Upcoming seminars
July 16, 2026 at 13:00 CEST (institute Seminar building !!!)
TOLIMAN and its advanced scientific principles behind searching for the next Earth
prof. Peter Tuthill
(School of Physics, University of Sydney, Australia)
Professor Peter Tuthill will present the scientific principles underpinning the TOLIMAN Space Telescope mission, a novel astrometric observatory designed to detect Earth-like exoplanets by nearby stars. The presentation will explore how precision measurement of stellar motion can reveal the gravitational influence of otherwise invisible planets, and how TOLIMAN’s unique diffractive pupil optical architecture enables ultra-high-precision astrometry within the constraints of a compact CubeSat platform. The presentation will also touch on advanced mathematical tools that enable postprocessing and analysis of the scientific data.
July 21, 2026 at 13:00 CEST
KrakenOS: A Python Library for General Optical Simulation
Carlos Alberto Guerrero Peña
(Facultad de Ciencias, Universidad Autónoma de Nuevo León, UANL, Mexico)
KrakenOS is an open-source library for general optical simulation developed in Python, intended as a multi-platform tool for sequential and non-sequential ray tracing through arbitrary optical systems. Its modular structure allows users to define surfaces, media, detector planes, and custom physical functions according to the requirements of a given problem. In this seminar, I will present the general design of the library and discuss its current capabilities for modeling astronomical optical systems. I will show a series of examples of increasing complexity, including telescope configurations, ray-tracing analyses, spot diagrams, and the introduction of optical aberrations. I will also briefly comment on recent applications related to detector effects and synthetic image generation in the context of astronomical instrumentation.
Held seminars in 2026
June 4, 2026 at 13:00 CEST
Unveiling companions and binary interaction of red supergiants with VLTI-GRAVITY
Daniel Jadlovský
(ESO Garching, Germany; Masaryk University Brno, Czech Republic)
The majority of massive stars are part of close binary systems that may interact during their evolution. The red supergiant (RSG) phase is a crucial point of stellar evolution, as the interaction (and mass loss) may drive the primary RSG to evolve towards an earlier spectral type, thus exploding as an interacting or even stripped-envelope supernova (SN). Nonetheless, while many RSGs are known binaries, only a few have constrained orbital parameters, and as a result, we have poor knowledge of the binary interaction during the RSG phase. We aim to constrain orbital parameters of known RSG systems and study their binary interaction. For our large observing campaign of RSG and post-RSG systems, we employ the unprecedented sensitivity and precision of VLTI-GRAVITY, allowing us to unveil massive companions with a separation down to a few au. For several interacting systems, where the companions are accreting from the RSG, we can trace the orbital motion of the companions using the Brackett γ line originating in the accretion disk. Namely, we demonstrate the mass transfer mechanism for the KQ Pup RSG system (orbital period 26 yr). We discovered that its B-type main-sequence companion is actually an eclipsing inner binary (TESS, 17.3 d). The system shows signatures of accretion from the RSG to the hot companions near periastron. With the RSG photosphere filling the Roche lobe only by ∼ 70% at periastron, the mass transfer is instead driven by Wind Roche-lobe Overflow (wind-RLOF) from the extended atmosphere of the RSG. The circumbinary accretion disk around the hot companions forms a few years before the periastron, as evidenced by the emergence of Balmer emission in the spectra and by signatures of occultation by the accretion disk in the TESS data. Due to weaker wind-accretion after the periastron, the accretion disk dissipates by apastron. Meanwhile, this is the first time that dynamical masses and orbital parallax could be determined for a RSG system. Our results show that due to the meausured extension of RSG atmospheres (up to ∼70 au), even very wide RSG systems can interact. Such extensions were usually not accounted for in the binary evolution models (where only the photospheric radius was used). This significantly widens the range of orbital parameters for which red supergiant systems can interact, altering the final evolution for many massive systems.
