Wednesday Colloquium


"My memories of Professor Bohdan Paczyński"

Rafał Moderski (Copernicus Astronomical Centre, Warsaw)


"How homogeneous is our Universe? New constraints from luminosity and age data"

Krzysztof Bolejko (Copernicus Astronomical Centre, Warsaw)


"Even more paradoxical twins"

Stanisław Bajtlik (Copernicus Astronomical Centre, Warsaw)


"Tidal evolution of Milky Way satellites"

Ewa Łokas (Copernicus Astronomical Centre, Warsaw)


"Supercritical accretion: how and where?"

Shin Mineshige (Department of Astronomy, Kyoto University)


"1. Hanny's Object; 2. DI Her and its apsidal motion"

Józef I. Smak (Copernicus Astronomical Centre, Warsaw)


"Neutron stars and black holes - predictions and observations"

Krzysztof Belczyński (New Mexico State University)


"Kazimierz Kord, nie tylko o Metropolitan Opera"

Specjalne Kolokwium Wielkanocne: Kazimierz Kord (Filharmonia Narodowa, Warszawa)


"The Highest Energy Cosmic Rays with JEM-EUSO"

Jacek Szabelski - Talk Canceled (A. Soltan Institute for Nuclear Studies (IPJ) - Lodz)


"The Highest Energy Cosmic Rays with JEM-EUSO"

Jacek Szabelski (A. Soltan Institute for Nuclear Studies (IPJ) - Lodz)


"New Class of Biological Detectors for Cold Dark Matter"

Andrzej Drukier (George Mason University, Fairfax, Virginia)


"The inner edge(s) of a black hole accretion disk"

Aleksander Sądowski (Copernicus Astronomical Centre, Warsaw)


"What can we learn about variable stars in M55 based on 4100 CCD frames?"

Janusz Kałużny I Kamil Złoczewski (Copernicus Astronomical Center, Warsaw)


"Understanding the origin of the rapid x-ray variability seen from accretion flows around black holes"

Chris Done (Durham University)


"CH Cyg and R Aqr: the first resolved accreting binary systems"

Joanna Mikołajewska (Copernicus Astronomical Center, Warsaw)


"Boosting hierarchical structure formation with self-interacting dark matter"

Wojciech Hellwing (Copernicus Astronomical Center, Warsaw)


"subject to ba announced"

Greg Madejski (Stanford University)


"The true story behind the "Casablanca" plot - Polish Intelligence during World War II"

Malgosha Gago (Arte Television, Paris)


"Interaction of neutron-star magnetic fields with accretion discs"

Luca Naso (Universita di Padova)


"Where gravity no longer dominates: the internal structure and evolution of the smallest asteroids"

Tomasz Kwiatkowski (Poznan Observatory, A.Mickiewicz University)

Asteroids are very diverse in composition. While the largest of them are spheroidal bodies, and the middle-sized ones are gravity-dominated, irregular rubble-piles, the smallest asteroids are boulders held together by the forces of cohesion. Observations suggest that the last named can be surpisingly weak bodies evolving under the infuence of the YORP effect.


"Understanding formation of supermassive black holes"

Isaac Shlosman (Department of Physics and Astronomy, University of Kentucky, Lexington)

Little is known but much is speculated about how when and where supermassive black holes form. With the detection of high redshift quasars, this issue was brought to the forefront and has been tied to Population III stars and to galaxy formation process. In my talk, I will review some options and discuss promissing leads to understand the formation of these enigmatic objects.


"Spin and Spine"

Rien Van De Weygaert (Kapteyn Institute, Groningen)

With the help of our Multiscale Morphology Filter we have searched for significant alignments of the spin of galaxies with respect to filaments in the Cosmic Web. Such alignments are a direct manifestation of large-scale tidal fields morphing the weblike large scale structure as well as the tidal torques spinning up dark halos. Instead of an orientation correlation study, we have chosen to identify the galaxies that carry the most significant fossil alignment in the cosmic Web. By restricting the analysis of the SDSS DR5 galaxy sample to edge-on galaxies, we guarantee a perfect and clean orientation signal. Following a local and individual statistical analysis based on three feature measures, we have found a significant signal of alignment. From our sample, we can point to fourteen galaxies that have an uncommon perpendilar orientation with respect to the filaments in which they are embedded.


