technique for the analysis of the line profile moment variations for stars pulsating in oblique non-radial modes. This represents an extension of the widely used spectroscopic moment mode…