General Seminar (2020)
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General Seminar takes place every Monday at 11.15 in Piwnice, radioastronomy seminar room.
Since April 27th, 2020 the seminar is in a remote mode.
Remote participation via the virtual seminar room.
13 January 2020
“Low frequency observations of blazars”
Dr Urszula Pajdosz-Śmierciak (Astronomical Observatory, Jagiellonian University, Kraków)
I would like to present low energy radio observations of a diffused blazars’ emission. This work has been done on the basis of available archival data, as well as dedicated observations using LOFAR, GMRT and JVLA radio interferometers. I am going to focus mainly on blazar SBS B1646+499, which merges the properties of BL Lacs and Flat Spectrum Radio Quasars. This little-known source turned out to possess extended radio emission, confirmed by the latest interferometric maps and reaching almost 1 Mpc in length. This kind of 0 class AGN has been observed for the first time. What is more, it has been proved that low-energy, high resolution observations with good sensitivity and dynamics, could provide the information on the past phases of blazars’ activity, which – in this case – should be considered in terms of the unification scheme of Active Galaxies.
20 January 2020
“How infrared observations change our knowledge about galaxies?”
Dr Katarzyna Małek (National Centre for the Nuclear Research, Warszawa)
Infrared (IR) radiation is the key wavelength range for investigating the formation of stars, both in the Milky Way and in other galaxies. Dusty clouds around newly formed young stars are heated by their UV emission, and this energy is re-radiated in the IR. The resultant spectrum of the IR radiation is a result of a complex interplay of dust absorption and scattering effects, known under a common name of dust attenuation. Consequently, the dust attenuation shapes the spectral energy distributions (SEDs) of galaxies themselves, and any SED modelling and fitting procedure must account for this process.
In my talk, I will present how the unique Herschel Extragalactic Legacy Project (HELP) data were used to study the dust attenuation properties in galaxies. The primary objective of the HELP project is to provide an exceptional, homogeneously calibrated, multiwavelength galaxy catalogues covering roughly 1300 deg2 of the extragalactic Herschel Space Observatory surveys at wide redshift range. Millions of galaxies with UV–FIR photometry make HELP an exceptional project which can push the boundaries of our scientific understanding of multi-λ data. I will show the recently measured dust attenuation curves of star-forming galaxies, and the influence of different attenuation laws, on the estimates of galaxy properties, including galaxy stellar mass – the key physical parameter of every galaxy.
27 January 2020
“Theory vs. observations – Some of the properties of cataclysmic variable stars”
Dr Karolina Bąkowska (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warszawa)
Cataclysmic variable stars are close binary systems containing white dwarf (the primary) and main sequence star (the secondary). In those system the matter flows from the secondary to the primary component. Due to non-zero momentum, in some of the systems, the matter does not hit the white dwarf directly, but it creates accretion disc or accretion columns around the primary component. In the light curves of some of cataclysmic variables, we can observe outbursts and superoutburst. Superoutbursts are about 1 magnitude brighter and they last longer than typical outbursts. During superoutbursts there are periodic tooth-shaped oscillations called superhumps. Time between outbursts and superoutburst when the amout of light observed in the lightcurves is approximately the same is called quiescence. Y. Osaki in his model assumes constant mass transfer during outbursts and superoutbursts and an eccentric disk and tidial instability as an orgin of superhumps and superoutbursts but in papers published by J. Smak it is presented that the mass transfer from the secondary is strongly enhanced and the orgin of superhumps and superoutbursts are variable hot spot brightness and enhanced mass transfer, respectively. Because of such discrepancy between proposed models the new observations and analysis for cataclysmic binary stars were strongly required. I would like to present the outcome of the campaign dedicated to analysis of a few eclipsing cataclysmic variables during quiescence and outbursts/superoutbursts.
2 March 2020
“Overview of recent highlights from HESS”
Prof. dr hab. Bronisław Rudak (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Toruń)
The High Energy Stereoscopic System is the ground-based TeV gamma-ray observatory, located in Namibia. Its results are of profound importance to the progress of high-energy astrophysics in the context of understanding a variety of galactic and extragalactic phenomena. The talk will present main achievements of HESS, including the first detection of a TeV gamma-ray afterglow of a bright gamma-ray burst. Prospects of multiwavelength observations with HESS as well as multi-messenger program will be discussed.
