Pulsars are fast rotating neutron stars that emit narrow beams of electromagnetic radiation at highly regular intervals. These cosmic lighthouses serve as extremely precise clocks that can be used for experiments in fundamental astrophysics. We use ASTRON’s radio facilities to search for and study pulsars and their emission mechanisms. Our group is also part of European and international collaborations that aim to directly detect gravitational waves using a global array of radio telescopes.

Pulsar Timing

Precise measurement of pulsar signals from millisecond pulsars (MSPs) , or pulsar timing, provides a powerful tool to test  the equation of state of super-dense matter, strong-field gravitational physics, the effects of cosmic strings that are predicted by gravitational string theories and more.

Pulsar timing can also be used to directly detect gravitational waves offering a complementary tool to existing gravitational wave detectors such as LIGO/Virgo.
Our group is part of the European Pulsar Timing Array and the International Pulsar Timing Array (PTA). These large-scale collaborations share resources and facilities to create a global array that can be used to detect and characterize gravitational wave created from the mergers of supermassive black holes in the early universe.

Members of our group are also involved in MeerTime, one of the key science programs on pulsar timing with MeerKAT array, which is a pathfinder facilities for the Square Kilometre Array located in South Africa. We also contribute  to the definition and scientific planning of the pulsar science program for the Square Kilometre Array.

Insterstellar medium and solar wind

In order to precisely measure the arrival of pulses from a pulsar, astronomers should account for and remove any distortion in their signals. The biggest contributor to such distortions is the ionised interstellar medium (it causes dispersive delays, scattering, faraday rotation, etc). The pulsar group at ASTRON collaborates closely with our colleagues  working on Solar physics and Space Weather to mitigate propagation effects on pulsar timing measurements.

Pulsar search

We use LOFAR to conduct an all-sky pulsar survey in search of new and exotic pulsars that can provide further insight into the physics of neutron stars. A discovery of one of the slowest-spinning radio pulsar know to date ( more than 10 times slower than a typical pulsar) sheds light on how various sub-classes of neutron stars are linked and evolve during their lives.

Millisecond pulsars shine brightest in gamma-rays and they can be detected with telescopes such as NASA’s Fermi gamma-ray space telescope. Our group uses LOFAR to look at sources discovered by Fermi that may be associated with pulsars.   The main goal is to discover a neutron star that spins so rapidly that we can tightly constrain its size and hence the properties of its hyper-dense interior.  Such studies are of great interest to astrophysicists and nuclear physicists alike. So far, we have  discovered the fastest-spinning radio pulsar in the Galactic field.

Pulsar Population and Emission Mechanism

It's been more than 50 years since the discovery of pulsars by Jocelyn Bell in 1967. Despite significant progress, astronomers do not yet have a complete understanding of how these fascinating objects work.  Using low-frequency observations across a wide band of frequencies, we can learn much about  pulsar radio emission and its interaction with magnetospheric plasma and fields.

Our group at ASTRON collaborates with international colleagues on a number of pulsar studies at low frequencies including the characterisation of known millisecond and slow pulsar populations, providing reliable estimates on pulsar dispersion measures, flux densities and spectra. The group is currently working to improve the polarisation calibration of LOFAR especially at the very low frequencies below 100 MHz in order to get reliable estimates of polarisation properties of pulsars and their evolution across the LOFAR frequency band.

Research staff

Jason Hessels

Vlad Kondratiev

Joeri van Leeuwen

Yogesh Maan

Golam Shaifullah

Andrzej Szary

Cees Bassa

Gemma Janssen

Golam Shaifullah

Caterina Tiburzi

Emma van der Wateren

Latest tweets

Daily image of the week

On June 13-17, the LOFAR Family Meeting took place in Cologne. After two years LOFAR researchers could finally meet in person again. The meeting brings together LOFAR users and researchers to share new scientific results.

Our renewed ‘Melkwegpad’ (Milky Way Path) is finished! The new signs have texts in Dutch on the one side and in English on the other side. The signs concerning planets have a small, 3D printed model of that planet in their centre.
#Melkwegpad @RTVDrenthe

Daily image of the week

The background drawing shows how the subband correlator calculates the array correlation matrix. In the upper left the 4 UniBoard2s we used. The two ACM plots in the picture show that the phase differences of the visibilities vary from 0 to 360 degrees.

Daily image of the week: Testing with the Dwingeloo Test Station (DTS)
One of the key specifications of LOFAR2.0 is measuring using the low- and the highband antenna at the same time. For this measurement we used 9 lowband antenna and 3 HBA tiles.