Cosmic Explosions 2019

27 mai 2019, 11:00 → 5 juin 2019, 14:15 Europe/Paris

Amphitheatre (Cargèse)

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 to carry out a research project in small groups 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:

https://www.azur-colloque.fr/DR04/inscription/inscription/145

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

• excursions

• ample time for using the private beach after lunch

List of speakers:

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

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.

Organisers / LOC:

Fabio Acero, Volker Beckmann, Pascale Chavegrande, Diego Götz, Karl Kosack, Jerome Rodriguez, Stephane Schanne

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

@CExplosions2019

lundi 27 mai

1 Bus Transfer Ajaccio Airport to Cargese

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.

2 Registration & room distribution

Orateurs: Diego Götz (CEA Saclay), Fabio Acero (CEA/Saclay), Karl Kosack (CEA Saclay), Volker Beckmann (CNRS / IN2P3)

18:00 Welcome Speech & Drink

mardi 28 mai

3 Theory: Radiation Processes

Orateur: Dr Renaud Belmont (IRAP)

Belmont_pdf.pdf

10:30 Coffee break

4 Theory: CRs & acceleration processes

Orateur: Dr Stefano Gabici

cosmicrays.pdf

12:30 Lunch

5 Observation: Radio

Orateur: Marta Burgay

BurgayRadioastronomy.pdf

6 Observation: IR/optical

Orateur: Mickael Rigault (LPC)

OpticalTransient_Cargèse.pdf

17:30 Coffee break

Students' presentations: Senniappan, Smirnova, Scott, Verna, Weerasekara

Président de session: Volker Beckmann (CNRS / IN2P3)

7 N. Smirnova: 3D Simulations of Pair Instability Supernovae Explosions

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.

Orateur: Nina Smirnova (LAPTh)

Smirnova_Cargese.pdf

SN_rho.mp4

SN_T.mp4

test.avi

8 M. Senniappan: Signal over Background discrimination for the ALTO observatory

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.

Orateur: Mohanraj Senniappan (Linnaeus University)

ALTO_Mohanraj.pdf

9 S. Scott: The Follow-up of Cosmic Explosions with VERITAS

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.

Orateur: Skyler Scott (UCSC)

03_Scott_The Follow-up of Cosmic Explosions with VERITAS.pdf

10 G. Verna: Searching for galactic PeVatrons with CTA

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.

Orateur: Gaia Verna

Verna.pdf

11 G. Weerasekara: The effect of peculiar motion of galaxies when calculating the gravitational lensing time delay

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.

Orateur: M. Gihan Weerasekara (University of Colombo)

05_Gihan.pdf

19:00 Welcome Cocktail

mercredi 29 mai

12 Theory: late stage of stellar evolution

Orateur: Norbert Langer

Norbert_Langer_presentation.pdf

10:30 Coffee break

13 Objects: Supernovae

Orateur: Jacco Vink (Anton Pannekoek Institute of Astronomy)

jvink_cargese_may_2019.pdf

12:30 Lunch

14 Theory: late stage of stellar evolution

Orateur: Norbert Langer

Norbert_Langer_presentation.pdf

15 Supernova Remnants (SNRs)

Orateur: Jacco Vink (Anton Pannekoek Institute of Astronomy)

17:30 Coffee break

Students' presentations: Abdalla, Aguilera-Dena, Balakina, Bugli

Président de session: Volker Beckmann (CNRS / IN2P3)

16 H. Abdalla: LIV Signatures in EBL absorption and Compton scattering

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.

1_Hassan Abdalla.pdf

17 D. R. Aguilera-Dena: Pre-explosion Core Properties of Superluminous Supernova and Long Gamma-Ray Burst Progenitors

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.

Orateur: David Ramon Aguilera Dena (Argelander Institut für Astronomie)

presentation.pdf

18 E. Balakina: Peculiar velocities of Type Ia Supernovae in clusters of galaxies

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.

3_Elena_Balakina.pdf

19 M. Bugli: The role of magnetic field topology in core-collapse supernovae

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.

Orateur: Matteo Bugli (CEA - Saclay)

cargese2019_web.pdf

20 Telescope observations

Orateurs: Nicolas DAGONEAU (CEA/Saclay - IRFU/DAp/LISIS), Stéphane Schanne (CEA Saclay)

jeudi 30 mai

21 Observations: X-rays

Orateur: Diego Götz (CEA Saclay)

Diego_Gotz_Cargese2019_X-ray.pdf

22 Observation: Gamma-rays

Orateur: Karl Kosack (CEA Saclay)

kosack-cargese-2019-gamma-rays.pdf

10:30 Coffee break

23 Objects: Gamma-Ray Bursts

Orateur: Frédéric Daigne (Institut d'Astrophysique de Paris - Université Pierre et Marie Curie)

cargese-2019-grb-daigne.pdf

12:30 Lunch

24 Observation: Neutrinos

Orateur: Véronique Van Elewyck (APC)

Neutrinos_Cargese2019.pdf

25 Observation: Gravitational Waves

Orateur: Nicolas Leroy (LAL IN2P3/CNRS)

GW_NLeroy.pdf

17:30 Coffee break

Students' presentations: Bylund, Cardillo, Chakraborty, Conte

Président de session: Diego Gotz (CEA Saclay)

26 T. Bylund: Blazar observations with the HESS telescope

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.

