General Seminar (2019)
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General Seminar takes place every Monday at 11.15 in Piwnice, radioastronomy seminar room.
7 January 2019
“On the origin of gravitational wave source”
Prof. Tomasz Bulik (Astronomical Observatory, University of Warsaw)
The recent detections of coalescences of compact object binaries in gravitational waves bring forward the question of the origin of such binaries. We review the basic properties of the known coalescences. These properties set quite strong constraints on the models of formation of merging binaries of compact objects. We discuss these constraints and briefly outline the major challenges that must be met in order to unravel the origin of these objects.
14 January 2019
“New types of transients in the era of all-sky surveys”
Dr Mariusz Gromadzki (Astronomical Observatory, University of Warsaw)
Last decade is a period of an extensive development of all-sky surveys, which reveal discovery of new types of transients such as Super Luminous Supernovae, Tidal Disruption Events and other rapidly evolving objects. In my talk I will present a brief review of this exciting topic.
21 January 2019
“Tidally induced bars in interacting galaxies”
Prof. Ewa Łokas (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warszawa)
I will talk about the interactions between galaxies and how they influence their dynamics and morphology. The presentation will focus on recent results of simulations following an interaction of two similar disky galaxies on unbound orbits. It turns out that the result of the interaction can be very different depending on the relative orientation of the galaxy’s internal spin and its orbital angular momentum. In the case of aligned spins and a sufficiently strong interaction, it can result in the formation of a tidally induced bar. I will discuss in detail the properties of such bars and the so-called buckling instability that occurs in them, when the bar becomes distorted out of the initial disk plane. I will present different measures of asymmetry in the edge-on view as well as kinematic signatures of buckling. I will demonstrate that tidally induced bars offer a unique possibility to obtain insight into the nature of buckling instability.
25 February 2019
“Modelowanie kształtu i parametrów rotacji planetoid w oparciu o dane fotometryczne”
Dr Przemysław Bartczak (Institute Astronomical Observatory, Adam Mickiewicz University, Poznań)
Planetoidy stanowią ważną grupę ciał w Układzie Słonecznym. Prowadzone badania nad ich własnościami fizycznymi wzbogacają naszą wiedzę na temat powstawania, budowy i ewolucji układów planetarnych. Prawidłowe wyznaczenie parametrów fizycznych i ich niepewności jest wyzwaniem dla astronomów od 120 lat. W czasie prezentacji przedstawiona zostanie nowa metoda oraz wyniki modelowania kształtu i parametrów rotacji.
4 March 2019
“Waveplates on the sky: the origin of complex radio pulsar polarization”
Dr hab. Jarosław Dyks (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Toruń)
Pulsar radio signals consist of two elliptical orthogonal polarization modes attributed to birefringence of magnetospheric plasma. In addition to regular noncoherent polarization effects expected for such combined signals, the radiation exhibits a number of astonishing complex phenomena, such as bifurcations of polarization angle tracks, half-orthogonal polarization angle jumps, different handedness of circular polarization in a single mode, orthogonal polarization mode jumps at maximum circular polarization, and others. The effects prove the importance of phase-sensitive coherent wave superposition in pulsar magnetosphere. First principle theoretical models (such as polarized ray tracing) were used to model the polarization, but they have not reached the level that allows us to reproduce or explain the data. I will show that empirical models are capable to interpret the effects in geometrical terms, both as a function of pulse longitude and frequency.
11 March 2019
“Obserwacyjne wskaźniki statusu ewolucyjnego mgławic planetarnych”
Dr Marcin Hajduk (University of Warmia and Mazury, Olsztyn)
Do badania ewolucji mgławic planetarnych tradycyjnie zastosowanie mają pomiary jasności i temperatury, lokujące te obiekty na diagramie HR. Pomiar jasności jest obarczony różnymi niepewnościami. Gwiazda emituje maksimum swojego promieniowania poza zakresem widzialnym. Oszacowania odległości czy ekstynkcji międzygwiazdowej dla mgławic planetarnych są niepewne. Z kolei jasność gwiazd centralnych jest silną funkcją masy, w wyniku czego niewielki błąd jasności propaguje się na duży błąd w wyznaczeniu masy i odpowiedniego toru ewolucyjnego. Bardzo dobrą obserwablą do badania gwiazd centralnych jest tempo zmian temperatury. Wielkość tą można wyznaczyć stosunkowo łatwo porównując stosunki strumieni linii mgławicowych czułych na temperaturę zmierzone w odpowiednim odstępie czasu. Ewolucja temperatury młodych gwiazd centralnych jest mierzalna w skali czasowej lat i dekad. Co ważne, wyznaczenie tempa zmiany temperatury nie zależy od odległości. Inną cechą gwiazd centralnych, mającą istotny wpływ na określenie ich statusu ewolucyjnego, jest ich podwójność. Według niektórych autorów ona jest główną przyczyną powstawania niesferycznych mgławic. Podczas seminarium przedstawię wyniki prowadzonych badań i przyszłe plany.
