Atelier API "Ondes gravitationnelles et objets compacts"

16 nov. 2023, 09:00 → 17 nov. 2023, 18:00 Europe/Paris

salle du château (Observatoire de Paris - site de Meudon)

L'atelier annuel de l'action incitative "ondes gravitationnelles et objets compacts" aura lieu du 16 au 17 novembre 2023 dans la salle de conférence du château de Meudon.

L'atelier est organisé autour d'une session de type "hands-on" visant à diffuser l'expertise sur des outils ciblés (Black Hole Perturbation Toolkit cette année), des contributions orales plus "classiques", tout en laissant du temps pour les discussions.

Orateur invité:

• Niels Warburton (University College Dublin, Ireland) : Black Hole Perturbation Toolkit
   

plan_meudon_291117-1200_lowres.pdf

jeudi 16 novembre

09:30 → 10:00 Presentations: collaborations - tools

09:30 Virgo and ET at Paris Observatory

Orateur: Jérôme Novak (LUTH, CNRS - Observatoire de Paris)

VirgoET.pdf

09:50 Observatoire numérique e-Novas

Orateur: Raphaël Mignon-Risse (CNES/APC)

10:00 → 10:40 Presentations: contributed

10:00 Signatures of circumbinary disks around pre-merger binary black holes

Despite the re-birth of multi-messenger astronomy, no unambiguous electromagnetic (EM) counterpart to binary black hole (BBH) pre-/post-merger has been reported. Detecting the EM pre-merger counterpart would allow for optimal follow-up. However, the accretion properties onto pre-merger BBHs and EM signatures are not firmly identified because few numerical codes are able to model accretion and emission around BBHs in General Relativity (GR). Instead, the luminosity is often assumed to be proportional to the mass accretion rate, hence neglecting any relativistic effect.

In this talk, I will present recent results obtained with e-NOVAs ("extended Numerical Observatory for Violent Accreting systems"), a GRMHD+GR ray-tracing code recently extended to dynamical spacetimes and now incorporating an analytical BBH spacetime. Using e-NOVAs, I will study a BBH circumbinary disk evolution and its EM observables. I will briefly present the accretion structures that could potentially help us distinguishing BBHs. I will show that their EM lightcurve is modulated by non-axisymmetric structures orbiting in the disk, with special relativistic effects such as relativistic beaming amplifying the modulations' amplitude. Thus, the amplitude depends on the source inclination and occurs on the orbital timescales linked to these structures, rather than on the accretion rate variation timescales. These timing signatures can be used from now on: the binary black holes hunt is open.

Orateur: Raphaël Mignon-Risse (CNES/APC)

Mignon-Risse_AI_slides.pdf

10:20 A census of compact objects in Galactic X-ray binaries

X-ray binaries are stellar systems that undergo mass transfer between a normal star and a compact object. They are ideal candidates to be the progenitors of double compact binaries that end up merging in a burst of gravitational waves. Evolutionary mechanisms such a supernova events or the common envelope phase have a crucial impact on the likelyhood of such binaries to merge in Hubble time.

I will present a complete census of the X-ray binaries known in the Milky Way, in the form of two catalogues dedicated to high-mass and low-mass systems. I will show how all this data can inform us on the past history of X-ray binaries (natal kick, birthplace and age), as well as the current (LVK) and future (LISA) gravitational landscape. This work consitutes a tool that could be used in population synthesis models to better link the current population of compact objects in X-ray binaries to the population of compact mergers that are and will be detected in the coming years.

Orateur: Francis Fortin (IRAP)

2023-11-16_Atelier-GW-COs_COs_in_Galactic_XRBs.pdf

10:40 → 11:10 Pause: café

11:10 → 12:30 Discussion session: Discussions

12:30 → 14:00 Pause: déjeuner

14:00 → 15:30 Hands-on session: BH perturbation toolkit

15:30 → 16:00 Pause: café

16:00 → 17:30 Hands-on session

vendredi 17 novembre

09:30 → 10:20 Presentations: collaborations - tools

09:30 LISA at Paris Observatory

Orateur: Adrien Bourgoin (SYRTE, Observatoire de Paris)

LISA_SYRTE.pdf

09:50 KADATH

Orateur: Philippe Grandclement (CNRS ; Observatoire de Paris)

pres_kadath.pdf

10:10 GRAVITY

Orateur: Karim Abd El Dayem (Observatoire de Paris (LESIA))

10:20 → 10:40 Presentations: contributed

10:20 Relativistic effects on the orbit of the closest stars to the black hole at the center of the Galaxy

In this presentation we investigate the detection of the angular momentum (or spin) and quadrupole moment of the black hole at the center of the galaxy called Sgr A. These parameters affect the astrometric and spectroscopic observations of stars in the close vicinity of the black hole (S stars). Here, we consider a collection of S stars as well as a
putative star called S2/10 that is identical to S2 but 10 times closer to Sgr A, and thus much more affected by the spin effects. Such a star might exist if it is too faint to have been already detected by GRAVITY. It is possible that either future observations of this instrument, or of its update GRAVITY+ that is under development, might detect such a faint inner star. In order to reach our objectives, we use the different relativistic models in order to generate the orbit and radial velocity of the S stars and analyze how they can be affected by the spin and quadrupole moment of Sgr A*. This, allows us to affirm the detectability of these quantities which will enable us to test the no-hair theorem and thus general relativity.

