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What is the origin of the soft excess in active galactic nuclei? (2007)
Journal Article
Sobolewska, M., & Done, C. (2007). What is the origin of the soft excess in active galactic nuclei?. Monthly Notices of the Royal Astronomical Society, 374(1), 150-158. https://doi.org/10.1111/j.1365-2966.2006.11117.x

We investigate the nature of the soft excess below 1 keV observed in active galactic nuclei. We use the XMM–Newton data of the low-redshift, optically bright quasar, PG 1211+143, and we compare it with the narrow-line Seyfert 1 galaxy, 1H 0707−495, w... Read More about What is the origin of the soft excess in active galactic nuclei?.

Spectral and Fourier analyses of X-ray quasi-periodic oscillations in accreting black holes (2006)
Journal Article
Sobolewska, M., & Zycki, P. (2006). Spectral and Fourier analyses of X-ray quasi-periodic oscillations in accreting black holes. Monthly Notices of the Royal Astronomical Society, 370(1), 405-414. https://doi.org/10.1111/j.1365-2966.2006.10489.x

We study energy dependencies of quasi-periodic oscillations (QPOs) from a number of black hole X-ray binaries. The selected sources were observed by RXTE at time periods close to state transitions and showed QPOs in the 1–10 Hz range. We have constru... Read More about Spectral and Fourier analyses of X-ray quasi-periodic oscillations in accreting black holes.

Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects (2005)
Journal Article
Zycki, P., & Sobolewska, M. (2005). Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects. Monthly Notices of the Royal Astronomical Society, 364(3), 891-898. https://doi.org/10.1111/j.1365-2966.2005.09619.x

We have constructed models of the quasi-periodic variability of X-ray emission from accreting compact objects. Assuming a general scenario of a propagation model of variability, with inverse Compton upscattering as the emission mechanism, we have con... Read More about Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects.

High-redshift radio-quiet quasars: Exploring the parameter space of accretion models. II. Patchy corona model (2004)
Journal Article
Sobolewska, M., Siemiginowska, A., & Zycki, P. (2004). High-redshift radio-quiet quasars: Exploring the parameter space of accretion models. II. Patchy corona model. Astrophysical Journal, 617(1), 102-112. https://doi.org/10.1086/425262

We modeled the spectral energy distribution of high-redshift radio-quiet quasars (high-z RQQs). We computed spectra in a patchy corona geometry in which an accretion disk extends to the last stable orbit and the Comptonizing active regions (hot cloud... Read More about High-redshift radio-quiet quasars: Exploring the parameter space of accretion models. II. Patchy corona model.

High-redshift radio-quiet quasars: Exploring the parameter space of accretion models. I. Hot semispherical flow (2004)
Journal Article
Sobolewska, M., Siemiginowska, A., & Zycki, P. (2004). High-redshift radio-quiet quasars: Exploring the parameter space of accretion models. I. Hot semispherical flow. Astrophysical Journal, 608(1), 80-94. https://doi.org/10.1086/392529

Two families of models are currently considered to describe an accretion flow onto black holes and production of the observed X-ray radiation: (1) a standard cold accretion disk with a hot corona above it and (2) an outer truncated accretion disk wit... Read More about High-redshift radio-quiet quasars: Exploring the parameter space of accretion models. I. Hot semispherical flow.

Spectral modeling of the three spectral states of the galactic microquasar GRS 1915+105 (2003)
Journal Article
Sobolewska, M., & Zycki, P. (2003). Spectral modeling of the three spectral states of the galactic microquasar GRS 1915+105. Astronomy & Astrophysics, 400(2), 553-558. https://doi.org/10.1051/0004-6361%3A20030020

We have analyzed Rossi X-ray Timing Explorer spectral data of the Galactic micro-quasar GRS 1915+105 in its various spectral states, as defined by Belloni et al. (2000). In states A and B the spectra are dominated by a strong soft thermal component,... Read More about Spectral modeling of the three spectral states of the galactic microquasar GRS 1915+105.