"On the transition from radio-loud to radio-quiet state in quasars in the framework of the XRB versus AGN unification"

Andrzej Marecki (Centre for Astronomy, N. Copernicus University, Toruń)

There are several lines of evidence that active galactic nuclei can be regarded as scaled-up X-ray binaries (XRB). The timescales of the evolutionary phenomena in these two classes are proportional to the black hole masses. Consequently, unlike in the case of XRBs, the evolution of AGNs is too slow to be followed directly. What could be done, however, is to assign particular types of active galaxies to different evolutionary stages observable in XRBs. We found three quasars with clear signatures of a recent transition from radio-loud to radio-quiet state and our own observations confirmed that, despite conspicuous relic large-scale radio structures, their cores can be labelled radio-quiet, anyway. It looks, therefore, that these objects were in the so-called Very High state before and now have shifted to High-Soft state. Analogous transitions in XRBs are well known.


"Accretion discs around magnetised Neutron Stars: distortion of magnetic field lines"

Luca Naso (SISSA, Trieste)

I will discuss a possible way of improving the old analytic models describing magnetic fields in accretion discs, with a semi-analytic approach. The results seem to show that the magnetic field profile can be very different from the suggested one for both the poloidal and the toroidal component. In particular the toroidal one is not governed only by the relative angular velocity between the disc and the star, as usually assumed.


"Thermal instability in accretion disks"

Włodzimierz Kluźniak (Copernicus Astronomical Centre, Warsaw)

Radiation pressure dominated alpha disks are thermally unstable. However, the resulting limit-cycle instability is not observed in binary X-ray sources. I will try to reconcile these two facts.


"Thick and luminous accretion disks in microquasars"

Aleksander Sądowski (Copernicus Astronomical Centre, Warsaw)

Microquasars' emission in the highśt state is dominated by the thermal disk component. At low luminosities it is well described by the classical Novikov and Thorne model of a radiatively efficient and thin accretion disk. The adopted assumptions, however, break down when the luminosity exceeds some critical value, e.g., 30 percent of the Eddington luminosity. In this talk I am going to present state-of-the-art hydrodynamical models of such luminous and geometrically thick accretion disks, discuss their applicability and describe the road-map for their development.


"On the structure of accretion disks with outflows"

Cheng-Liang Jiao (Department of Astronomy, School of Physics, Peking University, China)

We solve the set of hydrodynamic equations for accretion disks in the spherical coordinates to obtain the explicit structure along the theta direction. Our results indicate that the outflows should be common in various accretion disks and may be stronger in slim disks, where both advection and radiation pressure are dominant.


"Fulerens in space"

Ryszard Szczerba (Copernicus Astronomical Centre, Toruń)

The first fullerenes (C60, C70, etc.) were synthesized in lab in mid-eighties. For this discovery the team (Kroto, Curl, and Smalley) was awarded by Nobel Price in Chemistry in 1996. Since then fullernes were discovered in minerals and meteorities, but only in 2010 in Space using data from Spitzer Space Telescope. Surprisingly, they were found only in H-rich environments including planetary nebula in SMC. During this talk the recent discoveries of fullerenes in Space will be reviewed.


"The doubling of the superorbital period of Cyg X-1"

Andrzej Zdziarski (Copernicus Astronomical Centre, Warsaw)

In addition to X-ray and radio periodicity related to the orbital motion, Cyg X-1 shows a longer X-ray/radio period, so-called superorbital, presumably related to precession of its accretion disc and jet. Recently, Cyg X-1 underwent a striking doubling of this period from about 150 d to about 300 d, which presents a challenge to theoretical models. The periodicity appears as changes in the normalization of an intrinsic spectrum of constant shape, which implies it is not due to periodic changes of the accretion rate.


"V1309 Sco: merger of a contact binary"

Romuald Tylenda (Copernicus Astronomical Centre, Toruń)

Stellar mergers are expected to take place in numerous circumstences in the evolution of stellar systems. In particular, they are considered as a plausible origin of stellar eruptions of the V838 Mon type. V1309 Sco is the most recent eruption of this type in our Galaxy. The object was discovered in September 2008. It appears that V1309 Sco has been photometrically observed in course of the OGLE project since August 2001. The progenitor of the object was variable and we find out that it was a contact binary with an orbital period of ~1.4 day. The period was systematically decreasing with time. Similarly the light curve of the binary was also evolving. The system evolved toward its merger. The violent phase of the merger, marked by the systematic brightenning of the object, started in March 2008, i.e. half a year before the outburst discovery. We also investigate the observations of V1309 Sco during the outburst and the decline and show that they can be fully accounted for within the merger hypothesis. Thus, for the first time in the history, we show, from direct observations, that contact binaries indeed end up by merging into a single object, as it was suggested in numerous theoretical studies of these systems. Our study also shows that stellar mergers indeed result in eruptions of the V838 Mon type.


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

Jacek Baranowski (Department of Physics, Warsaw University)