Wednesday Colloquium

"Dwarf novae in period gap"

Arkadiusz Olech (NCAC, Warsaw)

"Mysterious gamma-ray flare in blazar PKS 1222+216"

Krzysztof Nalewajko (JILA, Boulder, CO)Show abstract

Cherenkov telescope MAGIC detected a Very-High-Energy flare with variability time scale of 10 minutes in PKS 1222+216. For the first time such a phenomenon was observed in a Flat-Spectrum Radio Quasar. This poses additional challenges to theoretical interpretations of rapid gamma-ray flares in blazars. We may need to completely re-think the established picture of parsec-scale AGN jets.

"On the mean profiles of radio pulsars"

Vasily Beskin (Lebedev Institute of Physics, Moscow)Show abstract

We study the influence of the propagation effects on the mean profiles of radio pulsars including into consideration the transition from geometrical optics to vacuum propagation, the cyclotron absorption, and the wave refraction simultaneously. The one-to-one correspondence between the signs of circular polarization and position angle derivative along the profile for both ordinary and extraordinary waves is predicted. Using the numerical integration we now can model the main profiles of radio pulsars.

"The Role of Relativistic Neutrons in the Production of AGN Jets"

Kenij Toma (Osaka University)Show abstract

AGN jets are considered to be produced by injecting magnetic and/or thermal energies into the dilute polar region, where the mass loading processes are essential for determining the jet properties. We discuss the role of the relativistic neutrons escaped from the accretion flow for the mass loading (as well as thermal energy injection).

"Emission of jets in black-hole binaries"

Andrzej Zdziarski (Copernicus Astronomical Center, Warsaw)Show abstract

We consider two examples, Cyg X-1 and Cyg X-3. In both cases, the jets appear to have two distinct dissipation regions, an inner one on the scale of the binary orbit (which is thus orbitally modulated) and outer one, resolved in radio images. We constrain the contribution of the jets to broad-band spectra, in particular to X-rays and gamma-rays, and estimate their kinetic power.

"Discovering Higgs"

Jan Kalinowski (Institute of Theoretical Physics, Warsaw University)Show abstract

In December last year both ATLAS and CMS collaborations presented their results on the Standard Model Higgs boson searches at the LHC experiments. Tantalising hints have been seen by both experiments in the 124-126 GeV mass region, however not strong enough to claim a discovery. In my lecture I will summarise the current state of the Higgs boson hunt and discuss possible theoretical implications of a discovery of the Higgs boson in the above mass range, if confirmed, as well as consequences for model building, if the observed excess turns to be a statistical fluctuation.

"Search for gravitational waves: today and tomorrow"

Andrzej Królak (Institute of Mathematics, PAN, Warsaw)Show abstract

I shall present astrophysical evidence for the existence of gravitational radiation. I shall describe the current and planned projects to detect such waves. I shall report results of current searches for gravitational waves in data of LIGO and VIRGO detectors. I shall also mention the current activity in this field in Poland.

"ACTA, SOPA, CETA, and even PIPA & CIPA. Untangling some four-letter acronyms"

Krzysztof Leszczyński (Polish Linux Users' Group)Show abstract

Last year we witnessed several attempts to regulate the intellectual properties laws in the age of technology. National and internation parliaments released several regulations—Acts, hence the suffix A. This is a probably a begin of long-term process of discussion and battles on untangling the term of intangible properties.

"OCRA - One Centimeter Receiver Array program on 32m Torun Radio Telescope. Hevelius 90m Radio Telescope - chances and challenges"

Andrzej Kus (Astronomical Center, Nicolaus Copernicus University, Toruń)Show abstract

