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| Author(s): |
Luna Costa Lacerda Espinosa
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD) |
| Defense date: | 2025-10-10 |
| Examining board members: |
María Victoria Del Valle;
Raniere Maciel de Menezes;
Vera Jatenco Silva Pereira;
Gustavo Esteban Romero
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| Advisor: | María Victoria Del Valle |
| Abstract | |
For decades it has been proposed that massive stars may be potential sources of Galactic cosmic rays. As their powerful stellar winds expand and interact with the interstellar medium, strong shock waves are generated. Recent studies indicate that winds from massive stars play an important role in the galactic production of cosmic rays, although their expected contribution is smaller than that of supernova remnants. A useful way to probe particle acceleration in astrophysical environments is through their non-thermal emission. In 2019, the first detection of non-thermal radio emission from the stellar bubble G2.4+1.4, associated with the Wolf-Rayet star WO2, was reported. The observed signal is consistent with synchrotron radiation produced by relativistic electrons, which are also expected to generate non-thermal emission at higher energies, particularly in the gamma-ray domain. Assuming that the particles are accelerated in the shocks produced in the bubble, we developed two models to estimate the non-thermal emission from electrons and protons: a homogeneous model and a spatially extended model, based on the classical theory for stellar bubbles. Our estimates yield maximum energies up to the TeV range for electrons and around hundred TeVs for protons. From the fitting of the observational data, a relatively strong magnetic field of 250 µG is required. Both models predict gamma-ray emission, with non-thermal electrons injected into the surrounding medium at efficiencies of 3% and 0.2% in the homogeneous and extended cases, respectively. Finally, we developed a general model to investigate the potential of bubbles from O and B-type stars to accelerate particles up to higher energies. Our findings indicate that the powerful winds of massive stars can accelerate particles up to hundreds of TeVs, in some cases, producing potentially observable gamma-ray emission. (AU) | |
| FAPESP's process: | 23/11877-2 - Modeling Nonthermal Emission in a Stellar Bubble |
| Grantee: | Luna Costa Lacerda Espinosa |
| Support Opportunities: | Scholarships in Brazil - Master |