18 March 2019
“Modeling energy-dependent propagation and dynamical effects of cosmic rays in galaxies”
Mgr Mateusz Ogrodnik
Recent theoretical and numerical studies incorporating cosmic rays (CRs) into global modeling of magnetized interstellar medium demonstrate that CRs play an important role in generation of large-scale galactic magnetic fields and, at the same time, in driving galactic winds. Cosmic-Ray-driven dynamos produce magnetic arms in galactic disks and large-scale helical magnetic fields in galactic halos.
A new element of our model is a population of CR electrons injected in SN remnants together with CR protons. I am going to present a novel implementation of energy dependent propagation of CR electrons in ”Cosmic Ray Energy SPectrum” (CRESP) module of PIERNIK MHD code. The overall propagation of cosmic rays is described by energy-dependent diffusion-advection equation, including adiabatic cooling and synchrotron losses of CR electrons. We use the CRESP module to study the propagation of CR electrons and their synchrotron emission in the magnetized interstellar medium of spiral galaxies. The resulting spatial distributions of gas, magnetic fields, and cosmic ray electrons are used to construct synthetic radio-maps of the modeled galaxies.
25 March 2019
“Eclipsing binaries in multiple systems”
Dr hab. Wojciech Dimitrow (Institute Astronomical Observatory, Adam Mickiewicz University, Poznań)
Stars form in multiple systems. The statistics of stellar multiplicity provide constraints on the initial parameters of the stellar clusters formation. All zero age stars are members of binary or multiple systems. This is confirmed with observation and simulations of collapsing molecular clouds. Some of the multiples contain close eclipsing pairs. The photometric and spectroscopic observations of those pairs enabled us to obtain the absolute parameters with an accuracy of 1% or better. Over the last decade we observed five multiple systems. For most of them we detected a new components. We calculated the models for the eclipsing subsystems. The star with higher multiplicity, which we investigated is quintuple. The main instruments used in this program are small 0.5-m and 0.7-m telescopes equipped with echelle spectrographs, but we also used spectra from 2-m class telescopes.
1 April 2019
“New picture of the Milky Way”
Dr hab. Paweł Pietrukowicz (Astronomical Observatory, University of Warsaw)
Milky Way is a complex system which exploration is hampered due to the presence of interstellar dust and the location of our Sun close to the Galactic plane. I will review the current knowledge on the structure and evolution of the Milky Way based on the most recent results obtained by large surveys.
8 April 2019
“Lokalna skala odległości we Wszechświecie”
Dr hab. Dariusz Graczyk (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Toruń)
Lokalna pozagalaktyczna skala odległości jest kalibrowana za pomocą trzech niezależnych punktów “zerowych”: odległości do galaktyki maserowej NGC 4258, paralaks trygonometrycznych galaktycznych cefeid oraz odległości do Wielkiego Obłoku Magellana (LMC). Odległość do LMC jest obecnie znana z dokładnością 1%, co pozwala na wyznaczenie parametru Hubble’a H0 z dokładnością lepszą niż 2%. Porównanie z globalną wartością H0 wyznaczoną z obserwacji mikrofalowego promieniowania tła (Planck+WMAP) oraz oscylacji akustycznych materii barionowej prowadzi jednak do znaczącej rozbieżności na poziomie 4.4sigma. Czy ta rozbieżność wskazywać może na “nową” fizykę rozciągającą się poza standardowy obecnie model kosmologiczny ΛCDM?
