arXiv subjects

Nicolas de Séréville

Publications and source records attributed to Nicolas de Séréville.

6 recordsLinked to original sources

arXiv2026

Gamma-Ray Burst Polarimetry with the COMCUBE-S CubeSat Swarm -- Design and Performance Simulations

COMCUBE-S (COMCUBE-S (Compton Telescope CubeSat Swarm) is a proposed mission aimed at understanding the radiation mechanisms of ultra-relativistic jets from Gamma-Ray Bursts (GRBs). It consists of a swarm of 16U CubeSats carrying a state-of-the-art Compton polarimeter and a bismuth germanium oxide (BGO) spectrometer to perform timing, spectroscopic and polarimetric measurements of the prompt emission from GRBs. The mission is currently in a feasibility study phase (Phase A) with the European Space Agency to prepare an in-orbit demonstration. Here, we present the simulation work used to optimise the design and operational concept of the microsatellite constellation, as well as estimate the mission performance in terms of GRB detection rate and polarimetry. We used the MEGAlib software to simulate the response function of the gamma-ray instruments, together with a detailed model for the background particle and radiation fluxes in low-Earth orbit. We also developed a synthetic GRB population model to best estimate the detection rate. These simulations show that COMCUBE-S will detect about 2 GRBs per day, which is significantly higher than that of all past and current GRB missions. Furthermore, simulated performance for linear polarisation measurements shows that COMCUBE-S will be able to uniquely distinguish between competing models of the GRB prompt emission, thereby shedding new light on some of the most fundamental aspects of GRB physics.

astro-ph.HE↗

arXiv2026

$γ$-Ray Lines -- Signatures of Nucleosynthesis, Cosmic Rays, Positron Annihilation, and Fundamental Physics

The nuclear $γ$-ray lines in the MeV range of the electromagnetic spectrum hold a vast variety of astrophysical, particle-physical, and fundamental physical information that is otherwise extreme difficult to access. MeV $γ$-ray line observations provide the most direct evidence for ongoing nucleosynthesis in galaxies by measuring freshly produced radioactive isotopes from massive stars, supernovae, classical novae, or binary neutron star mergers. Their flux ratios can determine the low-energy cosmic-ray spectrum in different objects and of the Milky Way as a whole. Different phases of the interstellar medium are traced by hot nucleosynthesis ejecta, cooling positrons, or cosmic-ray interactions with molecular clouds. Positron annihilation itself can be considered as an astrophysical messenger as their production and destruction in typical space environments is inevitable. Finally, as-of-yet unknown signatures from beyond standard model physics might have their elusive imprints in $γ$-ray lines. This Chapter gives an overview of historical $γ$-ray line measurements, newest results, and open questions that may only be solved by a new generation of MeV telescopes.

astro-ph.HE↗

arXiv2024

Origin of $^{60}$Fe nuclei in cosmic rays: the contribution of local OB associations

The presence of live $^{60}$Fe nuclei (lifetime of 3.8~Myr) in cosmic rays detected by the ACE/CRIS instrument suggests a nearby nucleosynthesis source. $^{60}$Fe is primarily produced in core-collapse supernovae, and we aim to clarify whether the detected $^{60}$Fe nuclei can be associated with a particular local supernova. We consider 25 OB associations and sub-groups located within 1 kpc of the solar system based on recent $Gaia$ census. A model is developed that combines stellar population synthesis within these OB associations, cosmic-ray acceleration within associated superbubbles, and cosmic-ray transport to the solar system. The most critical model parameter impacting $^{60}$Fe cosmic-ray production is the explodability criterion, which determines if a massive star ends its life as a supernova. Our study points to the Sco-Cen OB association as the most probable origin of the observed $^{60}$Fe nuclei, particularly suggesting they were accelerated in the Sco-Cen superbubble by a young supernova aged $\leq500$ kyr with a progenitor mass of approximately $13-20~M_\odot$. A less likely source is the supernova at the origin of the Geminga pulsar 342 kyr ago, if the progenitor originated in the Orion OB1 association. The contribution of local OB associations to the cosmic-ray density of stable $^{56}$Fe is estimated to be around 20\%, with some sensitivity to cosmic ray acceleration efficiency and diffusion coefficient. These findings shed light on the origins of cosmic-ray nuclei, connecting them to nucleosynthesis events within our local cosmic neighborhood.

