Wednesday Colloquium



Annual NCAC Conference (NCAC, Warsaw)


"Hello M4, how old are you?"

Janusz Kałużny (NCAC, Warsaw)

Detached eclipsing binaries allow robust determination of ages and distances of globular cluster. I will present analysis of 3 such systems belonging to the nearby cluster M4. This work is based on the data collected in years 1995-2008 at LCO and CTIO observatories. I will try to explain why it took so long. At the end I will comment on recent identification of two candidates for stellar mass black holes in M22.


"The Gaia-ESO Public Spectroscopic Survey"

Rodolfo Smiljanic (NCAC, Toruń)

The Gaia-ESO Public Spectroscopic Survey is a four years project that is obtaining high-quality spectroscopy of some 100 000 Milky Way stars, in the field and in open clusters. It covers all the major components of the Milky Way. This survey will provide the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. This alone will revolutionise knowledge of Galactic and stellar evolution. When combined with precision astrometry from the Gaia satellite, the survey will allow the quantification of the formation history and evolution of young, mature and ancient Galactic populations. I will describe the survey, its organization, scientific goals, operation and timescales. I will also present the first release of reduced spectra and some of the early science results.


"Paleomagnetism and its applications in planetary sciences"

Marek Lewandowski (Institute of Geological Sciences PAN, Warszawa)

Paleomagnetism is a branch of the Earth sciences, straddling geology and geophysics. Scientific potential of paleomagnetism gave a way to a revolution in understanding of the Earth system in the mid-50’s. The main paradigm of paleomagnetism is a geocentric axial dipole concept, a main tool being the study of the record of the Earth's magnetic field in rocks. Modern technics of identification a natural remanent magnetization of rocks enable us to conclude on continental drift, crustal blocks rotations, geomagnetic field inversion of polarity, as well as dating tectonic events, thermal history of rocks, fluids migrations through the rocks, and other applications in geosystem sciences.


"SPICA - The Next Generation Infrared Space Mission"

Ryszard Szczerba (NCAC, Toruń)

SPICA - SPace Infrared telescope for Cosmology and Astrophysics is a common project of JAXA and ESA with a 3 m class telescope, which will be cooled for the first time to about 6K. In this way SPICA will provide a unique environment where 3 planned instruments are limited only by the cosmic background itself. The wavelength range covered by the SPICA instruments will be from 5 up to 210 micrometers. The main scientific objectives of the mission are: --- formation and evolution of galaxies; --- formation and evolution of planetary systems; and --- life cycle of dust. During my talk I will present overview of the mission and possibility for Poland to join the SAFARI consortium. SAFARI - Spica FAR infrared Istrument - is one of the most important instrument planned for SPICA.


"Drift of light rays induced by nonsymetric cosmic flow: an observational test of homogeneity of the Universe + a few general comments on inhomogeneous models"

Andrzej Krasiński (NCAC, Warsaw)

Investigation of paths of light rays in inhomogeneous cosmological models shows that observers in favourable positions would see galaxies drift across the sky at a rate of up to $10^{-6}$ arc seconds per year. Such a drift would be possible to measure using devices that are under construction; the required time of monitoring would be approx. 10 years. This effect is zero in the FLRW models, so it provides a measure of inhomogeneity of the Universe. In the second part of the talk, the real-time cosmology program will be briefly described, and a few widespread misconceptions about the cosmological models will be pointed out and corrected.


"The Equations of Cosmoseismology"

Ed Spiegel (Columbia University )


"Heliosphere - do we understand it?"

Maciej Bzowski (Space Research Center, Warsaw)

Heliosphere is a complex, multicomponent astrophysical system where solar wind and interstellar plasma interaction is modulated by neutral atoms. Studies of the heliosphere are carried out both by in situ and remote sensing observations. In situ measurements provide detailed diagnostics of the solar wind multi-component plasma. Remote sensing studies, carried out mostly based on observations of neutral atoms, provide a more global view of the Local Interstellar Cloud and the boundary region of the heliosphere. We will attempt to present the present level of understanding of the heliosphere as it emerges from the synegry of observations from the Ulysses, Voyager, and IBEX missions.


