Research

Masers | Pulsars | My PhD project | My MSc project

Overview

Until I find the time to produce some text in these sections I will only list a few keyword regarding my research interests. My papers will give a more complete description of the projects I am involved in.
Masers:
My main study has been determining the pollarization of water maser emission to detect the strength and structure of magnetic fields. In the meantime I have expanded this to methanol masers as well. To accurately determine the magnetic field I have worked with, and slightly expanded upon, the current theories of maser amplification in a magnetic field. I have performed observations on stellar maser sources, masers in star formation regions as well as masers in the extra-galactic source NGC 3079. My main discovery is the magnetically collimated jet from the evolved star W43A, supporting models of magnetic shaping of planetary nebulae.

In addition to the 'regular' masers at cm wavelengths I have also started studying maser lines at submillimeter wavelengths as well as other molecular lines at those wavelengths to eventually study the small scale dynamics in both outflows of evolved stars and in star forming regions.

Finally, I have done several astrometric campaigns on maser sources, most notably enshrouded evolved stars, where occasionally OH maser emission is amplifying the underlying star. With this astrometric observations I have determined accurate proper motions and parallaxes to a small sample of stars.
Pulsars:
Through my astrometric work I have become involved in several pulsar astrometry projects. We have for instance discovered the fastest pulsar at over 1000 km/s (from direct measurements). Efforts are ongoing to significantly increase the number of pulsars with model independent distances and velocities. These can then be used to determine birth velocity distributions and birth location (such as the disrupted binary I discovered).

My pulsar work also extends in the participation in the ALFA consortium doing pulsar observations with the Arecibo multi-beam receiver as well as several survey to find pulsars close the the center of our galaxy.
My PhD project:
My PhD project, under supervision of Dr. H.J. van Langevelde, Prof.H.J. Habing and Prof.R.T. Schilizzi, was done between 1998 and 2002 at Leiden Observatory. In it I used both VLBA and MERLIN observations to study circumstellar masers and did theoretical modeling of both water and OH masers. Most of the topics are discussed in more detail in my current research interests. My PhD thesis can be downloaded here
My MSc project:
My MSc student project was performed in 1997/1998 in the Galactic Dynamics group of Prof.P.T. de Zeeuw at Leiden Observatory. In it I studied the projection of traxial galaxies including those with misaligned rotation axis. My MSc thesis can be found here.