Research Highlights

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

Cygnus A: a powerful galaxy with a stratified, two-side jet

December 11, 2015

A study led by the Bonn astronomer Bia Boccardi shows results from imaging at high resolution of the double jet in the heart of the galaxy Cygnus A.  This nearby object, at a distance of 249 Mpc, allows astronomers to probe regions of only 400 Schwarzschild radii from the central, powerful super massive black hole.  The new study, based partially on the PhD Thesis of Boccardi, shows a stratified structure in the jet of this source, with a fast and a slow layer with different acceleration gradients in the relativistic outflows from the source.  More information can be found in the original publication here.

Deep into the Center of the Milky Way
Event Horizon Telescope Reveals Magnetic Fields at the Central Black Hole of our Galaxy more

Far, far away: space VLBI observations of magnetic fields in the high-redshift quasar 0642+449

November 2, 2015

More information can be found in the original publication here

Pioneering observations at the highest VLBI frequency in the southern Hemisphere: 3C 279 and APEX

August 27, 2015

More information can be found in the original publication here.

Radio light curves in blazars deciphered

August 7, 2015

A team of astronomers led by Christian M. Fromm at the MPI für Radioastronomie has modeled the mechanisms of emission in radio light curves from a thoeretical study of the peaks in brightness and wavelength in the radio spectra (the so-called turnover frequency-turnover flux density plane).  For this, they applied the shock-in-jet scenario, commonly used to explain the spectral behaviour of active galactic nuclei.  These results are shown in detail in the lastest issue of Astronomy and Astrophysics, see here.

Giant radio flare in a micro quasar

July 21, 2015

The micro quasar LS I +61°303 was studied during radio outbursts by the radio telescope Effelsberg.  These observations, performed at several frequency bands, and led by the MPIfR PhD student Lisa Zimmermann, with the collaboration of the Bonn astronomers Lars Fuhrmann and Maria Massi, reveals a flat spectral index (that is, the same brightness at different wavelengths), with superimposed sub-flares with higher flux densities at lower wavelengths.  These characteristics resemble the microquasars XTE J1752-223 and Cygnus X-3.  These results have been presented at the last issue of the European journal Astronomy and Astrophysics.  For more information, see here.  

The galaxy NGC 3718 observed with radio and infrared telescopes

July 20, 2015

A team led by the astronomer K. Markakis from the MPI für Radioastronomie and the University of Cologne has observed the low-ionisation nuclear emission-line region L1.9 galaxy NGC 3718 at 56 million light years with the Subaru telescope at the infrared and the e-MERLIN telescope in the radio regime.  These observations show the existence of a supermassive black hole recoil.  The journal Astronomy and Astrophysics publishes theses results in the latest issue.  More information can be found here.

Discovery of the wandering base of a radio jet after a major X-ray flare

July 1, 2015

Based on VLBI observations of the radio source, Markarian 421, a team including Shoko Koyama from the MPI für Radioastronomie, led by Kotaro Niinuma (Yamaguchi University) has discovered have discovered a new phenomenon in which the position of a radio jet base, a type of object which had been thought to be stationary, "wanders" widely along the jet axis. Radio jets ejected from the vicinity of super-massive black holes lurking at the center of active galaxies have been being observed for many years, but the team shows the first time anyone in the world has directly detected this "wandering phenomenon" of the radio jet base. These results were published in the latest issue of the Astrophysical Journal Letters, see here.  Additional information, in the press release of Yamaguchi University, in English and in Japanese, as well as in the National Astronomical Observatory of Japan in Japanese.

Connecting brightness variability and motions in the jet of a blazar

June 15, 2015

A team of astronomers from the MPI für Radioastronomie led by Bindu Rani has found a connection between a flux disturbance in the base of the jet in the radio source S5 0716+714 and optical--to--gamma-ray variations upstream of the central feature in the jet of the source at parsec scales.  The relativistic doppler factors, however, are different for the gamma and the radio emission.  The radio images show a decline of the measured brightness temperature in the jet with distance with a power index of -2.36.  These results have been published in the latest issue of the journal Astronomy and Astrophysics.  For more information, see here.

How heavy are the stars in the southern AB Doradus system?

