News 2008

Feb 08, 2008
Ultra-compact detectors for high energy Astrophysics

A innovative hard X-ray camera X with excellent performances has been realized and tested at CEA. Result of three years of studies, this ultra-compact camera, called Caliste 64, is able to detect photons between 2 and 250 keV and therefore fills a gap between two domains, the low X-ray  and the gamma ray energy bands. Its peculiar design and its integrated electronic lead to excellent performances in term of imaging and spectroscopic capabilities. This opens a new window for high energy Astrophysics. The focal plane of the futur mission Simbol-X will be equiped with this new camera while the instrument Eclairs onboard the SVOM satellite will use its readout electronic module.

Apr 16, 2008
The MIRIM-OB instrument for JWST passed the test

The realization of MIRIM-OB, the optical bench of MIRI (Mid Infra Red Imager), one of the four instruments which will equip the forthcoming space telescope JWST has just completed an essential step with the demonstration that it fulfills the various and rigorous constraints imposed by its use in space. The exam, called the "Qualification Review", which included vibration-proof, temperature holding and survival against the various radiation hazards appropriate to the environment in space, was carried out in conjunction with specialists from the contract management agencies. This process being successfully completed it now allows the construction of the instrument which will be attached to the focal plane of JWST, whose launch date is expected for 2013.

Sep 29, 2008
No planets around Sirius ?

Sirius, the brightest star of the sky, is reported to have shown a change of colour, a possibility that has led some scientists to suspect a possible but yet undetected small companion.
Now using a specific mask and the modern technique of adaptive optics which allows to suppress most of the blurring of the atmosphere, Jean-Marc Bonnet-Bidaud and Eric Pantin of the C.E.A. Astrophysical Department have obtained the first and most sensitive image of the Sirius field, in the infrared domain. It is in this energy range that the smallest stars and even planets can be most easily detected.
The new image, despite its high spatial resolution (0,2 arcsecond) and superior contrast, does not reveal any other companion than the already known white dwarf Sirius-B. The limiting mass is that of a massive planet so that at least no big planets orbit Sirius.
The image also provides the first measurements of Sirius-B infrared fluxes and yields some surprise. It reveals a possible small infrared excess that may indicate the existence of circumstellar material around the white dwarf. Though still to be confirmed by further observations this may show that if planets exist around Sirius, it could be only planetary debris around Sirius-B, as already observed around other white dwarfs.
The results are published in the October issue of the Astronomy and Astrophysics Journal.

 

Images Images Audio Podcast J.M. Bonnet-Bidaud
  with Ciel&Espace Radio (in french)
Video Video-Animation
(fichier MOV 4.3 Mo)
Apr 16, 2008
The MIRIM-OB instrument for JWST passed the test

The realization of MIRIM-OB, the optical bench of MIRI (Mid Infra Red Imager), one of the four instruments which will equip the forthcoming space telescope JWST has just completed an essential step with the demonstration that it fulfills the various and rigorous constraints imposed by its use in space. The exam, called the "Qualification Review", which included vibration-proof, temperature holding and survival against the various radiation hazards appropriate to the environment in space, was carried out in conjunction with specialists from the contract management agencies. This process being successfully completed it now allows the construction of the instrument which will be attached to the focal plane of JWST, whose launch date is expected for 2013.

Nov 17, 2008
Dense electron clouds around neutron stars.

Neutron stars are the most magnetized objects in our Universe. Some of them, dubbed "Magnetars" have a record magnetic field of 1011 Tesla (T), which corresponds to one million of billions times that of the Sun during a quiescent phase. It's around this class of objects that an over-density of electrons has been discovered. These results, delivered by an international team of researchers that includes Diego Götz from the Service d'Astrophysique of CEA-Irfu, is the result of a careful analysis of the X-ray emission observed with the satellites of the European Space Agency (ESA) XMM-Newton and INTEGRAL. The enormous battery represented by the highly magnetized neutron stars provides its magnetosphere with electrons in a much efficient way, with respect to other neutron stars. These physical phenomena, completely inaccessible in laboratory experiments due to the enormous magnetic fields required, allow to better understand the behavior of matter in extreme conditions. This work has been published by The Astrophysical Journal, and has been the object of a press release by ESA.

Sep 29, 2008
No planets around Sirius ?

Sirius, the brightest star of the sky, is reported to have shown a change of colour, a possibility that has led some scientists to suspect a possible but yet undetected small companion.
Now using a specific mask and the modern technique of adaptive optics which allows to suppress most of the blurring of the atmosphere, Jean-Marc Bonnet-Bidaud and Eric Pantin of the C.E.A. Astrophysical Department have obtained the first and most sensitive image of the Sirius field, in the infrared domain. It is in this energy range that the smallest stars and even planets can be most easily detected.
The new image, despite its high spatial resolution (0,2 arcsecond) and superior contrast, does not reveal any other companion than the already known white dwarf Sirius-B. The limiting mass is that of a massive planet so that at least no big planets orbit Sirius.
The image also provides the first measurements of Sirius-B infrared fluxes and yields some surprise. It reveals a possible small infrared excess that may indicate the existence of circumstellar material around the white dwarf. Though still to be confirmed by further observations this may show that if planets exist around Sirius, it could be only planetary debris around Sirius-B, as already observed around other white dwarfs.
The results are published in the October issue of the Astronomy and Astrophysics Journal.

 

Images Images Audio Podcast J.M. Bonnet-Bidaud
  with Ciel&Espace Radio (in french)
Video Video-Animation
(fichier MOV 4.3 Mo)
Jan 10, 2008
INTEGRAL discovers a factory of positrons in the Milky Way (10 January 2008)

Surprisingly, an asymmetry in the distribution of antimatter in the central regions of our Galaxy has just been discovered. By adding all scientific data acquired since five years by the spectrometer SPI aboard the INTEGRAL satellite, a European research group, including scientists from the Service d'Astrophysique at CEA-IRFU , has observed a gamma-ray photon emission of an energy of 511 keV, which is characteristic for the annihilation of electrons and their antimatter particles, the positrons. The researchers could determine the morphology of the 511 keV emission in the central regions of our Galactic disk, which reveals to be asymmetric and very similar to the distribution of a certain type of X-ray binary sources. For some time already these objects are thought to be efficient factories for positron production, and could explain the origin of these antimatter particles in the central regions of our Galactic disk. This work has been published in the scientific journal Nature on January 10th, 2008.

 

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