## Glossary

Bin: A small piece of data. We usually refer to time bins (data collected in a small chunk of time) or frequency bins (data collected in a small chunk of observing frequency).

Binary Systems: A system consisting of a pulsar and companion star in orbit around one another.

Broad Band: Emission that occurs over a wide range of observing frequencies.

Dispersion Measure: A way measuring the number of electrons that a pulsar signal must pass through while traveling through space to the Earth. The units are parsecs per centimeter cubed.

Eclipsing Systems: A system consisting of a pulsar and companion star, in which the companion star sometimes blocks radio emission from the pulsar.

Electromagnetic Spectrum: The wide range of electromagnetic waves, or different types of light.

Electromagnetic Waves: Waves of energy carried by electric and magnetic fields. This is another term for light.

Fourier Transform: A mathematical tool that transforms data from one form to another. In pulsar astronomy, we use Fourier transforms to take our data from the time domain to frequency domain. Fourier transforms are very useful for finding repeating signals in a set of data.

Frequency: The number of times some event repeats in a single second. The units are hertz.

Magnetic Fields: A way of describing the influence of magnetic force. All magnetic fields have a north and south pole, just like a household bar magnet. Magnetic fields on Earth are relatively weak compared to those found around pulsars.

Narrow Band: Emission that occurs in only a small range of observing frequencies.

Neutrons: Subatomic particles that carry no electrical charge. Neutrons can be found in the nuclei of atoms, and are the primary constituent of neutron stars.

Neutron Star: A very dense star made almost entirely out of neutrons. Neutron stars are produced when massive stars die in large explosions.

Observing Frequency: The radio frequency that astronomy observations are made at, typically measured in MHz or GHz.

Period Derivative: The rate of change in the rotational period of the pulsar per unit time, which is unitless but usually written as seconds per second.

Phase: The fraction of a pulsar's full rotation that it has gone through.

Pulse Profile: The strength of a pulsar signal as a function of phase. Pulse profiles are made by folding the time domain data and adding up all the power at a given phase.

Radio Frequency Interference: Radio signals from man-made sources, that can often look like a pulsar signal. RFI can come from a variety of sources, and if there is a lot of it radio astronomy observations can be nearly impossible.

Radio Waves: Energy carried in the radio part of the spectrum. Radio waves are actually a form of light, fundamentally no different than the light we see with our eyes. However, radio waves carry less energy than visible light. Radio waves are not sound waves, but they are often used by humans to carry information that can then be turned into sound (for example, by a car radio).

Reduced $\chi^2$: A mathematical tool for measuring the goodness of a m easurement. The Reduced $\mathbf{\chi^2}$ is used to determine how well some data fit to a given model. Normally, a Reduced $\mathbf{\chi^2}$ of one is desirable. However, we want a high value for Reduced $\mathbf{\chi^2}$, because in our case the model is data with no pulsar, so a high Reduced $\mathbf{\chi^2}$ indicates that a pulsar (or at least RFI masquerading as a pulsar) does exist.

Spin Frequency: The frequency at which a pulsar rotates. Spin frequency is equal to the number of times a pulsar rotates in a single second.

Spin Period: The length of time it takes a pulsar to complete one rotation.

Sub-band: A small range of observing frequencies integrated together. Radio astronomy instruments typically break down the observing frequency into sub-bands.

Supernova: A huge explosion that occurs when stars several times more massive than our Sun exhaust the fuel that keeps them burning. Supernovae are among the most powerful explosions in our universe.

Transient Emission: Radio wave signals that are only present for part of an observation.

Time of Arrival: The moment that a pulsar signal is detected on the Earth. Astronomers can predict the time of arrival very accurately for pulsars. By comparing this prediction to the actual time of arrival, astronomers learn about pulsars, the environments in which they are found, and the properties of the galaxy between the pulsar and Earth.

Time Series: A representation of how the signal from a pulsar changes in time. Time series are plotted as the power at a given phase vs. time.

Visible Light: Light that our eyes are sensitive to. Although we cannot see them, radio waves, microwaves, and X-rays are all types of light.

Wavelength: The distance between two peaks in an electromagnetic wave, and a way of characterizing light.

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