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657
th ACADEMIC YEAR
2020/2021
Friday Seminars
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październik/october 2020 |
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2020-10-02 |
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dr ADAM ZADROŻNY |
National Centre for Nuclear Research, Warsaw |
ZN OA 1537 |
LSC-Virgo O3 Science Run, Multi-messenger astronomy and future possibilities
The aim of a talk is to give an overview current state gravitational wave
observations. During three science runs (2015-2016, 2016-2017, 2019-2020)
of Advanced LIGO-Virgo detectors observe multiple binary merger events.
Most of the events are binary black hole mergers, but nine detected events
had neutron star component. Those observations, especially GW170817,
brought additional way to study neutron stars. In the last part of the
talk I would focus on multi-messenger astronomy that could be done and
possible future challenges and opportunities in gravitational wave
astronomy.
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2020-10-09 |
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mgr DOMINIKA KRÓL |
Obserwatorium Astronomiczne UJ, Kraków |
ZN OA 1538 |
Accretion Induced Black Hole Spin-up in Numerical GR MHD Simulations
I will present an investigation of the accretion-induced spin-up of a
black hole via numerical simulations. The method is based on
general-relativistic hydrodynamics of the slowly-rotating flows in the
Kerr metric, with change of mass and spin of the black hole during
accretion taken into account. Simulations were performed using modified
versions of HARM code. The aim of this study was to verify whether the
high mass stellar black holes may be produced with large spins, even
though at birth the collapsars might have contained non-spinning, or
moderately-spinning cores.
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2020-10-16 |
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prof. dr hab. EWA L. ŁOKAS |
Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Warsaw |
ZN OA 1539 |
Tidal evolution of galaxies in clusters
Galaxies are subject to strong tidal evolution in the environment of clusters.
I will discuss this process using the example of the most massive cluster of
the IllustrisTNG-100 simulation that traces the formation and evolution of
galaxies in the cosmological context. For the purpose of this work, I selected
112 galaxies in the cluster, with the largest stellar masses at present, and
followed their properties over time. Using their orbital history, the sample is
divided into unevolved (infalling), weakly evolved (with one pericenter
passage), and strongly evolved (with multiple pericenters). The samples are
clearly separated by the value of the integrated tidal force from the cluster
the galaxies experienced during their entire evolution and their properties
depend strongly on this quantity. As a result of tidal stripping, the galaxies
lose mass and become significantly less dark matter dominated. The cluster
environment is also very efficient in stripping the galaxies of their gas and
quenching the star formation. The strongly evolved galaxies lose their gas
earlier and faster, and they become redder and more metal rich, so that at
redshift z=0.5 the population of galaxies in the cluster becomes
predominantly red. As a result of tidal stirring, the morphology of the
galaxies evolves from oblate to prolate and their rotation is diminished, thus
the morphology-density relation is reproduced in the simulated cluster. The
strongly evolved sample contains at least six convincing examples of tidally
induced bars and six more galaxies that had their bars enhanced by their
interaction with the cluster.
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2020-10-23 |
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dr MARIUSZ TARNOPOLSKI |
Obserwatorium Astronomiczne UJ, Kraków |
ZN OA 1540 |
Time Series and Power Spectral Density Analysis of Astronomical Light Curves: Blazars and Gamma-Ray Bursts
Light curves of astronomical objects, like active galactic nuclei or
gamma-ray bursts (GRBs), often exhibit complex variability. Current
instruments provide numerous high quality data, which allow to analyse
them with novel methods both in the temporal and spectral domains. I will
discuss some of these methods, and show the most recent results:
investigation of power spectral densities using global periodograms and
wavelet based approaches, as well as classification schemes of blazar and
GRB light curves in the A-T plane.
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2020-10-30 |
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dr PRZEMYSŁAW MRÓZ |
Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena CA, USA |
ZN OA 1541 |
Exploring the free-floating planet population with gravitational microlensing
Thousands of extrasolar planets have been discovered up to date. Although
many of the known exoplanets do not resemble those in our solar system,
they have one thing in common - they all orbit a star. However, theories
of planet formation and evolution predict the existence of free-floating
planets, gravitationally unattached to any star. Gravitational
microlensing is uniquely suited for finding free-floating planets. I will
present the current constraints on the frequency and properties of rogue
planets in the Milky Way based on long-term observations of microlensing
events in the Galactic bulge by the OGLE sky survey. I will also present
several of the most promising candidate free-floating planets discovered
to date. Finally, I will briefly discuss the future prospects for
determining the frequency and mass function of rogue planets by the
planned microlensing experiments.
