Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
Nine new gamma-ray pulsars
Discoveries in Fermi telescope data thanks to method used in gravitational-wave astronomy
November 03, 2011
Pulsars are the lighthouses of the universe. These compact and fast-rotating neutron stars flash many times per second in the radio or gamma-ray band. Pure gamma-ray pulsars are extremely difficult to find despite their high energy because they radiate very few photons per unit of time. Using an improved analysis algorithm, scientists from the Max Planck Society and international partners now discovered a set of previously unknown gamma-ray pulsars with low luminosity in data from the Fermi satellite. These pulsars had been missed using conventional methods. The number of known gamma-ray pulsars has thus grown to over 100. (The paper will be published in the Astrophysical Journal.)
Beacons in space - Pulsars are fascinating celestial bodies with an interesting history.
Pulsars are the lighthouses of the universe. These compact and fast-rotating neutron stars flash many times per second in the radio or gamma-ray band. Pure gamma-ray pulsars are extremely difficult to find despite their high energy because they radiate very few photons per unit of time. Using an improved analysis algorithm, scientists from the Max Planck Society and international partners now discovered a set of previously unknown gamma-ray pulsars with low luminosity in data from the Fermi satellite. These pulsars had been missed using conventional methods. The number of known gamma-ray pulsars has thus grown to over 100. (The paper will be published in the Astrophysical Journal.)
Images and multimedia in support of the news conference
Presenter 3: Bruce Allen, director, Max Planck Institute for Gravitational Physics in Hannover, Germany, and of the Einstein@Home project
Visual 9
Nine new Fermi pulsars (magenta) were located in LAT data thanks to new and more efficient analysis methods originally developed to search for gravitational waves. With these new finds, Fermi has detected more than 100 gamma-ray pulsars.
Nine new Fermi pulsars (magenta) were located in LAT data thanks to new and more efficient analysis methods originally developed to search for gravitational waves. With these new finds, Fermi has detected more than 100 gamma-ray pulsars.
You can find this video on YouTube. Click on the image to be redirected there.
This animation illustrates how analysis of Fermi data reveals new pulsars. Fermi's LAT records the precise time and position of the gamma rays it detects, but to identify a pulsar requires additional information -- its position in the sky, its pulse period, and the way the pulse changes over time. Additionally, even Fermi's sensitive LAT detects few gamma rays from these objects -- as few as one photon per 100,000 rotations. The Hannover team used new methods to execute a so-called blind search, using computers to check many different combinations of position and period against the 8,000 photons Fermi's LAT has collected during its three years in orbit. When photons from the pulses align in time, a new gamma-ray pulsar has been discovered.
Pulsar candidates from the blind search were analyzed in detail using the Atlas computing cluster at the Albert Einstein Institute in Hannover, Germany. Atlas is as powerful 3,500 typical desktop computers and brings to bear about a hundred times more computing power than that used in previous blind searches.
Pulsar candidates from the blind search were analyzed in detail using the Atlas computing cluster at the Albert Einstein Institute in Hannover, Germany. Atlas is as powerful 3,500 typical desktop computers and brings to bear about a hundred times more computing power than that used in previous blind searches.
Since 2005, the Einstein@Home distributed computing project has been using downtime on the desktop computers of thousands of volunteers to search for gravitational waves and for pulsars in radio data. In July, Einstein@Home users began receiving “work units” of Fermi LAT to search for gamma-ray pulsars.
Since 2005, the Einstein@Home distributed computing project has been using downtime on the desktop computers of thousands of volunteers to search for gravitational waves and for pulsars in radio data. In July, Einstein@Home users began receiving “work units” of Fermi LAT to search for gamma-ray pulsars.
Phase-time diagram and pulse profile for gamma-ray pulsar J2028+3332. Panel 9a shows the pulse phase (rotation angle of the star about its axis) at the arrival time of each photon. The gray-scale intensity represents the photon probability weight. In panel 9b, the upper plot shows the summed probability weights: the pulse profile. The four plots below resolve the pulse profile according to separate energy ranges. For clarity, the horizontal axis shows two pulsar rotations in each diagram.
Positions of the nine gamma pulsars (Pletsch et al., ApJ), with stellar constellations in the background.
Astronomers find and study multiple rare and unusual pulsars in dense stellar cluster using the South African Radio Astronomy Observatory’s MeerKAT and the U.S. National Science Foundation Green Bank Telescope.
