Press Release

New Data on Composition of Relativistic Jets from Black Holes

By SpaceRef Editor
December 2, 2013
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It is known that black holes launch relativistic jets both in stellar-mass binary systems and at the centers of galaxies, in the so-called ‘quasars’. Although jets have been studied for decades, their composition has remained uncertain. Now, a work, published in Nature and led by researchers from the University of Barcelona (UB, Spain), the German headquarters of the European Southern Observatory (ESO), and Curtin University (Australia), presents the detection of atomic nuclei in the relativistic jets from the black hole binary system 4U 1630-47.

“In this work, we have found the composition of relativistic jets launched from around black holes; however, more studies are needed to understand if results can be extrapolated to other relativistic jet sources,” explains Simone Migliari, from the Institute of Sciences of the Cosmos of the UB (ICCUB). According to the researcher, the research proves that relativistic jets might be ‘heavy jets’ containing atomic nuclei, rather than ‘light jets’ consisting of electrons and positrons only.” “The finding — he adds — implies that ‘heavy jets’ carry away significantly more energy from the black hole than ‘lighter’ ones.”

Such baryonic jets, composed by heavy matter, are more likely to be powered by the accretion disc rather than the spin of the black hole. “If baryons can be accelerated to relativistic speeds, these systems should be strong sources of gamma rays and neutrino emission,” concludes Migliari.

Black holes in binary systems catch companions’ matter in order to create a disc that rotates around the black hole at high speed. Consequently, matter is compressed and it gets hot enough to emit X-rays. The research also provides an accurate estimate of the speed of the jets, which was found to be 2/3 of the speed of light, by detecting the presence of Fe [iron] atomic nuclei in Doppler-shift.

In 2012, observations were done nearly simultaneously by means of two types of facilities: on one hand, the telescopes XMM-Newton of the European Space Agency, which enable to perform X-ray observations in order to observe the disc that surrounds the black hole; and on the other hand, the Australia Telescope Compact Array (ATCA), used to carry out radio observations to see the relativistic jet.

Concerning the relevance of the work published in Nature, it is important to highlight that 4U 1630-47 is a common binary system in accreting black holes; therefore, these results can be extrapolated to other similar systems.


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Maria Diaz Trigo, James C.A. Miller-Jones, Simone Migliari, Jess W. Broderick, Tasso Tzioumis. ‘Baryons in the relativistic jets of the stellar-mass black-hole candidate 4U1630-47’. Nature, November 2013.

The University of Barcelona is the top public university in Catalonia due to its size of student population, 87,486, and its course offering. It is also the top Spanish university in scientific production, so it is the main university research center in Spain and one of the most important in Europe, as its number of research programs and the excellence it has attained prove.

The UB has a prominent position in the most prestigious international rankings: it is the only Spanish university which is among the 200 best worldwide universities in 26 out of 30 subject areas, according to the QS World University Rankings 2013 by Subject, and it holds the national top position in Leiden Ranking and URAP.

The University of Barcelona is member of the most important international excellence university networks, such as the League of European Research Universities. It has overseen the creation of two campuses of international excellence, the Barcelona Knowledge Campus (BKC) and the Health University of Barcelona Campus (HUBc). It has assimilated their goals as its own to increase competitiveness; these goals include the attraction of academic and research talent, full internationalization, the enhancement of teaching quality and scientific quality, and an increase in the transfer of knowledge generated at the university to wider society.

SpaceRef staff editor.