Highlights — Some exciting recent scientific results from our group

Two astronomers from Bonn have proposed a new path for the formation of a newly discovered class of millisecond pulsars with similar orbital periods and eccentricities. In the scenario of Paulo Freire and Thomas Tauris, a massive white dwarf star accretes matter and angular momentum from a normal companion star and grows beyond the critical Chandrasekhar mass limit. However, it does not collapse immediately into a neutron star because it is rotating very fast and is thus sustained by centrifugal forces. After the mass transfer ceases, this massive white dwarf loses rotational energy and eventually collapses directly into a millisecond pulsar, without the need for further accretion. The associated instantaneous release of gravitational binding energy is expected to produce the characteristic eccentricities observed in such systems. The new hypothesis makes several testable predictions about this recently discovered sub-class of millisecond pulsars. If confirmed, it opens up new avenues of research into the physics of stars, in particular the momentum kicks and mass loss associated with accretion induced collapse of massive white dwarfs.

Surprising Image Reveals New Tool to Study Magnetic Fields of Galaxies

An international group of astronomers, including Marita Krause and Rainer Beck from Max-Planck-Institut für Radioastronomie (MPIfR) in Bonn, has found a surprising and useful new probe of galactic magnetic fields. While studying gas halos around nearby galaxies, they were surprised when detailed studies with the Karl G. Jansky Very Large Array (VLA) showed that one of their subjects is not a single galaxy, but rather two, nearly perfectly superimposed on the sky to masquerade as one. The discovery allowed them to use the alignment to learn otherwise-unobtainable facts about the nearer galaxy.

The combination of globally distributed computing power and innovative analysis methods proves to be a recipe for success in the search for new pulsars. Scientists from the Max Planck Institutes for Gravitational Physics and Radio Astronomy together with international colleagues have now discovered four γ-ray pulsars in data from the Fermi space telescope. The breakthrough came using the distributed computing project Einstein@Home, which connects more than 200,000 computers from 40,000 participants around the world to a global supercomputer. The discoveries include volunteers from Australia, Canada, France, Germany, Japan, and the USA.

The combined computing power of 200,000 private PCs helps astronomers take an inventory of the Milky Way. The Einstein@Home project connects home and office PCs of volunteers from around the world to a global supercomputer. Using this computer cloud, an international team lead by scientists from the Max Planck Institutes for Gravitational Physics and for Radio Astronomy analysed archival data from the CSIRO Parkes radio telescope in Australia. Using new search methods, the global computer network discovered 24 pulsars – extraordinary stellar remnants with extreme physical properties. These can be used as testbeds for Einstein's general theory of relativity and could help to complete our picture of the pulsar population.

Radio astronomers use pulsar with strong magnetic field to investigate supermassive black hole

Astronomers have discovered a magnetar at the centre of our Milky Way. This pulsar has an extremely strong magnetic field and enables researchers to investigate the direct vicinity of the black hole at the heart of the galaxy. An international team of scientists headed by the Max Planck Institute for Radio Astronomy in Bonn have, for the first time, measured the strength of the magnetic field around this central source and were able to show that the latter is fed by magnetic fields. These control the inflow of mass into the black hole, also explaining the x-ray emissions of this gravity trap.

An international research team led by astronomers from the Max Planck Institute for Radio Astronomy (Bonn, Germany) used a collection of large radio and optical telescopes to investigate PSR J0348+0432, a newly discovered pulsar, and its white dwarf companion. The observations revealed a system with unusual properties: weighing twice as much as the Sun, making it the most massive neutron star measured to date. This, in combination with its short orbital period of only 2.5 hours, provides insight into binary stellar evolution and makes this system a strong emitter of gravitational radiation. The energy loss through this radiation has already been detected in the radio observations of the pulsar, making it a laboratory for General Relativity in extreme conditions not accessible before. The findings are in excellent agreement with Einstein's theory.

An international team - led by Dutch astronomers (SRON, NOVA and ASTRON) - has made a tantalizing discovery about the way pulsars emit radiation. The emission of X-rays and radio waves by these pulsating neutron stars is able to change dramatically in seconds, simultaneously, in a way that cannot be explained with current theory. It suggests a quick change of the entire magnetosphere. In their research the team combined observations from the X-ray space telescope XMM-Newton and the radio telescope LOFAR (among others).