15 April 2019
“Pomiary odległości i rotacja Galaktyki”
Prof. dr hab. Jacek Krełowski
Odległości wewnątrz naszej Galaktyki można mierzyć stosując metody: standardowego pręta (paralaksy trygonometrycznej), standardowej świecy (paralaksy spektroskopowej) lub pomiaru gęstości kolumnowej gazu międzygwiazdowego. Krzywa rotacji Drogi Mlecznej (przyjmowana za płaską poza orbitą Słońca) może być skonstruowana dzięki pomiarom odległości i prędkości radialnych dostatecznie odległych obiektów. Test płaskości krzywej rotacji wykonano bazując na obserwacjach międzygwiazdowych linii H i K zjonizowanego wapnia. Linie te pozwalają na pomiar zarówno odległości, jak i prędkości radialnej. Do testu użyto widm gwiazd OB z cienkiego dysku Galaktyki, zebranych spektrografem UVES. Widma pokazują wyraźnie, że momentalne prędkości radialne gwiazd nie nadają się do testu z racji krotności obserwowanych obiektów. Natomiast wysoka rozdzielczość spektrografu pozwala mierzyć prędkości radialne obłoków z dużą precyzją. Odległości wyznaczano albo z natężeń linii H i K albo z niedawno opublikowanych paralaks trygonometrycznych satelity Gaia. Te dwa rodzaje pomiarów najwyraźniej zgadzają się statystycznie, ale w indywidualnych obiektach mogą być znacząco różne. Uzyskane krzywe rotacji również zgadzają się statystycznie. Pojawił się tu bardzo ciekawy wynik: o ile prędkość orbitalna maleje na zewnątrz orbity Słońca (co można wytłumaczyć keplerowskim charakterem krzywej rotacji) o tyle maleje ona również ku centrum i to zjawisko pozostaje niezrozumiałe.
29 April 2019
“Building a disc galaxy after a major merger in Illustris”
Dr Nicolas Peschken
The major merger of two galaxies has long been thought to create elliptical galaxies due to the destruction of the progenitors in the violent relaxation phase of the merger. However in case of wet mergers it has been shown that accretion of gas after the merger can create a new disc component in the remnant, both from observations and from simulations of isolated galaxies. In our work we investigate this phenomenon in the larger frame of a cosmological context using the hydrodynamical simulation Illustris. We select a sample of major mergers creating disc galaxies in Illustris, and study their formation and evolution after the merger, and in particular the formation of the disc component in the remnant galaxy. We then derive from those cases the conditions necessary for the formation of a disc after a major merger.
6 May 2019
“Hen 3-160 – the first symbiotic binary with Mira variable S star”
Dr Cezary Gałan (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warszawa)
Symbiotic stars (SySt) are binary systems composed of a star in the late stage of evolution and a stellar remnant. The enhanced mass loss of the evolved star leads to strong interactions and the mass exchange what makes these systems useful laboratories for understanding binary evolution. There are a number of reasons to believe that many of these systems should containchemically peculiar giants, an extrinsic C (C-rich) and/or S (Zr-rich) stars. Observations, however, pointed to the deficit of such objects among SySt with ‘normal’ red giants. The problem remained not carefully investigated by analysis of the spectral line profiles and chemical abundance measurements so in the recent years we carry out the dedicated program to look for chemically peculiar giants in a large sample of SySt. I will present our results concerning one poorly studied so far but particularly interesting case of Hen 3-160, that turned out to be the first known symbiotic system with Mira variable S star. This object is reported in Belczynski et al.’s (2000) catalog as a symbiotic binary system with M7 giant donor. Using V- and I-band photometry collected over 20 years we have found that the giant is a Mira variable pulsating with 242.5-day period. The period-luminosity relation locates Hen 3-160 at the distance of about 9.4 kpc, and its Galactic coordinates (l=267.7∘, b=−7.9∘) place it ∼1.3 kpc above the disc. This position combined with relatively high proper motions indicates that Hen 3-160 has to be a Galactic extended thick-disc object. Our red optical and infrared spectra show the presence of ZrO and YO molecular bands that appear relatively strong compared to the TiO bands. We proposed that the giant in this system is intrinsic S star, enriched in products of slow neutron capture processes occurring in its interior during an AGB phase.