astro-ph.HE↗

arXiv2021

Transfer reactions as a Tool in Nuclear Astrophysics

Nuclear reaction rates are one of the most important ingredients in describing how stars evolve. The study of the nuclear reactions involved in different astrophysical sites is thus mandatory to address most questions in nuclear astrophysics. Direct measurements of the cross-sections at stellar energies are very challenging - if at all possible. This is essentially due to the very low cross-sections of the reactions of interest (especially when it involves charged particles), and/or to the radioactive nature of many key nuclei. In order to overcome these difficulties, various indirect methods such as the transfer reaction method at energies above or near the Coulomb barrier are used to measure the spectroscopic properties of the involved compound nucleus that are needed to calculate cross-sections or reaction rates of astrophysical interest. In this review, the basic features of the transfer reaction method and the theoretical concept behind are first discussed, then the method is illustrated with recent performed experimental studies of key reactions in nuclear astrophysics.

nucl-ex↗

arXiv2020

Correlated Energy Uncertainties in Reaction Rate Calculations

Context. Monte Carlo methods can be used to evaluate the uncertainty of a reaction rate that arises from many uncertain nuclear inputs. However, until now no attempt has been made to find the effect of correlated energy uncertainties in input resonance parameters. Aims. To investigate the impact of correlated energy uncertainties on reaction rates. Methods. Using a combination of numerical and Monte Carlo variation of resonance energies, the effect of correlations are investigated. Five reactions are considered: two fictional, illustrative cases and three reactions whose rates are of current interest. Results. The effect of correlations in resonance energies depends on the specific reaction cross section and temperatures considered. When several resonances contribute equally to a reaction rate, and are located either side of the Gamow peak, correlations between their energies dilute their effect on reaction rate uncertainties. If they are both located above or below the maximum of the Gamow peak, however, correlations between their resonance energies can increase the reaction rate uncertainties. This effect can be hard to predict for complex reactions with wide and narrow resonances contributing to the reaction rate.

astro-ph.IM↗

arXiv2014

Light Element Nucleosynthesis in a Molecular Cloud Interacting with a Supernova Remnant and the Origin of Beryllium-10 in the Protosolar Nebula

The presence of short-lived radionuclides in the early solar system provides important information about the astrophysical environment in which the solar system formed. The discovery of now extinct $^{10}$Be in calcium-aluminum-rich inclusions (CAIs) with Fractionation and Unidentified Nuclear isotope anomalies (FUN-CAIs) suggests that a baseline concentration of $^{10}$Be in the early solar system was inherited from the protosolar molecular cloud. In this paper, we first show that the $^{10}$Be recorded in FUN-CAIs cannot have been produced in situ by cosmic-ray (CR) irradiation of the FUN-CAIs themselves. We then show that trapping of Galactic CRs (GCRs) in the collapsing presolar cloud core induced a negligible $^{10}$Be contamination of the protosolar nebula. Irradiation of the presolar molecular cloud by background GCRs produced a steady-state $^{10}$Be/$^9$Be ratio ~2.3 times lower than the ratio recorded in FUN-CAIs, which suggests that the presolar cloud was irradiated by an additional source of CRs. Considering a detailed model for CR acceleration in a supernova remnant (SNR), we find that the $^{10}$Be abundance recorded in FUN-CAIs can be explained within two alternative scenarios: (i) the irradiation of a giant molecular cloud by CRs produced by >50 supernovae exploding in a superbubble of hot gas generated by a large star cluster of at least 20,000 members and (ii) the irradiation of the presolar molecular cloud by freshly accelerated CRs escaped from an isolated SNR at the end of the Sedov-Taylor phase. The second model naturally provides an explanation for the injection of other short-lived radionuclides of stellar origin into the cold presolar molecular cloud ($^{26}$Al, $^{41}$Ca and $^{36}$Cl) and is in agreement with the solar system originating from the collapse of a molecular cloud shocked by a supernova blast wave.

astro-ph.HE↗