Cosmic Explosions 2019

Europe/Paris
Amphitheatre (Cargèse)

Amphitheatre

Cargèse

Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
Description

The most violent and energetic phenomena observed in our Universe are in their vast majority linked with objects in the “stellar graveyard”. These transient events can be associated with the collapse of a massive star (supernova and gamma-ray bursts), to accretion processes in binary systems that include a compact object (neutron star or black hole) or the coalescence of two of those compact sources; emitters of the gravitational wave signals recently detected. For historical reasons, “Cosmic Explosions” have been studied and presented at summer schools independently. Bridging the gap between different communities that are studying the various facets of a same family of objects would allow young researcher entering the field to see the global picture and the evolutionary link between them.

This school is organised in the context of the multi-messenger (photons, neutrinos, and gravitational waves) era and the large number of existing or upcoming telescopes to study the transient sky. This school will bring together international experts from different domains in order to prepare the future generation of young researchers to the revolution of time-domain, and multi-messenger astronomy.

The morning sessions will focus on theory and presentations of astrophysical objects, whereas the afternoon sessions will present the observational context and data analysis hands on sessions. Time slots will be arranged for PhD students and postdocs to present their current research and carry out in small groups, a research project during the school.

Registration is now closed.

The registration fees are 600 € and cover lodging, lunch, conference dinner, and excursion. The fees can be paid online by credit card or by wire transfer on the CNRS website:

You need to first create an account and then pay the fees.

Students planning to present a talk or poster will need to submit an abstract in pdf format specifying talk or poster in the title.

For students requesting financial support, please specify your research interests and how this school can help you carrying out your project.

The school is acknowledged as an “Ecole thématique du CNRS”, hence applicants under CNRS contract (permanent and non-permanent) will be exempted from the registration fee.

Activities during the School:

  • interactive hands-on sessions

  • small projects

  • student presentations (oral + posters)

  • excursions

  • ample time for using the private beach at lunch

List of confirmed speakers:

Nicolas Leroy, Sera Markoff, Frederic Daigne,  Jacco Vink, Marta Burgay, Renaud Belmont, Mickael Rigault, Stefano Gabici, Norbert Langer, Diego Götz, Karl Kosack, Veronique Van Elewyck, Ed Porter, Henri Triou, ...

Logistics:

The school will take place in Cargèse, Corsica. The nearest airport is Ajaccio and a bus will be scheduled on Monday (May 27) at 3 pm, in order to collect and bring the participants to Cargèse. The Ajaccio airport is served from Paris Orly, Paris CDG, Nice and Marseille. It is highly recommended to tune your travel schedule to take the Cosmic Bus, due to the paucity of public transportation in Corsica. If you don't want to take the school bus, note that a taxi can be an expensive (> 100 ) alternative.

For any inquiries please contact the director of the school Fabio Acero (@ cea.fr)

@CExplosions2019

    • 15:00 16:30
      Bus Transfer Ajaccio Airport to Cargese 1h 30m Ajaccio Airport

      Ajaccio Airport

      Aéroport Napoléon Bonaparte, Route de Campo Dell Oro, 20090 Ajaccio

      We will provide a bus transfer from Ajaccio Airport to the school location in Cargese on Monday afternoon. It's a small airport, so don't worry: either you find us or we will find you.

    • 16:30 18:00
      Registration & room distribution 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speakers: Diego Gotz (CEA Saclay), Fabio Acero (CEA/Saclay), Karl KOSACK (CEA Saclay), Volker Beckmann (CNRS / IN2P3)
    • 18:00 19:30
      Welcome Speech & Drink 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 09:00 10:30
      Theory: Radiation Processes 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Dr Renaud Belmont (IRAP)
    • 10:30 11:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Theory: CRs & acceleration processes 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Stefano Gabici (DIAS, Dublin)
    • 12:30 13:30
      Lunch 1h Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 16:00 16:45
      Observation: Radio 45m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Marta Burgay
    • 16:45 17:30
      Observation: IR/optical 45m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Mickael Rigault (LPC, Clermont)
    • 17:30 18:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 18:00 19:00
      Students' presentations: Senniappan, Smirnova, Scott, Verna, Weerasekara Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      • 18:00
        M. Senniappan: Signal over Background discrimination for the ALTO observatory 10m

