The Institute of Corpuscular Physics (IFIC), which is located in the scientific-academic area of the Science Park of the University of Valencia, as well as being a joint center of the CSIC and the University of Valencia, is involved in a major breakthrough to detect a type of neutron star, one of the densest objects in the universe, difficult to identify by other means such as radio telescopes or low-energy gamma rays, but visible through their extended emissions of very high-energy gamma rays.
IFIC researcher Sara Coutiño de León co-leads a study that has observed a characteristic structure in signals emitted by middle-aged pulsars, a particular type of neutron star. This structure, in the form of halos, would make it possible to detect populations of pulsars which might go undetected by traditional observation methods. The finding is published in Physical Review Letters.
A neutron star is the remnant of a star much more massive than the Sun after a supernova explosion. This rest is very dense, and in some cases behaves like a pulsar, emitting regular pulses of electromagnetic radiation. If their radiation beams point towards the Earth during its rotation, they are detected as regular pulses of light, which is why they are known as pulsars. It is as if a rotating flashlight turns on and off periodically when passing in front of people.
"Many middle-aged pulsars are not easily detectable in radio, X-ray or even less energetic gamma rays. Therefore, detecting this type of halos allows to reveal a population of hidden pulsars that otherwise would go unnoticed", Sara Coutiño de León, IFIC researcher and colider of the study
Pulsars are natural particle accelerators that convert the rotational energy of a neutron star into the kinetic energy of particles. "In a young pulsar, the charged particles it accelerates are trapped in its magnetic field. But by reaching an age of tens of thousands of years (between 20,000 and 100,000 years), this field weakens and allows the particles to escape into the interstellar medium. There, interacting with surrounding radiation fields, they produce the so-called gamma rays, the most energetic light in the universe", explains Sara Coutiño, researcher at IFIC and one of the main authors of the work.
Now, the international collaboration operated by the HAWC (High-Altitude Water Cherenkov) gamma-ray observatory has identified a characteristic structure in the form of halos around some pulsars, observable in the emission of very high energy gamma-rays. The result of the study indicates that these gamma rays, inferred from the particles detected by HAWC from its location at more than 4,000 meters above sea level in Mexico, could originate from particles accelerated by pulsars that escape into the interstellar medium and interact with surrounding radiation.
In 2017, the HAWC observatory was the first to discover the existence of very high-energy gamma-ray halos (so-called TeV halos) around two pulsars. This pioneering finding opened up new questions about the origin of these halos and their possible presence in other similar systems. Since then, the HAWC collaboration has been investigating whether these halos are exceptional phenomena or if they represent a common feature in middle-aged pulsars. In this new study, 36 such pulleys were analyzed, statistically demonstrating that the presence of these halos could be a generalized feature in this population of objects.
"Many middle-aged pulsars are not easily detectable in radio, X-ray or even less energetic gamma rays. Therefore, detecting this type of halos allows to reveal a population of hidden pulsars that would otherwise go unnoticed", summarizes the IFIC researcher. "Although the physical mechanism of halos production is still an open issue, the results of this work support the hypothesis that these halos could be common, which constitutes an important step towards understanding their origin and prevalence. In addition to its potential for revealing hidden pulsations, the study of gamma-ray halos also offers a unique opportunity to understand how cosmic rays accelerate and propagate in the interstellar medium, a key process in high-energy astrophysics".
Source: UV News