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listopad/november 2020 |
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2020-11-06 |
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mgr ANITHA RAVISHANKAR |
Obserwatorium Astronomiczne UJ, Kraków |
ZN OA 1542 |
Kinematics of Coronal Mass Ejections and their association with Solar Energetic Particles
Solar transients such as solar flares, coronal mass ejections (CMEs) and
solar wind are topics that require utmost importance of research as they
generate geomagnetic storms causing catastrophic damages to power grids on
Earth and are serious radiation threat to satellites on low-Earth orbit
and their crew during spacewalks. As a consequence of these powerful
outbursts on the Sun, energetic protons and ions, known as solar energetic
particles (SEPs), are accelerated at high speeds. The acceleration is
mainly due to shocks induced by CMEs or at the magnetic reconnection
regions of solar flares. As a practical consequence, Earth-directed (halo)
large SEPs are of immediate concern as they can penetrate the
magnetosphere causing widespread electrical disruptions in the regions
close to the poles and to the passengers of high-altitude aircraft flying
in polar routes. This is an introduction to an interesting topic called
Space Weather where I would stress the importance of this field of
research highlighting it's beauty and the danger. In addition we present
results of our recent statistical analysis on 38 non-interacting CMEs and
their associated SEPs during the quadrature configuration of Solar
TErrestrial RElations Observatory (STEREO) with respect to the Earth.
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2020-11-13 |
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dr hab. MICHAŁ MICHAŁOWSKI |
Astronomical Observatory Institute, Adam Mickiewicz University, Poznań |
ZN OA 1543 |
The fate of the interstellar medium in early-type galaxies
The way galaxies stop forming new stars (quenching) is a key aspect of
galaxy evolution. This is connected with removal of gas, the fuel of star
formation. I will review what we know about the mechanism of the removal
of interstellar medium (ISM) from galaxies and how fast this process is. I
will then present an alternative way to study the ISM removal by selecting
dusty early-type galaxies, for which the decrease of gas and dust can be
tracked as a function of age. This led to the first direct measurement of
the ISM removal timescale and to the conclusion that the cold ISM is
likely removed by feedback from old stellar populations.
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2020-11-20 |
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dr hab. JERZY KRZESIŃSKI |
Obserwatorium Astronomiczne UJ, Kraków |
ZN OA 1544 |
Search for planetary-mass companions to evolved stars and binaries from Kepler Field
According to recent studies, the vast majority of the stars in our Galaxy
are orbited by exoplanets. Most of them have been detected around main
sequence stars. However, the number of detected exoplanets around
subdwarfs or white dwarfs remains very low. This is in spite of the fact
that these evolved and compact stars should be the most suitable objects
for exoplanetary study. In this talk you will hear about the current
status of our investigation on the substellar bodies presence in the
proximity of the pulsating blue subdwarfs (sdB), white dwarfs (WD) and
short period binary systems containing sdB or WD stars. Our methods of
analysis rely on the detection of exoplanetary signals hidden in
photometric time series data from the Kepler space telescope, and they are
based on natural clocks within the data itself, such as stellar pulsations
and eclipse times.
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2020-11-27 |
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dr MICHAL PAWLAK |
Obserwatorium Astronomiczne UJ, Kraków |
ZN OA 1545 |
Connection between the Long Secondary Period phenomenon and the red giant evolution
The mechanism behind the Long Secondary
Period (LSP) observed in pulsating red giants still remains unknown. I
investigate the connection between the Red Giant Branch and Asymptotic
Giant Branch evolution and the appearance of the LSP. I use the OGLE-III
sample of the Long Period Variables in the Large Magellanic Cloud. I
construct the density maps in the period-luminosity as well as
color-magnitude planes for the stars showing LSP and compare them to the
remaining giants. I also fit the spectral energy distribution to test
whether additional source of reddening is present in the LSP stars. I show
that the LSP phenomenon is clearly related to a transition between
different pulsation period-luminosity sequences. I also show that the
overabundance of the stars showing Long Period Variables can be observed
around the Tip of the Red Giant Branch, and much more prominently, at the
upper end of the Asymptotic Giant Branch. The main over-density region
appears to be slightly fainter and redder than the bulk of the Asymptotic
Giant Branch. It also seems to correspond to the area of the
Hertzsprung-Russell diagram, where stable winds and high mass loss are
present. The LSP is likely to be a recurring phenomenon appearing and
disappearing in various points of the red giant evolution. The LSP stars
appear to be more reddened than other giants, which suggests the intrinsic
nature of the reddening, likely related to large dust emission. The
analysis seams to confirms the hypothesis about relation between the mass
loss due to the presence of strong stellar wind and the appearance of LPS.
