Présidents de session
Students' presentations: Abdalla, Aguilera-Dena, Balakina, Bugli
- Volker Beckmann (CNRS / IN2P3)
Students' presentations: Bylund, Cardillo, Chakraborty, Conte
- Diego Gotz (CEA Saclay)
Students' presentations: Carotenuto, Diesing, Duque, Jacquemin Ide, El Mellah
- Volker Beckmann (CNRS / IN2P3)
Students' presentations: Lescaudron, Dagoneau, Mate, Mohapatra, Muller
- Il n'a pas de président de session pour ce bloc
Students' presentations: Müller Bravo, Palla, Reboul-Salze,Saikia, Samuelsson
- Volker Beckmann (CNRS / IN2P3)
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29/05/2019 18:00
At energies approaching the Planck energy scale 1E19 GeV, several quantum-gravity theories predict that familiar concepts such as Lorentz (LIV) symmetry can be broken. Such extreme energies are currently unreachable by experiments on Earth, but for photons traveling over cosmological distances the accumulated deviations from the Lorentz symmetry may be measurable using the Cherenkov Telescope...
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David Ramon Aguilera Dena (Argelander Institut für Astronomie)29/05/2019 18:15
Modeling the evolution and mass loss history of rapidly rotating massive stars at low metallicity, we found that chemically homogeneously evolving stars with enhanced rotational mixing could be suitable candidates for both SLSNe in the magnetar-driven scenario and for lGRBs in the collapsar scenario. They retain a high angular momentum in their cores, enough to power these types of explosions,...
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29/05/2019 18:30
Type Ia supernovae (SNe) are excellent distance indicators. Observations of distant SNe Ia led to the discovery of the accelerating expansion of the Universe. The most recent analysis of SNe Ia indicates that considering a flat ΛCDM cosmology, the contribution of dark energy in the total density of the Universe is ∼ 70%. Cosmological parameters are estimated from the “luminosity...
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Matteo Bugli (CEA - Saclay)29/05/2019 18:45
The characteristics of the initial magnetic field present in a supernova progenitor prior to collapse and the dynamics of the field amplification due to different dynamo mechanisms (such as MRI, convective motions, etc.) are to this date quite uncertain.
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We investigate the effects of multipolar magnetic field topologies of different radial extents on the dynamics of core-collapse supernovae... -
30/05/2019 18:00
Imaging Atmospheric Cherenkov Telescopes (IACT) are among the most sensitive instruments available to study the very high energy non-thermal sky, and the High Energy Stereoscopic System (HESS) is the largest such system operating in the world. This makes HESS an excellent tool for probing the extreme environment of Blazar jets. In this talk I will give a brief introduction to the principles...
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Martina Cardillo (INAF-Osservatorio astronomico di Arcetri)30/05/2019 18:10
In the last years, the improvement of performances of high-energy instruments, both from Earth and Space, has provided a great amount of data relating to Cosmic-Rays (CRs). In particular, in the gamma-ray band, we had the first evidence of CR energization at the Supernova Remnant (SNR) shocks. Several models were developed, assuming that the emission was due to freshly accelerated CRs, in...
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Sudip Chakraborty (Tata Institute of Fundamental Research, Mumbai, India)30/05/2019 18:25
An estimate of the jet inclination relative to the accreting black hole's spin can be useful to probe the jet triggering mechanism and the disc-jet coupling. Tidal Disruption Event (TDE) of a star by a supermassive spinning black hole provides a unique astrophysical laboratory to study the jet direction through the possibility of jet precession, induced by the Lense-Thirring precession of the...
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Francesco Conte (Max-Planck-Institut für Kernphysik)30/05/2019 18:40
The Cherenkov Telescope Array (CTA) project is a next generation observatory for Very-High Energy gamma-ray astronomy. Two sites, in the northern and in the southern emisphere, have already been officially announced by the CTA consortium and will constitute the world largest detector for gamma rays. To push the energy sensitivity in the range of hundreds of TeV, about 70 small-sized telescopes...
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Francesco Carotenuto (Université de Paris, CEA/Saclay-Irfu/Dap/AIM)31/05/2019 18:00
The very bright transient MAXI J1348-630 was discovered in X-rays by MAXI in January 2019 and was then detected also in radio and optical. Immediately after its discovery, it was classified as a black hole candidate based on its X-ray behaviour.
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We present an intense radio monitoring of the transient at 1.284 GHz with the new MeerKAT radio interferometer (64 antennas) located in the Karoo... -
31/05/2019 18:10
Using a semi-analytic model of non-linear diffusive shock acceleration, we model the spectrum of cosmic ray (CR) electrons accelerated by supernova remnants (SNRs). Because electrons experience synchrotron losses in the amplified magnetic fields characteristic of SNRs, they exhibit substantially steeper spectra than protons. In particular, we find that the difference between the electron and...
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31/05/2019 18:20
The binary neutron star inspiral signal GW170817 was a historical event and inaugurated the era of multi-messenger astronomy with gravitational waves. It was accompanied by electromagnetic counterparts, namely a kilonova, a weak and short gamma-ray burst and a long-lasting multi-wavelength afterglow. Altogether, these brought a wealth of information on the unraveling of the merger and...
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31/05/2019 18:30
Semi-analytical models of disk outflows have successfully described magnetically-driven, self-confined super-Alfvenic jets from near Keplerian accretion disks (Ferreira 1997). These Jet Emitting disks (JED) are possible for high levels of magnetization, close to the equipartition, leading to supersonic accretion and deeply affecting the emitted spectrum (see eg. Marcel et al 2018). However,...
