Radio pulsars are detected through regular, periodic "pulses" of radio emission. Pulsars are actulaly rapidly spinning neutron stars. A neutron star (NS) contains about as much material as the Sun, packed into a ball 20-30 km across. As the NS rotates, beams of radiation sweep around like light beams from a lighthouse. We see a pulse whenever the one of the beams shines directly at us. Pulsars have spin periods from several seconds (impressive enough) down to nearly 1 millisecond!

Polarization profile of millisecond-pulsar B1821-24 (spin period = 3.05ms)
(Backer & Sallmen, 1997, The Astronomical Journal, 114, 1539)

Research Projects

Dr. S. spent much of her graduate career trying to figure out what makes pulsars shine. They pulse because they're spinning, but what is going on to produce the beam? The polarization properties of millisecond pulsars are an important clue, as is analyzing the pulse statistics and pulse shape stability of these objects. Determining that the Crab Pulsar's giant pulses occur simultaneously at widely separated frequencies was a highlight. Her Ph.D. thesis is Millisecond Pulsars: Decoding Magnetospheres.

In addition, pulsars are extremely useful beasts. Pulsar timing can tell us about planetary companions to pulsars. Binary pulsars can be used to test predictions of Einstein's Theory of General Relativity, and a Pulsar Timing Array could potentially detect Gravitational Waves. Simple web searches can help you find more about all of these!

While at UW-L Dr. S. and undergraduate students reduced and analyzed 6 years of archival radio pulsar data (from NRAO's 85-foot telescope in Green Bank, WV) on the Vela pulsar to investigate the properties of the ISM and the Vela Supernova Remnant.

Online Pulsar Introductions

Back to Website for Dr. Shauna Sallmen

Last updated August, 2014