Wednesday Colloquium


"72-hour WEBT campaign on blazar 0716+714 - A study of microvariability in blazar"

Gopal Bhatta (Astronomical Observatory, Jagiellonian University, Cracow)

The international Whole Earth Blazar Telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This object was chosen due to its bright apparent magnitude range, its high declination, and its very large duty cycle for micro-variations. We report here on the long continuous optical micro-variability light curve of 0716+714 obtained during the multi-site observing campaign during which the bazar showed almost constant variability over a 0.5 mag range. Thirty-six observatories in sixteen countries participated in this continuous monitoring program and the resulting light curve was analyzed using several techniques including Fourier transform, Wavelet and noise analysis techniques. Those results led us to model the light curve by attributing the variations to a series of synchrotron pulses. We have interpreted the observed microvariations in this extended light curve in terms of a new model consisting of individual stochastic pulses due to cells in a turbulent jet which are energized by a passing shock and cool by means of synchrotron emission. We obtained an excellent fit to the 72- hour light curve with the synchrotron pulse model.


"Tidally induced bars in dwarf galaxies"

Ewa L. Łokas (NCAC, Warsaw)

One of the plausible mechanisms for the formation of dwarf spheroidal galaxies in the Local Group involves tidal stirring of disky progenitors embedded in dark matter halos. After being accreted by a host galaxy, the dwarfs are affected by tidal forces from the bigger galaxy and lose mass. The stellar disks undergo morphological transformation into spheroids and the rotation of their stars changes into random motions. An important intermediate stage of such evolution is the formation of a tidally induced bar, usually at the first pericenter passage. I will discuss the properties of such a bar, the evolution of its strength, length and pattern speed as a function of time and the orbits of stars within the bar. I will also present possible candidates for barred galaxies among the Local Group dwarfs.


"Firewalls at the horizon"

Włodzimierz Kluźniak (CAMK)

Attempts to marry quantum mechanics with general relativity at the event horizon have created a storm of controversy. It is now universally accepted that no information is lost in black holes: their evolution from collapse to evaporation is (supposed to be) described by a unitary matrix. However, no specific scenario of resolving Hawking's information paradox has gained universal acceptance. A recent suggestion that disentanglement of quantum states leads to the formation of a wall of fire near the black hole horizon, in which any infalling observer will burn up, has been extensively discussed. I will present limits on the firewall density and mass derived in my paper with M. Abramowicz and J-P. Lasota (Phys. Rev. Lett. 2014, accepted). Terms from the current literature such as entanglement monogamy, complementarity, smoke and mirrors, will be mentioned, and may even be explained.


"May be low mass WIMPS: mini-review"

Andrzej Drukier (BioTraces, George Mason University, VA)