Journal Club


"Detection of Time Lags Between Quasar Continuum Emission Bands based on Pan-STARRS Light-curves"

Maitrayee Gupta (CAMK, Warsaw)

based on Jiang et al., arXiv:1612.08747


"When the Jeans Don't Fit"

Klaudia Kowalczyk (CAMK, Warsaw)

based on El-Badry et al. arXiv:1610.04232


"Thermal Disk winds in X-ray binaries"

Deepika Bollimpalli (CAMK, Warsaw)

based on HigginBottom et al. arXiv:1612.08996 and Done et al. arXiv:1612.09377


"The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters"

Pawel Bielewicz (CAMK, Warsaw)

based on Louis et al. arXiv:1610.02360


"Timing the warm absorber in NGC 4051"

Tek Prasad Adhikari (CAMK, Warsaw)

based on C. V. Silva et al. A&A, 2016


"V404 Cyg - an unusual black-hole transient"

Andrzej Zdziarski (CAMK, Warsaw)

partly based on Plotkin et al. ApJ 834 (2017)


"A long term study of AGN X-ray variability. Structure function analysis on a ROSAT-XMM quasar sample"

Justyna Średzińska (CAMK, Warsaw)

Based on Middei et al. eprint arXiv:1612.08547


"Towards self-consistent modelling of the Sgr A* accretion flow: linking theory and observation"

Wenchi Yan (CAMK, Warsaw)

based on Roberts et al. MNRAS (2017)


"The catastrophic effect of mergers on the angular momentum and morphology of galaxies in EAGLE"

Nicolas Peschken (CAMK, Warsaw)

based on Lagos et al. arXiv:1701.04407


"A 16-yr photometric campaign on the eclipsing novalike variable DW Ursae Majoris"

Karolina Bąkowska (CAMK, Warsaw)

based on Boyd et al., MNRAS 466 (2017)


"New insight into dissipation and stability of relativistic jets"

Krzysztof Nalewajko (CAMK, Warsaw)

Based on Barniol Duran et al., eprint arXiv:1612.06929


"Effective temperatures of cataclysmic-variable white dwarfs as a probe of their evolution"

Diogo Belloni (CAMK, Warsaw)

based on Pala et al. MNRAS 466 (2017)


"Imaging of the stellar binary and the innermost jet clouds of R Aqr"

Krystian Ilkiewicz (CAMK, Warsaw)

based on Schmid et al., arXiv 1703.05624


"Machine learning (not only) in astronomy & astrophysics"

Magdalena Sieniawska (CAMK, Warsaw)

based on Ball & Brunner, International Journal of Modern Physics D 19 (2010).


"Indication of a massive circumbinary planet orbiting the Low Mass X-ray binary MXB 1658-298"

Nazma Islam (CAMK, Warsaw)

based on Jain et al. MNRAS (2017) and Iaria et al. arXiv:1703.05294


"An imminent Nova in 2022?"

Janusz Ziółkowski (CAMK, Warsaw)

based on on Molnar et al., arXiv:1704.05502 and Gazeta Wyborcza, 16.01.2017


"Gamma rays from binaries and the case of transitional pulsars"

Andrzej Zdziarski (CAMK, Warsaw)

based partly on Torres et al., 2017, ApJ, 836, 68


"Kinetic and radiative power from optically thin accretion flows and visualization in simulation"

Wenchi Yan (CAMK, Warsaw)

based on Sądowski & Gaspari, MNRAS 468 (2017)


"Tidally Induced Stellar Pulsations in Eccentric Binaries"

Zhao Guo (CAMK, Warsaw)

Based partly on de Wit et al. ApJL (2017).