        ALTO is a future ground-based very high energy gamma-ray observatory based on water Cherenkov technique, which samples the secondary particles produced in the extensive air showers. This technique also provides long-term, continuous and wide field of view gamma-ray observations. Despite many advantages, the detection technique alone cannot determine the type of primary particle which gives rise to the shower. Hence every recorded event either belongs to the category of gamma-ray induced (signal) or cosmic-ray induced (background) shower. In the data analysis, the signal over background (S/B) discrimination procedure is performed to identify the event either as a signal or background. In the presentation, I will discuss the procedure used for S/B discrimination in the ALTO observatory and the practical difficulties in reaching complete background rejection.

      • 18:10
        M. Smirnova: 3D Simulations of Pair Instability Supernovae Explosions 10m

        PISN is the explosions of supermassive, up to 1000 solar masses, stars of the III generation with low metallicity, which are on the cosmological distances from the Earth in the young universe. In present time there are not many publications exist on this topic what is explained by observational difficulties. These kinds of stars are unavailable for direct observations now, but the advanced instruments are developed fastly and there is no doubt that in a few years the topic became very popular branch of astrophysics.
        For better understanding of the hydrodynamical process of pair instability supernovae explosion numerical simulation is crucial. The results of the 3D hydrodynamic simulation of pair-instability supernovae with core of 70, 90 and 100 solar masses will be presented. For each case the amount of nuclear energy release and lost through neutrino losses during the explosion will be shown. The results of 3D simulations will be compared with results of 1D and 2D simulations from other works.

        Speaker: Nina SMIRNOVA (LAPTh)
      • 18:20
        S. Scott: The Follow-up of Cosmic Explosions with VERITAS 10m

        Much can be learned about the particle acceleration and emission processes involved in cosmic explosions through the study of gamma rays in the very-high-energy (VHE; E > 100GeV) regime. Ground-based imaging atmospheric Cherenkov telescopes (IACTs), which are sensitive to VHE gamma-ray photons, therefore have much to contribute in the effort to characterize these transients. VERITAS, an IACT array located at Whipple Observatory in southern Arizona, has actively followed up gamma-ray bursts (GRBs) since 2006. In the last few years, VERITAS has also initiated programs to investigate LIGO/Virgo gravitational wave events and IceCube neutrino alerts. This presentation will cover the current status and future of the VERITAS transient follow-up programs.

      • 18:30
        G. Verna: Searching for galactic PeVatrons with CTA 10m

        One of the major scientific objectives of the future Cherenkov Telescope Array (CTA) Observatory is the search of PeVatrons. PeVatrons are the cosmic-ray factories able to accelerate nuclei at least up to the knee feature seen in the spectrum of Cosmic-Rays measured from Earth. CTA will perform a survey of the full Galactic plane at TeV energies and beyond with unprecedented sensitivity. The determination of efficient criteria to identify PeVatron candidates during the survey observations is essential in order to trigger further dedicated observations. At CPPM we are working to determine these criteria through a study based on a full simulation. The outcome of this study is a PeVatron figure of merit, which is a metric that provides relations between spectral parameters, observation times and spectral cut-off energy lower limit.
        I will give a general overview of this study with particular attention on the results obtained using the two prototype scientific tools for CTA: Ctools and GammaPy. The possibility of different observation strategies particularly suitable for PeVatron search will be also mentioned.