Orateur: Karim Abd El Dayem (Observatoire de Paris (LESIA))

API_OGOC_Karim.pdf

10:40 → 11:10 Pause: café

11:10 → 12:50 Presentations: contributed

11:10 Study of photon rings in the images of black holes

The Event Horizon Telescope (EHT) collaboration released in 2019 the first horizon-scale images of the supermassive black hole M87*, dominated by a bright, unresolved ring. General relativity (GR) predicts that embedded whitin this images lie observable, thin, ring-shaped features produced by photons on extremely bent orbits: the "photon rings".
In a parametric framework of GR, the idea of this study is to consider these predicted photon rings and to analyse their dependence on the choice of the metric and on the emission process of the matter orbiting around the black hole.
The images are produced using numerical simulations of the electromagnetic radiation, and the features of interest are then retrieved via an additional data analysis code.

Orateur: Irene Urso (LESIA, Paris Observatory)

API_Urso.pdf

11:30 Towards a more robust algorithm for computing the Kerr quasinormal mode frequencies

Leaver's method has been the standard for computing the quasinormal mode (QNM) frequencies for a Kerr black hole (BH) for a few decades. We start with a spectral variant of Leaver's method introduced by Cook and Zalutskiy (arXiv: 1410.7698) and propose improvements in the form of computing the necessary derivatives analytically, rather than by numerical finite differencing. We also incorporate this derivative information into qnm, a Python package which finds the QNM frequencies via the spectral variant of Leaver's method. We confine ourselves to first derivatives only.

Orateur: Sashwat Tanay (LUTH, Paris Observatory)

sashwat_tanay.pdf

11:50 The gravitational-wave phase at 4.5PN

The main observable for the detection of gravitational waves in general relativity generated by compact binary systems is the phase of the wave. Within the post-Newtonian approximation, where the objects are assumed to be well-separated and to have small velocities, one can obtain analytical expressions for the phase as a series in $(v/c)^2$. Before this work, the phase (as well as the complete waveform) was known up to 3.5 post-Newtonian (PN) order. In this talk, I will discuss our recent computation of the flux and phase at 4.5PN order, as well as the $(\ell,m)=(2,2)$ mode at 4PN order. I will then give a brief overview of the tails-of-memory computation, which was a difficult but crucial step of the computation. Finally, I will discuss what is needed to obtain all the $(\ell,m)$ modes entering the 4PN waveform, and how the tail-of-memory methodology will be central to it.

Orateur: David Trestini (IAP et LUTH)

Presentation API.pdf

12:10 ET-WST synergy for next generation multi-messenger observations

The Einstein Telescope (ET) will be an innovative next generation gravitational wave (GW) interferometer. With ET it will be possible to detect thousands of binary neutron star systems mergers (BNS) per year, up to z>3. The corresponding electromagnetic (EM) counterparts will likely be faint and to be searched in the large error regions of ET GW signals. Beyond the detection, the bottle neck of multi-messenger (MM) science will be to gather spectroscopic data to identify and characterize EM counterpart candidates. Integral Field Spectroscopy and Multi-Object Spectroscopy, traditionally used for galaxy surveys, can play a key role to achieve this goal. I will talk about the study that I am carrying out on the synergy of ET and the Wide-field Spectroscopic Telescope on the next generation MM observations. I will present the results of the predictions of spectroscopic observations of kilonovae and gamma-ray burst afterglows associated to simulated BNS events detected by ET.

Orateur: Sofia Bisero (GEPI, Observatoire de Paris, Université PSL, CNRS)

APIatelier_BISERO.pdf

12:30 AGN interferometric observations to measure cosmological distances

The AGN MELBA project aims to construct a precise multi-scale and multi-wavelength model of nearby AGNs by combining various high angular resolution adaptive optics and interferometric observations. A crucial goal of this project is to enhance the "SARM method", which allows for the measurement of cosmological distances independently from classical methods.

I will provide an overall presentation of the project while emphasizing my contribution, which involves developing a new image reconstruction algorithm that improves the quality of adaptive optics and interferometric images of nearby AGNs.

Orateur: Pierre Vermot (LESIA)

Pres_Vermot.pdf

12:50 → 14:20 Pause: déjeuner