Imagine the Universe!
Imagine Home | You Be the Astrophysicist! |

Identifying the Parts of an X-ray Light Curve

Below is a sample of an X-ray light curve from an eclipsing X-ray binary such as HT Cas. See if you can correctly match the four labeled points in the light curve to the images below, showing what part of the orbit (as seen from Earth) that part of the light curve represents. The arrows show what direction the smaller (primary X-ray emitter) star is traveling. Use the mouse to click first on a red dot on the light curve and second on the corresponding binary configuration (as seen from Earth).
  • Dotted lines or a darkened secondary star are behind the primary star
  • Solid lines or a white secondary star are in front of the primary star.
lightcurve for one star passing behind another
smaller star crossing back
smaller star crossing front
smaller star going to back
smaller star coming to front

Data Take me to the HT Cas X-ray data.

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

DVD Table of Contents
Educator's Index