Researchers focus on massive ‘spider’ pulsar

Pulsars: Celestial Guardians of the Universe

In the vastness of space, pulsars shine like cosmic beacons, revealing the mysteries of theuniverse. But what exactly is a pulsar? Imagine a massive star that, after burning all its nuclear fuel, collapses on itself to form an incredibly dense neutron star. This small star, measuring only a few kilometers in diameter, rotates at a dizzying speed on its own axis, emitting beams of radiation at regular intervals. These emissions, detected on Earth as regular pulsations, are what we call pulsars. Among these pulsating stars, millisecond pulsars are distinguished by their rotation period of less than 30 milliseconds. Scientists believe that they are born in binary systems, where a massive star evolves into a neutron star that, attracted by the matter of its stellar companion, begins to rotate rapidly.

Spider pulsars: enigmatic companions

That said, some binary pulsars stand out for their complex and fascinating dynamics. Called spider pulsars, these pulsating stars have unique characteristics that have attracted the attention of astronomers around the world. In these binary systems, the neutron star, formed from the collapse of a massive star, emits a wind of relativistic particles that extends into space. This wind, composed of charged particles traveling at speeds close to that of light, interacts with the wind emitted by its stellar companion. This phenomenon creates a region of turbulence at the boundary between the two winds, known as an intrabinary shock. The intrabinary shock is therefore a region where particles from the two winds collide, creating magnetic forces and shock waves that propel radiation emissions into the surrounding space. These emissions, detectable from Earth, allow astronomers to observe and study the dynamics of the binary system and to explore the complex relationship between the pulsar and its stellar companion. Note that spider pulsars are often associated with two types of stellar companions. “Black widows” are low-mass companion stars that have lost much of their material under the gravitational influence of the pulsar. “Redbacks,” on the other hand, are more massive companion stars that maintain a more balanced gravitational interaction with the pulsar. Illustration of a binary pulsar. Credit: NASA That said, in a recent observing campaign, leading astronomers at Stanford University trained their telescopes on the massive pulsar PSR J2215+5135, a “red back,” for several reasons. First, we know that this pulsar belongs to the category of spider pulsars, which are known to exhibit complex and fascinating dynamics. Given their importance in understanding the physics of neutron stars and binary systems, the study of these pulsars is of paramount interest to astronomers. Furthermore, PSR J2215+5135 is a massive pulsar, which means that it could provide crucial information about the physical processes taking place inside neutron stars and how they interact with their stellar environment. By closely examining PSR J2215+5135 in X-ray and optical light, the researchers hoped to obtain detailed data on its internal structure, rotational dynamics, and interaction with its stellar companion. This information would not only help us better understand this specific pulsar, but also deepen our knowledge of spider pulsars in general, opening up new perspectives in the field of stellar astrophysics.

What did the researchers learn?

These new observations have revealed fascinating details about PSR J2215+5135. First, the pulsar’s neutron star was estimated to have a mass of about 2.15 solar masses, while its stellar companion is losing mass at a surprisingly slow rate, about 0.0003 Earth masses per year. This mass loss could eventually lead PSR J2215+5135 to become an isolated millisecond pulsar. In addition, X-ray analysis confirmed the presence of an intrabinary shock, or IBS, and that it remained wrapped around the pulsar. This observation is characteristic of “redback” spider pulsars, where the wind emitted by the stellar companion dominates that of the pulsar, causing the IBS to form around the pulsar itself. Conversely, in “black widow” systems, it is the IBS that wraps around the companion object. Finally, PSR J2215+5135 was located at a distance of about 10,800 light-years from Earth, and its rotational power was measured at 52 decillion ergs per second. These data provide valuable insight into the physics and dynamics of this binary system, inviting us to deepen our understanding of these fascinating cosmic phenomena. Source: Arxiv