PhD subjects

3 sujets IRFU

«««

• Astrophysics

A study of high energy emissions in microquasars: a spectro-polarimetric approach

SL-DSM-15-0006

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Jérôme RODRIGUEZ

CEA
DSM/IRFU/SAp/LEPCHE

Starting date : 01-10-2015

Contact person :

Jérôme RODRIGUEZ

CEA - DSM/IRFU/SAp/LEPCHE

01 69 08 98 08

Thesis supervisor :

Jérôme RODRIGUEZ

CEA - DSM/IRFU/SAp/LEPCHE

01 69 08 98 08

Accretion-ejection coupling in microquasars

SL-DSM-15-0131

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Stéphane CORBEL

Université Paris 7
LEPCHE

Starting date : 01-10-2014

Contact person :

Stéphane CORBEL

Université Paris 7 - LEPCHE

01 69 08 45 62

Thesis supervisor :

Stéphane CORBEL

Université Paris 7 - LEPCHE

01 69 08 45 62

X-ray binairies with jets (aka microquasars) are excellent laboratories to probe the physics

in extreme environments. They consist of a "normal" companion star and a compact object

(either a neutron star or a black hole). We have, over the past years, shown that relativistic

jets are able to cary a large amount of the accretion energy. This finding has been made

possible thanks to the broad band study (much beyond the radio domain where they are

predominantly seen) of the emission of jets. Understanding these phenomena necessarily requires

multi-wavelength observations and, therefore, a large panel of tasks to perform.



Accretion is the most efficient energy source of the Universe and is seen in a large variety of celestial sources: from the early stages of star formation to active galactic nuclei. Thanks to their variability on "human" time scale (ie fraction of second to days), microquasars allow us to perform a dynamical study of the accretion-ejection coupling by observations mainly done in the X-ray and radio domains. Given the universality of the accretion-ejection, understanding microquasars, will allow a large panel of celestial objects to be understood.



The goal of the thesis is to systematically study muti-wavelength observations of a sample of microquasars mainly in the X-ray and radio domains. Spectral and temporal aspects will be investigated over the totality of their outburst. The parameters (frequency, températures, ...) will then be compared to the theoretical predictions of the models developed by the collaborators of our team.
Binary systems: formation, evolution and environment

SL-DSM-15-0070

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Sylvain CHATY

Université Paris Diderot et Institut Universitaire de France
LEPCHE/Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Starting date : 01-10-2015

Contact person :

Sylvain CHATY

Université Paris Diderot et Institut Universitaire de France - LEPCHE/Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

01 69 08 43 85

Thesis supervisor :

Sylvain CHATY

Université Paris Diderot et Institut Universitaire de France - LEPCHE/Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

01 69 08 43 85

More : http://plus.wikimonde.com/w/index.php?title=Sylvain_Chaty

More : http://irfu.cea.fr/Sap/

Massive stars live in pair...

A recent study shows that more than 70% of massive stars live in a stellar pair (Sana et al. 2012). This binarity has a major impact on the stellar evolution, strongly influenced by the presence of a "companion" star, especially via the transfer of material, angular momentum, and presence of intense stellar winds (Chaty 2013).

The fate of pairs of massive stars is determined by the evolution of each component, the most massive collapsing first in the supernova explosion, giving rise to a neutron star or a black hole (Tauris & van den Heuvel, 2006). This is the birth of a compact binary system -a compact object orbiting the companion star-, probably the most fascinating objects in the Universe. The compact object, immersed in the intense stellar wind of the massive companion star, attracts and accretes part of this wind, which accumulates on the surface, heated to temperatures of several million degrees, emitting mainly in X-rays. These celestial objects are subject to extreme variations in brightness, of several orders of magnitude on scaletime ranging from seconds to months.



... and influence their environment!

On one hand, it is now well established that the collapse of massive stars in supernova plays a key role in the enrichment of interstellar medium -from heavy atoms to complex molecules-, as well as in triggering the formation of new stars. On the other hand, the study of impact and feedback from massive stars on their environment throughout their life, has long been neglected, and remains largely unknown. However, all the material ejected through the stellar wind, and not intercepted by the compact object, is dispersed into the surrounding environment, thus colliding with a dense interstellar medium, potentially triggering new starbirth, as indicated by our recent observations with the Herschel satellite (Chaty et al. 2012 Coleiro et al. 2014).



This PhD thesis, covering many fields of Astrophysics, proposes to study the formation of pairs of massive stars, whose role is essential for the cycle of matter in galaxies, along with their evolution, and the impact on their environment, based on multi-wavelength observations.
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