The 2nd fastest pulsar, now with gamma rays | Space

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Artist concept of a pulsar. In this illustration, the pulsar rotates its radio (green) and gamma (magenta) beams beyond the Earth with each rotation, so we see it as an impulse. Image via NASA.

Supernova explosions can crush ordinary stars into neutron stars, composed of extremely dense exotic matter. Neutron stars are about 20 km long, unlike hundreds of thousands of kilometers for stars like our sun. Yet they contain a mass in the range of 1.4 times that of our sun. Neutron stars have strong magnetic fields. They emit powerful jets of radiation along their magnetic field lines. If, as a neutron star rotates, its beams of radiation periodically point to the Earth, we see the star as a source of radio or pulsed gamma rays. Then, the neutron star is also called pulsar, often compared to a cosmic lighthouse. Modern astronomers know that pulsars rotate with astounding rapidity. The second fastest – called PSR J0952-0607 – runs about 707 times per second! Scientists at the Max Planck Institute for Gravitational Physics in Hannover, Germany, announced on September 19, 2019 that this pulsar, J0952-0607 – previously seen only at the end of the radio spectrum – was now pulsating also in the gamma rays.

J0952-0607 – the number refers to the position of the object in the sky – was discovered in 2017. Originally, it emitted pulses in radio waves, but not in gamma rays. The international team studied it in detail – and recently published new work on it in the Astrophysical Journal – stated in a statement:

The pulsar rotates 707 times in one second and is therefore the fastest wire in our galaxy outside the dense stellar environments of globular clusters.

The artist's concept of a supernova remnant with a neutron star in its center. Neutron stars are born in supernovae. When the outer parts of the star explode to the outside, the inner part of the star implodes. The constituent parts of ordinary atoms – electrons and protons – are ground together by gravity to form neutrons. Want to know more about neutron stars? Try this explanatory, of The conversation. Image via ESA.

Astronomers have stated that this pulsar gravitated around the common center of mass in 6.2 hours with a companion star. The companion is extremely light, with a mass of one fiftieth of that of our sun. The companion star can be locked to the pulsar, in the same way that the Earth's moon is also locked, so that one side of the moon is still facing the Earth. If one side of the companion star is still facing the pulsar, that side of the star would be heated by the gamma radiation of the pulsar. Astronomers have believed they see the warm side of the "day" and the "colder" side of the companion, brighter in color and color as the companion's star and pulsar gravitate around their common center of mass.

These details were made possible because in this new study, astronomers analyzed a lot of data on this pulsar and his companion. They used 8.5 years of data from NASA's Fermi Gamma space telescope, two years of LOFAR radio observations, as well as observations from two large optical telescopes and gravitational wave data from LIGO detectors. The main author of this new research is Lars Nieder, PhD. student at the Albert Einstein Center (Max Planck Institute) in Hanover. Data analysis is one of his fields of study. He commented:

This research is extremely difficult because the Fermi gamma ray telescope recorded the equivalent of about 200 gamma rays emitted by the weak pulsar during the 8.5 years of observation. Meanwhile, the pulsar itself has turned 220 billion times. In other words, a gamma ray was only observed once in a billion rotations!

For each of these gamma rays, the search must identify exactly when, at each 1.4 millisecond rotation, it was emitted.

Lars Nieder, a PhD student in astrophysics at the Albert Einstein Institute in Hanover, led the new research on PSR J0952-0607. Image via Max Planck.

According to the statement of these astronomers:

This requires browsing the data with a very fine resolution so as not to miss any possible signal. The computing power required is huge. The very sensitive search for low gamma-ray pulsations would have taken 24 years to be done on a single computer heart. Using the Atlas information cluster at AEI Hannover, everything ended in just two days.

Astronomers reported finding surprises in the data. They were surprised, for example, to not find gamma pulsations before July 2011. They said:

The reason the pulsar seems to show only pulsations after this date is unknown. The variations in the amount of gamma rays it emitted might be one of the reasons, but the pulsar is so weak that it has not been possible to test this hypothesis with sufficient accuracy. Changes in the orbit of pulsars observed in similar systems may also provide an explanation, but the data do not even suggest that this was happening.

For the moment, the absence of gamma pulsations before 2011 is a mystery.

Bruce Allen is director of the Albert Einstein Institute in Hanover and the doctorate of Nieder. supervisor. Image via Max Planck.

Astronomers have pointed out that fast-rotating pulsars such as J0952-0607 are probes of extreme physics. They said:

The speed with which neutron stars can rotate before separating from centrifugal forces is unknown and depends on unknown nuclear physics. The millisecond pulsars, like J0952-0607, rotate so fast because they have been accelerated by the accumulation of matter on their mate. This process is thought to bury the magnetic field of the pulsar. With long-term gamma ray observations, the research team has shown that J0952-0607 has one of the ten lowest magnetic fields ever measured for a pulsar, which is in line with theoretical expectations.

Bruce Allen, Ph.D. of Nieder Supervisor and Director of the Albert Einstein Institute of Hanover, added:

We will continue to study this system with gamma, radio and optical observatories, because questions remain unanswered on this subject. This discovery also shows once again that extreme pulsar systems are hiding in the Fermi LAT catalog.

We also use Einstein @ Home, our distributed science based citizen science project, to search for binary gamma – ray pulsar systems in other Fermi LAT sources and are confident that we can do it again. other exciting discoveries in the future.

The pulse profile (distribution of gamma ray photons during a pulsar rotation) of J0952-0607 is shown at the top. You will find below the corresponding distribution of individual photons over the 10 years of observation. The gray scale shows the probability (photon weight) that individual photons come from the pulsar. From mid-2011, the photons line up along the tracks corresponding to the pulse profile. This shows the detection of gamma-ray pulsations, which was not possible until mid-2011. Image via the L. Nieder / Max Planck Institute of Gravitational Physics.

The final result: PSR J0952-0607 runs at 707 times per second, making it the second fastest and fastest pulsar outside of globular clusters. Astronomers have just discovered that this pulsar emits gamma rays of high energy.

Source: Detection and synchronization of Pulsar 707 Hz gamma-ray pulsations J0952 to 0607

Via Max Planck Institute for Gravitational Physics