One of the fundamental issues on CMB observational cosmology is to detaily describe radiation contribution from all known objects on the way - the foregrounds. These are local Galaxy extended and desecrate sources as well as extragalactic starburst and AGNs. Various identified effects, which change or could change intensity, spectrum or polarization of relict photons have to be considered and accounted for. The evolution of galaxies at high redshift, by itself is an interesting and challenging problem, thus the studies of weak (in sense of luminosity) and also most distant objects can illuminate some of the unknowns. Physical properties of radio sources and their cosmological evolution and variability have serious implications on reliability of CMB anisotropy. To study this population the OCRA system has been designed/built and installed on 32m RT in Piwnice. In this seminar the description of the OCRA project will be presented and the obtained observational results on radio sources at 30 GHz (1 cm wavelength) evaluated in general context of the foregrounds. Second part of the seminar will update information on activities to build in Poland 90m class radio telescope. The proposed instrument is a world class, the unique - wide field, extremely broadband radio camera to conduct radio surveys of the sky in cm (1,5 - 10) range and contribute to European VLBI Network. Other programs like pulsar studies, radio spectroscopy, polarimetry will be run in parallel continuously. Basics of construction and proposed research will be presented. The project is going to be financed from Regional European Infrastructure Funds and is not competing with any other proposal vital for Polish astronomy.

"The enigma of CK Vul - the oldest 'nova'"

Marcin Hajduk (Astronomy Center, Nicolaus Copernicus University, Toruń)Show abstract

The star has not been observed since its outburst in 1670-1672. The remnants of the outburst had been found in 1982. The nature of CK Vul remains unknown. Proposed hypotheses include a nova scenario, very late thermal pulse and stellar merger. We studied the object using new observations of the nebula and the field stars.

"KEPLER observations of RR Lyrae-type stars"

Paweł Moskalik (Copernicus Astronomical Center, Warsaw)Show abstract

I will present newest observations of RR Lyrae-type stars. obtained with the KEPLER space telescope. Thanks to unprecedented quality of the data, new phenomena have been discovered. The emerging picture of the RR Lyrae-type pulsators is much richer and more complex than recognized before.

"The intriguing Case of the Supergiant Fast X-Ray Transients: an Update"

Pietro Ubertini (Institute for Space Astrophysics and Planetology Rome, Italy)Show abstract

Supergiant Fast X-ray Transients (SFXTs) are an intriguing subclass of High Mass X-ray Binaries hosting a supergiant companion. They display brief outbursts composed by bright flares lasting a few thousands seconds, during which an X-ray luminosity of 1E36-1E37 erg/s is reached. Their extreme X-ray variability, with a dynamic range of 3 to 5 orders of magnitudes from quiescence to the outburst peak, is still a matter of debate The determination of pulse and orbital periodicities are crucial to cast light on the outburst mechanism and on the evolutionary status of these X-ray binaries. The number of SFXTs where X-ray periodicities have been discovered is indeed continuously growing thanks to timing analysis of large datasets, especially from INTEGRAL/IBIS and Swift/BAT. We will review the most outcome and implication for the physical mechanisms proposed to explain the SFXTs outbursts

"Investigation of the Orientation of Galaxies in Structures"

Włodzimierz Godłowski (Opole University)Show abstract

The investigation of the orientation of galaxies is a standard test of scenarios of galaxies’ formation, because different theories of galaxy formation make different predictions regarding to the angular momentum of galaxies. We analyzed the orientation of galaxy groups in the Local Supercluster (LSC). It is strongly correlated with the distribution of neighboring groups in the scale till about 20 Mpc. Moreover, we analyzed the orientation of galaxies in groups and clusters. The results show the dependence of alignments with respect to clusters richness. The implication of the results for theory of galaxy formation is discussed as well.

"Confessions of an ex-astrophysicist"

Marek Gierlinski (College of Life Sciences, University of Dundee)Show abstract

I used to be an astrophysicist. Three years ago I took the plunge and got a new career in bioinformatics. In this talk I will explain what bioinformatics is about, why biologists need bioinformaticians and why (attention students!) physicists are highly sought after. I will share my personal view on modern life sciences. Biology is now a far cry from clichéd butterfly counting and in recent years has been completely transformed by cutting-edge technologies. I will focus on one particular example and describe how DNA sequencing works and show how it revolutionised our understanding of living systems.

