Wednesday Colloquium



CAMK Conference



CAMK Conference


"The impact of the ionosphere on ground-based detection of the global Epoch of Reionisation"

Marcin Sokołowski (Curtin University, Perth, Australia)

The redshifted 21cm line of neutral hydrogen (HI), which can potentially be observed at low radio frequencies (~ 50-200 MHz), is a powerful probe of the physical conditions of the inter-galactic medium during Cosmic Dawn and the Epoch of Reionisation (EoR). The sky-averaged HI signal (global EoR) is expected to be extremely weak (of the order of 100 mK) in comparison to the foregrounds of up to 10000 K at the lowest frequencies. Moreover, the tiny signature of the EoR has to be identified amongst instrumental effects. Precision better than 10mK at 80 MHz requires tens of hours of integration with a highly calibrated system, however the overall accuracy can be affected by propagation effects in the ionosphere. BIGHORNS (Broadband Instrument for Global HydrOgen ReioNisation Signal) is a total power radiometer designed and build at Curtin University (Perth, Western Australia) to detect signature of the global Epoch of Reionisation in the-sky averaged spectrum. After several test deployments in remote, radio-quiet locations in Western Australia, in October 2014 the system with a conical log spiral antenna was permanently deployed at the Murchison Radio-astronomy Observatory (MRO), where it also monitors radio-frequency interference (RFI) at the future site of the low-frequency component of the Square Kilometre Array (SKA). I will present the BIGHORNS instrument and address the main challenges of the global EoR measurement. I will also present analysis of the 2014/2015 data collected at the MRO assessing the significance of the ionospheric effects on the ground-based detection of the global EoR signal. Finally, I will give a brief overview of some SKA-low activities in Western Australia.


"Highlights from the ongoing search for symbiotic stars in the Local Group of Galaxies"

Joanna Mikołajewska (NCAC, Warsaw)

I will present and discuss basic characteristics of the first symbiotic stars detected in M31 and M33 as well well as some serendipitous discoveries.


"Cosmic microwave background anomalies at large angular scales"

Paweł Bielewicz (NCAC, Warsaw)

Studies of the cosmic microwave background (CMB) are today one of the most important pillars of observational cosmology. They provide information not only on the initial conditions of the Universe but also on scales comparable to the horizon of the observable Universe. This gives a unique opportunity to pose important questions about very fundamental assumptions made in the standard cosmological model such as statistical isotropy and Gaussianity of the initial fluctuations. Since the COBE and WMAP data releases, considerable effort has been spent on analyzing the statistical properties of the CMB maps at large angular scales. Remarkably, this effort has resulted in several reports of a breaking of statistical isotropy, as established by many qualitatively different methods. Recently, these observations has been confirmed for the Planck data. I will review these studies and few hypotheses concerning the observed anomalies paying special attention to prospects of testing them using future cosmological observations.


"ROSETTA cometary mission; 18 months of the 67P/C-G comet observations"

Włodzimierz Kofman (Space Research Center, Warsaw)

ROSETTA space mission studies the comet Churyumov-Gerasimenko (67P / C-G). The mission is composed of an Orbiter and Philae lander. The payload contains multiple instruments performing the teledetection and in situe measurements. The probe is accompanying the comet on its journey around the sun on the orbits close to a nucleus on the distance from tens to hundreds kilometers. The scientific objective of the mission is the study the cometary material, the surface and the internal structure of the comet and their evolution on the their journay around the sun. The main scientific questions are: How formed and evolved comets? What are the physical propreties, structure of surface and interior of comets? What is the composition of the ice grains, molecules, organic? Have they played a role in the evolution of the planets? The instruments on board the probe continued observations for over a 18 months. On 12 November 2014 Philae lander, landed on the surface of the comet. This is a spectacular success and the first cometary landing in the history of the exploration of the solar system. The observations lasted for 63 hours. In our presentation we will describe the payload of the probe and Philae. We will present and discuss certain observations by orbiter and also by Philae and some scientific results. We will describe more specifically CONSERT experience. CONSERT is a bistatic radar on the ROSETTA, which the primary scientific goal is to investigate the deep interior of the nucleus of comet 67/P Churyumov-Gerasimenko. The radar had operated between the Rosetta spacecraft and Philae lander and through radio tomographic mapping between the lander and the main spacecraft, obtained important scientific results. The measurement made on 12-13 November 2014, during the first science sequence begun to reveal the internal structure of Comet 67P/Churyumov-Gerasimenko.