      • 18:40
        G. Weerasekara: The effect of peculiar motion of galaxies when calculating the gravitational lensing time delay 10m

        An intervening galaxy acts like a gravitational lens and produces multiple images of a single source such as a more remote galaxy. In such a scenario the source, the lens and the observer all have peculiar motions in any random direction in addition to the overall expansion of the universe due to the dark energy. There is a difference in light arriving times from images of a single source, known as the time delay. In calculating such time delays, the peculiar motions of the source, the lens and the observer are generally neglected. In this study, realistic time delays are calculated considering such peculiar motions. The results show that peculiar motions contribute to measurable differences to the observed time delays.

    • 19:00 20:30
      Welcome Cocktail 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 09:00 10:30
      Theory: late stage of stellar evolution 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Norbert Langer
    • 10:30 11:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Objects: Supernovae 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Jacco Vink
    • 12:30 13:30
      Lunch 1h Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 16:00 17:30
      Supernova Remnants (SNRs) 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Jacco Vink
    • 17:30 18:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 18:00 19:00
      Students' presentations: Abdalla, Aguilera-Dena, Balakina, Breuhaus, Bugli Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      • 18:00
        H. Abdalla: LIV Signatures in EBL absorption and Compton scattering 10m

        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 Array (CTA). To study the spectral hardening feature observed in some VHE gamma-ray blazars, we calculate the reduction of the EBL gamma-gamma opacity due to the existence of underdense regions along the line of sight to VHE -gamma ray sources and we compared with the possibility of a LIV signature. Considering the LIV effect, we found that the cosmic opacity for VHE-gamma rays with energy more than 10 TeV can be strongly reduced. I will further discuss the impact of LIV on the Compton scattering process, and how future CTA observations may open an exciting window on studies of the fundamental physics.

      • 18:10
        D. A. Aguilera-Dena: Pre-explosion Core Properties of Superluminous Supernova and Long Gamma-Ray Burst Progenitors 10m

        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, and have masses, abundances and magnetic fields that could also be consistent with observations of SLSNe and the hypernovae associated with lGRBs; particularly reproducing the observed the lack of He in their envelopes. The outcome of core collapse is determined by whether core collapse results in the formation of a fast spinning neutron star or a black hole. We analyze the evolution of these progenitors, as well as the parameter space where NS formation might favored over BH formation, and properties of their cores and of their CSM at core collapse.

      • 18:20
        E. Balakina: Peculiar velocities of Type Ia Supernovae in clusters of galaxies 10m

        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 distance-redshift” relation of SNe using the Hubble diagrams. Currently a lot of attention is paid to standardization of SNe, i.e. to increase of the accuracy of luminosity distance determination. The uncertainty on the redshift is quite often considered negligible. The redshift used in “luminosity distance-redshift” relation is a cosmological redshift, i.e. the redshift due to the expansion of the Universe. In fact the redshift observed on the Earth also includes the contribution from the unknown peculiar velocities. To minimize the influence of poorly constrained peculiar velocities, in cosmological analyses a standard value of 300-400 km/s peculiar velocity dispersion is added in quadrature to the redshift uncertainty. It has nonetheless been observed that velocity dispersion can exceed 1000 km/s in galaxy clusters and therefore, the dispersion inside the cluster can be greater than the one usually assumed in cosmological analyses and can affect the distance measurements. To take this effect into account we study SNe Ia that are exploded in the galaxy clusters. As a supernova sample we use ”Pantheon” — the largest combined sample of SN Ia (HST, SNLS, SDSS, low-z samples and Pan-STARRS1) consisting of a total of 1048 objects ranging from 0.01 < z < 2.3. For those SNe Ia that belong to the galaxy clusters we are going to use the galaxy cluster redshift instead of the host galaxy redshift and examine the effect of this correction on the Hubble diagram.
        In the epoch of large transient surveys (such as LSST), a study of the second order effects and all possible sources of systematical uncertainties in the cosmological analysis is of high priority.