"Hidden Broad Line Regions in Seyfert 2 Galaxies"

Swayamtrupta Panda (CAMK/CFT, Warsaw)

based on Pu Du et. al ApJL (2017)


"Pulse Profiles: A tool to probe into the accretion geometry of Accretion Powered X-ray pulsars"

Aru Beri (University of Southampton)

In the case of high magnetic field neutron star binary systems (1012 -1013 Gauss), stellar magnetic field plays an important role in channelling of matter onto the surface of a neutron star. Physics of boundary layer (magnetosphere) is quite complicated. The pulse profiles of accretion powered pulsars and its dependence on energy, luminosity and time provide clues about the accretion geometry of the emission region, beaming pattern, reprocessing etc. In this talk, I will discuss the pulse profiles of two unique pulsars, 4U 1626-67 and LMC X-4. Using all the available data of the accretion powered X-ray pulsar 4U 1626–67 over the last 40 years since its discovery, we have established a clear link between the accretion torque and its pulse profile. I will also discuss an interesting feature known as dips in the pulse profiles. In particular, I will show results from a very detailed pulse profile evolution study of an X-ray pulsar LMC X–4. LMC X-4 is one of the very few sources that show strong X-ray flares. Using the long observations of LMC X-4 that contain both flares and persistent emission we have estimated the timescales required for the formation of accretion stream that caused dip in the pulse profiles of LMC X–4, after the accretion region and the beaming etc is disturbed during flares in this system.


"A 3D map of Galactic dust"

Gregory Green (Stanford U.)

Dust is a critical foreground for many areas of astronomy, extinguishing and reddening sources in the ultraviolet, optical and near-infrared regions of the spectrum, and contaminating our view of the cosmic microwave background in the far-infrared. Dust also traces the interstellar medium, and is therefore itself an interesting probe of Milky Way structure. Maps of interstellar dust therefore find wide application in astronomy. Up until recently, most such maps have been two-dimensional in nature, tracing the column density of dust with angle on the sky. However, in order to correct observations of sources embedded in the Milky Way, or to study dust clouds within the Galaxy, a three-dimensional map that traces dust density with distance is desirable. I present a three-dimensional map of interstellar dust reddening, covering the northernmost three-quarters of the sky out to a distance of several kiloparsecs, based on optical and near-infrared stellar photometry from Pan-STARRS 1 and 2MASS. The map is probabilistic, yielding the uncertainty in dust reddening along each line of sight. It has an angular resolution ranging from 3.4' to 13.7', and a distance resolution of ~25%. The map reveals detailed structure within the Milky Way, from filaments to large cloud complexes. Out of the plane of the Galaxy, where we c an see through the entire dust column, we find good agreement with previous two-dimensional dust maps. In the plane of the Galaxy, our map gives distances to dust clouds which are consistent with known literature distances. In order to extend the map further into the Southern Hemisphere, I have completed an optical/near-infrared survey of the Galactic plane south of a declination of -30 degrees, using the Dark Energy Camera on the 4m Blanco telescope on Cerro Tololo. In the near future, the addition of Gaia parallaxes and spectrophotometry will help us to refine the distances in our map.


" Constraining Superfluidity in Dense Matter from the Cooling of Isolated Neutron Stars"

Vadym Khomenko (CAMK, Warsaw)

based on Beloin et al. arXiv:1612.04289


"Ultraluminous X-ray sources"

Sergei Fabrika (Special Astrophysical Observatory RAS, Laboratory of Stellar Physics)

The origin of Ultraluminous X-ray Sources (ULXs) in external galaxies whose X-ray luminosities exceed those of the brightest black holes in our Galaxy by hundreds and thousands of times is mysterious. The most popular models for the ULXs involve either intermediate mass black holes (IMBHs) or stellar-mass black holes accreting at super-Eddington rates. Here we review the ULX properties. Their X-ray spectra indicate a presence of hot winds in their accretion disks supposing the supercritical accretion. In recent years, new surprising results were discovered in X-ray data, ULX-pulsars and high-velocity outflows up to 0.2c. They are also in accordance with the super-Eddington accretion. However, the strongest evidences come from optical spectroscopy. The spectra of the ULX counterparts are very similar to that of SS433, the only known supercritical accretor in our Galaxy. The spectra are apparently of WNL type (late nitrogen Wolf-Rayet stars) or LBV (luminous blue variables) in their hot state, which are very scarce stellar objects. We find that the spectra do not originate from WNL/LBV type donors but from very hot winds from the accretion disks, which have similar physical conditions as the stellar winds from these stars. Recent data were obtained with Subaru telescope, these two ULXs have very unusual spectra. 