"The first direct detection of gravitational waves"

Piotr Jaranowski (University of Bialystok)

On September 14, 2015 the two LIGO detectors simultaneously observed a gravitational-wave signal coming from the merger of two stellar-mass black holes. After very quick look at the history of gravitational-wave research, the observation as well as detectors, search algorithms, and source properties will be described in more detail, some astrophysical implications of the observation will also be sketched. The contribution of the Polish POLGRAW group to the discovery will be presented.


"The nature and origin of ultra-high energy cosmic ray particles"

Peter Biermann (Max Planck Institut für Radioastronomie, Bonn)

The origin of ultra high energy cosmic ray particles is still not settled, but there is growing recognition, that at the highest energies the abundances are mostly nuclei such as Carbon or heavier. At lower energies we now detect the expected proton component, possibly coming from high redshifts. This implies due to propagation constraints, that the maximal energy particles come from just a few Mpc, and the arrival directions suggest the radio galaxy Centaurus A, as was predicted 1963 by Ginzburg. Radio galaxies as sources of ultra high energy cosmic rays are also required to explain in situ observations of spectra. This allows then to connect to one plausible origin of very high energy neutrinos, recent mergers of super-massive black holes, in turn a source of a predicted low frequency gravitational wave background.


"How to determine the mass of the black hole"

Janusz Ziółkowski (NCAC, Warsaw)


"Levitating Atmospheres and Radius Expansion Bursts"

Włodzimierz Klużniak (NCAC, Warsaw)


"DRAGON million-body globular cluster simulations: The possible origin of detected Gravitational Wave of black hole binary merging"

Long Wang (KIAA Kavli Institute for Astronomy and Astrophysics, Peking University)

Introducing the DRAGON simulation project, we present direct N-body simulations of four massive globular clusters (GCs) with 10^6 stars and 5% primordial binaries at a high level of accuracy and realism. The GC evolution is computed with NBODY6++GPU and follows the dynamical and stellar evolution of individual stars and binaries, kicks of neutron stars and black holes, and the effect of a tidal field. Our model show a large fraction of black holes (BHs) are retained in the GCs. This BHs form a dense system can significantly change the GC evolution. Since recently the gravitational waves (GW) emitted by a BH-BH binary is discovered by advanced-LIGO. We also investigate the BH properties in our models and check whether the BH-BH binaries can reach the merging cases via GW radiations. The detailed comparison with Monte-Carlo methods (MOCCA and CMC) for BH properties are also provided.


"The coming of age of X-ray polarimetry: the X-ray Imaging Polarimetry Explorer (XIPE)"

Giorgio Matt (University of Rome)

X-ray astronomy is now a mature and consolidated field, as far as imaging, spectroscopy and timing are concerned. On the other hand, X-ray polarimetry is very much lagging behind, the only positive measurement dating back to the 70s. This is due to the combination of instrinsic difficulties (polarimetry is a photon hungry technique) and to technical limitations. The advent of a new type of detectors, based on the photoelectric effect, make it now possible to meaningfully search for polarization on hundreds of X-ray sources. I will review the main open astrophysical questions that will benefit from X-ray polarimetry (including the use of cosmic sources as laboratory for fundamental physics), and present XIPE, a mission selected by ESA for a phase A study (with the final selection expected in summer 2017).


"X-ray reverberation in accreting black holes"

Barbara De Marco (Max-Planck-Institut für extraterrestrische Physik)

Accreting black hole (BH) systems are characterized by strong, aperiodic variability on a wide range of time scales. The variable primary X-ray radiation interacts with any surrounding matter, including the accretion disc. Short light travel time delays are expected between the primary and the reprocessed emission in the disc. These, so-called “X-ray reverberation lags” can be used to map the geometry of the very inner regions of the accretion flow. I will review recent studies of X-ray reverberation lags in accreting BH systems, discussing the analogies between X-ray reverberation lags in active galactic nuclei (AGN) and in BH X-ray binaries (BHXRB), and showing how the latter give indirect evidence of evolving disc geometry during the outburst.