"Contact Binary Stars: 45 Years after Lucy"

Stefan Mochnacki (University of Toronto)

In 1968, Leon Lucy proposed a compelling model for W U Ma stars involving a close binary surrounded by a common convective envelope. I will review what we now know about contact binaries, and whether this model has fundamental difficulties. I also will briefly touch upon the challenges of computing light curves and spectra when space-based observations are a hundred times more precise than theoretical calculations using methods first devised by Lucy.


"Forty years of the Shakura-Sunyaev ISCO paradigm "

Marek Abramowicz (NCAC, Warsaw)

One of the key concepts in the Shakura-Sunyaev black hole accretion disk model is the existence of ISCO. I will briefly discuss ISCO's original meaning, and at length a few recent papers that address a relevance of the concept of the "inner disk edge" in the context of the magneto-rotational (Balbus-Hawley) instability.


"Galactic Wind Haze"

Peter L. Biermann (MPI for Radioastronomy, Bonn, Germany)

We present a comprehensive interpretation of the Galactic wind haze at radio and gamma-ray wavelengths: We propose that the solution is an unsteady Galactic wind, driven by cosmic rays and massive star activity. With this ansatz we discuss i) the Planck and WMAP haze, ii) the Fermi haze and the Fermi bubble, iii) the cosmic ray electron and positron data, iv) the 511 keV emission line, v) the 130 GeV feature, vi) the magnetic fields in the wind, vii) the radial profile, viii) the energetics, and ix) the non-stationarity and spectrum of magnetic irregularities in the wind.


"Radio and optical monitoring of blazars and the RT90 progress report"

Andrzej Kus (Astronomy Center, Nicolaus Copernicus University, Toruń)

A progress reports and recent achievements will be presented on two subjects: 1. Radio monitoring of Fermi sources on Torun 32m RT in combination with similar programs performed at OVRO (Caltech) 40m and MPIfR 100m RT. A new development to observe polarization at optical range within RoboPol collaboration (Crete University, Caltech, MPIfR, UMK) using Skinakas 1.3m telescope will be described. The program should start this spring in semi and then full automatic modes to routinely observe ~300 blazars and ToO transients. Torun has 25% share in the polarimeter investment. 2. Preparatory work and the current situation with the proposal for large Polish radio telescope will be detaily presented. The chances for the success are high both in funds availability as in the country's technical capabilities. The concept study including 3D computer model of RT90+ and the scientific programs will be reviewed. The project creates great challenge for the logistics, technology development and broad aspects research. The new telescope will be an important part of European research infrastructure, sustainable for many decades and for variety of present and future research programs.


"Climate physics - global warming"

Szymon Malinowski (Institute of Geophysics, Warsaw University)

The talk is planned as an overview of contemporary climate physics. In the first part physical principles of the climate system will be reminded. Then history of climate science, beginning from Joseph Fourier through John Tyndall, Svante Arrhenius to Edward N. Lorenz and modern times will be stressed. Observing systems and theoretical methods commonly used in climate research will be discussed after the introduction. The particular attention will be paid to attribution of the recent climate change . Advances in climate science in context of the forthcoming 5th Assessment Report of the Intergovernmental Panel on Climate Change will be summarized in the final part of the talk.


"Winds versus accretion disk atmospheres in GBHBs"

Agata Różańska (NCAC, Warsaw)

We show that continuum X-ray spectrum of 4U 1630-472 being in the high/soft state with iron absorption lines can be satisfactorily modeled by the spectrum from an accretion disk atmosphere. Our models of disk emission seen at different viewing angles, computed using full radiative transfer code ATM21 are then fitted to high resolution X-ray spectra of 4U 1630-472 obtained by SUZAKU satellite. We model continuum and line spectra using a single model. Iron absorption line profiles computed with natural, thermal and pressure broadenings match very well observations. According to any global disk models considered for the mass of central object of the order 10 solar masses or less, the effective temperature of the inner radii reaches $10^7$K. In such a case possible origin of absorption lines from accretion disk atmospheres should be taken into account in modeling of winds in X-ray binaries. During talk I will discuss the wind model versus accretion disk atmospheres in GBHBs.