9 March 2020
“Kinematics of Coronal Mass Ejections and the associated Large Solar Energetic Particles during Solar Cycle 24”
MSc Anitha Ravishankar (Astronomical Observatory, Jagiellonian University, Kraków)
A detailed study of the properties of Solar Energetic Particles (SEPs) and their correlation with the associated Coronal Mass Ejections (CMEs) and Solar Flares is crucial for Space Weather forecast. It is well known that the CME speeds and SEP fluxes have good correlation. We have further examined this correlation by employing instantaneous speed (maximum speed, speed at SEP peak flux and Mach number at SEP peak flux) to check if they are a better indicator of SEP fluxes than the average speed. Our preliminary results show a better correlation by this approach (R=0.810 for >10 MeV energy band). We have extended this approach by studying the delay between the peak CME speed and peak SEP flux at multiple energy bands. We add the onset of type II radio burst to study the shock parameters associated with each event in our sample. In contrary, peak X-ray flux of solar flares and SEP peak flux show a poor correlation in our preliminary results (R=0.084 for >10 MeV energy band). We would like to investigate the contribution of flares to impulsive SEP events at close proximity to the Sun. In addition, we present our preliminary results on correlation between flare X-ray flux and electron and other ion fluxes. Furthermore, we would like to extend our sample to other solar cycles by using GCS model. The data of SOHO and STEREO are used for CMEs, GOES for particle fluxes and WIND/Waves for shock parameters. The scientific merit of our work is to provide a potential model for prediction of large geoeffective SEPs.
27 April 2020
“If the Universe were flat, galaxies could not have formed”
Prof. Boudewijn Roukema
Interpretations of extragalactic observations within the family of homogeneous isotropic solutions of the Einstein equation – the FLRW models – are usually described as showing that the Universe is very close to being flat. But is this really possible physically? The curvature that is usually associated with primordial density perturbations is often described as a gauge choice – an interpretation rather than an intrinsic physical, geometrical property. The turnaround epoch of an overdensity is the moment when instead of expanding more and more slowly than the surrounding Universe, the overdensity switches to a contracting phase. The relativistic Zel’dovich approximation method of modelling both cosmological expansion and structure formation shows that at this epoch, the curvature parameter is typically above five times the critical density parameter in amplitude, corresponding to a strongly positive curvature. If the spatial section of the Universe were really flat, galaxies could not have formed.
Reproducibility script: https://bitbucket.org/broukema/1902.09064
11 May 2020
“Absorption spectra of interstellar clouds”
Prof. Jacek Krełowski
Translucent interstellar clouds produce 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 500 unidentified diffuse interstellar bands (DIBs). The latter are commonly believed to be carried by complex molecular species; however, none of them was until now identified beyond a doubt. The talk will compare the above mentioned absorptions in different interstellar clouds. It is to be emphasized that physical conditions inside individual clouds can be drastically different. It seems important that any change of the extinction law is accompanied by changes in molecular and diffuse spectra. This demonstrates complex chemistry of translucent interstellar clouds. The observed molecular species are likely building bricks for prebiotic molecules.
25 May 2020
Dr Asta Heinesen (CRAL-ENS, UCB Lyon)
I will give an introduction to the field of inhomogeneous cosmology focusing on averaging schemes for formulating a large scale cosmological theory from a general relativistic space-time. An important insight from the averaging formalism discussed is that structure in a relativistic space-time induces violation of the spatial curvature conservation law of the Friedmann-Lemaitre-Robertson-Walker class of models usually used for interpreting cosmological data. Such a violation, if significant, would have important physical and observational consequences. I will mention some questions of interest in inhomogeneous cosmology and talk about some of my own work in relation to these questions.
1 June 2020
“Nowa Hewelusza (1670) – efekt koalescencji małomasywnego czerwonego olbrzyma z ?”