"Multi-wavelength Variability and QPOs in Blazars"

Dr. Alok C. Gupta (Aryabhatta Research Institute of Observational Sciences (ARIES) )

Blazar is a subclass of radio loud AGN which show flux variation in the complete EM spectrum on diverse timescales ranging from as short as a few tens of minutes and as long as several years. The blazar emission is predominantly non-thermal. In the present talk, I will discuss some of interesting recent results published by my group based on multi-wavelength ground and space based data. We have detected flux variation in blazars on diverse time scales, cross-correlated multi-wavelength flux and spectral variabilities. We have also detected quasi-periodic oscillations (QPOs) in time series data of blazars in optical and X-ray bands. I will also briefly describe which are dominant AGN standard models which can explain our findings.


"Ultraluminous X-ray sources with neutron star accretors"

Grzegorz Wiktorowicz (CAMK, Warsaw)

Ultraluminous X-ray sources have luminosities significantly above the Eddington limit for a stellar mass black hole. A recent discovery of pulsars in a few ULXs seems to prove that the superEddinton emission is possible. We analysed mass transfer rates onto neutron stars in X-ray binaries in order to verify if they can be high enough to power a ULX. We found out that NS accretors may constitute a significant fraction of the ULX population and even dominate it in old stellar systems.


"The Search for Failed Supernovae with the Large Binocular Telescope: Confirmation of a Disappearing Star"

Abbas Askar (CAMK, Warsaw)

The talk is based on Adams et al. MNRAS, 468, 4968-4981 (2017).


"Long term study of the light curve of PKS 1510-089 in GeV energies"

Raj Prince (Raman Research Institute, Bengaluru )

We have analyzed data from Blazar FSRQ PKS 1510-089 collected over a period of eight years from 2008 August to 2016 December with the Fermi-LAT. We have identified the several flares of this highly variable source, studied their temporal and spectral properties in detail. Five flares and few sub-flares have been identified in our study. I will talk about these five flares in detail.


"Discovery of a new, 2.2 Mpc Giant Radio Galaxy at a redshift of 0.57"

Katarzyna Rusinek (NCAC, Warsaw)

The talk is based on Sebastian et al., arXiv:1710.06182.


"Hydrodynamic simulations of moonlet-induced propellers in Saturn’s rings: Application to Bleriot"

Alex Markowitz (NCAC, Warsaw)

Talk is based on


"A young contracting white dwarf in the peculiar binary HD 49798/RX J0648.0–4418 ?"

Ananda Deepika Bollimpalli (NCAC, Warsaw)

Based on


"Hitomi Observation of Radio Galaxy NGC 1275: The First X-ray Microcalorimeter Spectroscopy of Fe-Kα Line Emission from an Active Galactic Nucleus"

Dominik Gronkiewicz (NCAC, Warsaw)

The talk is based on


"Discovery of 21 New Changing-Look AGNs"

Swayamtrupta Panda (NCAC, Warsaw)

The talk is based on


"AGN and Relativistic Corrections of Cutoff Energy "

Lydia Stofanova (Czeska Akademia Nauk)

Hard X-ray spectra of accreting black holes in active galactic nuclei are characterized by a power-law shape with an exponential cut-off energy at several tens up to a few hundred of keV. The value of the cut-off energy is related with the temperature of a hot corona that reprocesses and inversely Comptonise thermal emission from the accretion disc. The exact geometry of the corona is, however, unknown. Several observations suggest it to be very compact and in a close proximity to the compact black hole. Such location implies strong relativistic effects on the resulting spectra.