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31/05/2019 18:45
The historical gravitational wave detections of last years ushered in a new era for the study of massive binaries evolution. In high mass X-ray binaries, a transient albeit decisive phase preceding compact binaries, a compact accretor orbits a massive star and captures part of its intense stellar wind. From the stellar photosphere down to the vicinity of the compact object, the flow undergoes...
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Stéphane Schanne (CEA Saclay)31/05/2019 19:00
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03/06/2019 18:00
Most of the galaxies host a supermassive BH in their centre and we observe a co-evolution of the galaxy and its central BH. The BH is expected to have a key role in the regulation of the quantity of gas and stars : it accretes matter from its surrounding and releases a fraction of this rest-mass energy into the host galaxy, providing “feedback”. The BH angular momentum or spin directly...
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Nicolas Dagoneau (CEA/Saclay - IRFU/DAp/LISIS)03/06/2019 18:10
It has recently been pointed out that ultra-long gamma-ray bursts (ULGRBs), with very atypical durations of more than 1000 seconds, could form a new class of GRBs (Levan+13). ULGRBs could have a different progenitor than standard GRBs and be produced by the core collapse of a low metallicity supergiant blue star (Gendre+13) or the birth of a magnetar following the collapse of a massive star...
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Sujay Mate (IRAP)03/06/2019 18:20
The Space Variable Object Monitor (SVOM) is a Chinese-French astrophysics mission for the study of high-energy transients, in particular Gamma-Ray Bursts. One of the key instrument on SVOM is the ECLAIRs gamma-ray camera which is a large field of view (FoV) coded mask imager working in the energy range of 4 -150 keV. The primary focus of the instrument is to detect and localize new GRBs with...
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Abhishek Mohapatra (NIT Rourkela, India)03/06/2019 18:30
In this talk, I will present detailed photoionization models of well-aligned optically thin doubly ionized carbon (C III) absorption components at 2.1 ≤ z ≤ 3.4. Our inferred density and overdensity (∆) favor the absorption originating from gas associated with circumgalactic medium and probably not in hydrostatic equilibrium. We discuss statistically significant redshift evolution of our...
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Jacques Muller03/06/2019 18:40
Cherenkov telescope arrays such as H.E.S.S. or the planned future CTA are systems of imaging atmospheric Cherenkov telescopes. They detect high energy photons above 10GeV (gamma-rays) from cosmic sources based on the Cherenkov emission of charged particles produced when these photons enter the atmosphere. They need to be calibrated to be able to compare and combine the measurements of the...
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Tomas Müller Bravo (University of Southampton)04/06/2019 18:00
Type Ia Supernovae (SNe Ia) have been studied for many years as standardisable candles for cosmological distance measurement. In addition, these objects have shown to be standard candles in the Infrared (IR), where they are less affected by extinction, probing to be exceptional for cosmology. With the large number of on-going (e.g., ZTF, ATLAS, VEILS) and future surveys (e.g., LSST), both in...
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Marco Palla (Università degli Studi di Trieste)04/06/2019 18:10
We try to identify the nature of high redshift long Gamma-Ray Bursts (LGRBs) host galaxies by comparing the observed abundance ratios in the interstellar medium with detailed chemical evolution models accounting for the presence of dust. What we have done is to compare abundance data from LGRB afterglow spectra to abundance patterns as predicted by our models for different galaxy types...
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Alexis Reboul-Salze (CEA Saclay)04/06/2019 18:20
The magnetorotational instability (MRI) is considered to be a promising mechanism to amplify the magnetic field in fast-rotating protoneutron stars. Many local studies have proven that the magnetic field could be amplified on small scales. But to explain the dipolar magnetic field strength of the magnetars (10¹⁴-10¹⁵ G), a large scale magnetic field needs to be generated by the MRI. To study...
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Payaswini Saikia (Nyuad)04/06/2019 18:30
Compact, continuously launched jets in black hole X-ray binaries (BHXBs) produce radio to optical–infrared (OIR) synchrotron emission. These jets are launched in the hard X-ray state, and are quenched in the soft state. They are not spatially resolved except in a few cases using VLBI radio observations. One of the basic properties of these jets is the bulk Lorentz factor, which defines how...
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Filip Samuelsson (KTH Royal Institute of Technology)04/06/2019 18:40
The acceleration site for UHECR is still an open question despite extended research and GRBs are considered one of the most promising source candidates. Under the likely assumption that electrons are also accelerated at the UHECR acceleration site, synchrotron emission from these co-accelerated electrons is inevitable. We characterize this synchrotron emission and compare it to observed GRB...
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Semi-analytical models of disk outflows have successfully described magnetically-driven, self-confined super-Alfvenic jets from near Keplerian accretion disks (Ferreira 1997). These Jet Emitting disks (JED) are possible for high levels of magnetization, close to the equipartition, leading to supersonic accretion and deeply affecting the emitted spectrum (see eg. Marcel et al 2018). However,...
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η Carinae is a unique laboratory in which to study particle acceleration to high energies under a wide range of conditions, including extremely high densities around periastron. So far no consensus has emerged in the origin of the GeV γ-ray emission in this important system. With a re-analysis of the full Fermi-LAT data set for η Carinae, we show that the spectrum is consistent with a pion...
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The study of astrophysical accretion phenomenon and binary systems is undoubtedly useful to better understand the role of gravitation in producing high-energy, X-ray and gamma-ray, emission. In particular close gravitationally bound binaries of supermassive black holes (SMBHs) in some active galactic nuclei and blazars are expected to induce cyclical modulations in the observed flux. In the...
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