Prof. Romuald Tylenda (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Toruń)
Przedstawie wyniki obserwacyjnego wyznaczenia skladu chemicznego i izotopowego materii w CK Vul (pozostalosc po wybuchu Nowej Cygni obserwowanej przez Jana Heweliusza w latach 1670-72). Na ich podstawie pokaze, ze przed wybuchem byl to malomasywny (0.9-1.3 Mo) czerwony olbrzym, ktory zapewne ulegl koalscencji z innym obiektem gwiazdowym w 1670 r.
3 June 2020
Special Institute of Astronomy Seminar
“Particle acceleration mechanisms”
Dr Grzegorz Kowal (Escola de Artes, Ciências e Humanidades, Universidade de São Paulo.)
The first observations of high-energy radiation, commonly known as cosmic rays, took place over one hundred years ago. Soon after the discovery of cosmic rays, Victor Hess in 1912 confirmed with his observations, that they are mostly of galactic or extragalactic origin. Their origin and nature still puzzles the modern astrophysics and is considered one of the problems which is not yet resolve. In the first part of my talk I will briefly describe what we know about the properties of cosmic rays from observations. The following part will be dedicated to the discussion on the physical mechanisms, such as diffusive shock acceleration and turbulence, believed to be responsible for accelerating thermal particles to high energies. Finally, in the last part I will present the results of our studies on first-order Fermi acceleration by fast turbulent reconnection.
8 June 2020
“HIRES, the high resolution spectrograph for the ELT: the phase A study and the path to construction”
Prof. Alessandro Marconi (Department of Physics & Astronomy University of Florence, Italy, Associated to INAF-Arcetri Astrophysical Observatory)
I will present the current status and the path to construction of HIRES, an optical-infrared High Resolution Spectrograph for the ELT. A successful Phase A study has been completed in 2018 by a consortium of more than 30 institutes, including the university of Torun from Poland. The consortium is now preparing for Phase B and to bring the instrument to the telescope. I will present an overview of the project, describing the science case and the baseline design. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature’s fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists of a modular fiber-fed cross-dispersed echelle spectrograph providing a simultaneous range of 0.4-1.8 µm at a resolution of 100,000 and with several observing modes. I will then conclude by presenting current activities and the path to construction.
22 June 2020
“Looking at Galactic metal-poor stars with Gaia and large spectroscopic surveys”
Prof. Rodolfo Smiljanic (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warszawa)
Recently, thanks to Gaia kinematic data, it has become evident that the inner part of the Galactic halo is strongly dominated by accreted stars. The accreted system originally had a mass similar to the one of the Small Magellanic Cloud and merged with the Milky Way about 8-10 Gyr ago. The study of chemical abundances in accreted and in situ stars can reveal the star forming conditions in the different sub-systems that formed the halo and the thick disk. I this context, I will report on preliminary results of a chemo-kinematic analysis of metal-poor stars observed by the Gaia-ESO Survey. The analysis uses machine learning techniques to disentangle the various stellar populations at the low-metallicity regime, including the thick disk, the metal-weak thick disk, and the different halo components. I will also briefly mention our related efforts to separate accreted and in situ stars using data from other large spectroscopic surveys.
5 October 2020
“How to find a nearby black hole?”
Dr hab. Łukasz Wyrzykowski (Astronomical Observatory, University of Warsaw)
Black holes (BH) are everywhere, there should be hundreds of millions of stellar-origin black holes in our Milky Way Galaxy. However, we only know about 50 or so cases, mostly from X-ray binaries, where a BH accretes matter from its stellar companion, or from binary system involving a star and a BH. Single black holes, even if nearby, are essentially black and invisible.
Gravitational microlensing offers an opportunity to discover black hole and other dark objects just by the fact they are massive and bend the background light. There have been thousands of microlensing events discovered by OGLE, Gaia, ZTF and other projects. However, in order to uniquely recognise a black hole lens and distinguish from a regular stellar lens, it is required to measure the size of the Einstein Radius as well as the distances of both lens and the source. Gaia space mission’s astrometric data will allow measuring Einstein radii for all events, however, without a dense photometric coverage of their light curves, the parallax effect will not be measurable.