"Investigating the intriguing A-type stars"

Simon Murphy (University of Central Lancanshire)

The A-type stars exhibit a plethora of fascinating phenomena, offering testbeds to an array of research areas. The Am and Ap stars have chemical peculiarities that are influenced by radiation pressure, diffusion and mixing. The magnetic Ap stars display the effects of magnetic fields on astrophysical plasmas, strongly influencing processes such as convection. The range of rotation velocities stretches from stars rotating at walking speed to those on the border of Keplerian break-up. All of these properties influence perhaps the most important observed phenomenon of all: pulsation. The variety of pulsation classifications found here, at the junction of the classical instability strip and the main sequence, is the densest of the whole HR-diagram and is being probed at revolutionary precision with the Kepler Space Telescope. In this presentation, we will review these fascinating phenomena along with some exciting new results obtained with Kepler.


"The MOST and BRITE satellite projects"

Sławomir Ruciński (University of Toronto)

The MOST and BRITE satellite projects The satellite project MOST was started in 1997 by a successful application to the Canadian Space Agency. It was launched in 2003 and since then has provided high precision (10-5 to 10-3), continuous (up to 2 months), high cadence (typically 6 times per minute), photometric data on variability of bright stars of 1 to 12 mag. MOST has been the first photometric micro-satellite (<100 kg) and the important lessons from its performance have been implemented in planning of the CoRoT and Kepler missions. The satellite project BRITE, originally conceived as a very inexpensive mission of two nano-satellites (<10 kg), has grown since its inception in 2004 into the BRITE Constellation of 6 satellites, to be launched in pairs by Austria (already in orbits, since 24 February 2013), Poland and Canada in 2013 - 2014. The BRITE satellites will concentrate on continuous photometry of brightest stars (<4 mag) in longer times scales than MOST, typically hours to several months. The talk will describe how it came to both projects and what are their main scientific advantages and weaknesses.


"Modeling radio emission from G2 cloud bow shock"

Aleksander Sądowski (CfA, Harvard University)

The giant molecular cloud of gas called 'G2' is currently approaching the supermassive black hole in the Galactic center. It is moving through the accretion flow with a supersonic velocity and therefore a bow shock forms ahead of it. I will discuss the radio synchrotron emission that is expected to arise in the bow shock and report on most recent observations.


"The power of jets - the radio view"

Heino Falcke (Radboud Universiteit Nijmegen, The Netherlands)

Jets are an integral part of most accreting system, particularly in black hole system of all masses. In the deep gravitational wells of black holes, matter falls towards the event horizon producing a hot, magnetized plasma producing bright radiation. Magnetic fields are wound up and produce powerful relativistic outflows, which leave the system along the rotation axis of the black hole. The overall kinetic and magnetic power released in jets can be an appreciable fraction of the overall energy produced in the accretion process. The highly magnetized plasma and relativistic speeds seem to provide ideal conditions for accelerating relativistic particles, which leads to synchrotron and inverse Compton emission ranging from radio to gamma rays. Hence, jets are inherently broad-band sources as well as candidate sources for ultra-high energy cosmic rays. Radio telescopes are particularly suited to pick out and study jets on all scales, ranging form the largest scales, probed, e.g. by the new LOFAR telescope, down to the event horizon, probed by very long baseline interferometry. The talk summarizes some of our basic understanding of radio jets and presents some recent results obtained with LOFAR and other telescopes.

The lecture will be heald (as an exception) at 3:15 pm.