"The luminous fate of the EROS-2 data…"

Jean-Baptiste Marquette (Institut d'Astrophysique, Paris)

"Pulsars and PWN at very high energies: prospects for CTA"

Bronisław Rudak (NCAC, Toruń)

"From period doubled BL Her star to Blazhko Effect"

Radosław Smolec (Copernicus Astronomical Center, Warsaw)Show abstract

I will discuss the discovery of the first BL Her star showing the period doubling effect and present its nonlinear modelling. I will also discuss the models in which periodic and chaotic modulation of pulsation was found. Although the effect is not observed in any BL Her star, it is a common property of their lower luminosity siblings - RR Lyrae stars showing the Blazhko effect. These models provide a support for a radial resonance model proposed recently to explain the Blazhko mystery.

"SN 1987A at 25 years"

Claes Fransson (Swedish Natl. Comm. for Astronomy )Show abstract

SN 1987A is arguably the most important supernova in our life time. I will summarize the main discoveries during the first years after the explosion and then emphasize more recent developments. This includes the understanding of the core collapse, the ejecta structure, nucleosynthesis and interaction with the circumstellar ring. I will also discuss the relation of this somewhat peculiar supernova with other core collapse supernovae.

"MOCCA Simulations of Large Stellar Systems - First Results about Channels of Formation of Blue Stragglers"

Mirosław Giersz and Arkadiusz Hypki (NCAC, Warsaw)Show abstract

We will discuss a major upgrade of Monte Carlo code which previously used in many studies of dense stellar clusters. We outline steps needed in to calibrate the results of MOCCA code against N-body simulations for large N systems. The MOCCA code incorporates direct FewBody integrator for small N interactions and a new treatment of the escape process. We will also discuss the first results of the studies of Blue Stragglers' properties in dynamically evolving stellar clusters, their channels of formation and processes leading to changes of their types. The MOCCA code is at present the most advanced code for simulations of a real star clusters.

"Teleportation"

Arkadiusz Orłowski (The Faculty of Applied Informatics and Mathematics, Warsaw University of Life Sciences (SGGW))

"Radiation pressure on disks: avalanches and instabilities"

Paweł Artymowicz (Physical Sciences, University of Toronto)Show abstract

The bulk of gas in gas-and-dust disks of young planetary systems disappears about 10 million years. However, even systems as old as the solar system feature observable disks of dust derived from collisions and evaporation of planetesimals. Beta Pictoris, Fomalhaut, AU Mic, and other stars have prominent dusty disks with nontrivial, resolved nonaxisymmetric morphology. Planets are one possible explanation, but there are also dust+gas+radiation effect which can mimic the action of planets and produce somewhat similar effects. Avalanches of dust can develop in disks and limit the dustiness of circumstellar disks with small gas contents. A newly discovered radiation pressure instability involves nothing else than the radiation pressure from the central object. It produces growing nonaxisymmetric modes in optically thick inner parts of the disk, which in the nonlinear regime transform into numerous vortices at first, coalescing into a few larger ones in the end. Linear theory predicts very well well the numerically determined growth rates of these modes. Breaking of the initial axial symmetry and the production of spiral and vortical structure can occur in a wide class of optically thick astrophysical disks, for instance in accretion disks around compact objects.

"Thermal and rotational evolution of neutron stars"

Morgane Fortin (NCAC, Warsaw and Laboratoire Univers et Théories, Paris-Meudon Observatory)Show abstract

I will discuss the modelling of two aspects of the evolution of neutron stars. On the one hand, I will focus on the thermal evolution of isolated and accreting neutron stars. Its modelling requires the precise description of the microphysics inside neutron stars, in particular the composition and superfluid properties. X-ray observations provide us with surface temperature measurements and enable to probe the properties of the interior of neutron stars. On the other hand, I will discuss the rotational evolution of neutron stars, in particular of millisecond pulsars. These are rapidly rotating neutron stars with a lower-than-average magnetic field. They are in fact old pulsars that have been revived by the accretion of matter from a companion star. This process has led to the decay of their magnetic field. I will report a new modelling of this process, that, together with evolutionary constraints, allows to estimate the properties of the progenitor neutron star of currently observed millisecond pulsars.

