“INTEGRAL – The Extreme Universe“ with Enrico Bozzo (Department of Astronomy, University of Geneva, Switzerland)

The INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a space telescope for observing the sky in the hard X-rays to soft Gamma-rays. It was launched in 2002 into an elongated 3 days-long orbit around the Earth and originally designed to provide for two years imaging and spectroscopy of cosmic sources in an energy domain that was poorly explored at that time. INTEGRAL is a truly international mission. It is led by the European Space Agency (ESA) in collaboration with many ESA member states and features also a substantial participation from United States and Russia.

INTEGRAL is equipped with a complex and robust suite of complementary instruments, providing overall a wide energy coverage, ranging from 3 keV to about 10 MeV. These instruments are capable of performing observations of cosmic sources with good spectroscopy and good imaging capabilities, providing also a high cadence monitoring of large fractions of the sky at once in both the X-ray and optical energy bands.

As of today, INTEGRAL is the only spacecraft of the European Space Agency (ESA) fleet performing scientific observations in the hard X-rays to Gamma-ray domain. Its principal targets are violent explosions known as gamma-ray bursts, powerful phenomena such as supernova explosions, and regions in the Universe thought to contain black holes and other compact objects. In the past two decades, the mission has greatly improved our understanding of the variable and transient Universe, providing, among others, the first detection of radioactive decays in the material expelled after a Supernova explosion, detailed mapping of the super-bubbles produced by supernovae and massive stars in the Milky Way though a spatially resolved image of the sky in the energy range of the 26Al unstable radioactive isotope line, and gamma-ray polarimetric measurements of the emission from bright black-hole binaries. Since 2002, INTEGRAL is also providing unique means to discover peculiar hard X-ray transient sources that so much have to teach us about physics under extreme conditions.

Among these sources, we find the accreting millisecond X-ray pulsars, which are key objects for understanding the physics of matter at supra-nuclear densities; the supergiant fast X-ray transients, which are the gates to understand potential implications of super-strong magnetic fields onto accretion processes; and last but not least, black-hole binaries, which give us unique data to understand the formation and evolution of accretion disks, as well as the production of jets and other ejection mechanisms (as for example ultra-fast outflows).

In 2013, INTEGRAL has provided the decisive observational evidence to validate the so-called pulsar recycling scenario by discovering the first truly swinging pulsar between radio and X-rays. In 2020, INTEGRAL has firmly established the long-sought association between fast radio bursting sources and super-strongly magnetized neutron stars. During every year of INTEGRAL operations, new kinds of transient hard X-ray to Gamma-ray emitters are being discovered. Each object provides the community with unique opportunity to study high energy physical processes in different environments and comprehend the ramifications of evolutionary paths.

INTEGRAL has far exceeded its originally planned lifetime but still today, after more than 18 years of successful operations in space, it is providing the international community with yet breakthrough discoveries and unique observational capabilities. The key role played by INTEGRAL in the discovery of the first counter-part to a gravitational wave event in 2017 has given further new life to the mission. It has now been widely recognized that INTEGRAL is a fundamental partner in the huge multi-wavelength effort being put in place to hunt for future counterparts of gravitational wave sources, as well as Neutrino sources.

Enrico Bozzo got his PhD in Astronomy at the University of Rome. After a first post-doc in Rome, he moved in 2009 to the INTEGRAL Science Data Center in Versoix, Department of Astronomy of the University of Geneva, Switzerland. Dr. Bozzo’s main scientific interest is focused on accreting X-ray binaries hosting neutron stars, both from a theoretical and observational perspective. He is involved in the development of future space missions for Astronomical and Astrophysical research, including Euclid, THESEUS, eXTP, and Athena. For the INTEGRAL mission, he is co-cordinating since 2009 part of the science ground segment operations, involving the overviewing of the data processing and distribution to the community, as well as the quick-looking.

Seminar was recorded on November 5, 2020