"Pulsation Modelling of the Binary Evolution Pulsators"

Radosław Smolec (NCAC, Warsaw)

I will present the results of nonlinear modelling of 0.26-solar masses singly-periodic, large-amplitude pulsator with light and radial velocity curves mimicking the typical RR Lyrae curves. The star is a member of the well-detached eclipsing binary system and hence, its basic parameters are well known. I will show that the shape of the radial velocity curve results from resonant mode interaction just as in the case of the Cepheid bump (Hertzsprung) progression. The presence of the resonance strongly constrains the stellar model and allows for independent determination of stellar parameters.


"How philosophy begins? The Rigveda - an ancient Indian text"

Joanna Jurewicz (Department of Oriental Studies, University of Warsaw)

Read about Joanna Jurewicz and her research on:


"Links between Galactic Black Hole Binary and AGN accetion"

Małgorzata Sobolewska (Harvard Smithsonian Center for Astrophysics)

Spectral and temporal signatures of black hole accretion show striking similarities for a wide range of black hole masses. I will present recent evidence for common accretion engine in all classes of accreting black holes coming from the studies of the energy spectra and lightcurves in the optical/X-ray/gamma-ray bands. I will particularly focus on the properties of the so-called hard spectral state.


"A search for nontoroidal topological lensing in the SDSS quasar catalog"

藤井宏和 (Hirokazu Fujii) (University of Tokyo)

Our Universe could possess multiply connected topology on large scales, and in that case multiple images of single objects would be observed (topological lensing). In this talk, we first introduce a four-point statistics of spatial distribution of cosmic objects that is designed to detect nontoroidal (generated by screw motion or glide reflection) flat topologies, and compare it to CMB-based methods. We next present some results of applying the method to SDSS high-z quasars.


"The bright and dark side of cosmic voids"

Krzysztof Bolejko (School of Physics, The University of Sydney)

More than half of the volume of our Universe is occupied by cosmic voids. Cosmic voids are regions where matter density is much below the mean density of the Universe. In galaxy surveys they appear as vast empty spaces between filaments, which contain very few or no galaxies. Cosmic voids are not merely regions of galaxy avoidance they also affect optical properties of the Universe. During the talk I will discuss how imagines of background objects are distorted when observed through cosmic voids. I will show how these distortions can help us to understand various phenomena and how we can use them to learn more about dynamics of cosmic voids and global properties of our Universe.


"The CTA site search"

Tomasz Bulik (Astronomical Observatory, Warsaw University)

I will describe the detailes of the CTA site search and the current site choice process.


"Probing the Cosmic X-ray and MeV Gamma-ray Background Radiation through the Anisotropy"

Yoshiyuki Inoue ( 井上 芳幸) (KIPAC / SLAC / Stanford)

The origin of the cosmic hard X-ray and MeV gamma-ray background is not fully understood. It is expected that Seyferts including Compton thick population may explain the cosmic hard X-ray background. At MeV energy range, Seyferts having non-thermal electrons in coronae above accretion disks or MeV blazars may explain the background radiation. I will discuss that future measurements of the angular power spectra of anisotropy of the cosmic X-ray and MeV gamma-ray backgrounds will be key to deciphering these backgrounds and the evolution of active galactic nuclei.


"What makes the jet production efficiency in AGN so diverse"

Marek Sikora (NCAC, Warsaw)

Magnetic fluxes required to power jets in radio-loud quasars are significantly greater than those that can develop in standard accretion disks. The required levels of those fields are achievable only by the accumulation process, which proceeds via advection of magnetic fields by the accreting matter. Eventually, this leads to the formation of a magnetosphere around the black hole and the innermost portions of the accretion flow. Since such an advection is expected not to work efficiently in geometrically thin disks, we suggest that such an accumulation of magnetic flux occurs via hot, quasi-spherical accretion. Without this pre-phase, the cold accretion events would result in radio quiet (or at most, moderately radio-loud) quasars.


"Could IMBH be formed in a globular cluster?"