"Role of unconventional natural gas production in Poland and other European countries"

Jan Winter (Polish Oil and Gas Company (PGNiG), Warsaw)Show abstract

Scope of presentation: 1. Polish Gas Market issues and corporate profile of Polish Oil and Gas Company (POGC) 2. European and Polish energy policy vs a number of benefits from a new unconventional gas production 3. Definitions of unconventional natural gas production ( shale gas, calbed methane gas, tight gas, hydrates gas ) 4. Resources (reserves) of conventional and unconventional natural gas in Poland and elsewhere 5. Economic, financial, technical and environmental issues dealing with unconventional natural gas extraction 6. Golden Rules for a Golden Age of Gas* 7. Some comments and Discussion

"NuSTAR"

Grzegorz Madejski (SLAC, Stanford University)Show abstract

NuSTAR is the first satellite-based NASA mission featuring optics capable of imaging celestial hard X-rays. It has been launched successfully a few weeks ago and is undergoing in-orbit checkout phase. This presentation wıll provide the overview and the current status of the mission as well as the highlights of the observing program.

"Surprises from the Crab"

Mitch Begelman (JILA, University of Colorado, Boulder)Show abstract

The unexpected discovery of gamma-ray flares from the Crab Nebula may have surprising implications for plasma astrophysics. Standard particle acceleration mechanisms cannot account for the energies of the flaring photons. Instead, these observations point toward an acceleration process involving rapid destruction of magnetic field through reconnection. I will discuss the extreme particle acceleration process that may lead to the flares, and the likely role of current-driven instabilities in triggering reconnection in the Crab and elsewhere.

"The Local Group as a springboard to the early Universe: the case of Fornax dSph"

Andres del Pino Molina (Instituto de Astrofísica de Canarias)Show abstract

: I will present the full Star Formation History as a function of radius of the Fornax dSph galaxy as well as some preliminary results on the spatial distribution of the stellar populations. We found significant differences in the populations as a function of the galactocentric radius, in addition to strong asymetries in the distribution of the youngest stellar populations which may be the result of interactions between Fornax and other systems. This study is based on FORS1@VLT photometry as deep as I~24.5 and the IAC-star, IAC-pop and MinnIAC codes.

"The Classical Cepheids one hundred years after discovery of the Period - Luminosity relation"

Wojciech Dziembowski (NCAC, Warsaw, OAUW )Show abstract

I will begin with a review of various applications of Cepheids in astronomy and the road to understanding of their pulsation. New data from the OGLE project significantly expanded data base on Cepheids in the Magellanic Clouds. Some of these data present an intriguing challenge to the stellar pulsation theory.

"Eddington capture sphere around luminous stars"

Maciej Wielgus (Warsaw University of Technology)Show abstract

The phenomena related to test particle motion in the vicinity of a compact luminous star in Schwarzschild metric will be discussed. It will be shown that the corresponding equations of motion display a critical point, located between the stellar surface and infinity for mildly super-Eddington luminosities. The stability of the equilibrium state in the critical point will be discussed. The term “Eddington capture sphere” (ECS) refers to the set of such critical points, which form a sphere that separates super-Eddington region inside it from the sub-Eddington region outside. Particles infalling onto the star are likely to be trapped on the ECS, which may have a substantial impact on the accretion. Toy model of the oscillatory behavior in optically thin accretion, related to the periodic appearance and disappearance of the ECS will be presented.

"Discovering new hot Jupiters with the WASP transit survey and probing planetary atmospheres with occultation measurements"

Alexis Smith (NCAC, Warsaw)Show abstract

I will talk about two aspects of my exoplanet research, firstly the SuperWASP (Wide Angle Search for Planets) project, which is the leading ground-based discoverer of transiting planets. I will give an overview of the project, and briefly mention some of our discoveries and discuss the future of WASP in the Kepler era. Secondly, I will discuss some of my characterisation work on hot Jupiter atmospheres, specifically occultation measurements made with Spitzer and with ground-based telescopes. These observations allow us to begin to probe the atmospheric structure and composition of worlds beyond our solar system.