"New results of the accretion-jet model in X-ray binaries and AGNs "

Fu-Guo Xie (谢富国) (Shanghai Astronomical Observatory)

The central engine in X-ray binaries (XRBs) and AGNs is under active debate in recent years. One leading theoretical scenario is the accretion-jet model. This model has achieved great success, as it can explain a large body of observed phenomena in these systems, including the broadband spectrum, the timing properties, and the radio/X-ray luminosity correlation (the so-called fundamental plane in AGNs, where black hole mass is taken into account). In this talk, I will discuss several new progresses, e.g. the numerical simulation realization of the two-phase accretion stage during the outburst evolution in XRBs, the three branch relationship between the index and X-ray flux in XRBs and AGNs, and the unified paradigm on the two radio/X-ray correlations observed in XRBs


"(Nearly) Complete Census of Cepheids and RR Lyrae Stars in the Magellanic Clouds"

Igor Soszyński (Astronomical Observatory, Warsaw University)

More than a century after the pioneering works of Henrietta Leavitt we are close to identify and catalog all Cepheids and RR Lyrae stars in the Large and Small Magellanic Clouds. The OGLE-IV fields cover a large area in the Magellanic System, including its outskirts and the Magellanic Bridge spreading between both galaxies. The OGLE collection of pulsating stars is a basis of many extensive astrophysical studies on stellar evolution and pulsation theories, models of the structure and dynamics of the Magellanic Clouds, and the extragalactic distance scale.


" The study of the ionized interstellar medium using radio pulsar observations."

Wojciech Lewandowski (Zielona Góra University)

When propagating through the interstellar medium the radio signals from pulsars are affected by a few phenomena occuring in the ionized matter. We see the evidence for the interstellar dispersion of radio waves, the scattering as well as the interstellar scintillations. While for the majority of pulsar astronomers these effects are a nuissance that has to be removed from the data, to be able to study these objects, they can be also a great source of information about the ionized fraction of the interstellar medium - its physical properties, turbulent nature and distribution within the Milky Way galaxy.


"Meteorites - from exploration to research"

Zbigniew Tymiński (National Centre for Nuclear Research)


"Gravitational waves from rapidly rotating neutron stars"

Brynmor Haskell (NCAC, Warsaw)

The recent detection of gravitational waves by Advanced LIGO is the beginning of the era of gravitational wave astronomy. Neutron stars are one of the main targets for current and future gravitational wave detectors, and detecting signals from such sources would allow us to constrain fundamental physics in regimes inaccessible with terrestrial experiments. In this talk I will discuss `continuous’ signals from rapidly rotating neutron stars, and discuss some of the main emission mechanisms that have been proposed, i.e. deformations, or ‘mountains’, sustained by the crust or magnetic field, and unstable modes. In particular I will focus on the r-mode instability in Low Mass X-ray Binaries, and show how combining gravitational wave and X-ray observations can constrain the interior dynamics of the star.


"Creating and Building the Hubble Space Telescope"

Charles Robert O’Dell (Vanderbilt University, Nashville, TN)

Unlike Athena, who sprang full grown from the forehead of Zeus, the Hubble Space Telescope had a long and difficult gestation. It was one of the original goals in building Earth orbiting satellites, but finally came under serious consideration only in 1971. The next two decades first saw battles to gain support from astronomers and financial support from the US and European governments. The next phase saw the challenges of designing and building something that had never been done before—a long duration observatory in space. I’ll then close out with an explanation of the problems with the primary mirror, how these were corrected, and a brief report on the observatory’s condition.


"New vision of the local Group and the specific case of Andromeda II"

Sylvain Fouquet (NCAC, Warsaw)

Since 2000, our vision of the Local Group has evolved a lot. Thanks to new instruments, measures and large surveys, the number of dwarfs galaxies have been multiplied by nearly 3 and new constrains has been found to understand the formation and evolution of the dwarf galaxies. However, a lot of questions that I will present remain open. In this general field of research, I will focus on one specific M31 dwarf galaxy: Andromeda II. I present an evolutionary model for the origin of Andromeda II. The model is an extension of the scenario proposed by Łokas et al. 2014 involving a major merger between two gas-rich disky dwarf galaxies. I also take into account the interaction between the remnant of the merger and M31. This could explain the lack of gas in And II and the sudden stop of the star formation 5 Gyr ago."


