Posters

The Extreme Universe Space Observatory on a Super Pressure Balloon (EUSO-SPB1) [1] is the second balloon pathfinder of the JEM-EUSO collaboration, it is a nadir pointing UV telescope which aims at observing Ultra High Energy Cosmic Rays (UHECR) air showers through their fluorescence emission with it's Photo Detector Module [bacholle2017]. It was Launched the 24th of April, 2017 from the NASA balloon launch site in Wanaka, New Zealand. During it's flight EUSO-SPB1 took data during 12 moonless nights until the termination of the mission. In this poster we present events found in the data saved by the first level trigger [3] while searching for air showers. We classify these events into different populations whose characteristics and origins we discuss. We show that the majority of our triggered events are direct Cosmic Ray hits. No air shower candidate have been found in this analysis.

Criteria for detecting Galactic accelerators at PeV energies can be applied to the Cherenkov Telescope Array (CTA) simulated instrumental response, in order to assess it's ability to find and characterize these elusive sources. The outputs of this kind of studies are called the PeVatron metrics. Following the example of [1], we computed PeVatron metrics for CTA, assuming an observation livetime of \( 10\, h \). This means: (i) simulating the \( \gamma \)-ray emission from sources caracterized by very hard spectra with cutoffs at different energies, (ii) convolving it with a given production of simulated CTA IRFs and then (ii) fitting the data both with simple powerlaws (PL) and exponential-cutoff powerlaw spectra (ECPL). The comparison between the fit statistics in the two cases (TS) allows to determine whether the cutoff can be detected or not, under the given assumptions. As a first step, we reproduced the results of [1] using gammapy ([2]), thus providing a crosscheck to the ctools study and also validating our analysis pipeline. Then, we introduced new features that go beyond the reference study: for the first time, we computed the metrics using 3D (space + energy) analysis, instead of standard 1D aperture photometry. Furthermore, we introduced realistic hadronic models using naima ([3]-[4]): we simulated and fitted \( \gamma \)-ray models depending directly on the spectral shape of the parent population of CR protons. This way, we built the metrics in the proton's parameter space, i.e.\ directly in the space of interest for PeVatron searches.

The origin of cosmic rays is a long standing problem in astrophysics. In the standard theory, Galactic CRs below knee energy are accelerated by the diffusive shock acceleration (DSA) in galactic supernova remnants(SNRs). In a perpendicular shock region, CRs cannot diffuse to the far upstream region compared with the parallel shock case because it is hard for CRs to diffuse perpendicular to the magnetic field line. As a result, the acceleration time in the perpendicular shock becomes smaller than that in the parallel shock [3]. One of problems for the acceleration in the perpendicular shock is the spectral index of the accelerated particle. The rapid acceleration at the perpendicular shock requires a small amplitude of the fluctuated component. It is shown that if the magnetic field fluctuation is weak in the upstream and downstream regions, the energy spectrum of accelerated particle at the perpendicular shock becomes steeper than expected from observations [5]. However, some observations [6, 2] and simulations [8,7,4,1] suggest that the magnetic field is strongly amplified in the downstream region. Therefore, there is a possibility of a weak fluctuation in the upstream region and a strong fluctuation in the downstream region. In this work, we first investigate the particle acceleration in that case. In our model, The particle motion is gyration in an upstream region and Bohm diffusion in a downstream region. We investigate the acceleration time in a perpendicular shock region by using the three dimensional global test particle simulations, We show the change of the shock velocity dependence for acceleration time. In this case, we also show that the spectrum index of accelerated particles is the same as the standard DSA prediction.

AMS-02 is a particle physics detector installed onboard the International Space Station, which provides precise measurements of the different cosmic ray species. The AMS results have revealed unpredicted features on their spectra, which cannot be accounted within the current understanding of the production and propagation of galactic cosmic rays.

On the one hand, the positron flux shows an excess above ~10 GeV [1] which cannot be explained by a pure secondary origin. For most of the explanations the inclusion of primary sources is required; typically, being classified in two scenarios: dark matter and astrophysical sources.

On the other hand, the proton [2] and nuclei [3] spectra deviate from a single power law and the spectral index progressively hardens above ~ 100 GV. The origin of these effects may also reveal the existence of local sources or a change in their propagation mechanisms.

In all cases, the contribution of nearby sources may induce some degree of anisotropy in the arrival directions of the different cosmic ray species that would support or disfavor some of the aforementioned scenarios.

The directionality can be studied by comparing the data sample to a reference map, which represents the expectation for an isotropic flux; any deviation will be regarded as a signal. The large scale anisotropy can be described at first order by a dipole which is determined by its projection onto three orthonormal axes. Results on the dipole anisotropy in galactic coordinates for different charged cosmic rays from the first 7.5 years of data taking with AMS-02 will be presented. The expected upper limits on the dipole amplitude are 1.7% for

The structure of the stellar progenitor and the complex phases in the evolution of the parent supernova (SN) play an important role in determining the physical, chemical, and morphological properties of the supernova remnant (SNR) [1]. In particular, the remnant may reflect possible asymmetries developed soon after the SN explosion and keep memory of the nature of the stellar progenitor. The aim of this work is to bridge the gap between core-collapse (CC) SNe and their remnants by investigating how post-explosion anisotropies of ejecta influence the structure and chemical properties of the remnant at later times. This work combines 1D hydrodynamic (HD) models [2] of core-collapse SN explosions with 3D magnetohydrodynamic (MHD) models describing the subsequent evolution of the blast wave expanding through the circumstellar medium (CSM). Here we focused the analysis on the case of a progenitor red supergiant of \( 19.8 \) M\( _{\odot} \) [3]. We investigated how a post-explosion large-scale anisotropy in the SN affects the ejecta distribution and the matter mixing of heavy elements in the remnant, during the first 5000 years of evolution. In the case of a spherically symmetric SN explosion without large-scale anisotropies, the remnant roughly keeps memory of the original onion-like layering of ejecta soon after the SN event. Nevertheless, as soon as a reverse shock develops, the distribution of the elements does not evolve following a homologous expansion, because of the slowing down of outermost ejecta layers due to interaction with the CSM. As a result, layers including the high-Z elements expands from 30% up to 45% of the radius of the forward shock at \( t= 5000 \)~yr. In the case of a large-scale anisotropy developed in the SN, we found that the chemical stratification in the ejecta can be strongly modified and the original onion-like layering is not preserved. The anisotropy may cause spatial inversion of ejecta layers, for instance leading to Fe/Si-rich ejecta physically exterior to the O shell, and may determine the formation of Fe/Si-rich jet-like features that may protrude the remnant outline. The level of matter mixing and the properties of the jet are sensitive to the initial physical (density and velocity) and geometrical (size and position) initial characteristics of the anisotropy.