May 25, 2015

Astrometrical observations of the double star AB Doradus B in the complex system AB doradus have revealed the exact, dynamical masses of both stars.  The Ba star has a weight of 28 solar masses, whereas AB Doradus weighs 0.25 solar masses.  Those measurements contradict the predictions by evolutionary models, which should be revised.  Models overestimate those masses.  The results of this work, performed with the Australian Long Baseline Array and led by the PhD student Rebecca Azulay from the MPI für Radioastronomie and the University of Valencia, have been published this week in the scientific journal Astronomy & Astrophysics, see here.

Observations of weak blazars with the European VLBI Network

April 28, 2015

A team of astronomers led by Franco Mantovani from the Bonn MPI für Radioastronomie has studied a sample of radio weak blazars with the European VLBI Network.  This sample was selected from a group of X-ray emitting galaxies.  All observed 87 sources were detected, 39 of those are point-like at VLBI scales, and 48 show a jet structure.  56 of these sources can be considered blazars.  The results of this work have been published this week at the journal Astronomy & Astrophysics, see here.

A Sharp View into Black Holes
Planet-Sized Telescope Connects Chile and the South Pole more

Where is located the black hole in the galaxy CTA 102?

March 25, 2015

A team of astronomers led by the Bonn scientist Christian Fromm (MPI für Radioastronomie) has measured the position of the supermassive black hole at the centre of the galaxy CTA 102.  This black hole is as heavy as several billion times our Sun.  This object was already notorious in the 1960s as a candidate for hosting aliens, given its regular radio emission.  Nowadays we know it is a powerful, remote quasar.  The black hole is located at several ten thousand gravitational radii from the brightest radio point in astronomical images.  These results have been published in the latest issue of the journal Astronomy & Astrophysics.  An onlne version of the publication can be found  here.

A Missing Link in the Family Tree of Cosmic Black Holes
Intermediate-mass black hole with a powerful jet more

Gamma-loud narrow-line Seyfert 1 galaxies studied in the radio

February 23, 2015

A international team led by Dr. Emmanouil Angelakis from the MPI for Radio Astronomy in Bonn has studied the radio jet emission from a puzzling class of active galactic nuclei: the narrow-line Seyfert 1 galaxies emitting gamma rays at the GeV range of energies.  They studied four objects which were detected by the space gamma-ray satellite Fermi and in the radio, discovered in the early 2010s.   As of today, seven of these objects have been discovered.  The four studied sources show the typical characteristics of blazars such as intensive variability, spectral evolution corresponding to traveling plasma shocks, and Doppler factors indicating mildly relativistic speeds in the jet. This work has been published in the last issue of the international journal Astronomy & Astrophysics. [more]

Radiation from the heart of the powerful quasar RX J2314.9+2243

February 4, 2015

An international team lead by S. Komossa from the MPI for Radio Astronomy, has observed the quasar RX J2314.9+2243 in the optical, ultra-violet, X-rays, and radio bands.  A fifth of all active galaxies is radio loud.  A new class of these objects was discovered in the last years, the narrow-line Seyfert 1 galaxies.  Those objects have extreme emission properties.  One of them, with a high radio loudness, has been observed systematically by the Bonn team.  The results show an energy distribution originated by electrons under the influence of strong magnetic fields (synchrotron radioation).  This quasar shows as well a powerful outflow in the optical part of the spectrum.  The results of this work have been published in the latest issue of Astronomy & Astrophysics. [more]

How compact and bright can be a source in the sky?

January 30, 2015

The answer of this question can be better answered after the last development published in the last issue of Astronomy & Astrophysics by Andrei P. Lobanov from the MPI for Radio Astronomy.  The physical properties of compact sources can be characterised by the brightness temperature.  The new method presented by Lobanov, which allows us to compute the brightness temperature limits from interferometric measurements, has been successfully tested with data from the MOJAVE project and from mm-VLBI observations.  Its application to space VLBI obsrvations promises new limits in the brightness temperature of compact, remote objects, for future observations. [more]

A new method to analyse astronomical images

January 27, 2015

A new, automatic method for astronomical image analysis has been developed by the graduate student Florent Mertens and his supervisor, Andrei Lobanov, both at the MPI for Radio Astronomy.  This mehtod is based on wavelet functions to determine distinct regions in astronomical images and to study their evolution, following the wavelet-based image segmentation and evaluation (WISE) approach.  This was successfully tested in the sources 3C 273 and 3C 120.  The two-dimensional evolution of the features of the jets in both sources was studied, and it is compatible with the effect of Kelvin-Helmholtz instabilities.  This work was published in the last issue of the journal Astronomy & Astrophysics [more]

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