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grudzień/december 2020 |
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2020-12-04 |
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prof. dr hab. JERZY W. MIETELSKI |
Institute of Nuclear Physics, Polish Academy of Sciences, Kraków |
ZN OA 1546 |
Baryonic dark matter impacts and their possible isotopic record on Earth
The existence of not discovered yet ultra-dense baryonic dark matter came
from astrophysicist Edward Witten (Witten, 1984). In his concept the
pieces of early Universe containing quarks s did not underwent inflation
and could exists currently as one of a kind of dark matter. It was
suggested, that due to ultrahigh density such matter can penetrate the
Earth (Herrin & Toeplitz, 1996, Rafelski et al., 2012). It was also
proposed, that such penetration can left traces in Earth in form of
kimberlite pipes (Paszkowski & Mietelski, 2013). The kimberlite pipes are
perhaps the most unique geological structures present on Earth. There are
narrow tubes having even few meters in diameter but at least several tens
of kilometers length. They are filled with ultramafic mantle breccia
mixed with crustal xenoliths, connecting the deep mantle with the
planet's surface. Almost 6000 such objects were found so far on Earth
(Tappe et al., 2018). They are famous due to their diamond content, which
is evidence for the direct mantle origin of kimberlite rock. The present
state of knowledge cannot propose a widely convincing mechanism to explain
how these structures were formed. The most popular ("classical") model
try to explain their formation by gas eruption from mantle gas deposits,
originating from decomposition of subducted sediments. In our dark matter
impact model, the high-energy massive projectile forms a narrow tunnel
which is immediately enlarged by explosive degassing of deeper rocks. The
empty tunnel is then raidly filled up with pyroclastic material from
mantle mixed with some crust rocks fallen from tunnel walls.
One of possible such baryonic dark matter impact was Tunguska event in
1908 (Refelski et al, 2012, Paszkowski & Mietelski 2013, Froggatt &
Nielsen, 2015). So far the possible explanation of what happened there was
meteoroid of comet impact, "classical" kimberlite (not induced) gas
eruption (Kundt, 2001) or even micro black hole Earth chord transition
(Jackson & Ryan Jun, 1973). Proposed explanation is based on scenario
when impact of condensed ultra- dense object (CUDO) made of baryonic dark
matter "seed" surrounded by aggregate of normal matter occurred. During
atmospheric passage a fractionation of ordinary matter and dense "seed"
happened. The first one produced all effects typical for normal meteoroid
impact, whereas the "seed" penetrated Earth chord like micro black hole
causing gas eruption and kimberlite-pipe emplacement process, finally the
dense "seed" escaped from Earth in North Atlantic area rising to
stratosphere hot water vapors plume, what caused famous night air glow
observed from Europe in time of Tunguska event. So, this scenario
compromise all proposed explanation in one explaining all aspects of
Tunguska event.
It was proposed in our model, that during such dark matter object impact
the energy was high enough to generate nuclear reactions and therefore
they can left some isotopic unusual signature. The experimental part of
project is mostly based on search for hard to explain in other models
possible existence of traces of non-typical radionuclides. In case of
Tunguska area samples search for any activation product will be
conducted. In case of old (~100 Ma) kimberlite material search for long
lived radionuclides like: U-236 (T1/2=23.4 Ma), Pu-244 (T1/2=80.8 Ma),
Cm-247 (T1/2=15.6 Ma) or Sm-146 (T1/2=64 Ma) is proposed. The strange or
unique isotopic signatures for stable isotopes in material from
kimberlite pipes are known already.
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2020-12-11 |
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prof. dr hab. GERALD HANDLER |
Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Warsaw |
ZN OA 1547 |
Tidally tilted pulsators
The tidally tilted pulsators are a new type of oscillating stars in close
binary systems. They appear to pulsate principally in one hemisphere because
their pulsation axes have been tilted into the orbital plane by the tidal
forces exerted by a close companion star. We have so far discovered three of
those systems in TESS space photometry data as well as noticed some related
cases in the literature. Aside from all pulsators being Delta Scuti stars, and
the orbital periods being shorter than two days, all those systems are
different in terms of their pulsational behaviour, secondary star and Roche
Lobe filling factor. We will present an overview of those stars, as well as our
initial results and work in progress.
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2020-12-18 |
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dr Marek Weżgowiec |
Obserwatorium Astronomiczne UJ |
ZN OA 1548 |
Can we observe reconnection heating in the magnetic arms of spiral galaxies?