Mirosław Giersz (NCAC, Warsaw)

I will discuss a new scenario for intermediate mass black hole (IMBH) formation in dense stellar clusters. The new scenario does not need any special conditions. In this scenario IMBH is formed as a result of dynamical interactions of a hard binary, containing a stellar mass black hole (BH), with other stars and binaries. The mass of the BH constantly increases due to mergers with incoming stars and mass transfer from companions. I will discuss the necessary conditions to initiate the process of IMBH formation and dependence of the rate of IMBH mass increase on the global cluster properties.


"Mysterious long-period variables"

Igor Soszyński (Astronomical Observatory, Warsaw University)

Pulsating red giants are probably the least understood of all variable stars. I will discuss two unresolved issues concerning long-period variables: which modes of pulsation are associated to different period-luminosity relations and what is the origin of the phenomenon of long secondary periods observed in one third of semiregular variables? I will present new observational results that may be important to solve both problems.


"Astrophysics in Horava's quantum gravity"

Ronaldo Vieira (Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, Brazil)

Abstract: Horava gravity has received much attention in the recent years. The Kehagias-Sfetsos (KS) solution, a Schwarzschild-like solution to a modified version of the theory, was used to constrain the Horava parameter in many Solar-system tests. In this talk we discuss some qualitative properties of this solution such as the near-Schwarzschild and naked singularity cases, as well as the stability of circular geodesics.


"Emission of compact jets powered by internal shocks"

Julien Malzac (University of Cambridge )

I will present an internal shock model for the variable radio to infrared emission of the jets of X-ray binaries in the hard state.


"General relativistic magnetohydrodynamical (GR MHD) simulations of accretion disk around Sgr A*"

Bhupendra Prakash Mishra (NCAC, Warsaw)

The talk will cover current status of General Relativistic MagnetoHydroDynamical (GR MHD) simulations. I shall also give a short introduction of the GRMHD code COSMOS++, and its abilities for a wide range of research problems. Since we know that Sgr A* is the best laboratory in space to test our knowledge of general relativity, my main interest in this talk will be to present GR effects in MHD accretion flows around rotating Sgr A*. The results for accretion disk around Sgr A* will be presented for different magnetic field configurations, poloidal as well as toroidal in the torus and also for different spin parameters of the Sgr A*, by this way we can see the very strong effects of magnetic field configuration in the accretion flows in GR regime. The theoretical model to setup the numerical code is based on classical polish doughnut model to which we slightly modified by including an essential parameter in the accretion flows which is magnetic field in the torus. I shall also talk about whether the cooling processes are important in GRMHD accretion flows or not.


"Three players in the interstellar clouds: dust grains, free radicals and diffuse band carriers"

Jacek Krełowski (Astronomy Center, Toruń)

Translucent interstellar clouds produce typically three kinds of absorptions: continuous extinction, believed to be caused by interstellar dust particles, identified bands of simple radicals (OH, OH+, CH, CH+, NH, CN, C2 and C3) and more than 400 unidentified diffuse interstellar bands. The latter are commonly believed to be carried by some complex molecular species but none of them was until now identified beyond a doubt. The talk will present the above mentioned absorptions in different interstellar clouds. It seems important that that any change of the extinction law is accompanied by changes in molecular and diffuse spectra. This demonstrates a complex chemistry of translucent interstellar clouds. The observed molecular species are likely building bricks for prebiotic molecules.


"Galactic starburst clusters: witnesses of extreme star formation events"

Christoph Olczak ( Astronomische Rechen-Institut, Heidelberg )

Starburst clusters are dense young stellar systems with total masses above 10,000 solar masses and tens of extremely luminous O stars. Various authors have speculated about a strong effect of these harsh environments on the star formation process, leaving in particular characteristic imprints in their mass functions. At present, we know only a dozen starburst clusters in our own Galaxy. I will present detailed numerical models of the particularly well observed NGC 3603, Westerlund 1, and the Arches cluster that indicate a plethora of peculiar properties.


"BRITE - three weeks after the launch"

Aleksander Schwarzenberg-Czerny (NCAC, Warsaw)


"What was the last Nobel Prize in Physics given for?"

Krzysztof Meissner (Institute of Theoretical Physics, University of Warsaw)