Slide2:
One of the brightest sources observed by INTEGRAL, an X-ray binary and microquasar GRS 1915+105, was extensively studied by the HESA group at the Observatory, University of Helsinki. This source contains a black hole weighing more than 10 Solar masses and a red giant star (upper left: artist’s impression of GRS 1915+105). Part of the hot gas spiralling in towards the black hole is expelled into a two-sided jet moving away from the system close the to speed of light, which is typical for Galactic microquasars. INTEGRAL observations of GRS 1915+105, carried out in March 2003, revealed a new phenomenon: an X-ray pulse repeating in about a 5 minute cycle (lower left: X-ray light curve showing the pulsations). Probably the pulse represents a new type of instability in the disk of gas surrounding the black hole.
In the very same images a new transient gamma-ray source close to GRS 1915+105 appeared during the March 2003 observations. This source, called IGR J19140+09, is clearly seen in the right-hand side image.
Further images at visible light and infrared wavelengths have been obtained to reveal whether this source is another X-ray binary, perhaps similar to GRS 1915+105. Microquasar studies with the INTEGRAL satellite
Slide3:
In this superb gamma-ray image obtained with INTEGRAL we see numerous powerful energy sources in the central region of our Galaxy. The nucleus of the Galaxy, located at the zeropoint of the coordinate grid, is believed to hide a giant black hole, perhaps a few million times more massive than our Sun. In this image, however, most of the sources are much less massive X-ray binaries, where a compact star (a neutron star or black hole) and a mass losing normal star orbit each other. The gas of the companion falls in towards the compact star and heats up to millions of degrees. As a result the gas radiates X- and gamma-rays in the strong gravitational field of the compact star.
The HESA group (Observatory, Univ. of Helsinki) participates actively in the INTEGRAL studies of the Galactic X-ray binaries. Powerful energy sources in the Galactic centre
Slide4:
X-ray binaries are often very small as compared, for example, to our Solar system. The components of an X-ray binary make one full orbital cycle in a matter of hours or days at most. In this image we see the relative sizes of several X-ray binaries on the same scale with the distance between the Sun and the planet Mercury. The mass-losing companion star is always to the right, and the black hole with the surrounding disk of gas to the left.
Despite their small size X-ray binaries can produce energy even a million times more efficiently than our Sun. X-ray Binaries: tiny but extremely powerful Credit: Jerome A. Orosz
Slide5:
The HESA group (Observatory, Univ. of Helsinki) was actively involved in the INTEGRAL studies of the puzzling X-ray binary Cyg X-3. This source has effectively eluded all attempts to study its characteristics in detail due to its thick cocoon of dust, expelled by the giant companion star. However, energetic gamma-rays originating close to the compact star can more easily penetrate the cocoon and uncover the core of the binary system. On the right-hand side we see an INTEGRAL gamma-ray image from the constellation Cygnus. The bright dot at lower right is a massive X-ray binary Cyg X-1, whereas the fainter source to the upper left is Cyg X-3. The diagram on the left-hand side presents results from joint observations of INTEGRAL and another X-ray satellite. The diagram shows the X-ray intensity (vertical axis) versus energy (horizontal axis), and the colors denote observations obtained at different epochs.
This result resembles very much the observations of GRS 1915+105, which is a Galactic microquasar containing a more than 10 Solar mass black hole. Hence, we believe that the compact star in Cyg X-3 is most probably a black hole too. New evidence of a black hole in an enigmatic X-ray binary