"Black Holes and Neutron Stars in our Galaxy as Laboratories for Strong Gravity"

Tomaso Belloni (Osservatorio Astronomico di Brera)

Binary systems containing a black hole or a neutron star offer the best possibility to test prediction of General Relativity in the strong field regime. The plasma stripped from the non-degenerate companion star reaches the space time in the immediate vicinity of the compact object and releases strong X-ray emission. The spectral and variability properties of this emission contain the signatures of predicted effects such as the presence of an innermost stable orbit and black hole spin. I discuss the current observational status with particular emphasis onto sub-second time variability, which constitutes the most direct measurement of the properties of the plasma accreting onto a collapsed star. I present recent results that led to a precise measurement of the spin of a stellar-mass black hole through the measurement of GR effects from fast time variability.


"Thermal instability (or not?) in three-dimensional, global, radiative GRMHD simulations of geometrically thin discs"

Bhupendra Mishra (NCAC, Warsaw)

I shall present results of a set of three-dimensional, general relativistic radiation magnetohydro- dynamics simulations of thin accretion discs to test their thermal stability. We consider two cases, one that is initially radiation-pressure dominated and expected to be thermally unstable and another that is initially gas-pressure dominated and expected to remain stable. Indeed, we find that cooling dominates over heating in the radiation-pressure-dominated case, causing the disc to collapse vertically on the local cooling timescale. On the other hand, the gas-pressure- dominated case, which was run for twice as long as the radiation-pressure-dominated case, remains stable, with heating and cooling roughly in balance. Because the radiation-pressure- dominated disc collapses to the point that we are no longer able to resolve it, we had to terminate the simulation. Thus, we do not know for sure whether it might find a much thinner, stable solution or if it will make a transition to unstable expansion and exhibit limit-cycle be- havior. However, the fact that the cooling rate seems to be dropping faster than heating as the disc collapses suggests that the disc may be headed toward a stable, albeit thinner, solution. It is not clear, though, if the disc will remain radiation-pressure-dominated in that new state.


"A brief history of phonography - the origins, development and decline. Sound: digital or analogue?"

Mieczysław Stoch (ArtReco, Warsaw)


"Blueshifts in the Lemaitre-Tolman and quasi-spherical Szekeres models"

Andrzej Krasiński (NCAC, Warsaw)

In Lemaitre-Tolman models that have nonconstant Big Bang (BB) function, light rays emitted radially from the BB reach every observer with infinite blueshift (i.e. z = -1). These blueshifted rays have several properties in common with the observed gamma-ray bursts. The quasi-spherical Szekeres (QSS) models have in general no symmetry, so there are no radial directions in them. However, in axially symmetric QSS models with nonconstant BB numerical calculations show that very strong blueshifts can appear on those rays that intersect every space of constant time on the symmetry axis. In general QSS models with nonconstant BB, numerical calculations show that two preferred directions exist, on which blueshifts are equally strong. Astrophysical applications of these results will be briefly discussed.


"Absorption line variability in BALQSOs and NGC 4151"

Conor Wildy (University of Leicester)

