On the Planet and the Disk of CoKuTau/4

Spitzer observations of the young star CoKuTau/4 reveal a disk with a 10 AU hole that is most likely caused by a newly formed planet. Assuming that the planet opened a gap in the viscous disk, we estimate that the planet mass is greater than 0.1 Jupiter masses. This estimate depends on a lower limit to the disk viscosity derived from the time scale needed to accrete the inner disk, creating the now detectable hole. The planet migration time scale must at least modestly exceed the time for the spectrally inferred hole to clear. The proximity of the planet to the disk edge implied by our limits suggests that the latter is perturbed by the nearby planet and may exhibit a spiral pattern rotating with the planet. This pattern might be resolved with current ground based mid-infrared cameras and optical cameras on the Hubble Space Telescope. The required sub-Myr planet formation may challenge core accretion formation models. However, we find that only if the planet mass is larger than about 10 Jupiter masses, allowing for a high enough surface density without inducing migration, would formation by direct gravitational instability be possible.Comment: Submitted to ApJ

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.The French contribution to X-IFU is funded by CNES, CNRS and CEA. This work has been also supported by ASI (Italian Space Agency) through the Contract 2019-27-HH.0, and by the ESA (European Space Agency) Core Technology Program (CTP) Contract No. 4000114932/15/NL/BW and the AREMBES - ESA CTP No.4000116655/16/NL/BW. This publication is part of grant RTI2018-096686-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This publication is part of grant RTI2018-096686-B-C21 and PID2020-115325GB-C31 funded by MCIN/AEI/10.13039/501100011033

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged).Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editin

L'instabilité d'accrétion-éjection dans les disques d'accrétion magnétisés d'étoiles compactes

The major problem is accretion physics come from the origin of angular momentum transfer in the disk. My PhD deal with a mechanism (the Accreation-Ejection Instability, AEI) able to explain and link together accretion in the inner region of the disk and ejection. This instability occurs in magnetized accretion disk near equipartition with gas pressure. We first study the impact of some relativistic effects on the instability, particularly on the m = 1 mode. And compared the results with the Quasi-Periodic Oscillation (QPO) observed in microquasars. In the second part we study analytically and numerically the Alfven wave emission mechanism which re-emit the angular momentum and energy taken from the inner region of the disk into the corona. The last part deals with MHD numerical simulation. First of all a 2D non linear disk simulation which contribute to QPO modelisation. The last chapter is about a beginning collaboration on 3D simulation in order to study the Alfven wave emission in the corona.Le problème majeur de la physique de l’accrétion est l’origine du transport du moment angulaire dans le disque, et son lien avec les jets. Cette thèse porte sur un mécanisme (l’instabilité d’Accrétion-Ejection, AEI), non seulement à même d’expliquer l’accrétion dans la partie la plus interne du disque et de la relier aux éjections. Cette instabilité se produit dans des disques modérément magnétisés. La première partie est consacrée à l’étude de certains effets relativistes sur l’instabilité, et à la comparaison avec les Oscillations Quasi- Périodiques des micro-quasars à partir d’observations existantes et nouvelles. La seconde partie de ce travail a consisté en l’étude, à la fois analytique et numérique, du mécanisme par lequel l’AEI ré-émet vers la couronne du disque, sous forme d’ondes d’Alfvén, l’énergie et le moment angulaire qu’elle extrait du disque : ce mécanisme est donc une explication possible pour le lien entre accrétion et éjection. La dernière partie traite des différentes simulations numériques liées à l’instabilité. Tout d’abord des simulations MHD 2D du disque d’accrétion qui contribuent à la modélisation des Oscillations Quasi-Périodiques, puis un dernier chapitre consacré au projet de simulation 3D de la couronne afin d’étudier les ondes d’Alfven provenant de cette instabilité

Impact of the QPO models on the pulse profile

International audienceQuasi-periodic oscillations (QPO) are an important probe of the timing properties of black-hole binaries. Many models are proposed in order to account for these features and it is difficult to differentiate them with current data. Here we aim to look at the actual pulse profile from each model in order to see how they could be differentiated and what kind of sources are the best targets for such a test. We consider three classes of simple models: elongated hot spots, tori and spirals. We perturb the equilibrium temperature of a thin disk to create these structures. The perturbed disk is supposed to emit blackbody radiation at the local temperature. Radiation is ray-traced in the Schwarzschild metric to a distant observer. We study the dependency with the source inclination of the pulse profile for different frequencies for these three models. The departure from a pure sinusoid of certain models at high inclination will be visible in the power density spectra by a higher presence of harmonics. In particular, hot spots and spirals lead to a (complete or partial) harmonic series which is lacking for a radially oscillating tori. We conclude that analyzing the first harmonics of the dominant power density spectrum peak for high-inclination sources is an interesting probe and it might make it possible to differentiate between axisymmetric (tori) and non-axisymmetric (hotspots and spirals) models

Impact of the QPO models on the pulse profile

International audienceQuasi-periodic oscillations (QPO) are an important probe of the timing properties of black-hole binaries. Many models are proposed in order to account for these features and it is difficult to differentiate them with current data. Here we aim to look at the actual pulse profile from each model in order to see how they could be differentiated and what kind of sources are the best targets for such a test. We consider three classes of simple models: elongated hot spots, tori and spirals. We perturb the equilibrium temperature of a thin disk to create these structures. The perturbed disk is supposed to emit blackbody radiation at the local temperature. Radiation is ray-traced in the Schwarzschild metric to a distant observer. We study the dependency with the source inclination of the pulse profile for different frequencies for these three models. The departure from a pure sinusoid of certain models at high inclination will be visible in the power density spectra by a higher presence of harmonics. In particular, hot spots and spirals lead to a (complete or partial) harmonic series which is lacking for a radially oscillating tori. We conclude that analyzing the first harmonics of the dominant power density spectrum peak for high-inclination sources is an interesting probe and it might make it possible to differentiate between axisymmetric (tori) and non-axisymmetric (hotspots and spirals) models

Reproducing the correlations of the C low-frequency quasi-periodic oscillation parameters in XTE J1550-564 with a spiral structure

International audienc

Impact of the QPO models on the pulse profile

International audienceQuasi-periodic oscillations (QPO) are an important probe of the timing properties of black-hole binaries. Many models are proposed in order to account for these features and it is difficult to differentiate them with current data. Here we aim to look at the actual pulse profile from each model in order to see how they could be differentiated and what kind of sources are the best targets for such a test. We consider three classes of simple models: elongated hot spots, tori and spirals. We perturb the equilibrium temperature of a thin disk to create these structures. The perturbed disk is supposed to emit blackbody radiation at the local temperature. Radiation is ray-traced in the Schwarzschild metric to a distant observer. We study the dependency with the source inclination of the pulse profile for different frequencies for these three models. The departure from a pure sinusoid of certain models at high inclination will be visible in the power density spectra by a higher presence of harmonics. In particular, hot spots and spirals lead to a (complete or partial) harmonic series which is lacking for a radially oscillating tori. We conclude that analyzing the first harmonics of the dominant power density spectrum peak for high-inclination sources is an interesting probe and it might make it possible to differentiate between axisymmetric (tori) and non-axisymmetric (hotspots and spirals) models