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Zdziarski A.A.,Centrum Astronomiczne im. M. Kopernika
Monthly Notices of the Royal Astronomical Society | Year: 2014

We apply a recently developed technique of calculating the minimum jet kinetic power to the major mass ejections of the black hole binary GRS 1915+105 observed in radio wavelengths in 1994 and 1997. We derive for them the distance-dependent minimum power, and the corresponding mass flow rate and the total energy and mass content. We find that a fast increase of the jet power with the increasing distance combined with the jet power estimates based on the bolometric luminosity imply that the source distance is ≲10 kpc. If the jet in GRS 1915 contains ions, their bulk motion dominates the jet power, which was either neglected or not properly taken into account earlier. We also reconsider the parameters of the binary, and derive the current best estimates of the distance-dependent black hole mass and the inclination based on existing measurements combined with the kinematic constraints from the mass ejections. We also find that the measurement of the donor radius of Steeghs et al. implies the distance to the system of ≲10 kpc, in agreement with the estimate from the jet power. © 2014 The Author.

Malyshev D.,NASU Bogolyubov Institute for Theoretical Physics | Zdziarski A.A.,Centrum Astronomiczne im. M. Kopernika | Chernyakova M.,Dublin City University
Monthly Notices of the Royal Astronomical Society | Year: 2013

We have obtained measurements and upper limits on the emission of Cyg X-1 in the photon energy range of 0.03-300 GeV based on observations by Fermi. We present the results separately for the hard and soft spectral states, as well as for all of the analysed data. In the hard state, we detect a weak steady emission in the 0.1-10 GeV range with a power-law photon index of γ {minus tilde} 2.6 ± 0.2 at a 4σ statistical significance. This measurement, even if considered to be an upper limit, strongly constrains Compton emission of the steady radio jet, present in that state. The number of relativistic electrons in the jet has to be low enough for the spectral components due to Compton upscattering of the stellar blackbody and synchrotron radiation to be within the observed fluxes. If optically thin synchrotron emission of the jet is to account for the MeV tail, as implied by the recently claimed strong polarization in that energy range, the magnetic field in the jet has to be much above equipartition. The GeV-range measurements also strongly constrain models of hot accretion flows, most likely present in the hard state, in which γ -rays are produced from decay of neutral pions produced in collisions of energetic ions in an inner part of the flow. In the soft state, the obtained upper limits constrain electron acceleration in a non-thermal corona, most likely present around a blackbody accretion disc. The coronal emission above 30 MeV has to be rather weak, which is most readily explained by absorption of γ -rays in pair-producing photon-photon collisions. Then, the size of the bulk of the corona is less than a few tens of the gravitational radii. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Zdziarski A.A.,Centrum Astronomiczne im. M. Kopernika | Pjanka P.,Obserwatorium Astronomiczne Uniwersytetu Warszawskiego
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present simple and accurate analytical formulas for the rates of Compton scattering by relativistic electrons integrated over the energy distribution of blackbody seed photons. Both anisotropic scattering, in which blackbody photons arriving from one direction are scattered by an anisotropic electron distribution into another direction, and scattering of isotropic seed photons are considered. Compton scattering by relativistic electrons off blackbody photons from either stars or cosmic microwave background takes place, in particular, in microquasars, colliding-wind binaries, supernova remnants, interstellar medium and the vicinity of the Sun. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Zdziarski A.A.,Centrum Astronomiczne im. M. Kopernika | Misra R.,Inter-University Center for Astronomy and Astrophysics | Gierlinski M.,Durham University
Monthly Notices of the Royal Astronomical Society | Year: 2010

We consider implications of a possible presence of a Thomson-thick, low-temperature, plasma cloud surrounding the compact object in the binary system Cyg X-3. The presence of such a cloud was earlier inferred from the energy-independent orbital modulation of the X-ray flux and the lack of high frequencies in its power spectra. Here, we study the effect of Compton scattering by the cloud on the X-ray energy and power spectra, concentrating on the hard spectral state. The process reduces the energy of the high-energy break/cut-off in the energy spectra, which allows us to determine the Thomson optical depth. This, together with the observed cut-off in the power spectrum, determines the size of the plasma to be ∼2 × 109 cm. At this size, the cloud will be in thermal equilibrium in the photon field of the X-ray source, which yields the cloud temperature of ≃3 keV, which refines the determination of the Thomson optical depth to ∼7. At these parameters, thermal bremsstrahlung emission of the cloud becomes important as well. The physical origin of the cloud is likely to be collision of the very strong stellar wind of the companion Wolf-Rayet star with a small accretion disc formed by the wind accretion. Our model thus explains the peculiar X-ray energy and power spectra of Cyg X-3. © 2009 The Authors. Journal compilation © 2009 RAS.

Zdziarski A.A.,Centrum Astronomiczne im. M. Kopernika
Astronomy and Astrophysics | Year: 2016

We discuss the idea of maximal jets introduced by Falcke & Biermann (1995, A&A, 293, 665). According to it, the maximum possible jet power in its internal energy equals the kinetic power in its rest mass. We show this result is incorrect because of an unfortunate algebraic mistake. © ESO, 2016.

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