Absorption lines are commonly observed in AGN spectra, ranging in FWHM from a few hundred km/s (narrow) to >10000 km/s (broad absorption lines in BALQSOs). Many are observed at wavelengths blueward of the object rest-frame, indicating an origin in powerful outflowing winds, possibly contributing to galaxy feedback effects. Follow-up spectral observations indicate that AGN absorption lines can change strength over time, however there is no consensus regarding the dominant mechanism responsible for this variability. Two main possibilities exist: (1) varying emission-source covering fraction due to absorbing clouds moving across the line-of-sight, and (2) variable ionizing continuum flux changing the ionization state of the absorbing gas. Our study of 50 SDSS-selected BALQSOs showed no evidence of correlation between quasar luminosity and absorption line variability for Si IV λ1400 and C IV λ1549 BALs. This tentatively suggests ionization changes are not predominantly responsible for BAL variability in the quasar population, as less luminous quasars show greater continuum variability. One object in this sample showed extreme BAL variability, defying the predictions of a random-walk model which accurately predicted BAL behaviour in a large BALQSO study. Changes in BAL strength in this object are co-ordinated, despite large veloctiy separations. This, together with Cloudy photoionization simulations and the behaviour of the continuum, strongly suggests that changes in the ionization state of the absorber induced by continuum variability is responsible for the BAL variability in this quasar. The Seyfert 1 galaxy NGC 4151, notable for its continuum variability, also exhibits blueshifted absorption features. Examination of a variable, narrow metastable helium absorber suggests ionization changes are driving its variability. Taken together, these results indicate ionization changes definitely contribute to variability of very different types of AGN absorption line, without ruling out covering fraction changes as a contributor to AGN absorption line variability in general.


"Intrinsic morphology and global kinematics of Andromeda satellite galaxies"

Jean-Baptiste Salomon (CAMK, Warsaw)

The ΛCDM model represents nowadays the best understanding of the formation and the evolution of large scale structures in our Universe. Nevertheless, this paradigm is not predictive and successful yet at smaller scales. In this context, satellites in the Local Group (LG), the simpler and closer galactic systems, are one of our best chance to test this model and to improve our comprehension of galaxy formation at smaller scales. In this talk, I will present a method to derive analytically the intrinsic (3D) morphology of 25 Andromeda (M31) satellites. Results suggest that the LG is in fact more disturbed than what was previously thought. After this individual approach, I will further expose a recent result on the global kinematics of the M31 system. This new estimation suggests for the first time a high transverse velocity for this system with respect to the Milky Way. These values could lead to redefine the entire dynamic of the LG and its surroundings.


"The MESSIER orbiter: lifting the veil on the ultra-low surface brightness Universe"

David Valls-Gabaud (Observatoire de Paris, CNRS)

The S-class MESSIER satellite has been designed to explore the extremely low surface brightness universe at UV and optical wavelengths. The two driving science cases target the mildly- and highly non-linear regimes of structure formation to test two key predictions of the LCDM scenario: (1) the detection of the putative large number of galaxy satellites, and (2) the identification of the filaments of the cosmic web. The satellite will drift scan the entire sky in 6 bands covering the 200-1000 nm wavelength range to reach the unprecedented surface brightness levels of 34 mag/arcsec^2 in the optical and 37 mag/arcsec^2 in the UV. Many important secondary science cases will result as free by-products and will be discussed in some detail, such as the luminosity function of galaxies, the contribution and role of intracluster light, the cosmological background radiation at UV and optical wavelengths, the molecular hydrogen content of galaxies at z=0.25, time domain studies of supernovae, GRBs and tidal disruption events, the chemical enrichment of the interstellar medium through mass loss of red giant stars and the accurate measure of the BAO scale at z=0.7 with over 30 million galaxies detected in Lyman-alpha at this redshift. It will provide the astronomical community the first space-based reference UV-optical photometric catalogue of the entire sky, and synergies with GAIA, EUCLID and WFIRST will also be discussed. Technical issues will likewise be addressed for possible improvements on the current design.


"First Light And Reionization Explorer"

Denis Burgarella (Laboratoire d'Astrophysique de Marseille)

There has been enormous progress over the past decade in finding galaxies which existed early in the history of the Universe (within a billion years of the Big Bang, at z > 6). The next few years will see the “high redshift frontier” pushed even further with the JWST and ground-based ELTs. However, the limited field of view of these facilities, and sensitivity only out to the near-infrared (λ<2μm) for the WFIRST and Euclid wide-field imaging space missions, mean that a crucial piece of the jigsaw remains missing: a wide-field imaging survey, working at mid-infrared wavelengths (necessarily from space) is needed to find the most massive and luminous galaxies at the highest redshifts, the progenitors of which are likely to be the first galactic structures to form. We propose FLARE (First Light And Reionization Explorer), a space mission to study galaxy evolution at the earliest times, with the key goals of detecting a statistically significant (> 100 at z = 14) sample of first galaxies. FLARE is a space mission whose primary goal (~70% of lifetime) will be to identify and study the universe before the end of the reionization at z > 6, detect, identify and study “first light” galaxies at dawn of time (13 < z < 15). A secondary objective (~25% of lifetime) is to survey star formation in the Milky Way and build a 5000 deg2 survey in the Milky Way. More information:


