True identity of mysterious gamma-ray source revealed

Date:
February 3, 2021
Source:
University of Manchester
Summary:
An international research team has shown that a rapidly rotating
neutron star is at the core of a celestial object now known as
PSR J2039?5617.



FULL STORY ========================================================================== [Neutron star | Credit: (c) Artsiom P / stock.adobe.com] Neutron star illustration (stock image; elements furnished by NASA).

Credit: (c) Artsiom P / stock.adobe.com [Neutron star | Credit: (c)
Artsiom P / stock.adobe.com] Neutron star illustration (stock image;
elements furnished by NASA).

Credit: (c) Artsiom P / stock.adobe.com Close An international research
team including members from The University of Manchester has shown that
a rapidly rotating neutron star is at the core of a celestial object
now known as PSR J2039-5617

==========================================================================
The international collaboration used novel data analysis methods and the enormous computing power of the citizen science project Einstein@Home
to track down the neutron star's faint gamma-ray pulsations in data
from NASA's Fermi Space Telescope. Their results show that the pulsar
is in orbit with a stellar companion about a sixth of the mass of our
Sun. The pulsar is slowly but surely evaporating this star. The team also
found that the companion's orbit varies slightly and unpredictably over
time. Using their search method, they expect to find more such systems
with Einstein@Home in the future.

Searching for the so-called 'Spider' pulsar systems -- rapidly spinning
neutron stars whose high-energy outflows are destroying their binary
companion star, required 10 years of precise data. The pulsars have been
given arachnid names of 'Black widows' or 'Redbacks', after species
of spider where the females have been seen to kill the smaller males
after mating.

New research published in, Monthly Notices of the Royal Astronomical
Society, details how researchers found a neutron star rotating 377
times a second in an exotic binary system using data from NASA's Fermi
Space Telescope.

The astronomer's findings were uniquely boosted by the Einstein@Home
project, a network of thousands of civilian volunteers lending their
home computing power to the efforts of the Fermi Telescope's work.

The group's search required combing very finely through the data in
order not to miss any possible signals. The computing power required is enormous. The search would have taken 500 years to complete on a single computer core. By using a part of the Einstein@Home resources it was
done in 2 months.



==========================================================================
With the computing power donated by the Einstein@Home volunteers, the
team discovered gamma-ray pulsations from the rapidly rotating neutron
star. This gamma-ray pulsar, now known as J2039-5617, rotates about 377
times each second.

"It had been suspected for years that there is a pulsar, a rapidly
rotating neutron star, at the heart of the source we now know as
PSR J2039-5617," says Lars Nieder, a PhD student at the Max Planck
Institute for Gravitational Physics (Albert Einstein Institute; AEI)
in Hannover. "But it was only possible to lift the veil and discover
the gamma-ray pulsations with the computing power donated by tens of
thousands of volunteers to Einstein@Home," he adds.

The celestial object has been known since 2014 as a source of X-rays,
gamma rays, and light. All evidence obtained so far pointed at a rapidly rotating neutron star in orbit with a light-weight star being at the
heart of the source. But clear proof was missing.

The first step to solving this riddle were new observations of the stellar companion with optical telescopes. They provided precise knowledge about
the binary system without which a gamma-ray pulsar search (even with Einstein@Home's huge computing power) would be unfeasible.

The system's brightness varies during an orbital period depending on
which side of the neutron star's companion is facing the Earth. "For J2039-5617, there are two main processes at work," explains Dr. Colin
Clark from Jodrell Bank Centre for Astrophysics, lead author of the
study. "The pulsar heats up one side of the light-weight companion,
which appears brighter and more bluish.

Additionally, the companion is distorted by the pulsar's gravitational
pull causing the apparent size of the star to vary over the orbit. These observations allowed the team to get the most precise measurement possible
of the binary star's 5.5-hour orbital period, as well as other properties
of the system." With this information and the precise sky position
from Gaia data, the team used the aggregated computing power of the
distributed volunteer computing project Einstein@Home for a new search
of about 10 years of archival observations of NASA's Fermi Gamma-ray
Space Telescope. Improving on earlier methods they had developed for
this purpose, they enlisted the help of tens of thousands of volunteers
to search Fermi data for periodic pulsations in the gamma-ray photons registered by the Large Area Telescope onboard the space telescope. The volunteers donated idle compute cycles on their computers' CPUs and GPUs
to Einstein@Home.

The new knowledge of the frequency of the gamma-ray pulsations also
allowed collaborators to detect radio pulsations in archival data from the Parkes radio telescope. Their results, also published in Monthly Notices
of the Royal Astronomical Society,show that the pulsar's radio emission
is often eclipsed by material that has been blown off the companion star
by its nearby Redback pulsar.


========================================================================== Story Source: Materials provided by University_of_Manchester. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Artist's_impression_of_PSR_J2039-5617_and_its_companion.

========================================================================== Journal Reference:
1. C J Clark, L Nieder, G Voisin, B Allen, C Aulbert, O Behnke,
R P Breton,
C Choquet, A Corongiu, V S Dhillon, H B Eggenstein, H Fehrmann,
L Guillemot, A K Harding, M R Kennedy, B Machenschalk, T R
Marsh, D Mata Sa'nchez, R P Mignani, J Stringer, Z Wadiasingh,
J Wu. Einstein@Home discovery of the gamma-ray millisecond pulsar
PSR J2039-5617 confirms its predicted redback nature. Monthly
Notices of the Royal Astronomical Society, 2021; 502 (1): 915 DOI:
10.1093/mnras/staa3484 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/02/210203123346.htm

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