Maitrayee Gupta (CAMK, Warsaw)
based on Jiang et al., arXiv:1612.08747
Klaudia Kowalczyk (CAMK, Warsaw)
based on El-Badry et al. arXiv:1610.04232
Deepika Bollimpalli (CAMK, Warsaw)
based on HigginBottom et al. arXiv:1612.08996 and Done et al. arXiv:1612.09377
Pawel Bielewicz (CAMK, Warsaw)
based on Louis et al. arXiv:1610.02360
Tek Prasad Adhikari (CAMK, Warsaw)
based on C. V. Silva et al. A&A, 2016
Andrzej Zdziarski (CAMK, Warsaw)
partly based on Plotkin et al. ApJ 834 (2017)
Justyna Średzińska (CAMK, Warsaw)
Wenchi Yan (CAMK, Warsaw)
based on Roberts et al. MNRAS (2017)
Nicolas Peschken (CAMK, Warsaw)
based on Lagos et al. arXiv:1701.04407
Karolina Bąkowska (CAMK, Warsaw)
based on Boyd et al., MNRAS 466 (2017)
Krzysztof Nalewajko (CAMK, Warsaw)
Diogo Belloni (CAMK, Warsaw)
based on Pala et al. MNRAS 466 (2017)
Krystian Ilkiewicz (CAMK, Warsaw)
based on Schmid et al., arXiv 1703.05624
Magdalena Sieniawska (CAMK, Warsaw)
based on Ball & Brunner, International Journal of Modern Physics D 19 (2010).
Nazma Islam (CAMK, Warsaw)
based on Jain et al. MNRAS (2017) and Iaria et al. arXiv:1703.05294
Janusz Ziółkowski (CAMK, Warsaw)
based on on Molnar et al., arXiv:1704.05502 and Gazeta Wyborcza, 16.01.2017
Andrzej Zdziarski (CAMK, Warsaw)
based partly on Torres et al., 2017, ApJ, 836, 68
Wenchi Yan (CAMK, Warsaw)
based on Sądowski & Gaspari, MNRAS 468 (2017)
Zhao Guo (CAMK, Warsaw)
Based partly on de Wit et al. ApJL (2017).
Swayamtrupta Panda (CAMK/CFT, Warsaw)
based on Pu Du et. al ApJL (2017)
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.
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.
Vadym Khomenko (CAMK, Warsaw)
based on Beloin et al. arXiv:1612.04289
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.
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.
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.
Abbas Askar (CAMK, Warsaw)
The talk is based on Adams et al. MNRAS, 468, 4968-4981 (2017).
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.
Katarzyna Rusinek (NCAC, Warsaw)
The talk is based on Sebastian et al., arXiv:1710.06182.
Alex Markowitz (NCAC, Warsaw)
Talk is based on https://arxiv.org/abs/1701.04641.
Ananda Deepika Bollimpalli (NCAC, Warsaw)
Based on https://arxiv.org/pdf/1711.02449.pdf.
Dominik Gronkiewicz (NCAC, Warsaw)
The talk is based on https://arxiv.org/abs/1711.06289.
Swayamtrupta Panda (NCAC, Warsaw)
The talk is based on https://arxiv.org/abs/1711.08122.
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.