Bylund_2019-05-30-CosmicExplosions.pdf

27 M. Cardillo: CR and SNR love story and re-acceleration between them

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.

Orateur: Martina Cardillo (INAF-Osservatorio astronomico di Arcetri)

Cardillo_Cargese2019_3.pptx

28 S. Chakraborty: Jet inclination relative to the black hole spin for the TDE Swift J1644+57

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.

Orateur: Sudip Chakraborty (Tata Institute of Fundamental Research, Mumbai, India)

CE2019_talk_Sudip.pdf

29 F. Conte: Development of a Compact High-Energy Camera for the Cherenkov Telescope Array

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.

Orateur: Francesco Conte (Max-Planck-Institut für Kernphysik)

Conte_CE2019.pdf

30 CTA: Cargèse Telescope Array

Orateur: Stéphane Schanne (CEA Saclay)

31 CTA: Cargèse Telescope Array observations

We set up the telescope on the road towards the villa

Orateur: Stéphane Schanne (CEA Saclay)

vendredi 31 mai

32 Theory: Accretion

Orateur: Frédéric Daigne (Institut d'Astrophysique de Paris - Université Pierre et Marie Curie)

cargese-2019-accretion-daigne.pdf

10:30 Coffee break

33 Objects: Black Holes

Orateur: Prof. Sera Markoff (University of Amsterdam)

Markoff_Cargese2019_black_holes.pdf

12:30 Lunch

34 Objects: Binaries

Orateur: Prof. Sera Markoff (University of Amsterdam)

Sera Markoff Cargese 2019 slides on binaries / black holes

17:30 Coffee break

Students' presentations: Carotenuto, Diesing, Duque, Jacquemin Ide, El Mellah

Président de session: Volker Beckmann (CNRS / IN2P3)

35 F. Carotenuto: The new black hole transient MAXI J1348-630 observed through MeerKAT’s eyes

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.

Orateur: Francesco Carotenuto (Université de Paris, CEA/Saclay-Irfu/Dap/AIM)

36 R. Diesing: On the spectrum of electrons accelerated in supernova remnants

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.”

2_CosmicExplosions_Diesing.pdf

37 R. Duque: Prospects for Electromagnetic Counterparts to Neutron Star Mergers in the Gravitational Wave Era

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.

3_Duque_Cargese.pdf

38 J. Jacquemin Ide: Magnetically-driven jets and winds from MRI-active accretion disks

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.

5_Cosmic_explosion.key

39 I. El Mellah: Enhanced accretion and wind-captured discs in high mass X-ray binaries

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.

Ileyk.pdf

40 CTA: Cargèse Telescope Array

Orateur: Stéphane Schanne (CEA Saclay)

6_20190531_CargèseTelescopeAcademy.pdf

samedi 1 juin

41 Projecs: From science requirements to missions

Orateur: Henri Triou (CEA/Saclay)

From scientific requirement to a space mission Henri TRIOU 01-06-2019.pdf

10:30 Coffee break

42 Projects: Introduction

Orateurs: Fabio Acero (CEA/Saclay), Karl Kosack (CEA Saclay), Stéphane Schanne (CEA Saclay), Volker Beckmann (CNRS / IN2P3)

12:30 Lunch

43 Practical Session: "How to apply for stuff?"

• Some initial thoughts on the whole process
• Strategy/resources
• Different kinds of positions and other general advice for job hunting strategy
• How to write a good application & deal with letters of recommendation
• Group discussion (the most important part!)

Orateur: Prof. Sera Markoff (University of Amsterdam)

how2apply_cargese2019.pdf

44 Social Dinner

Dinner_Saturday.png

dimanche 2 juin

45 Social Activity: Bus tour

We meet at 2 pm down at the insitute. Then the bus passes by Cargese and you can enter also on the square in front of the Spar supermarket around 2:15 pm.

Orateurs: Karl KOSACK (CEA Saclay), Stéphane Schanne (CEA Saclay), Volker Beckmann (CNRS / IN2P3)

Bus_Cargese_Sunday.png

lundi 3 juin

46 Objects: Neutron Stars

Orateur: Marta Burgay

Burgay_NeutronStar.pdf

10:30 Coffee break

47 Practical Sessions

12:30 Lunch

48 Project: work

17:30 Coffee break

Students' presentations: Lescaudron, Dagoneau, Mate, Mohapatra, Muller

49 S. Lescaudron: Black holes spin evolution in merging galaxies

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.

BH_Lescaudron.pdf

Densite_AxeX.mp4

Stochastic_Density.mp4

50 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.

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.