13 May 2019
“Young Stellar Objects in the Central Molecular Zone”
mgr Alya Amirah Azman
The Galactic Center (GC) environment provides unique and extreme conditions for star formation within the Milky Way. Candidate young stellar objects (YSOc) in the GC have previously been identified using Spitzer 24 micron emission. Star formation rates determined directly from YSOs counts are much higher than the value estimated from other methods. In addition, the YSOc distribution shows a puzzling asymmetry such that they are preferentially located at negative Galactic longitudes, while the molecular gas distribution is mostly concentrated to positive longitudes. To resolve the nature of these YSOc, we have conducted spectral line observations of these sources with APEX at 230GHz and characterized the dense gas associated with them. We also examine the far-infrared and submm properties of the YSOc using Hi-GAL and ATLASGAL survey data. Furthermore, using 70 micron data from Herschel Hi-GAL survey, we produce an independent catalog of YSOc. These confirm the known sites of star formation, as well as reveal new ones. Interestingly, based on our spectral line and dust continuum analysis, we find no evidence for the previously reported asymmetry. We conclude that some previous YSO catalogues were likely affected by contaminants, resulting in biased estimates of the star formation rate and its spatial distribution in the GC.
“VUV-Absorption cross section at high temperature and warm exoplanet atmosphere modeling”
mgr Ngân Lê
The discovery of extrasolar planets has been developed strongly during the past two decades. Spectroscopy observations during transit can allow us to detect the presence of molecules in the exoplanetary atmospheres. Chemical kinetics models have been used to interpret the observational data. However, the absorption cross-sections of many molecules used in the model are mainly at the room temperature while the exoplanets atmosphere is often very hot. In this talk, I will present a study concerning the evolution of VUV acetylene (C2H2) absorption cross-sections with temperature. The absorption cross-sections of C2H2 at 300, 500, and 600 K were fitted with Gaussian functions and then used to run the chemical kinetics model. Replacing the absorption cross-section of C2H2 at 300 K by the ones at higher temperature affects the molecular abundances in exoplanetary atmospheres.
20 May 2019
“Determining star formation rates in high-redshift galaxies from IRX-beta relation”
dr Maciej Koprowski
Precise determination of star formation rates for many galaxies at high redshifts is very difficult, as they often lack IR observations, sensitive to the starlight re- processed by dust. In order to account for this, one has to, therefore, utilize alternative methods, most popular of which involves estimating the energy re-emitted in the IR (infrared excess, IRX=LIR/LUV) based on the amount of reddening in the rest-frame UV (UV slope, β) via the so-called IRX-β relationship. Many works, however, seem to indicate that this local relation may not necessarily hold at high redshifts.
In this talk I will present the stacking analysis of a large sample of optically-selected Lyman-break galaxies (LBGs) in the JCMT SCUBA2 and Herschel SPIRE bands that was done in order to re-calibrate the IRX-β relationship at redshifts 3−5. I will show that at high redshifts, the average galaxy suffers from the dust attenuation law which is characteristic of local sources. I will also explain how different methods of estimating the UV slope, β, can cause the resulting relation appear flatter and therefore often consistent with the SMC-like attenuation law. In addition, I will show how the individual values of the IRX and β were calculated for a sample of 41 z~3 LBGs, detected in the recently-finished ALMA follow-up survey of the UDS SCUBA-2 sources. I will explain how the apparent scatter in the IRX-β plane is driven by the relative distribution of the stars and dust, as encoded in the shapes of the attenuation curves, as well as show how the shapes of the assumed attenuation curves affect the resulting stellar masses, as estimated via SED fitting. The results presented in this talk indicate that while, on average, star formation rates for high-redshift galaxies can be estimated from UV data alone, the values for the individual sources cannot be trusted in the absence of the IR data.
27 May 2019
“Konkurs na nazwy planet i inne projekty na stulecie IAU”
dr Krzysztof Czart (IAU NOC Poland)
W tym roku Międzynarodowa Unia Astronomiczna (IAU) obchodzi 100 lat swojego istnienia. Z tej okazji zorganizowała akcję o nazwie IAU100, w ramach której w trakcie całego roku prowadzone są projekty skierowane do różnorodnych grup odbiorców (członków IAU, miłośników astronomii, nauczycieli, uczniów, społeczeństwa). Jednym z nich jest konkurs na nazwy planet pozasłonecznych IAU100 NameExoWorlds, który wystartuje na początku czerwca. Każdy kraj otrzyma prawo nazwania jednej z planet i jej gwiazdy. W tym celu będą prowadzone krajowe konkursy. Inne przykłady działań w ramach IAU100 to Astronomy Translation Network, AstroVoices, globalne obserwacje Księżyca w 50. rocznicę załogowego lądowania na Srebrnym Globie. Z kolei Polskie Towarzystwo Astronomiczne przygotowuje akcję “Astronomers in Schools” (wizyty astronomów w szkołach).