      • 18:30
        M. Breuhaus: Further support for a hadronic origin for the γ-ray emission from η Carinae 10m

        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 decay spectrum and not with a broken power law connecting to the X-ray emission as has been claimed. We show with a simple physical model that pion-decay emission is the most likely origin of all of the γ-ray emission, with inverse Compton emission from primary electrons dominating the hard X-ray emission detected with NuSTAR at most phases. Very close to periastron it seems possible that secondary electrons interacting away from the shock cap dominate the emission. Future observations with H.E.S.S., CTA and NuSTAR should enable this scenario to be further constrained.

      • 18:40
        M. Bugli: The role of magnetic field topology in core-collapse supernovae 10m

        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.
        We investigate the effects of multipolar magnetic field topologies of different radial extents on the dynamics of core-collapse supernovae and the properties of the forming proto-neutron star (PNS). Using axisymmetric relativistic MHD simulations, we find that higher multipolar magnetic configurations lead to generally less energetic explosions, with the central PNS increasing its spin and becoming more massive. Models with a low order multipolar configuration tend to produce more oblate PNS which in some cases are surrounded by a rotationally supported toroidal structure. This change is the PNS shape can be directly associated with higher neutrino luminosities along the equatorial plane but smaller along the poles.

    • 09:00 09:45
      Observations: X-rays 45m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Diego Gotz (CEA Saclay)
    • 09:45 10:30
      Observation: gamma-rays 45m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Karl KOSACK (CEA Saclay)
    • 10:30 11:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Objects: Gamma-Ray Bursts 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Frédéric Daigne (Institut d'Astrophysique de Paris - Université Pierre et Marie Curie)
    • 12:30 13:30
      Lunch 1h Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 16:00 16:45
      Observation: neutrinos 45m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Véronique Van Elewyck (APC)
    • 16:45 17:30
      Observation: Gravitational Waves 45m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Nicolas Leroy (LAL IN2P3/CNRS)
    • 17:30 18:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 18:00 19:00
      Students' presentations: Bylund, Cardillo, Carotenuto, Chakraborty, Ciprini Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      • 18:00
        T. Bylund: Blazar observations with the HESS telescope 10m

        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 behind IACT's, recent Blazar studies done by HESS, and report some preliminary results on very distant BL Lac.

      • 18:10
        M. Cardillo: CR and SNR love story and re-acceleration between them 10m

        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 order to isolate the hadronic component from the leptonic one and to find the first direct proof of CR acceleration at a SNR shock. Because of some spectral features in disagreement with the Diffusive Shock Acceleration (DSA) theory, however, the role of pre-existing CR re-acceleration was taken into account, finding that not only its contribution is not negligible but also that it could explain some important characteristic of CR particle and gamma-ray spectra. Here we briefly summarize the main results obtained in the study of CR re-acceleration, showing its fundamental contribution in the middle-aged SNR shocks and, likely, in the forward shock (FS) of stellar winds. Our aim is to fix the importance of re-energization of pre-existing CRs in the Galaxy and the need to consider it in the explanation of detected CR particle and gamma-ray spectra.

        Speaker: Martina Cardillo (INAF-Osservatorio astronomico di Arcetri)
      • 18:20
        F. Carotenuto: The new black hole transient MAXI J1348-630 observed through MeerKAT’s eyes 10m

        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.
        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 desert in South Africa, as part of the ThunderKAT Large Survey Programme. All typical X-ray spectral states have been observed. A strong radio flare (likely associated with an ejection event) was detected coincidently with a transition from the hard to the soft accretion state, as inferred from Swift and INTEGRAL observations. We discuss the overall behaviour of this binary during its outburst, along with results from the multi-wavelength campaign.

