Research Highlights

Here we show recent research results from the Radio Astronomy/Very-Long-Baseline Interferometry department.

How the black hole in M87 launches a jet
New observations reveal the powerful jet emerging from the black hole in the centre of the galaxy M87 more

Testing Gravity with Black Holes: Can we tell them apart?

16 March 2023

A team of researchers led by the PhD candidate Jan Röder at the MPIfR has used computer simulations to test their ability to distinguish between two theories of gravity under different accretion and emission scenarios. They carried out 3D simulations of two black holes, one based on the Kerr solution to general relativity and the other on ton a branch of solutions to Einstein-Maxwell-dilaton-axion gravity, the dilaton black hole. Further, they modelled thermal synchrotron emission and applied a non-thermal electron distribution function to compare with multi-wavelength observations. The study found that differences between the two black hole spacetimes are not always distinguishable with current observational technology, and that the choice of emission model has a greater effect on the spectra than the accretion model or the choice of spacetime.  More information is available directly at the publication in the last issue of Astronomy and Astrophysics, here.

Peering into the heart of a distant quasar with the Event Horizon Telescope
13 February 2023

A global collaboration of scientists including  Maciek Wielgus of the Max Planck Institute for Radio Astronomy (Bonn, Germany) used the Event Horizon Telescope (EHT), to investigate the innermost parts of the quasar NRAO 530.  Astronomers are trying to understand the complicated physics of quasars and their central engines, struggling with questions like how the jets emanating from the central region are powered and created, and what is the role of magnetic fields in their formation. The EHT offers extremely high, unprecedented angular resolution, allowing astronomers to image the previously unseen structures in the very central region of NRAO 530 (Original Paper: S. Jorstad, M. Wielgus, et al.: "The Event Horizon Telescope Image of the Quasar NRAO 530", in Astrophysical Journal ApJ 943 170 (2023); EHT Blog Entry, February 08, 2023). more

General relativity and the twinkling of Sgr A* in Infrared and X-Ray light

18 January 2023

An international team of astronomers led by Sebastiano von Fellenberg at the MPI für Radioastronomie has studied the supermassive black hole at the center of the Milky Way, called Sagittarius A*.  Astronomers have observed occasional bright flares of near-infrared and X-ray light. These flares are thought to come from the black hole's innermost accretion flow. By analyzing data from the Spitzer and Chandra observatories, the researchers identified 25 near-infrared and 24 X-ray flares. Using a computer program that takes into account the effects of general relativity, the researchers modeled the trajectories of "hot spots" and examined the light curves of the flares for signs of these effects. They found that, despite their varying shapes, all flares share a common, exponential impulse response. This impulse response is symmetric, meaning that the rise and fall times are the same, and has an exponential time constant of about 15 minutes. The researchers determined that the characteristic flare shape is not consistent with hot-spot orbits viewed edge-on, and were able to estimate the inclination of the orbital plane of the hot spots with respect to the observer (about 30 degrees, but less than 75 degrees) and the characteristic timescale of the intrinsic variability (a few tens of minutes).
More information, at the original publication in the Astronomy & Astrophysics journal, here.

Journey to the Heart of a Cosmic Beast: Uncovering the Connection Between Radio Waves and Gamma Rays in 3C 84

03 January 2023

A team of radio astronomers, led by the young scientist Georgios F. Paraschos at the MPI für Radioastronomie, has studied the conection between the high-energy and the radio emission in the nearby quasar 3C 84. The team compared the radio and gamma-ray light curves of 3C 84 (aka NGC 1275) to understand how its jets are formed. By analyzing the time differences between the flares seen in these light curves, they found that the energy of the particles and magnetic fields in the jets are balanced. They also determined the location of the "jet apex" and found that the gamma-ray emission is related to the radio emission. Additionally, the team led by Dr. Paraschos calculated two parameters that describe the properties of the jet, and the results are consistent with a mechanism proposed in 1977 by Blandford and Znajek for jet formation. These findings provide new insights into the mysterious and complex processes that drive the formation and evolution of cosmic jets.
More information at the original publication in the Astronomy & Astrophysics journal, here



Go to Editor View