3 June 2019
“On planet frequency around giants”
prof. dr hab. Andrzej Niedzielski
Evolved stars, giants, are not the best targets in search for exoplanets due to their variability. However, these objects represent perfect laboratories to study the population of planets around intermediate-mass stars and star-planet interactions. One of the largest projects devoted to search for planet around evolved stars in the Pennsylvania-Toruń Planet Search (PTPS). In my talk I will present all radial velocity based searches for planets around evolved stars and a general summary of their results as well as the recent results of PTPS.
10 June 2019
“Historia astronomii wciąż potrafi zaskakiwać, czyli Edward Gresham i jego Astrostereon”
prof. dr hab. Jarosław Włodarczyk (IHN PAN, Warszawa)
Wyniki badań nad zapomnianym rękopisem, zachowanym w Bibliotece Bodlejańskiej w Oksfordzie i w londyńskiej Bibliotece Brytyjskiej, rzucają nowe światło na recepcję teorii heliocentrycznej w Anglii w epoce Shakespeare’a, na kontekst pierwszych teleskopowych obserwacji Księżyca, poprzedzających odkrycia Galileusza, czy wreszcie na kwestię pierwszeństwa w wymyślaniu astronomii księżycowej. Autorem tego rękopisu, zatytułowanego Astrostereon or the Discourse of the Falling of the Planet i spisanego w 1603 roku, jak również zawartych w nim oryginalnych pomysłów astronomicznych był astrolog i lekarz Edward Gresham (1565–1613) – postać nieznana badaczom dziejów astronomii i niemal zupełnie zapomniana przez historyków przełomu epok elżbietańskiej i jakubińskiej. W swoim wystąpieniu przedstawię najciekawsze kwestie, poruszane przez Greshama, i spróbuję wskazać, w jaki sposób wzbogacają one naszą wiedzę o drogach rozwoju astronomii początku XVII stulecia.
17 June 2019
“Comparing radio-loud Swift/BAT AGN with their radio-quiet counterparts”
Maitrayee Gupta (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warszawa)
Some AGN are known to be efficient producers of strong, relativistic jets which power the extended radio sources. Most spectacular in respect of powers and sizes are the radio sources associated with AGN hosted by giant elliptical galaxies. However even among them, the production of powerful jets is a very rare phenomenon and the unanswered question remains why it is so. Since relativistic jets are most likely powered by rotating BHs via the Blandford-Znajek mechanism, one might expect that the parameters deciding about efficient jet production are BH spins and magnetic fluxes. If their values are large, then the innermost portions of accretion flow should be affected by the jet production and this should be imprinted in their radiative properties. In order to verify whether this is the case, we compare the radiative properties of radio-loud (RL) and radio-quiet (RQ) AGN selected from the Swift/BAT catalog with similar BH masses and Eddington ratios. As we have found the only significant difference concerns the hard X-ray luminosities, which are about two times larger in radio-loud AGN than in radio-quiet AGN. One might speculate that this difference comes from having in RL AGN X-ray contribution not only from the innermost, hot portions of accretion flow, but also from a jet. However, this interpretation is challenged by our following findings: (1) hard X-ray spectra of RL AGN have similar slopes and high-energy breaks to those of RQ AGN; (2) hard X-ray radiation is to be in both RQ and RL AGN quasi-isotropic. Hence we argue that production of hard X-rays in the RL AGN is like in the RQ AGN, dominated by hot, central portions of accretion flows, while larger X-ray production efficiencies in RL AGN can be associated with larger magnetic fields and faster rotating BHs in these objects.