The Time-Domain work package of the EC’s Horizon 2020 OPTICON grant has been established in order to coordinate global long-term time-domain observations, such as of candidates for lensing black holes. In years 2021-2024, these actions will be extended also to radio time-domain observations, within the new Horizon 2020 grant OPTICON-RadioNET PILOT (ORP), where UMK will be also a partner. In my talk, I will describe the current state of the black hole microlensing searches and will present the results obtained so far with the OPTICON Time-domain telescope network. I will also present the possibilities of extending the microlensing black hole search to radio sources.
12 October 2020
“The latest TDE science news”
Dr Mariusz Gromadzki (Astronomical Observatory, University of Warsaw)
In Astronomy, the term Tidal Disruption Event (TDE) is reserved for transients caused by disruption of a star by a Supermassive Black Hole (SMBH). Those phenomena proposed in the mid 70’s show a variety of physical processes including streams interaction, accretion disk formation and high-velocity outflows. They give evidence of SMBH presence in centres of quiet galaxies, allowing for estimates of BH masses and in some cases also their spin. After almost thirty years first candidates were discovered. Currently, nearly forty has been observed. In this seminar talk, I will present progress which happened in recent years in this field, emphasising the role of ESO ePESSTO programmes.
19 October 2020
“Planetary tides in the WASP-12 and WASP-18 systems”
Dr hab. Gracjan Maciejewski, prof. NCU (Institute of Astronomy, Nicolaus Copernicus University)
Massive exoplanets on extremely tight orbits, so called hot Jupiters, induce equilibrium tides in their host stars. The tidal fluid flow in the stars can be detected with the radial velocity (RV) method. Using precise RV measurements acquired with the HARPS-N spectrograph at the Telescopio Nazionale Galileo and the HIRES instrument at the Keck-I telescope we show that the subtle RV signal of the photosphere following the planetary tidal potential can be distilled for the host stars in the WASP-12 and WASP-18 planetary systems. For WASP-18, the amplitude of those tides was found to agree with both theoretical predictions of the equilibrium tide approximation and an ellipsoidal modulation observed in an orbital phase curve. For WASP-12, the tides turned out to be 50% larger than expected. Those findings open new possibilities in probing the physical properties of stellar interiors.
26 October 2020
“The origin of the [WC] central stars of planetary nebulae”
Dr Marcin Hajduk (University of Warmia and Mazury, Olsztyn)
[WC] stars are central stars of planetary nebulae (PNe) which show spectra dominated by broad emission lines of carbon and helium. The lines originate from intense and fast winds blowing from their surface, similar to massive Wolf-Rayet (WR) stars of carbon sequence. Different theoretical models predict different evolution speed and chemical composition of [WC] stars. I have determined the temperature evolution of a sample of [WC] stars, which indicates that [WC] stars originate from more massive progenitors than hydrogen-rich central stars.
9 November 2020
“The orbital architecture and stability of the HR 8799 planetary system”
Prof. dr hab. Krzysztof Goździewski (Institute of Astronomy, Nicolaus Copernicus University)
A system of four planets of ~10 Jupiter mass around HR 8799 is the first multi-planet configuration discovered via the direct imaging (Marois+, Science 322, 2008; Nature 468, 2010). The system’s architecture is still unresolved, due to narrow observing window of ∼20 yr that covers tiny arcs of orbits with periods from roughly 50 to 500 yr. Unconstrained best-fitting astrometric configurations self-disrupt rapidly due to mutual gravitational interactions. For a decade, we argue that the HR 8799 system may be long-term stable when locked in a particular mean-motion resonance (MMR), similar to the 4:2:1 Laplace resonance of the Galilean moons. We present new results of modeling this intriguing planetary system, taking into account the broader perspective of planetary systems detected via the direct imaging.
16 November 2020
“The Nobel Prize in Physics 2020”
Prof. Jean-Pierre Lasota (CNRS Institut d’Astrophysique de Paris; Sorbonne Université, Nicolaus Copernicus Astronomical Center, Warsaw)
I will present and discuss the discoveries and services to physics that have been rewarded by this year Nobel Prize in Physics. In particular, I will try to explain why Roger Penrose has been rewarded for his work on black holes while Reinhard Genzel and Andrea Ghez got the prize for the discovery not of a black hole but of a “supermassive compact object” at the centre of our galaxy.
