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21 Jan 2026 - Prof. Ersin Göğüş (Sabanci University, Turkey) ** cancelled*
21 Jan 2026 - Prof. Ersin Göğüş (Sabanci University, Turkey) ** cancelled*
"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"
Speaker info: link
Title: "Collisionless Shocks in the Heliosphere: Transient Processes and Particle Energization"
Abstract: Collisionless shocks are the primary sites for particle acceleration across the Universe, yet the specific mechanisms that bridge the gap from thermal seeds to relativistic cosmic rays remain a subject of active research. This seminar explores the evolving paradigm of shock acceleration, at planetary bow shocks, moving beyond steady-state models to highlight the critical role of upstream transient processes.
Focusing primarily on Earth's bow shock using high-resolution data from NASA’s MMS and THEMIS, alongside ESA’s Cluster missions, we discuss how the dynamic region upstream of a shock (the foreshock) is not merely a precursor zone but an extended environment of elevated particle acceleration. By examining the formation and evolution of foreshock transient structures, we demonstrate how these local disturbances fundamentally alter the broader shock environment. These transients facilitate a reinforced shock acceleration process, injecting suprathermal particles and providing the confinement necessary for energization through a multiscale process that includes adiabatic and non-adiabatic acceleration processes as they transition downstream. Finally, we scale these physical insights to larger systems, using recent observations from Jupiter’s bow shock via NASA’s Juno mission, to demonstrate that these processes are a universal feature of planetary environments. By bridging these in-situ observations with broader scaling laws, we show how localized transient dynamics can be potentially used to constrain the maximum limits of particle acceleration at shocks.
11 Mar 2026 - Dr. Ioannis Contopoulos (Academy of Athens, Greece) ** in person**
11 Mar 2026 - Dr. Ioannis Contopoulos (Academy of Athens, Greece) ** in person**
"Pulsars with PINNs"
Abstract: TBA
18 Mar 2026 - Prof. Fabio Bacchini (KU, Leuven, Belgium)
18 Mar 2026 - Prof. Fabio Bacchini (KU, Leuven, Belgium)
"Fully Kinetic Simulations of Compact-object Accretion and Outflows"
Abstract: TBA
Friday 20 Mar 2026 - Prof. Vassilis Angelopoulos (UCLA, USA) ** in person**
Friday 20 Mar 2026 - Prof. Vassilis Angelopoulos (UCLA, USA) ** in person**
"Exploring magnetospheric dynamics using combined low- and high-altitude observations"
Abstract: Conjunctions between polar-orbiting low altitude and equatorial high-altitude missions allows disentangling space and time variations and mapping magnetospheric phenomena to the ionosphere and aurora. The recent availability of high-resolution energy and pitch angle spectra from the ELFIN mission in conjunction with low altitude, and high-altitude missions, reveals new methods for exploring magnetospheric processes and provides new perspectives on the dynamics of substorms, charge particle precipitation and the aurora. It has been realized that one of the most intense particle precipitation occurs at latitudes with equatorial magnetic footpoints at the transition region from tail-like to dipole like field lines. Poleward (tailward) of that magnetic latitude (equatorial distance) lie auroral zone (plasma sheet) field lines. The energy spectrum and flux variations of the precipitating-to-trapped flux ratio of energetic particles (>50keV, unaffected by potential drops) can be used to infer the dynamics of the equatorial plasma sheet. Such information from low altitude can explore the magnetospheric drivers and field-aligned current sources of the precipitation and of various auroral forms, when imaging is available. The global magnetic flux redistribution in the plasma sheet during substorms and the emergence of reconnection outflow activity are both visible in low altitude spectra. The contribution of waves excited by injections (EMIC, whistler mode chorus, ECH waves and TDS) and of field-line scattering are also evident. The combined observations from a range of altitudes demonstrate the key role of mesoscale DFBs in controlling the dynamics of the inner magnetosphere. Arguably, the value of small satellite missions (such as CubeSats) is not only scientific. They afford quick-turnaround, low-cost experimentation for maturation of advanced technologies, and are invaluable for workforce training and incubation of startups.
1 Apr 2026 - Prof. Kanaris Tsinganos (University of Athens, Greece) ** in person**
1 Apr 2026 - Prof. Kanaris Tsinganos (University of Athens, Greece) ** in person**
"Solar Eclipses and Results from Proba 3.0 Mission"
Abstract: TBA
29 Apr 2026 - Prof. Claudio Ricci (University of Geneva, Switzerland)
29 Apr 2026 - Prof. Claudio Ricci (University of Geneva, Switzerland)
"Extreme and Rapid Accretion in Supermassive Black Holes"
Abstract: TBA
6 May 2026 - Prof. Henrik Latter (DAMTP, Cambridge, UK)
6 May 2026 - Prof. Henrik Latter (DAMTP, Cambridge, UK)
"TBA"
Abstract: TBA
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