      • 18:30
        S. Chakraborty: Jet inclination relative to the black hole spin for the TDE Swift J1644+57 10m

        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 disc or by other mechanisms. In this work, we investigate the Swift XRT light curve of a well-sampled jetted TDE, Swift J1644+57. We use a new method to compare some useful aspects of the dips of this X-ray light curve with our jet precession model to find an upper limit of the jet inclination angle. This method does not require a known jet precession period and works even if many dips are not due to jet precession. Employing this method for the thick disc regime of the X-ray light curve, we conclude that the jet inclination with respect to the black hole spin axis, or the black hole spin-precession axis if the spin axis precesses, is likely less than 10 degrees for Swift J1644+57. We will then discuss its effect on the stellar dynamics near the supermassive black hole.

      • 18:40
        S. Ciprini: The binary supermassive black hole conjecture for two jetted gamma-ray blazars 10m

        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 past years, two jetted gamma-ray blazars have been suggested to harbour binary SMBHs: i.e., OJ 287 and PG 1553+113. I will introduce these two peculiar blazars, and present recent achievements made possible thanks to 10-year continuous monitoring observations of their GeV gamma-ray emission by the Fermi Large Area Telescope. In addition data collected thanks to dedicated observations by the Swift, Kepler and Spitzer space telescopes will be also presented.

    • 09:00 10:30
      Theory: Accretion 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Frédéric Daigne (Institut d'Astrophysique de Paris - Université Pierre et Marie Curie)
    • 10:30 11:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Objects: Black Holes 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Sera Markoff
    • 12:30 13:30
      Lunch 1h Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 16:00 17:30
      Objects: Binaries 1h 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Sera Markoff
    • 17:30 18:00
      Coffee break 30m Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 18:00 19:00
      Students' presentations: Conte, Diesing, Duque, El Mellah, Jacquemin Ide Amphitheatre

      Amphitheatre

      Cargèse

      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      • 18:00
        F. Conte: Development of a Compact High-Energy Camera for the Cherenkov Telescope Array 10m

        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 (SSTs) will be deployed in the southern hemisphere, covering an area of about four square kilometers. Here I present the development status of the Compact High-Energy Camera (CHEC), the camera designed for SST-2M GCT (one of the proposed SST prototypes). It focuses on the higher-end of CTA energy range and thanks to the use of dual-mirror optics CHEC can be very compact and low-cost, despite a precision of 10 arcmin and a field of view of 8 degrees, providing an unprecedented sensitivity and angular resolution with respect to any existing Imaging Atmospheric Cherenkov Telescopes (IACTs). The camera contains 2048 pixels with a physical size of 6×6 mm 2 . It relies on electronics based on TARGET (TeV Array Readout with GSa/s sampling and Event Trigger) Application-Specific Integrated Circuits (ASICs) and Field Programmable Gate Arrays (FPGAs) allowing a continuous sampling of the full waveform with the precision of 1 ns. CHEC-S, the current prototype, features silicon photomultipliers (SiPM) which provide many advantages over classical photomultiplier tubes (PMTs), and even over multi-anode PMTs as proven with the first prototype, CHEC-M. This contribution is meant to give an overview on CHEC-S design and status, showing in particular how it answers the peculiar needs of Cherenkov ground-based gamma-ray detection, which requires a completely different approach with respect to IR/optical detection. Finally, latest results from laboratory measurements and calibrations are presented.

      • 18:10
        R. Diesing: On the spectrum of electrons accelerated in supernova remnants 10m

        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 proton spectral index (power law slope) ranges from 0.1 to 0.4. Our findings must be reckoned with in theories of Galactic CR transport and may especially have implications for the observed “positron excess.”

      • 18:20
        R. Duque: Prospects for Electromagnetic Counterparts to Neutron Star Mergers in the Gravitational Wave Era 10m

        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 strengthened the link between neutron star mergers and the short gamma-ray bursts. During the next science runs of the gravitational interferometer network, more such electromagnetic counterparts are expected. This talk will concern the population of mergers we expect to detect jointly in the gravitational wave and electromagnetic domains. We couple population methods to jet induced afterglow and kilonova models to describe the population of these counterparts to come. This allows us to explore the new insights they will provide on the formation of neutron star binaries, the environments of their mergers, the geometry of the ejectas therein and the physics of short gamma-ray bursts.

