相关论文: Phase-modulated X-ray Emission from Cepheids due t…
We present the results of the analysis of Type II and anomalous Cepheids using the data from the Kepler K2 mission. The precise light curves of these pulsating variable stars are the key to study the details of their pulsation, such as the…
The Cepheid variables in SMC, LMC, the Milky Way, M33 and M31 are used to examine the dependence of pulsation mode on metallicity which was previously found in red supergiants. The initial samples of Cepheids are collected from the Cepheid…
We compute the phase lags between the radial velocity curves and the light curves $\Delta \Phi_1= \phi^{V_r}_1 - \phi^{mag}_1$ for classical Cepheid model sequences both in the linear and the nonlinear regimes. The nonlinear phase lags…
Pulse profiles from X-ray pulsars often exhibit strong energy dependence and both periodic and aperiodic variations with time. The great variety of profiles observed in various sources, and even from individual sources, makes it difficult…
A model is proposed for the observed combination of power-law and thermal emission of keV X-rays from rotationally powered pulsars. For gamma-ray pulsars with accelerators very many stellar radii above the neutron star surface, 100 MeV…
The Crab Nebula and the Pulsar have been pointed several times by the BeppoSAX satellite. We analysed all these observations, summed together, to study the main spectral properties with a good phase resolution. A new accurate estimate of…
We have investigated line profiles in a large sample of Cepheid spectra, and found four stars that show unusual (for Cepheids) line profile structure (bumps or/and asymmetries). The profiles can be phase dependent but the behavior persists…
The star BW Vul excites an extremely strong radial pulsation that grows in its envelope and is responsible for visible shock features in the continuum flux and spectral line profiles emerging in the atmosphere At two phases separated by 0.8…
We report on the discovery of polarized X-ray emission from an accreting millisecond pulsar. During a 10-day-long coverage of the February 2024 outburst of SRGA J144459.2-604207, the Imaging X-ray Polarimetry Explorer (IXPE) detected an…
The reflection of X-ray radiation produced near a compact object from its stellar companion contributes to the orbital variability of polarization in X-ray binaries. The X-rays are reflected mainly via Thomson scattering resulting in a high…
We present CCD phase-binned light curves at 490 nm for 97 Cepheid variable stars in the bar of the LMC. The photometry was obtained as part of the French EROS project and has excellent phase coverage, permitting accurate decomposition into…
The Imaging X-ray Polarimetry Explorer (IXPE) detected X-ray polarization in the nearest Seyfert 2 galaxy, the Circinus galaxy, for the first time. To reproduce the IXPE results, we computed the degree of polarization based on two types of…
Energetic pulsars power winds of relativistic leptons which produce photon nebulae (so- called pulsar wind nebulae, PWNe). Their spectral energy distribution has a double-humped structure: the first hump lies in the X-ray regime, the second…
Ultraluminous X-ray sources (ULXs) are enigmatic sources first discovered in the 1980s in external galaxies. They are characterized by their extraordinarily high X-ray luminosity, which often exceeds $10^{40}\, \rm{erg \; s^{-1}}$. Our…
A few Galactic classical Cepheids were observed in the programmes of space missions as Coriolis, MOST and Kepler. An appealing opportunity was to detect additional nonradial modes, thus opening the possibility to perform asteroseismic…
Cepheid masses derived from pulsations or binary dynamics are generally lower than those derived from stellar evolution models. Recent efforts have been dedicated to investigating the effects of abundances, mass loss, rotation, convection…
We report results on the timing and spectral analysis of observations of the millisecond pulsar PSR B1821-24 with RXTE, BeppoSAX and Chandra. The X-ray light curve is characterized by two narrow peaks at a phase distance of 0.452+/-0.002.…
Context: In addition to coherent pulsation, many accreting neutron stars exhibit flaring activity and strong aperiodic variability on time scales comparable to or shorter than their pulsation period. Such a behavior shows that the accretion…
We report on the BeppoSAX monitoring of a giant outburst of the transient X-ray pulsar XTE J1946+274 in 1998. The source was detected with a flux of ~ 4 x 10^(-9) erg cm^(-2) s^(-1) (in 0.1 - 120 keV range). The broadband spectrum, typical…
This article is the first in the series that analyze about 1.87 million periods of PSR B0531+21 (Crab pulsar), observed by the PCA detector aboard the RXTE x-ray observatory. The Crab pulsar's x-ray light curve shows little variation over…