Commit 0eea15a8 authored by Holger Pletsch's avatar Holger Pletsch
Browse files

Some text edits and additions.

parent e70d83a4
...@@ -16,17 +16,16 @@ They are rapidly spinning neutron stars that emit pulses, observable from radio ...@@ -16,17 +16,16 @@ They are rapidly spinning neutron stars that emit pulses, observable from radio
gamma-ray wavelengths.</p> gamma-ray wavelengths.</p>
<p>Searching for new pulsars is an enormous computational challenge, because their spin <p>Searching for new pulsars is an enormous computational challenge, because their spin
frequencies, sky position and other parameters are unknown. Thus, this requires a blind frequencies, sky position and other parameters are unknown in advance. Hence this is called a "blind" search, where one explicitly searches over a dense grid in parameter space. However, the
search, where one explicitly searches over a dense grid in parameter space. However, the
number of discrete grid points to cover such multi-dimensional parameter spaces is number of discrete grid points to cover such multi-dimensional parameter spaces is
tremendous and renders "brute forces approaches" computationally unfeasible.</p> tremendous and renders "brute forces approaches" computationally unfeasible.</p>
<p>We have developed novel and much more efficient data-analysis methods for the volunteer <p>We have developed novel and much more efficient data-analysis methods for the volunteer
supercomputer Einstein@Home, which ranks among the fastest 25 computer systems worldwide. supercomputer Einstein@Home, which ranks among the fastest 25 computer systems worldwide.
Einstein@Home has now discovered four new gamma-ray pulsars that were previously Einstein@Home has enabled the discoveries of new gamma-ray pulsars that were previously
inaccessible on computational grounds.</p> inaccessible on computational grounds.</p>
<p>These radio and gamma-ray pulsar discoveries provide important contributions to advance <p>These gamma-ray pulsar discoveries provide important contributions to advance
our (yet very poor) understanding these stellar objects, their population, and their role our (yet very poor) understanding these stellar objects, their population, and their role
in our Universe.</p> in our Universe.</p>
<br> <br>
...@@ -34,36 +33,12 @@ in our Universe.</p> ...@@ -34,36 +33,12 @@ in our Universe.</p>
<!-- <a target="blank" href="img/skymap.jpg"><img align="left" vspace="20" hspace="20" style="width: 450px;" alt="skymap" src="img/skymap_small.jpg"></a> <!-- <a target="blank" href="img/skymap.jpg"><img align="left" vspace="20" hspace="20" style="width: 450px;" alt="skymap" src="img/skymap_small.jpg"></a>
!--> !-->
<h3>New Einstein@Home gamma-ray pulsar discoveries</h3>
<p>This page contains information about the Einstein@Home gamma-ray pulsar discoveries. For <h3>The Einstein@Home searches for new gamma-ray pulsars</h3>
each pulsar we list the volunteers whose computers discovered the pulsar, and the date at
which the pulsar was found.</p>
<p>The plots on the right show the pulse profile of each pulsar in green, and the phase-folded <p>In 2014, we began the 4<sup>th</sup> Einstein@Home survey for gamma-ray pulsars, or
arrival times of all the gamma-ray photons on the far right. These plots require precise
knowledge of the pulsar sky position, its spin frequency, and spin frequency derivative.