      • 18:30
        I. El Mellah: Enhanced accretion and wind-captured discs in high mass X-ray binaries 10m

        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 successive phases. Our numerical simulations offer a comprehensive picture of the accretion process along this journey. They unveil complex and highly variable geometries produced by the wind beamed towards the accretor. Overdense small scale regions in the wind produce stochastic variability but also trigger instabilities at the outer rim of the neutron star magnetosphere or around the black hole, depending on the nature of the accretor. For wind speeds of the order of the orbital speed, accretion is significantly enhanced and provided cooling is accounted for, transient disc-like structures form, with dramatic consequences on the torques applied to the compact object. The recent observational reports on the limited extent of the accretion disc in Cygnus X-1 suggest that the disc is produced by this mechanism rather than a Roche lobe overflow of the companion star. We will also discuss the consequences for Vela X-1 and the coupling between the flow and the neutron star magnetosphere.

      • 18:40
        J. Jacquemin Ide: Magnetically-driven jets and winds from MRI-active accretion disks 10m

        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, these solutions prove difficult to compare with cutting edge numerical simulations, for the reason that numerical simulations show wind-like outflows but in the domain of small magnetization. In this work, we present for the first time self-similar solutions for accretion-ejection structures at small magnetization. We will elucidate the role of the magneto-rotational instability in the acceleration processes that drive this new type of solutions. The generalized parameter space and the astrophysical consequences will then be discussed. We believe that these new solutions could be a stepping stone in understanding the way astrophysical disks drive either winds or jets.

    • 09:00 10:30
      Projects: Introduction 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speakers: Fabio Acero (CEA/Saclay), Karl KOSACK (CEA Saclay), Volker Beckmann (CNRS / IN2P3)
    • 10:30 11:00
      Coffee break 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Project: Work 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 13:30 15:00
      Practical Sessions 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 20:00 22:30
      Social Dinner 2h 30m
    • 10:00 18:00
      Social Activity 8h Surprise!

      Surprise!

      Voyage surprise!

    • 09:00 10:30
      Objects: Neutron Stars 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 10:30 11:00
      Coffee break 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Objects: Coalescence 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      Speaker: Edward Porter (APC/CNRS)
    • 12:30 13:30
      Lunch 1h Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 16:00 17:30
      Practical Sessions 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 17:30 18:00
      Coffee break 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 18:00 19:00
      Students' presentations: Lescaudron, Dagoneau, Mate, Mohapatra, Muller Amphitheatre

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      • 18:00
        S. Lescaudron: Black holes spin evolution in merging galaxies 10m

        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 influences the fraction of energy released and radiated during accretion events. On the other hand galaxy mergers have a crucial role in triggering peaks of central BH activity, allowing strong gas accretion. The spin of the BH changes with the combination of gas accretion and the possible coalescence of BHs. Models of spin evolution during BHs merger will allow gravitational waves predictions. In this context, I performed idealised simulations of galaxy mergers including mass and spin evolution of supermassive black holes, using Ramses, an hydrodynamical and N-body code with adaptive mesh refinement developed by Romain Teyssier (2002). These simulations are run for different configurations of the angular momentum orientation of the galaxies, varying the angle between the galactic angular momenta and the orbital angular momentum. The orbital configuration influences the BHs encounter history, mass growth and spin evolution, which happen either on the primary or on the secondary BH.