23 November 2020
“Periodic maser flares in high-mass star-forming regions”
MSc Mateusz Olech (Institute of Astronomy, Nicolaus Copernicus University)
The 6.7 GHz methanol maser emission is identified as an important tracer of early stages of high-mass star formation. Thanks to its characteristics we can study properties and dynamics of matter as close as 1000au from the protostar, region not easily reachable by other methods of observations. In recent years, long-term monitoring of methanol masers led to the discovery of small subgroup of 26 objects displaying periodic flares with periods ranging from less than a month to almost 2 years. To this day the mechanism driving those flares is not known and many competing theories were proposed. In my talk, I will summarize near 10 years of research conducted by Toruń maser group in this field and present our latest findings.
30 November 2020
“Metal-poor massive stars: The theory linking gravitational waves, star-formation and the dawn of the Universe”
Dr Dorottya Szécsi (Institute of Astronomy, Nicolaus Copernicus University, University of Cologne)
What do gravitational waves have in common with ancient globular clusters? What links these to cosmic explosions like gamma-ray bursts, to the energetic radiation in star-forming galaxies and even to the dawn of our Universe? What they have in common, is that all these phenomena — and more — have been theorized to stem from metal-poor massive stars, in one way or another. In my talk, I will explain these theories, and suggest new perspectives on how to combine them.
7 December 2020
“Diffuse Emission from the Inner Galaxy as measured with the HAWC Observatory”
MSc Amid Nayerhoda (Institute of Nuclear Physics, Polish Academy of Sciences, Kraków)
The Galactic gamma-ray diffuse emission is produced by the interaction of cosmic rays with ambient gas and electromagnetic radiation fields in the interstellar medium (ISM). Studying this radiation helps reconstructing the particle transport mechanisms and the particle distribution in the Galaxy. The analysis of HAWC TeV emission from a region of the Galactic plane is presented here. The energy and spatial distributions of the diffuse Galactic gamma-ray emission have been studied after subtracting extended and point sources detected with greater than 5 sigma significance from the region map. The spectral and morphological features of the measured emission are compatible with the gamma-ray emissivity obtained from the locally measured proton spectrum, convolved with the gas distribution in the Galaxy.
14 December 2020
“Chemical Complexity in the Protostellar Environment”
Dr Hannah Calcutt (Chalmers University of Technology, Sweden | Institute of Astronomy, Nicolaus Copernicus University)
Complex organic molecules are found everywhere in the interstellar medium, especially in the warm and dense gas close to forming stars, from which planets eventually emerge. Understanding the origin of these molecules and their chemistry is important to determine the complexity of chemistry that can develop, and its potential implications to life in the universe. These molecules can also be used as tools to understand the mechanisms central to the formation of stars. ALMA has revolutionised the observation of these molecules, providing the tools to perform unbiased surveys of the molecular content on solar system scales. This talk will explore the many challenges of large chemical surveys in star-forming regions. I will present the key results from my work expanding our understanding of the physical structure and evolution of star-forming regions and discuss how far we have come in building up a unified picture of chemical variability in the protostellar environment and how far we have to go.
21 December 2020
“Dissecting star-forming regions toward IRAS 22147+5948”
Dr Maciej Koprowski (Institute of Astronomy, Nicolaus Copernicus University)
Outer Galaxy consists of star-forming regions spanning various galactocentric distances and thus allows us to trace the impact of the environment on star formation. The star-forming region associated with IRAS 22147+5948 suffers from cloud confusion and unclear status based on radio continuum observations, suggesting a presence of supernova remnant or HII region. In this talk, I will explain how the machine-learning techniques, spectral energy distribution modelling, clustering, and gas and dust maps were used to disentangle and characterize distinct populations of YSOs associated with IRAS 22147+5948. I will also describe all the analysis that was performed in order to confirm the status of IRAS 22147+5948 region as a star formation site.