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21 Jan 2026 - Prof. Ersin Göğüş (Sabanci University, Turkey) ** in person**
21 Jan 2026 - Prof. Ersin Göğüş (Sabanci University, Turkey) ** in person**
"The Strongest Magnets in the Milky Way and Beyond"
Abstract: Magnetars are isolated neutron stars that possess the strongest magnetic fields in the Universe. The most striking characteristic of magnetars is their emission of energetic bursts -- brief events lasting only a fraction of a second yet typically releasing energies exceeding 10^40 erg. On rare occasions, magnetars produce giant flares, which exhibit distinctive morphologies and release energy reaching or even surpassing 10^44 erg. This talk will provide an overview of magnetar bursts detected mostly with the Gamma-ray Burst Monitor on board Fermi Gamma-ray Space Telescope, with a particular focus on a prolific magnetar: SGR J1935+2154. This magnetar has emitted short radio bursts, including the first ever Galactic fast radio burst (FRB). There will also be a review of recent observations of magnetar giant flares from nearby galaxies.
11 Feb 2026 - Prof. Nick Kylafis (University of Crete, Greece) ** in person**
11 Feb 2026 - Prof. Nick Kylafis (University of Crete, Greece) ** in person**
"Pulsars and Magnetars: facts and possible fiction ?"
Abstract: Pulsars and Magnetars [i.e., Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs)] are believed to be isolated magnetic neutron stars. Pulsars have dipole magnetic fields of the order of $10^{12}$ G, while magnetars are thought to have dipole magnetic fields three orders of magnitude larger and even larger internal toroidal magnetic fields. Pulsars are relatively old, isolated neutron stars and it is therefore natural for them to rotate in vacuum. Magnetars, on the other hand, are relatively young isolated neutron stars and might be surrounded by matter left over from their formation. If this is the case, then their spin down may not be due to magnetic dipole emission, but rather due to the interaction between the magnetosphere of the neutron star and the surrounding matter. As a consequence, matter may fall along dipole magnetic-field lines onto the neutron star, producing X-ray emission. We have proposed that the quiescent and transient X-ray luminosity of AXPs and SGRs is the result of accretion from a fallback disk onto neutron stars with dipole magnetic fields in the range $10^{12} – 10^{13}$ G. Our picture is similar to that of normal X-ray pulsars; only the accretion rate is significantly smaller in AXPs and SGRs. Within the very stringent model of accreting pulsars, we have been able to explain quantitatively a) the comparable soft and hard X-ray luminosities, b) the X-ray spectra (soft and hard), c) the energy-dependent pulse profiles and d) the period derivative resulting from the accretion torque. Our model makes the prediction that no AXP/SGR will ever be observed with a hard X-ray power-law spectrum extending beyond 400 keV. The magnetar model, on the other hand, allows the power law to extend to 1 MeV or more. For the outbursts with super-Eddington luminosities, our model proposes that they are produced by magnetic field decay in localized, super-strong ($10^{14} – 10^{15}$ G) multipole fields. The extent of the X-ray power law and the existence or non-existence of fallback disks around magnetars will decide whether the accretion picture or the classical magnetar picture is the correct one.
18 Feb 2026 - Prof. Maria Charisi (Washington State University, USA) ** in person**
18 Feb 2026 - Prof. Maria Charisi (Washington State University, USA) ** in person**
"Multi-messenger astrophysics with pulsar timing arrays"
Abstract: A Pulsar Timing Array (PTA) is a galactic-scale detector that relies on precision timing of milli-second pulsars. Recently, all major PTA collaborations have found evidence of a low-frequency gravitational wave background. The most likely origin of this background is a population of supermassive black hole binaries (SMBHBs) formed in galaxy mergers. I will present the exciting recent results from the North American Nanohertz Observatory for Gravitational waves (NANOGrav) collaboration, and their meaning for SMBHB evolution. I will also describe the next major milestone, which is likely the detection of an individual resolved binary. These systems, which should stand above the background, are also expected to be bright sources of electromagnetic emission, and can be detected as quasars with periodic variability. I will summarize the status of current electromagnetic searches, challenges in their detection and prospects for the future with the Rubin Observatory. Finally, I will discuss recent work which combines electromagnetic and gravitational-wave data and aims to deliver the first multi-messenger detection of a SMBHB.
25 Feb 2026 - Dr. Savvas Raptis (Johns Hopkins University Applied Physics Laboratory, USA) ** in person**
25 Feb 2026 - Dr. Savvas Raptis (Johns Hopkins University Applied Physics Laboratory, USA) ** in person**
"Collisionless Shocks in the Heliosphere: Transient Processes and Particle Energization"
Abstract: TBA
25 Feb 2026 - Dr. Savvas Raptis (Johns Hopkins University Applied Physics Laboratory, USA) ** in person**
25 Feb 2026 - Dr. Savvas Raptis (Johns Hopkins University Applied Physics Laboratory, USA) ** in person**
"Collisionless Shocks in the Heliosphere: Transient Processes and Particle Energization"
Abstract: TBA
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