7 October 2019
“Inhomogeneous Cosmology: A no-compromise application of general relativity to our real Universe, its challenges and advantages”
dr Mohammad Ahsan Nazer
The standard model of cosmology applies the Friedmann-Lemaı̂tre-Robertson-Walker (FLRW) exact solution of the Einstein equations to model the evolution of the Universe. This exact solution possesses rotational and translational symmetries and is used to estimate the age of the Universe, its expansion history and to obtain distance-redshift relations. Initially small violations of these symmetries are assumed to have given rise to the current structure of the Universe that includes galaxies, walls of galaxies and voids. The perturbed FLRW solution (metric) with a spatially flat background is then used to model the observed matter distribution with some limitations that are attributed to the perturbative approach itself. A more complete treatment of structure formation relies on Newtonian cosmological (N-body) simulations. It is not clear if other problems such as the tension between the present Hubble constant H0 value from supernovae experiments and the cosmic microwave background anisotropies is because of the perturbative approach or the non-applicability of the FLRW exact solution.
Inhomogeneous cosmology refers to the modelling approach in which the rotational and translational symmetries are abandoned at the cost of increasing complexity but with the potential benefit of removing some of the problems in standard cosmology. I argue that inhomogeneous cosmology is a “conservative” approach of applying General Relativity (GR) to the universe in which problems in structure formation, the Hubble constant tension, and the cause of the accelerated expansion are explained by adopting a “back to first principles” paradigm. I will first give an overview of the averaging and backreaction concepts in inhomogeneous cosmology and I will end with an account of our attempts to use the Relativistic Zeldovich Approximation (RZA) to improve N-body simulations of structure formation.
14 October 2019
“Modeling cosmic acceleration through the equation of state”
dr Mariana Jaber Bravo
Currently, the Universe goes through an accelerated expansion, different observations have proven such fact: (SNeIa, BAO, CMB anisotropies, LSS formation, Weak Lensing). Even more, future projects and surveys are underway or being proposed to discover the underlying cause of this phenomena. The current cosmological paradigm, LCDM, models the dark energy (DE) component as a constant term that produces late time acceleration. However some degrees of tension have appeared among different data sets which has renewed the interest on alternative models that can provide an acceleration mechanism. Parametric approaches are a useful way to study alternative models for DE.
In this talk I present two different parametric forms for the equation of state for DE. The first is motivated by scalar field dynamics such as in quintessence models and recovers the widely used CPL equation but allows for a richer behavior. The second parametrization can reproduce a f(R)-like evolution with sub percent precision over the numerical solutions. In both cases the constraints using observations are discussed. I will also mention the ongoing work for using voids as an observable of large scale structure and test among different cosmological models.
21 October 2019
“Thermal properties of slowly rotating asteroids”
dr Anna Marciniak (Institute Astronomical Observatory, Adam Mickiewicz University, Poznań)
Asteroids are remnant building blocks left over from planetary formation. Studying them reveals clues about the origin and formation of ours but also other planetary systems.
Asteroids seen in the thermal infrared reveal their intrinsic properties like size, albedo, thermal inertia or surface roughness. Determining these parameters is only possible though, when at least spin period and spin axis orientation are known. To fully utilize the potential in variety of thermal data from infrared space missions like WISE, AKARI, IRAS or Herschel, a precise shape model of an asteroid is also needed.
Spin and shape models of asteroids are routinely created using convex inversion method from multi-apparition data in the visible light. However, due to various selection effects there is a lack of spin and shape models for slow rotators, especially when slow rotation is coupled with small amplitude of the lightcurve. These features make such targets perfect asteroid calibration sources for ground and space-based infrared observatories like ALMA, APEX or IRAM. Also, there are hints of increasing thermal inertia with the rotation period, but due to very small number of slow rotators with TPM applied, they still lack firm confirmation.
I am going to present our campaign aimed at decreasing these selection effects, and show results of applying our spin and shape models in detailed thermophysical modelling, simultaneously joining data from different infrared observatories.
28 October 2019
“GAME and how to play it – FFTS observations and data reduction”
MSc Rafał Sarniak
The GAME (Great Astronomical Map Executor) program was created for the purpose of observation with the RT4 radio telescope at the Astronomical Observatory of the Astronomy Center of the Nicolaus Copernicus University in Toruń. Its main purpose is to use the FFT spectrograph with 100 MHz bandwidth for observation and to enable their reduction.
During my speech I will present new possibilities for spectral observations with the RT4 radio telescope and the FFTS broadband spectrograph. The GAME software and the observation modes it provides will be discussed.
