The seminar of the Astro & Theory Section takes place normally on Tuesdays in D5-144, starting at 14:00. If you would like to suggest a seminar speaker or want to be added to the email list, please contact the organizer (maksat.satybaldiev@ntnu.no).

The (planned) seminars in 2026 are

  • 15.01. Teo Muñoz-Darias (Instituto de Astrofisica de Canarias): Accretion and outflows in stellar-mass black holes

Abstract: Accreting stellar-mass black holes in X-ray binaries offer a unique view of black hole accretion in environments that are simpler, and on time-scales that are much shorter, than those typical of AGN and quasars. In recent decades, X-ray and radio continuum observations have been used to study in detail the coupling between accretion and ejection in these systems. Only recently have we begun to systematically explore how their X-ray, optical and infrared spectral lines evolve.
I will briefly review the state of the art in the field and then focus on the dramatic changes now seen in the optical and infrared spectra of X-ray binaries, thanks to dedicated programmes on some of the largest telescopes in the world (e.g. GTC 10.4 m and VLT 8.2 m). I will show that this variability in the spectral lines is, in most cases, linked to the presence of powerful outflows, as inferred from wind-related signatures such as P-Cygni profiles.
I will also discuss the relation between the different kinds of outflows in X-ray binaries (radio jets, X-ray winds and optical–infrared winds), their impact on black hole accretion – including some extreme cases – and how their main observational properties appear to be closely connected with those of the accretion flow.

  • 10.02. Abraham Kaleb Plascencia Perez Paez: Higgs inflation in geometrical scalar-tensor theory of gravity

Abstract: In this talk, I start with a pedagogical overview of the cosmological principle and its role in constructing inflationary models of the universe. I then discuss slow-roll inflation as a concrete framework, before introducing a Higgs model non-minimally coupled to gravity. I show how a non-Riemannian geometric structure allows the Higgs energy scale to generate a viable inflationary scale consistent with observations.

  • 02.06. Montserrat Armas Padilla (Instituto de Astrofisica de Canarias): UltracompCAT and the Hunt for New Ultra-Compact X-ray Binaries

Abstract: The ultra-compact family of low-mass X-ray binaries (LMXBs) consists of systems with orbital periods shorter than 80 minutes. Such short periods imply small Roche lobes, into which only degenerate (hydrogen-poor) donor stars can fit. They are unique laboratories for studying accretion processes in hydrogen-deficient environments, as well as key stages of binary evolution. They are also expected to be primary sources for low-frequency gravitational-wave studies with the upcoming LISA mission.
I will present UltraCompCAT, a catalogue of ultra-compact and short orbital period X-ray binaries compiling the available multi-wavelength information for the currently known population of these objects. This homogeneous framework allows us to study, for the first time, this tantalising family of X-ray binaries as a population. I will review the current state of the field, discuss some of the main global properties of the population, and present ongoing efforts aimed at identifying new ultra-compact X-ray binaries.

  • 19.08. Alisha Roberts (University of Wisconsin-Madison): A Multimessenger Analysis of the High-Energy Milky Way: Source Populations Contribute Significantly to IceCube's Galactic Neutrino Flux. Wednesday 14:00

Abstract: In this talk, I discuss recent results from a joint analysis of the high-energy neutrino emission observed from the Galactic Plane by IceCube and the diffuse ultra-high-energy gamma-ray emission measured by LHAASO. We compare this data to models that include diffuse emission from cosmic-ray interactions in the interstellar medium, unresolved TeV halos, and unresolved Galactic neutrino sources. We find that the gamma-ray emission can be explained by a combination of diffuse processes and unresolved TeV halos. The observed neutrino emission cannot be generated by cosmic-ray interactions in the interstellar medium alone, but requires contributions from one or more unresolved source populations. Across a wide range of assumptions about Galactic cosmic-ray transport, we find that Galactic neutrino sources contribute significantly to the neutrino flux observed from the Galactic Plane and are likely responsible for most of this emission.

  • 21.08. Vaso Pavlidou and Kostas Tassis (University of Crete): PASIPHAE and the Milky Way atlas it will enable. Friday 10:30

Abstract: More than just our cosmic “you are here” dot, the Milky Way is the environment that gave rise to the solar system, the Earth, and life itself, as well as the lens through which we obsere the Universe at large. The 3D structure of our Galaxy is an ever-present veil, which distorts our view of both distant galaxies and the early Universe. Combining latest and upcoming astronomical data with algorithms drawing from information field theory, our team is creating a self-consistent, uncertainty-aware 3D map of all Galactic components: the mw-atlas. Central to this reconstruction will be new data from PASIPHAE: an optopolarimetric survey aiming to measure the linear polarization from millions of stars. These, together with stellar distances from Gaia, can be combined to probe tomographically the magnetic field threading dust clouds within the Milky Way. 3D Galacic magnetic field maps enabled by PASIPHAE will provide invaluable information for future CMB B-mode experiments,  for the physics of the interstellar medium and star formation, and for the propagation of cosmic rays through the Galaxy.

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