In some spiral galaxies the so-called 'magnetic arms' have been reported, being
interarm areas with significant polarized radio emission that suggests high
ordering of the magnetic field. The most prominent example of such a galaxy is
NGC6946.
The nature of these magnetic features is still under debate. One of the possible
explanations is the action of reconnection heating that could convert the energy
of the turbulent magnetic field into thermal
energy of the surrounding gas, which would result in a higher ordering of the
magnetic field and increase in the temperature of the gas.
We summarize the analysis of the radio and X-ray emission (measured with
XMM-Newton) from NGC6946 and M83 and conclude that we might see hints for such
reconnection heating.
A similar analysis is on-going for further galaxies that show prominent magnetic
arms in their polarized radio intensity maps.
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2020-12-25 |
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przerwa świąteczna / Holiday break
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styczeń/january 2021 |
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2021-01-01 |
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przerwa świąteczna / Holiday break
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2021-01-08 |
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dr hab. SEBASTIAN SZYBKA |
Obserwatorium Astronomiczne UJ, Kraków |
ZN OA 1549 |
Exact spacetimes: waves beyond linear approximation
Gravitational waves detected by LIGO and VIRGO are extremely weak and as
such they are well described far from sources by linearized general
relativity. However, Einstein field equations are highly nonlinear. The
exact solutions which correspond to gravitational waves imply effects
not predicted by the linear theory. In this talk, I will present the
motivation behind our recent research on exact gravitational wave
spacetimes. The details of our results will be discussed next week in
the second part of the presentation.
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2021-01-15 |
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mgr SYED NAQVI |
Obserwatorium Astronomiczne UJ |
ZN OA 1550 |
Freely-falling bodies in a standing-wave spacetime
The phenomena of standing waves are mostly studied in the context of
mechanical or electromagnetic waves. In the context of General Relativity,
the issue of how to define standing gravitational waves was addressed by
Bondi and later by Stefani. We investigate an expanding universe filled with
standing gravitational waves. We study how freely falling particles in this
spacetime behave, namely, we investigate the geodesic equation and the
geodesic deviation equation. We show that antinodes attract freely falling
particles and we trace the velocity memory effect.
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2021-01-22 |
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mgr SZYMON NAKONECZNY |
National Centre for Nuclear Research, Warsaw |
ZN OA 1551 |
Photometric selection and redshifts for quasars in the Kilo-Degree Survey Data Release 4
During the talk, I will present a catalog of quasars with their
corresponding redshifts derived from the photometric Kilo-Degree Survey
(KiDS) Data Release 4. We achieved it by training machine learning (ML)
models using optical ugri and near-infrared ZYJHKs bands. We define
inference subsets from the 45 million objects of the KiDS photometric data
limited to 9-band detections, based on a feature space built from
magnitudes and their combinations. The model selection and fine-tuning
employs two subsets of objects: those randomly selected and the faintest
ones, which allows us to properly fit the bias vs. variance trade-off. We
test three ML models: Random Forest (RF), XGBoost (XGB) and Artificial
Neural Network (ANN). We find that XGB is the most robust and
straightforward model for classification, while ANN is the best for
combined classification and redshift. The ANN inference results are tested
using number counts, Gaia parallaxes and other quasar catalogs external to
the training set. Based on these tests, we derive the minimum
classification probability for quasar candidates which provides the best
purity vs. completeness trade-off. We find 158,000 quasar candidates in
the safe inference subset (r < 22), and further 185,000 in the reliable
extrapolation regime (22 < r < 23.5). Test-data purity equals 97%,
completeness is 94%, the latter dropping by 3% in the extrapolation to
data fainter by one magnitude than the training set. The photometric
redshifts are derived with ANN and modelled with Gaussian uncertainties.
Test-data redshift error (mean and scatter) equals 0.009 +/- 0.12 in the
safe subset, and -0.0004 +/- 0.19 in the extrapolation, averaged over
redshift range 0.14 < z < 3.63. Our success of the extrapolation
challenges the way that models are optimised and applied at the faint data
end. The resulting catalog is ready for cosmological and Active Galactic
Nucleus (AGN) analysis. We publicly release the catalog at
kids.strw.leidenuniv.nl/DR4/quasarcatalog.php.
