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| Home > Publications database > Investigating the Microquasar SS 433 and the PeVatron Candidate MGRO J1908+06 with a Novel Extended Source Analysis Method |
| Dissertation / PhD Thesis | PUBDB-2025-00242 |
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2024
Humboldt-Universität zu Berlin
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Please use a persistent id in citations: urn:nbn:de:kobv:11-110-18452/29497-4 doi:10.3204/PUBDB-2025-00242
Abstract: The origins of galactic Very-high energy; 100 GeV < E < 100 TeV (VHE) and Ultra-high energy; 100 TeV < E(VHE) cosmic rays remain largely unknown. However, recent studies suggest the existence of numerousgalactic sources known as PeVatrons, which have the ability to accelerate particles up to Petaelectronvolt (PeV)energies. These PeVatron candidates include Pulsar wind nebulae (PWNe), Supernova remnants (SNRs) aswell as micro-quasars. Investigating the gamma-ray emission at Gigaelectronvolt (GeV) and Teraelectronvolt(TeV) energies from these sources provides valuable insights into their physical properties and accelerationmechanisms. In the scope of this thesis, we analyse data from the Very Energetic Radiation Imaging TelescopeArray System (VERITAS) gamma-ray observatory, which consists of an array of four 12-meter Imagingatmospheric Cherenkov telescopes (IACTs) located in Arizona. Our focus is on understanding the propertiesof two extended galactic sources: MGRO J1908+06, a potential PeVatron candidate whose identification is yetto be established, and SS 433, a microquasar.We adopt for the first time in VERITAS a 3D maximum-likelihood analysis method as part of Gammapy toconstrain the properties of the investigated sources using spectromorphological models. This involves theproduction and validation of offset-dependent Instrument response functions (IRFs), including models thatdescribe the irreducible cosmic-ray background, and the validation of the analysis method using observationsof the Crab Nebula.We apply this new method to analyse the extended gamma-ray emission from MGRO J1908+06. We determinethat the gamma-ray emission exhibits energy-dependent morphology. By considering proton densities inthe region and analysing the emission characteristics, we conclude that the emission is likely a result ofsynchrotron radiation and inverse-Compton scattering. We explore a potential association with the pulsarPSR J1907+0602, suggesting that it could be the remnant of a supernova explosion where the subsequentreverse shock expelled the pulsar, leaving behind a relic pulsar wind nebula. To validate the 3D maximumlikelihood analysis, we employ a mimic data method, for performing a bias correction and for estimating theuncertainties of the analysis method.Additionally, we report significant gamma-ray emission from the microquasar SS 433, representing its firstdetection in the VERITAS data. The emission originates from the region where the jets interact with themedium of the W50 supernova remnant. SS 433, an X-ray binary system in the Milky Way, consists of ablack hole and an orbiting A-type star and exhibits two powerful jets. Through 3D analyses, we determinethat the gamma-ray emissions at the jet termination lobes exhibit an extended and elongated structure. In amultiwavelength analysis, we explore various scenarios to explain the origin of the gamma-ray emission,employing models that describe the particle populations responsible for the emission. Based on the estimatedjet power of SS 433, a leptonic origin for the observed gamma-ray emissions is favoured. Furthermore, wefind no significant gamma-ray emission from the black hole region and no evidence of variable gamma-ray emissions. Envisioning the future of gamma-ray astronomy, we conduct simulations to optimize thecharacteristics of Cherenkov Telescope Array (CTA), the next-generation IACT. Specifically, we focus onaddressing telescope shadowing effects and optimizing the placement of the illuminators.
Keyword(s): VERITAS ; CTA ; 3D Analysis ; PeVatron ; MGRO J1908+06 ; Microquasar ; SS 433 ; VERITAS ; CTA ; 3D Analysis ; PeVatron ; MGRO J1908+06 ; Microquasar ; SS 433 ; 530 Physik ; 520 Astronomie und zugeordnete Wissenschaften
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