April 28, 2026 at 13:00 CEST
Spotting Gravitational Wave progenitors in Hubble’s FUV spectra
Dorottya Szécsi
(Institute of Astronomy, Nicolaus Copernicus University, Toruń, Poland)
Amongst the stellar evolutionary pathways leading to GW emission, the so-called “chemically homogeneous evolution” channel predicts hot, early O type stars on the main sequence and Wolf–Rayet stars of class WO on the post-main sequence. But how can we find these objects observationally? Our best chance is to look into Hubble’s FUV spectroscopy of metal-poor local starbursts such as I Zwicky 18. However, doing that one faces the challenge of cross-matching STIS vs COS measurements for a dwarf galaxy that is spatially extended — a task that is far from trivial. In this talk, I present my decade-long hunt for proving the existence of chem.-hom.-evolving GW progenitors, which recently led me to conclude that Hubble did in fact probably see these stars (Szécsi+25, A&A): after a careful re-examination of the archives, observations seem fully consistent with what the theory predicts. This includes the presence/absence of famous emission bumps like C-IV (1550 Å) and He-II (1640 Å), the amount of He-II photoionization and spectral hardness, and more. Additionally, I discuss what this means for a potential future JWST detection.
April 27, 2026 at 13:00 CEST
Supernova astronomy in the survey era
Subhash Bose
(Department of Physics and Astronomy, Aarhus University, Denmark)
The past decade has witnessed a revolution in time-domain astronomy, driven by systematic, all-sky robotic surveys that have unveiled new classes of transient events. Current surveys enabled us to discover rare and peculiar objects, including potentially new kind of transient events. These events not only challenge our present understanding, but also open a new paradigm of supernova studies. These discoveries range from extremely luminous events with unknown power sources and explosion mechanisms to thermonuclear explosions that deviate from standard supernova luminosity relations, having cosmological implications. I would discuss some of such exciting findings and their broader implications. As ongoing and upcoming surveys expand the discovery space, we expect to encounter many more such elusive events. Unlocking their physics will require well-defined selection criteria and optimized follow-up strategies.
February 17, 2026 at 13:00 CET
Planetary Tidal Disruption Events as a Driver of Extreme Stellar Variability
Matías Montesinos Armijo
(Académico Departamento de Física, Universidad Técnica Federico Santa María, Chile)
Large-amplitude, long-duration stellar variability is often attributed to intrinsic instabilities in young stars or erratic accretion from protoplanetary disks. However, recent time-domain surveys have uncovered a population of “What Is This” (WIT) objects—transients whose light curves and thermal evolution defy standard classification as classical outbursts or stellar winds. In this talk, I propose that many of these extreme variability events can be explained by the Tidal Disruption Event (TDE) of a giant planet. Using 2D hydrodynamic simulations, I model the catastrophic disruption of Jupiter- and Neptune-mass planets and the subsequent formation of a luminous transient disk. I will show that the accretion of this planetary material produces multi-year transients with peak luminosities L ~ 10^38 erg s^-1 that can overwhelm the host star. A key focus is placed on how orbital eccentricity drives the variability: while circular inspirals produce smooth plateaus, plunging eccentric orbits create highly volatile, multi-peaked light curves. These signatures, combined with a characteristic “bluer-when-brighter” color evolution, provide a new framework for identifying planetary consumption in our galaxy and distinguishing it from classical stellar outbursts.
February 13, 2026 at 13:00 CET
Stellar Content and Star Formation in IRAS 18456-0223
Nilesh Pandey
(Astronomical Institute of CAS, CZ)
Star formation plays a critical role in galaxy evolution, yet the detailed relationship between local environmental conditions and the early stages of stellar and cluster formation remains constrained. In my master’s thesis at Indian Institute of Astrophysics (IIA), India, we address this research gap by performing a comprehensive multiwavelength investigation of star formation in IRAS 18456-0223. We identified young stellar objects (YSOs) using infrared color–color criteria, with proper motion and distance to the cloud refined by Gaia astrometry. The spatial distribution of YSOs was quantified via statistical techniques, revealing a hierarchical clustering that traces the filamentary structure of their natal molecular clouds. Individual physical parameters of the YSOs were constrained by fitting their spectral energy distributions (SEDs), yielding mass, temperature, and evolutionary stage estimates. Optical spectroscopy data reduction and analysis for selected sources were carried out utilizing the Himalayan Chandra Telescope’s HFOSC. Herschel far-infrared observations were analyzed produce high-mid resolution maps of dust temperature and column density. Our integrated approach demonstrates that regions with enhanced dust temperature and column density coincide with peaks in YSO clustering, thereby constraining the physical conditions that regulate star formation and the early evolution of embedded clusters.