      • 18:10
        N. Dagoneau: Image the hard X-ray sky with the ECLAIRs telescope onboard the SVOM mission, application to the detection of ultra-long gamma ray bursts. 10m

        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 (Greiner+14). However ULGRBs could also just represent the tail of the standard long GRB distribution (Virgili+13). In any case, it is clear that the duration of these bursts make them peculiar. To progress, the few ULGRBs detected so far by the Swift Burst Alert Telescope and some other instruments has to be increased. SVOM (Space-based multi-band astronomical Variable Objects Monitor, Wei, Cordier+16) is a French-Chinese mission dedicated to GRBs and transient events, currently under development and scheduled for launch after 2020. SVOM will help understanding ULGRBs, since its orbit and pointing strategy will permit to image the same portion of the sky continuously during nearly one day with the onboard coded-mask telescope ECLAIRs. Thanks to the image trigger foreseen onboard (Schanne+15), we expect to increase the sample of ULGRBs with SVOM. In this talk, I will present various methods developed to clean detector images from X-ray background and known X-ray source contributions in the onboard imaging process. Methods are based on detector model fitting (X-ray background model plus known X-ray source illuminations on the detector) and wavelet cleaning to remove large scales mainly containing the X-ray background. The cleaning performances of the methods will be presented. I will also focus on the capability of the image trigger to detect the currently available ULGRBs as well as a synthetic population of fainter and more distant ones, which help us to determine the ECLAIRs’ redshift horizon.

        Speaker: Nicolas DAGONEAU (CEA/Saclay - IRFU/DAp/LISIS)
      • 18:20
        S. Mate: Simulation and Optimisation of Space Gamma-ray Camera SVOM/ECLAIRs : Detecting Gamma Ray Bursts and High Energy Transients 10m

        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 help of onboard trigger software (in near real-time). Due to limitations on onboard computing power, the onboard trigger uses conservative methods. Hence, an important part of the program is to develop a software tools to detect GRBs on ground with more elaborate methods. This is possible because all the detected photon events will be sent to the ground. The ground search will be used in parallel to the onboard software (to detect longer timescale / faint GRBs) as well as a substitute when the onboard trigger is switched off due to technical constraints. I'll will give a brief overview of SVOM mission in general and my PhD work which concerns the development of these ground tools. I'll cover different aspects of the work such as simulation of raw data to create near real observing scenarios (with background, non-transient X-ray sources and GRB events) and the methods we are working on to detect the GRBs in this data.

        Speaker: Sujay Mate (IRAP)
      • 18:30
        A. Mohapatra: Physical conditions in high-z CIII absorbers: origin and stability 10m

        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 derived parameters. We show L vs. [C/H] can be well reproduced if L is governed by the product of gas cooling time and sound crossing speed as expected in the case of cloud formation under thermal instabilities. As noted in the literature survivability of such cloud over longer time-scale is an issue. Therefore, studying the optically thin C III absorbers over a large z range and probably correlating their z evolution with global star formation rate density evolution can shed light to the physics of circumgalactic medium formation and evolution.

      • 18:40
        J. Muller: Airborne inter-calibration of H.E.S.S. telescopes 10m

        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 different telescopes. So far this has been done with atmospheric muons as the expected energy distribution of atmospheric muons can be well deduced from simulations. This method has numerous drawbacks, such as the impossibility of a wavelength dependent inter-calibration, which is needed for future high precision arrays such as CTA. I will talk about the first single light source inter-calibration of a Cherenkov telescope array which was performed with an LED mounted on a drone. To do this, first simulations of the situation have been run and then the actual drone flights were operated above H.E.S.S. The inter-calibration with the data taken during these flights was consistent within about 5% with the muon inter-calibration. This result could even be improved by ameliorating, among other, the treatment of the drone-telescope distance, the atmospheric absorption and the pixel boundaries.

