The seminar of the Astro & Theory Section takes place normally on Wednesdays Tuesdays in D5-106, starting at 15 11AM. If you would like to suggest a seminar speaker or want to be added to the email list, please contact the organizer (Raphael.Mignon-Risse@ntnu.no).
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- tbd. Jens Oluf Andersen (IFY, NTNU): Pion condensation and pion stars
Abstract: In this talk I will discuss pion condensation in the context of two and three-flavor chiral perturbation theory. I will present results for quark and pion condensates as functions of the isospin chemical potential. The results compare favorably to those of lattice QCD. As an application, I will discuss pion condensation in a dense neutrino cloud and the possibility of pion stars. These are compact objects with a mass up to 20 solar masses and radii of up to 140km.
- 11.09. Jonas Tjemsland* (previously IFY, NTNU): How are the Norwegian electricity prices set? *Exceptional time: wednesday, 14:15.
Abstract:Despite Norway's self-sufficiency in hydro and wind power, its electricity prices are significantly influenced by external factors, such as European gas and coal prices. This issue became particularly noticeable during the 2021 energy crisis, sparking heated family debates. In this talk, I will provide an introduction to the Norwegian electricity market, aiming to enlighten potential future arguments. I will discuss how the electricity prices are determined in the Day-Ahead auction. Finally, I will offer insights into the short- and long-term outlook for Norwegian electricity prices.
- 17.09. tbd. Bidisha Sen (IFY, NTNU): TBD The Orbit and Companion of PSR J1622-0315: Variable Asymmetry and a Massive Neutron Star
Abstract: The companion to PSR J1622-0315, one of the most compact known redback millisecond pulsars, shows extremely low irradiation despite its short orbital period. We model this system to determine the binary parameters, combining optical observations from NTT in 2017 and NOT in 2022 with the binary modeling code ICARUS. We find a best-fit neutron star mass of $2.3 \pm 0.4\,\text{M}_\odot $, and a companion mass of $0.15 \pm 0.02\,\text{M}_\odot$. We detect for the first time low-level irradiation from asymmetry in the minima as well as a change in the asymmetry of the maxima of its light curves over five years. Using star spot models, we find better fits than those from symmetric direct heating models, with consistent orbital parameters. We discuss an alternative scenario where the changing asymmetry is produced by a variable intrabinary shock. In summary, we find that PSR J1622-0315 combines low irradiation with variable light curve asymmetry, and a relatively high neutron star mass. Slides available here: https://www.ntnu.no/wiki/download/attachments/195538250/Bidisha_Sen_PSR_J1622.pdf?api=v2
- 08.10. Valentina Richard Romei* (IPAG, Grenoble): Enhanced particle acceleration in a pulsar wind interacting with a companion *remote seminar
Abstract:Pulsar winds have been shown to be preferred sites of particle acceleration and high-energy radiation. Models have been constructed in order to better characterize their general structure in isolated systems. However, most of the galactic millisecond pulsars find themselves in binary systems. In this talk, I present the first Particle-in-cell (PIC) simulations of both the pulsar magnetosphere and the wind of the pulsar interacting with an unmagnetized spherical companion. This work considers a generic case that could be applied to various companions including planets, asteroids, white dwarfs, or even neutron stars. Our results show evidence of an enhanced conversion of Poynting flux into particle acceleration, via forced reconnection in the outflowing wind near the companion. Hence, the high-energy synchrotron radiation is also amplified and takes the form of an orbital-modulated hollow cone of light. We do not exclude long-period radio transient counterparts, that would be of significant interest, especially in the light of the recently discovered galactic long-period radio transients. Slides available here: https://www.ntnu.no/wiki/download/attachments/195538250/NTNU_seminar_VRR.pdf?api=v2