E5: Numerical Observatory of Violent Accretion systems NOVAs strong gravity and beyond

Check out the project news!

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  • first GR-HD simulation of a thin disk equilibrium GYOTO view of a GR accretion disk

    Collaboration between AIM, APC and LUTH

    The advent of high energy observation facilities in the last decades has proven the existence of powerful mechanisms emitting photons up to gamma-rays. It is now commonly admitted that the most energetic events are associated with compact objects believed to be relics of massive stars. These objects are prone to the most extreme gravity fields and are likely efficient attractors of the plasma present in their vicinity. The motion of plasma in the close neighborhood of compact objects is only properly described in the framework of general relativistic magnetohydrodynamic (GR- MHD). The equations governing GR-MHD are so complex that the only way to solve them is trough large-scale numerical simulations. The topic of the present demand is to sustain a computational effort dedicated to GRMHD simulations of accretion flows near compact objects and to link them to synthetic observations of the associated violent events, one of the major themes within LabeX ‘UnivEarths’.

     

    General Objective of the Project

    The quest to unveil the nature of the compact objects detected in the center of radio-loud galaxies, in X-ray binaries and also at the center of the Milky Way, is at the crossroads between high resolution, time-dependent, multi-wavelength observations and the coming of age of numerical GR-MHD codes. The project presented here plans to exploit this opportunity by setting a long- standing collaboration between members of three teams involved in the LabeX ‘UnivEarths’ which are already tackling, individually, the problem from the different angles of analytical and numerical studies, observations, and high-performance code development.

    While the french community is, at the moment, lacking a numerical code able to describe the dynamics of a magnetized plasma in a full GR framework, the LabeX ‘UnivEarths’ benefits from a unique conjunction where plasma numericists, high-energy observers and GR numericists are present in the same area and have had a good track-record on common past projects. By joining forces, our aim is to sustain the development of such a GR-MHD code in order to perform large-scale simulations of plasma accretion onto compact objects and subsequently create an ”observation” from it. Another innovative feature of our code will stem from its ability to handle any kind of GR metrics, not only conventional metric such as Schwarzschild or Kerr, but also metrics of alternative, non-GR, gravitation theories which generally do not have any analytical expression.

  • The three teams and interaction

    Our team, while approaching a new subject linking their respective research, is composed of people used to working together on a variety of topics such as GRBs and planet formation. For this project we plan on using our distinct approaches to tackle the creation the first full GR- MHD code coupled to a ray-tracing code able to provide synthetic observations of the environment of compact objects.

     

    AIM – high-energy observers axis led by J.Rodriguez. They are expert of multi-wavelengths observations of compact objects and have access (through dedicated and collaborative programs) to a wide range of observations. This broad range of data have allowed them to tackle the problems of accretion-ejection connections and mechanisms prevailing in those systems, including also the study of rapid X-ray variability.

    APC – ADAMIS simulation axis led by F. Casse and P. Varniere. Their expertise ranges from analytical to MHD numerical studies of the accretion-ejection system. They also do the extra step of linking their results with observations. They are developers in the mpi-amrvac project.
    LUTH – Relativistic fluid simulations axis, led by Z.Meliani and E.Gourgoulhon. ZM is long term developer on the mpi-amrvac project is now fully concentrating on implementing and using GR-MHD to study compact objects. EG is a leader in strong gravity calculation.

  • Distinguishing an ejected blob from alternative flare models at the Galactic centre with GRAVITY

    The black hole at the Galactic centre exhibits regularly flares of radiation, the origin of which is still not understood. In this article, we study the ability of the near-future GRAVITY infrared instrument to constrain the nature of these events. We develop realistic simulations of GRAVITY astrometric data sets for various flare models. We show that the instrument will be able to distinguish an ejected blob from alternative flare models, provided the blob inclination is >= 45deg, the flare brightest magnitude is 14 <= mK <= 15 and the flare duration is >= 1h30.

  • Distinguishing an ejected blob from alternative flare models at the Galactic centre with GRAVITY

    F. H. Vincent, T. Paumard, G. Perrin, P. Varniere, F. Casse, F. Eisenhauer, S. Gillessen, P. J. Armitage
    (Submitted on 24 Apr 2014)
    The black hole at the Galactic centre exhibits regularly flares of radiation, the origin of which is still not understood. In this article, we study the ability of the near-future GRAVITY infrared instrument to constrain the nature of these events. We develop realistic simulations of GRAVITY astrometric data sets for various flare models. We show that the instrument will be able to distinguish an ejected blob from alternative flare models, provided the blob inclination is >= 45deg, the flare brightest magnitude is 14 <= mK <= 15 and the flare duration is >= 1h30.

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