List of Seminars in 2019
|6 Feb 2019||Marta Burgay||Neutron stars as probes of fundamental physics|
|19 Feb 2019||Ruth Durrer||New development in Cosmic Microwave Background lensing|
|6 March 2019||Roberto Mignani||Pulsar astrophysics across the electromagnetic spectrum|
|3 Jun 2019||Luciano Rezzolla||The first image of a black hole|
|25 Sep 2019||Nils Andersson||Neutron stars: Probing the extremes of matter|
6 February 2019
Neutron stars as probes of fundamental physics
Marta Burgay (Osservatorio Astronomico di Cagliari)
Pulsars are fast spinning, highly magnetised neutron stars that emit beams of radio waves from their magnetic poles. Because of this, pulsars behave like cosmic lighthouses: once per rotation, if the emission cones cross the line of sight to the Earth, we observe a radio pulse. The fastest pulsars, spinning hundreds of times per second, have an extremely stable rotation and, if undisturbed, their signals arrive on earth like clockwork. If, however, something happens to the pulsar, or to the medium their signals travels through, or to the space-time between pulsar and Earth, the times of arrival of the radio pulses get affected in tiny but measurable ways. Thanks to this, pulsar can be used as probes in many different fields of astrophysics and fundamental physics: from the study of the equation of state of nuclear matter, to the study of the interstellar medium, to relativistic gravity etc. In this talk, after briefly introducing pulsars and the analysis techniques of their pulses times of arrival, I will discuss how they can be used as testbeds of general relativity and detectors of gravitational waves.
Pulsar astrophysics across the electromagnetic spectrum
Roberto Mignani (Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano)
Pulsars are rapidly spinning neutron stars that emit electromagnetic radiation (mostly) at the expenses of their rotational energy, hence also referred to as rotation-powered pulsars. part from the radio band, where the first of the over 2500 radio pulsars known to date was originally discovered, pulsars are also observed in X-rays, gamma rays, optical, infrared (IR), ultraviolet (UV), and the sub-millimeter In this talk, I will review the state of the art of pulsar identifications outside the radio band, I describe their observational properties, and I present some new results.
3 June 2019
The first image of a black hole
Luciano Rezzolla (Goethe University, Francoforte)
I will briefly discuss how the first image of a black hole was obtained by the Event Horizon Telescope collaboration. In particular, I will describe the theoretical aspects that have allowed us to model the dynamics of the plasma accreting onto the black hole and how such dynamics was used to generate synthetic black-hole images. I will also illustrate how the comparison between the theoretical images and the observations has allowed us to deduce the presence of a black hole in M87 and to extract information about its properties. Finally, I will describe the lessons we have learned about strong-field gravity and alternatives to black holes.
Neutron stars: Probing the extremes of matter
Nils Andersson (Università di Southampton)
With a mass similar to that of the Sun compressed inside a radius of about 10 km, neutron stars push matter to the extremes. At these high densities, the composition of matter (encoded in the so-called equation of state) depends on particle interactions in a regime that cannot be tested by collider experiments. In addition, the state of matter involves the full complement of concepts from low-temperature physics. The star’s outer layers have solidified into an elastic crust of neutron-rich nuclei, while the core contains an exotic superfluid-superconducting mixture. In this talk I will introduce the main issues involved in trying to understand these objects, paying particular attention to the relevance of superfluidity. I will outline how astrophysical observations, both electromagnetic and through gravitational waves, are helping us probe these exciting objects.