        Speaker: Jacques Muller
    • 09:00 10:30
      Practical Sessions 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 10:30 11:00
      Coffee break 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Project: work 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 12:30 13:30
      Lunch 1h Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 16:00 17:30
      Project: Work 1h 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 17:30 18:00
      Coffee break 30m Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 18:00 19:00
      Students' presentations: Müller, Palla, Reboul-Salze,Saikia, Samuelsson Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
      • 18:00
        T. Müller: PISCoLA: Python for Interactive Supernova Cosmology Light-curve Analysis 10m

        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 the Optical and IR, the samples of SNe Ia is rapidly increasing. However, we need not to focus only on the size of the samples, but also on how we analyse these data. Cosmology with SNe Ia usually relies on templates for the light curve fits, which introduces biases due to the underlying assumptions. For this reason we created "Python for Interactive Supernova Cosmology Light-curve Analysis" (PISCoLA), a new light curve fitting tool. PISCoLA relies on Gaussian Process, a non-parametric data-drive method, letting the data "speak" for itself. We analyse the multi-color light curves with machine learning techniques to search for new parameters for the standardisation of SNe Ia and further understanding of the physics behind these explosions.

      • 18:10
        M. Palla: GRB hosts identification through chemical abundances 10m

        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 (irregulars, spirals, ellipticals) . We analysed in particular [X/Fe] abundance ratios as functions of [Fe/H]. Different galaxies are, in fact, characterised by different star formation histories, which produce different [X/Fe] ratios (“time-delay model"). This allows us to identify the morphology of the hosts and to infer their age (i.e. the time elapsed from the beginning of star formation) at the time of the GRB events. Relative to previous works, we use newer models in which we adopt updated stellar yields and prescriptions for dust production, accretion and destruction. In the sample considered we found host galaxies of all the morphological types. The calculated ages of the host galaxies span from the order of 10 Myr to little more than 1 Gyr.

      • 18:20
        A. Reboul-Salze: A global model of the magnetorotational instability in proto-neutron stars 10m

        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 this question, a three dimensional pseudo-spectral code has been used to develop a global model of the MRI in a proto-neutron star. The hypothesis of an incompressible fluid allow us to simplify at maximum the model. We compare the turbulence in the global model and in local simulations. We also show that a strength of the dipolar magnetic field consistent with the values of magnetar’s strong fields can be generated by the MRI, even though it is lower than the small scale magnetic field. Overall, the results presented in this talk support the ability of the MRI to form magnetar-like large scale magnetic fields.

      • 18:30
        P. Saikia: Lorentz factors of compact jets in black hole X-ray binaries 10m

        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 fast and how relativistic these jets are. The bulk Lorentz factor is notoriously difficult to measure, with to date only weak constraints for a few BHXBs. Here, we adopt simple models to constrain the Lorentz factor of the compact jets in several BHXBs using the amplitude of the jet fade and recovery at infrared (IR) wavelengths over state transitions. We investigate why some BHXBs have prominent IR excesses and some do not, quantified by the amplitude of the IR quenching or recovery over the transition from/to the hard state. Using the amplitude of the IR fade/recovery, known orbital parameters and simple analytical models, we constrain for the first time the Lorentz factor of compact jets in several BHXBs. We also find that the very high amplitude IR fade/recovery seen repeatedly in GX 339–4 requires a much lower inclination angle than previously expected. Our results are strongly supportive of the IR excess being produced by synchrotron emission in a relativistic outflow, and demonstrates how useful OIR monitoring of BHXB is for studying jet properties.

      • 18:40
        F. Samuelsson: The problematic connection between gamma-ray bursts (GRBs) and ultra-high energy cosmic rays (UHECR) 10m

        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 spectra and find that for standard parameters, the synchrotron flux from these electrons would be much too luminous. This result challenges both high- and low-luminosity GRBs as accelerators of UHECR.

    • 09:00 10:30
      Project Reports Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 10:30 11:00
      Coffee break 30m Amphitheatre

      Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 11:00 12:30
      Project Reports Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE
    • 12:30 13:30
      Bus transfer to Airport 1h Amphitheatre

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      Institut d’Etudes Scientifiques de Cargèse Menasina F-20130 CARGÈSE

      Note that there is no lunch on the departure day. Please prepare your lunch box/sandwhich in advance or stay hungry until we arrive at the airport in Ajaccio.

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