4 November 2019
“Stellar-merger remnants: what is left after two stars collide”
Dr Tomasz Kamiński (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Toruń)
Red novae, a newly-recognized group of eruptive variable objects, are optical manifestations of merging non-compact stars that may be observed in real time. They represent transients erupting at luminosities intermediate between those of classical novae and supernovae. In red nova eruptions, stellar coalescence produces circumstellar environments very rich in molecular gas and dust. ALMA, NOEMA, and SMA have recently revealed the complexity of the cool remnants of such events, including their spatio-kinematic structure and a rich molecular inventory of peculiar molecular and isotopologic composition. The submillimeter observations have provided, for the first time, the masses dispersed during the merger events and revealed bipolar outflows, which strongly constrains hydrodynamic models of progenitor common-envelope systems and violent stellar mergers. Additionally, detailed studies of chemical composition of red-nova remnants have yielded many surprises and include the detection of complex organic molecules and the first observation in space of a “radioactive molecule”, 26AlF. I am going to give an overview of how merger remnants look like years, decades and centuries after the coalescence. This work constitutes a starting point of the MERGESTARS project soon to kick off in CAMK Toruń.
18 November 2019
“Periodic variability of 6.7 GHz methanol maser sources”
MSc Mateusz Olech
Methanol maser emission at 6.7 GHz is widely recognized as a tracer of high-mass young stellar objects. Its characteristics give us the opportunity to study in unprecedented detail the physical properties and dynamics of protostellar environment. In last 15 years long-term monitoring of methanol maser sources unveiled the existence of a small group of 26 objects displaying periodic variability. The periods range from 24 days up to 2 years with widely different flare profiles and amplitudes. Many mechanisms were proposed to explain this behaviour but there still is no consensus between researchers. In my talk I will summarize the progress of near 10 years of research conducted by our group in this field and present our latest findings.
25 November 2019
“AGN’s life cycle – short-lived radio sources”
MSc Aleksandra Wołowska
The evolution of extragalactic sources has been an important issue in the study of active galactic nuclei (AGNs) for many years and is still a subject of deliberation. Standard evolutionary model created based on numerous observations assumes that GPS (Gigahertz Peak Spectrum) and CSS (Compact Steep Spectrum) sources are precursors to a large-scale radio-galaxies of FRI/FRII type.
During their evolution the radio jets of compact sources try to leave their host galaxy and develop into a large-scale structures, however, statistical studies have revealed that there is a significant excess of small, low-luminosity sources in comparison to powerful, fully developed, luminous radio-galaxies. This indicates that not all GPS and CSS are able to evolve into large-scale structures, and some of them show intermittent, recurrent activity on a scale of several thousands years. Those objects represent a new population of transient active galaxies that is yet to be fully discovered and studied.
During my speech I will present extensive observational data, and their interpretation, for several transient AGNs discovered with JVLA Caltech-NRAO Stripe 82 Survey.
2 December 2019
“Zooming in on GW170817 at radio waves”
Dr Marcin Gawroński
The discovery of a gravitational wave/kilonova GW 170817 marked an important date in the history of modern astrophysics. GW 170817 afterglow was detected through the whole range of electromagnetic radiation, and an intense observing campaign then took place to study its physical properties. Our 32-m radio telescope was also involved in GW 170817 observations during two dedicated EVN experiments. Interpretation of the long-lived radio, optical, and x-ray emission suggested the launch of a jet from the remnant of the binary neutron star merger.
During my talk I will summarise results obtained so far in the radio domain, and present our recent findings based on the EVN data that were published in Science.
9 December 2019
“Nobel prize for physics 2019: co-winner Jim Peebles”
Prof. Boudewijn Roukema
Jim Peebles was the author and co-author of several key papers from the 1960s to the 1980s related to cosmological nucleosynthesis, the cosmic microwave background, the formation of large-scale structure in the Universe, the role of dark matter in solving several physical puzzles and the likely relevance of a cosmological constant required to fit cosmological observations within the context of the homogenenous isotropic family of cosmological solutions of the Einstein equation. An overview of these key contributions by Peebles to non-global aspects of physical cosmology, for which he was co-awarded the 2019 Nobel prize for physics, will be presented.
16 December 2019
“2019 Nobel Prize for 51 Peg b”
Prof. Andrzej Niedzielski
After three decades of exoplanet hunt we know of thousands of exoplanetary systems. Search for exoplanets and their characterisation became one of the main topics of astronomy these days, with a number of space missions already completed or ongoing, and new planned. But who found the first exoplanet ever? In my short introduction to exoplanets I will try to answer that question.