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2021-01-29 |
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przerwa egzaminacyjna / Exam break
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luty/february 2021 |
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2021-02-05 |
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przerwa egzaminacyjna / Exam break
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2021-02-12 |
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ferie zimowe / Holiday break
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2021-02-19 |
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przerwa egzaminacyjna / Exam break
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2021-02-26 |
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marzec/march 2021 |
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2021-03-05 |
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2021-03-12 |
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2021-03-19 |
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2021-03-26 |
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kwiecień/april 2021 |
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2021-04-02 |
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Wielki Piątek / Holiday break
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godzina 15:00 / at 3:00 p.m. MS TEAMS |
2021-04-09 |
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mgr ANITHA RAVISHANKAR |
OA UJ |
ZN OA 1552 |
Publiczna obrona pracy doktorskiej Study of coronal mass ejection (CMEs) using STEREO and SOHO observations
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2021-04-16 |
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2021-04-23 |
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2021-04-30 |
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maj/may 2021 |
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2021-05-07 |
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2021-05-14 |
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mgr RAMESHAN THIMMAPPA |
OA UJ |
ZN OA 1553 |
A Comprehensive and Novel Analysis of the Chandra X-ray Observatory Data for the Pictor A Radio Galaxy
Pictor A, recognized as the archetypal powerful radio galaxy of the FR II
type, is not only one of the brightest radio sources in the sky, but is
also particularly prominent in the X-ray domain. In this talk, I will
summarize our analysis of all the Chandra X-ray Observatory data available
for the Pictor A radio galaxy, consisting of multiple pointings spanning
over 15 years and the total exposure time of 464 ks. In particular, the
following three main research results discussed during my talk will be:
(i) investigating the X-ray structure of the termination shocks of
relativistic jets in Pictor A, the so-called "hotspots", by means of
detailed image deconvolution and timing analyses; (ii) investigating
correlations between the X-ray and radio emission features within the
extended lobes of the source; and (iii) an approach to the X-ray
spectroscopy of the active nucleus in Pictor A radio galaxy, carried out
in a regime of a severe instrumental pile-up.
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2021-05-21 |
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2021-05-28 |
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czerwiec/june 2021 |
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2021-06-04 |
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piątek po Święcie Bożego Ciała / Holiday break
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2021-06-11 |
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2021-06-18 |
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2021-06-25 |
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lipiec/july 2021 |
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godzina 10:00 / at 10:00 a.m. MS TEAMS |
2021-07-16 |
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mgr RAMESHAN THIMMAPPA |
OAUJ |
ZN OA 1554 |
Publiczna obrona pracy doktorskiej A Comprehensive and Novel Analysis of the Chandra X-ray Observatory Data for the Pictor A Radio Galaxy
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sierpień/august 2021 |
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wrzesień/september 2021 |
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ZOOM |
2021-09-03 |
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mgr KARTHIK BALASUBRAMANIAM |
OA UJ |
ZN OA 1555 |
Fluorescent Iron Lines in Various Types of Radio-Loud Active Galactic Nuclei
The X-ray radiation emitted by the accreting matter in active galactic
nuclei (AGN), is widely believed to originate close, or even very close to
the central super-massive black holes (SMBHs). First, when optical/UV disc
photons are inverse-Compton scattered by a corona of hot electrons around
the SMBH, the main X-ray continuum emission takes on a power-law shape.
Second, a fraction of this radiation is reflected and reprocessed by the
absorbing gas and dust located further away from the center. The
reprocessing of the X-ray continuum includes photoelectric absorption,
followed by fluorescent line emission. Out of all fluorescence features,
the iron feature is the most prominent; this is due to the combination of
the high relative abundance of iron, and its high fluorescence yield.
Moreover, when produced around the innermost orbits of the accretion
disks, the iron features may be relativistically broadened and
gravitationally redshifted, depending on the disk structure and the black
hole spin.
In my research, summarized in this talk, I have analyzed the X-ray
radiative output of three radio-loud AGN of various types, focusing, in
particular, on their Fe fluorescence emission. The analyzed systems are
the broad-line quasar 4C+74.26 with giant large-scale radio morphology,
the LINER-type AGN hosted by a post-merger disk galaxy CGCG 292-057,
with a multi-component radio morphology reflecting intermittent activity
of the central SMBH, and finally the youngest radio galaxies known,
1146+596, hosted by an elliptical NGC 3894 with a low-luminosity active
nucleus.
All in all, my research reveals a prevalent fluorescent iron line emission
in various types of radio-loud AGN, including both low- and
high-luminosity objects. There is a variety in the iron features in the
population of jetted AGN, including relativistically broadened lines,
ionized lines, and neutral lines with a larger range of equivalent widths.
The research I have carried out highlights, in general, the importance of
iron fluorescence studies for radio-loud AGN, for which the constraints
regarding the innermost structure of AGN, enabled exclusively by the X-ray
spectroscopy, can be uniquely complemented by the constraints on the
energetics and duty cycle of the systems following from the analysis of
their radio (jet) emission.
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