Orateur: Nicolas Dagoneau (CEA/Saclay - IRFU/DAp/LISIS)

CosmicExplosion_Dagoneau.pptx

Detection capability of Ultra-Long Gamma-Ray Bursts with the ECLAIRs telescope aboard the SVOM mission

SVOM White Paper

51 S. Mate: Simulation and Optimisation of Space Gamma-ray Camera SVOM/ECLAIRs : Detecting Gamma Ray Bursts and High Energy Transients

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.

Orateur: Sujay Mate (IRAP)

Cosmic Explosions 2019.pptx

52 A. Mohapatra: Physical conditions in high-z CIII absorbers: origin and stability

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.

Orateur: Abhishek Mohapatra (NIT Rourkela, India)

Mohapatra_A.pdf

53 J. Muller: Airborne inter-calibration of H.E.S.S. telescopes

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.

Orateur: Jacques Muller

Presentation_Cargese.pdf

54 Students' BBQ

For students only!

mardi 4 juin

55 Objects: Coalescence

Orateur: Edward Porter (APC / CNRS / IN2P3)

Porter_GWs_CE na.pdf

10:30 Coffee break

56 Project: work

projects.pdf

12:30 Lunch

57 Project: Work

17:30 Coffee break

Students' presentations: Müller Bravo, Palla, Reboul-Salze,Saikia, Samuelsson

Président de session: Volker Beckmann (CNRS / IN2P3)

58 T. Müller: PISCoLA: Python for Interactive Supernova Cosmology Light-curve Analysis

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.

Orateur: Tomas Müller Bravo (University of Southampton)

Low OrBit Survey Titan Extra-terrestrial Radio array (LOBSTER).pdf

Muller_Cosmic_Explosions_2019v2.pdf

59 M. Palla: GRB hosts identification through chemical abundances

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.

Orateur: Marco Palla (Università degli Studi di Trieste)

palla_cargese2019.pdf

60 A. Reboul-Salze: A global model of the magnetorotational instability in proto-neutron stars

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.

Orateur: Alexis Reboul-Salze (CEA Saclay)

Reboul_Salze_Cargese_2019_presentation.pdf

61 P. Saikia: Lorentz factors of compact jets in black hole X-ray binaries

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.

Orateur: Payaswini Saikia (Nyuad)

Payaswini_Saikia_Cargese.pdf

62 F. Samuelsson: The problematic connection between gamma-ray bursts (GRBs) and ultra-high energy cosmic rays (UHECR)

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.

Orateur: Filip Samuelsson (KTH Royal Institute of Technology)

5_Samuelsson_Cargese_2019.pdf

mercredi 5 juin

63 Empty your room before the lecture

You need to leave your room before the lecture:
- use a broom if necessary
- leave your key on the table in the room
- bring your luggage to the lobby

Project Reports: CHEAP, GROOT, SEXI, and LOBSTER

Président de session: Volker Beckmann (CNRS / IN2P3)

64 The CHEAP-Hunter project (Compact High-Energy Ambitious Pion-bump Hunter )

Orateurs: Francesco Conte (Max-Planck-Institut für Kernphysik), Gaia Verna, Martina Cardillo (INAF-Osservatorio astronomico di Arcetri)

1_CHEAP_Project.pptx

65 GROOT (Gamma-Ray Observatory using Onboard Telescopes): Precise all-sky GRB localisation

Orateurs: Fiona Murphy-Glaysher (LJMU), Jacques Muller, Mohanraj Senniappan (Linnaeus University), Skyler Scott (UCSC)

3_GROOT.pptx

66 SEXI: Imaging of XRB disks and outflows

Orateurs: Jean-Grégoire Ducoin (LAL - Virgo), Nicolas DAGONEAU (CEA/Saclay - IRFU/DAp/LISIS)

2_SEXI_XRB_imaging.pdf

67 LOBSTER: Low OrBit Survey Titan Energetic Radio array

Orateurs: Filip Samuelsson (KTH Royal Institute of Technology), Tomas Müller Bravo (University of Southampton)

4_LOBSTER_Low_OrBit_Survey_Titan_Extra-terrestrial_Radio_array.pdf

10:30 Coffee break

Project Reports: uGMRT, AMBREE, and MICROSCOPE

Président de session: Volker Beckmann (CNRS / IN2P3)

68 uGMRT+

Orateur: Payaswini Saikia (Nyuad)

5_uGMRT1.pdf

69 AMBREE: Astronomical Moon Based Radio Emission Experiment

Orateurs: Alexis Reboul-Salze (CEA Saclay), David Ramon Aguilera Dena (Argelander Institut für Astronomie), Matteo Bugli (CEA - Saclay)

6_AMBREE.pdf

70 MICROSCOPE: MICROSatellite-based COsmic Polarization Explorer

Orateurs: Nina SMIRNOVA (LAPTh), Sudip Chakraborty (Tata Institute of Fundamental Research, Mumbai, India), Sujay Mate (IRAP)

7_MICROSCOPE_X-ray polarization mesuarment mission.pdf

71 Students' project awards

CHEAP one the prize for the best project idea and presentation.
SEXI LOBSTER share the phantasy prize for most imaginiative project ideas (which are slightly off the feasibility track).

12:15 Bus transfer to Airport

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.