"Dynamics of topological excitations: from ultracold atomic gases to atomic nuclei and neutron stars"

Piotr Magierski (Faculty of Physics, Warsaw University of Technology)

Superfluidity and superconductivity are remarkable manifestations of quantum coherence at a macroscopic scale. The existence of superfluidity has been experimentally confirmed in a large number of systems: in various condensed matter systems, in nuclear systems including nuclei and neutron stars, in both fermionic and bosonic cold atoms in traps, and it is also predicted to show up in dense quark matter. Surprisingly the superfluid properties of many of these systems are qualitatively similar, and in particular various topological excitations can be observed in the form of vortices or solitons, leading possibly also to the quantum turbulent state. From the theoretical perspective dynamics of Fermi superfluids is quite complex and thus requires a suitable theoretical framework, which is provided by time-dependent density functional theory (TDDFT). TDDFT can be viewed as an exact reformulation of time-dependent quantum mechanical problem, where the fundamental variable is density instead of the many-body wave-function. During the lecture I will present various features related to dynamics of topological excitations in ultracold atomic gases (vortex reconnections, solitonic cascades), atomic nuclei (solitonic excitations in nuclear collisions) and neutron stars (vortex-impurity interaction in the crust).


" Are we seeing a new type of accretion disk around transitional pulsars?"

Alessandro Patruno (Leiden University)

Accretion disks in X-ray binaries (and cataclysmic variables) show a plethora of phenomena and it is in general difficult to understand the general principles that govern them. A good practice is to distinguish the properties common to several systems and those which are instead unique to specific systems. In this talk I will discuss some unique and still unexplained characteristics of accretion disks seen in the so-called transitional millisecond pulsars. These objects are neutron stars (with a low mass companion) that turn back and forth between a radio pulsar state and an accreting pulsar state. During the accretion process, the X-ray lightcurves (and also their radio and gamma ray behaviour) seems to be very different from those of other low mass X-ray binaries. What might causing such difference is still an open question. I will present some recent results of multiwavelength campaigns and focus on the geometry and observational constraints that can be placed on these systems.


"Stellar clusters, supernovae and the Sun"

Melvyn Davies (Lund Observatory)

Most stars form in some sort of cluster or association. These birth places are harsh environments. Massive, bright stars accelerate the photoevaporation of protoplanetary disks whilst other close encounters can destabilize pre-existing planetary systems. In this talk I will explain why it is thought that the Sun formed in a stellar cluster. I will discuss the consequences for our own Solar System and identify M67 as one possible host cluster.


"Broad-emission-line radio galaxies provide challenges to jet production theories"

Marek Sikora (NCAC, Warsaw)

Accretion onto supermassive black holes located in broad-emission-line radio galaxies (BLRGs) is predicted by theory to proceed via geometrically very thin accretion disks, which makes them most challenging objects regarding their ability to produce powerful jets. As recent numerical simulations indicate, even the magnetically-arrested-disk (MAD) scenario is not able to reproduce the jet power observed in these objects - those are measured to approach and sometimes even exceed the accretion luminosities. We discuss possible origins of this discrepancy and argue that it is most likely due to inappropriate approximations used to treat optically thick, radiatively efficient accretion disks within the MAD-zone.


"Superfluid vortex avalanches and pulsar glitches"

George Howitt (University of Melbourne)

Rotating neutron stars, or pulsars, are famously stable objects whose rotation periods lengthen over time. Some pulsars, however, experience sudden spin up events, known as glitches. It is widely believed that the cause of glitches is a sudden rearrangement of superfluid vortices in the neutron star interior, but the diverse phenomenology of glitches coupled with a lack of observational data makes this a difficult model to test. I will discuss work that tests the validity of the superfluid avalanche glitch model in observational data and numerical experiments.


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

Marek Napiórkowski (Institute for Theoretical Physics, Warsaw University)