"Modelling the Remnant and the Afterglow of Compact Binary Mergers "

Francesco Pannarale (Max Planck Institute for Gravitational Physics (Albert Einstein Institute))Show abstract

In recent years, several approaches were developed to calculate the final spin of the remnant of binary black hole mergers. I present a new model, based on one of these approaches, which allows for predictions on the spin and mass of the black hole remnant of black hole-neutron star binary mergers. I validate the model and assess its accuracy by testing it against numerical-relativity simulation results. I then investigate the space of parameters consisting of the binary mass ratio, the initial black hole spin, and the neutron star mass and equation of state, providing indirect support to the cosmic censorship conjecture. I further show that the presence of a neutron star affects the quasi-normal mode frequency of the black hole remnant, thus suggesting that the ringdown epoch of the gravitational wave signal may virtually be used to (1) distinguish binary black hole from black hole-neutron star mergers and to (2) constrain the neutron star equation of state. In the second part of the talk, I report on new fully general-relativistic numerical simulations of magnetized binary neutron star mergers leading to the formation of a rapidly and differentially rotating hyper-massive neutron star. I examine the resulting electromagnetic radiation and compare it to other recent simulations.

"Accretion in supergiant High Mass X-ray Binaries"

Antonios Manousakis (NCAC, Warsaw)Show abstract

Supergiant High Mass X-ray Binaries (sgHMXBs) consist of a neutron star accreting material from its early-type, massive, stellar companion. The interplay between the neutron star and the stellar companion can influence accretion significantly. Thanks to INTEGRAL, a hidden population of obscured sgHMXBs has been revealed. Subsequent XMM-Newton observations of the highly obscured eclipsing sgHMXBs IGR J17252-3616 has shown that the absorbing column density (nH) is highly variable. The variability of nH has been interpreted as the effect of a slow wind with an accretion wake formed around the neutron star. This hypothesis is now supported by the hydrodynamical simulations for this system. Such low stellar wind velocities are not expected in massive stars. In addition, the mass of the neutron star can be inferred. Besides the heavily obscured systems, classical sgHMXB Vela X-1 has also been studied in depth over the years. Recent results on hydrodynamical simulation combined with observed properties of this system are also discussed.

"Dark energy distribution from quasar monitoring: Reverberation strategy"

Ishita MaityShow abstract

I enumerate the various methods of determining the distribution of dark energy in universe and subsequently choosing the cosmological model that agrees with the observed data. I then discuss how quasars can be used as standard candles based on the theoretical model developed by Czerny and Hryniewicz and hence to test the properties of the universe. The aforementioned model gives a simple relation between the BLR radius and the absolute luminosity of a quasar. The advantage of this method over using Supernovae as standard candles lies in the fact that unlike supernovae, due to high metallicity of quasars, the relation between BLR radius and absolute luminosity is unlikely to depend on time or redshift. Having assumed this, we perform Monte Carlo simulations to estimate in advance the accuracy of determination of the time delay between the continuum observed from the central region and the emission lines. I discuss the errors we get from using different numerical methods and also varying parameters like the quasar variability amplitude, distribution of measurements in time, etc. We try to determine the threshold for the systematic error we have the liberty of introducing for which we can still recover the delay artificially introduced. Finally we check how these values and errors translate when calculating the luminosity distance to the source.

"Simulating observations in the vicinity of compact objects"

Frederic Vincent (NCAC, Warsaw)Show abstract

I will present two projects linked with simulating observation of phenomena in the vicinity of compact objects. (1) Simulations of light curves emitted by an accretion disk subject to the so-called Rossby wave hydrodynamical instability, that could account for microquasars QPOs. (2) Simulations of images of a collapsing neutron star, the first ray-traced simulations in a numerical spacetime.

"A cosmological perspective on the mergers double compact objects"

Michał Dominik (Astronomical Observatory, Warsaw University)Show abstract

Double compact objects consist of a pair of neutron stars, black holes or a mix of both objects. They are considered to be the most potent sources of gravitational waves. The developments in gravitational wave detection technology in the past decade prompts for predictions of potential detections of these sources. I will present some of the most recent developments in stellar evolution and their impact on the populations of double compact objects in a cosmological frame.

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

Arkadiusz Orłowski (The Faculty of Applied Informatics and Mathematics, Warsaw University of Life Sciences (SGGW))