Using these, each photon can be assigned a rotational phase, i.e., in which direction the
pulsar was pointing when the gamma-ray photon was emitted. Thus, we can reconstruct the
gamma-ray emission as a function of pulsar rotation phase and resolve the pulse profile.</p>
<p>We also provide a list of selected characteristics for each
of the pulsars. Right ascension is one of the two celestial coordinates that specify the
sky position of the pulsar. Declination is the second of these. The spin frequency describes
how many time per second the pulsar is rotating. The first frequency derivative describes
how much the pulsar is slowing down over time. The energy required to emit electromagnetic
radiation is drawn from the pulsar rotation. The characteristic age is a rough estimate of
the pulsar's age, computed from the spin frequency and its derivative. Finally, the
spin-down power is a measure of the total energy emitted by the pulsar. For comparison, our
Sun outputs roughly 4 x 10<sup>33</sup> erg per second. All pulsars below have a much higher
spin-down power.</p>
<br>
<h3>Update: Pulsar Discoveries from FGRP4</h3>
<p>In August 2014, we began the 4<sup>th</sup> Einstein@Home survey for gamma-ray pulsars, or
"FGRP4". This survey incorporated many new advances that we learned during our previous "FGRP4". This survey incorporated many new advances that we learned during our previous
investigation of blind search methods. In addition, we were able to utilised the superior "Pass 8" searches and investigation of blind search methods. In addition, we were able to utilised the superior "Pass 8"
data from the <i>Fermi</i>-LAT team, and search in longer data sets than ever before. In data from the <i>Fermi</i>-LAT team, and search in longer data sets than ever before. In
combination, these improvements led to FGRP4 being our most sensitive survey to date.</p> combination, these improvements led to FGRP4 being our most sensitive survey to date.</p>
...@@ -78,10 +53,38 @@ As always, we are extremely grateful to all of our volunteers, especially those ...@@ -78,10 +53,38 @@ As always, we are extremely grateful to all of our volunteers, especially those
contributed to these new discoveries. To say "we couldn't have done it without you!" would be a terrible contributed to these new discoveries. To say "we couldn't have done it without you!" would be a terrible
understatement!</p> understatement!</p>
<br> <p>Timeline of <i>Fermi</i>-LAT Blind-Search Pulsar Discoveries</p>
<h3>Timeline of <i>Fermi</i>-LAT Pulsar Discoveries</h3>
<img style="width: 500px;" alt="Timeline" src="img/psrs_vs_time.png"> <img style="width: 500px;" alt="Timeline" src="img/psrs_vs_time.png">
<br> <br>
<p>The above plot illustrates the number of gamma-ray pulsars discovered in blind searches using NASA's Fermi Gamma-ray Space Telescope as a function of time (when the discoveries were published). Since the launch of the Fermi satellite in 2008, it has continuously scanning the entire sky and thus is providing an ever increasing data set. In principle, having more data available allows us to do more sensitive pulsar searches. However, at the time, the computational cost increases also rapidly with the longer data time spans. Thus, as the graphics shows, over the last few years the only new such discoveries were made with Einstein@Home, owing to the massive collective computing power provided by the Einstein@Home volunteers.</p>
<br>
<h3>The discoveries made by Einstein@Home volunteers in detail</h3>
<p>Below we list for each pulsar the volunteers whose computers discovered the pulsar,
and the date at which the pulsar was found.</p>
<p>We also provide a list of selected characteristics for each
of the pulsars. Right ascension is one of the two celestial coordinates that specify the
sky position of the pulsar. Declination is the second of these. The spin frequency describes
how many time per second the pulsar is rotating. The first frequency derivative describes
how much the pulsar is slowing down over time. The energy required to emit electromagnetic
radiation is drawn from the pulsar rotation. The characteristic age is a rough estimate of
the pulsar's age, computed from the spin frequency and its derivative. Finally, the
spin-down power is a measure of the total energy emitted by the pulsar. For comparison, our
Sun outputs roughly 4 x 10<sup>33</sup> erg per second. All pulsars below have a much higher
spin-down power.</p>
<p>The graphics on the right show the pulse profile of each pulsar in green, and the phase-folded
arrival times of all the gamma-ray photons on the far right. These plots require precise
knowledge of the pulsar sky position, its spin frequency, and spin frequency derivative.
Using these, each photon can be assigned a rotational phase, i.e., in which direction the
pulsar was pointing when the gamma-ray photon was emitted. Thus, we can reconstruct the
gamma-ray emission as a function of pulsar rotation phase and resolve the pulse profile.</p>
<br>
<!-- <!--
<div style="text-align: center;"> <div style="text-align: center;">
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment