Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Génération et implémentation des donnés nucléaires pour la simulation Monte Carlo analogue

Nuclear data is in constant evolution as more experimental data is gathered, computational capabilities increase and evaluators verify their validity by means of stochastic and deterministic simulations. In the framework of this PhD thesis, the focus is on the simulation of nuclear reactions that produce more than two particles in the outgoing channel, which needs specific considerations to ensure the correlations between the particles and thus the conservation of energy and of translational and angular momenta. It is possible to adapt nuclear data and its exploitation to implement the so-called analog simulations of realistic reactions from the phenomenological point of view (as opposed to the historical need of variance reduction techniques), which increases computation time but allows the expansion of the transport codes capabilities.Les données nucléaires sont en constante évolution du fait de l'accumulation de nouvelles données expérimentales, de l'augmentation de la capacité de calcul informatique et du travail des évaluateurs qui testent la validité et cohérence des données par le biais de simulations stochastiques et déterministes. Dans le cadre de cette thèse, le focus porte sur les simulations de réactions nucléaires qui produisent plus de deux particules en voie de sortie, qui nécessitent des considérations spécifiques pour maintenir les corrélations entre ces particules et ainsi assurer la conservation de l'énergie et des moments cinétique et angulaire. Il est possible d'adapter les données nucléaires et leur exploitation pour les simulations - dites analogues - des réactions réalistes du point de vue phénoménologique (opposé au besoin historique de réduire la variance), ce qui augmente les temps de calcul mais permet d'élargir les capacités des codes de transport

Génération et implémentation des donnés nucléaires pour la simulation Monte Carlo analogue

Les données nucléaires sont en constante évolution du fait de l'accumulation de nouvelles données expérimentales, de l'augmentation de la capacité de calcul informatique et du travail des évaluateurs qui testent la validité et cohérence des données par le biais de simulations stochastiques et déterministes. Dans le cadre de cette thèse, le focus porte sur les simulations de réactions nucléaires qui produisent plus de deux particules en voie de sortie, qui nécessitent des considérations spécifiques pour maintenir les corrélations entre ces particules et ainsi assurer la conservation de l'énergie et des moments cinétique et angulaire. Il est possible d'adapter les données nucléaires et leur exploitation pour les simulations - dites analogues - des réactions réalistes du point de vue phénoménologique (opposé au besoin historique de réduire la variance), ce qui augmente les temps de calcul mais permet d'élargir les capacités des codes de transport.Nuclear data is in constant evolution as more experimental data is gathered, computational capabilities increase and evaluators verify their validity by means of stochastic and deterministic simulations. In the framework of this PhD thesis, the focus is on the simulation of nuclear reactions that produce more than two particles in the outgoing channel, which needs specific considerations to ensure the correlations between the particles and thus the conservation of energy and of translational and angular momenta. It is possible to adapt nuclear data and its exploitation to implement the so-called analog simulations of realistic reactions from the phenomenological point of view (as opposed to the historical need of variance reduction techniques), which increases computation time but allows the expansion of the transport codes capabilities

Génération et implémentation des donnés nucléaires pour la simulation Monte Carlo analogue

Nuclear data is in constant evolution as more experimental data is gathered, computational capabilities increase and evaluators verify their validity by means of stochastic and deterministic simulations. In the framework of this PhD thesis, the focus is on the simulation of nuclear reactions that produce more than two particles in the outgoing channel, which needs specific considerations to ensure the correlations between the particles and thus the conservation of energy and of translational and angular momenta. It is possible to adapt nuclear data and its exploitation to implement the so-called analog simulations of realistic reactions from the phenomenological point of view (as opposed to the historical need of variance reduction techniques), which increases computation time but allows the expansion of the transport codes capabilities.Les données nucléaires sont en constante évolution du fait de l'accumulation de nouvelles données expérimentales, de l'augmentation de la capacité de calcul informatique et du travail des évaluateurs qui testent la validité et cohérence des données par le biais de simulations stochastiques et déterministes. Dans le cadre de cette thèse, le focus porte sur les simulations de réactions nucléaires qui produisent plus de deux particules en voie de sortie, qui nécessitent des considérations spécifiques pour maintenir les corrélations entre ces particules et ainsi assurer la conservation de l'énergie et des moments cinétique et angulaire. Il est possible d'adapter les données nucléaires et leur exploitation pour les simulations - dites analogues - des réactions réalistes du point de vue phénoménologique (opposé au besoin historique de réduire la variance), ce qui augmente les temps de calcul mais permet d'élargir les capacités des codes de transport

Nuclear data generation & implementation for analog Monte Carlo simulation

Nuclear data is in constant evolution as more experimental data is gathered, computational capabilities increase, and evaluators verify its validity by means of stochastic and deterministic simulations. The focus here is on the analog Monte Carlo simulation of nuclear reactions that produce more than two particles in the outgoing channel, which needs specific considerations to ensure the correlations between the particles and thus the conservation of energy and of translational and angular momenta. It is possible to adapt nuclear data and its exploitation to implement realistic reactions from the phenomenological point of view (as opposed to the historical need of variance reduction techniques), which increases computation time but allows the expansion of the transport codes capabilities. Simulation anomalies were found concerning the kinematical calculations of photon energies emitted from neutron-induced inelastic scattering (n,n’γ), as well as concerning the photon multiplicity of 155Gd(n,γ) due to the presence of a rotational band in 156Gd. Recommendations are given for potential solutions for both anomalies

Tumefactive multiple sclerosis: A rare but serious variable in multiple sclerosis

Tumefactive multiple sclerosis is a rare variant of multiple sclerosis, characterized by the presence of brain lesions that may be solitary or multiple. Considering that these lesions have a pseudotumoral appearance, it is a challenge to differentiate them from central nervous system neoplasms through neuroimaging. Many cases are associated with the administration of monoclonal antibodies, and due to an increase in the incidence of cancer globally, it is expected that secondary to chemotherapeutic treatments, more and more cases may appear. Taking into account the above, the objective of this review is to review aspects of usefulness in clinical practice, on the diagnosis and approach of this pathological conditio

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta