Pulsars, X-Ray Binaries and Kilonovas

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Neutron stars are among the most captivating and extreme celestial objects in the universe, distinguished by their extraordinary density, rapid rotation, and potent magnetic fields. These stellar remnants are formed from the collapse of colossal stars following a supernova explosion, representing a pivotal stage in the life cycle of such celestial bodies. Neutron stars are frequently regarded as the precursors to black holes, embodying some of the most extraordinary states that matter can attain while still retaining its classification as matter. Consequently, they provide profound insights into the fundamental nature of the cosmos. A defining characteristic of neutron stars is their rapid spin, which arises from the conservation of angular momentum during the collapse of the progenitor star. This spin generates a substantial magnetic dynamo, producing intense magnetic fields that can surpass one billion teslas. These magnetic fields are instrumental in driving emissions observed in X-rays and gamma rays, leading to the categorization of neutron stars into two primary groups: pulsars and magnetars. Pulsars are neutron stars that emit beams of electromagnetic radiation as they rotate. These beams traverse space, generating periodic signals that can be detected by astronomers on Earth. The Crab Pulsar, situated at the center of the Crab Nebula, serves as a quintessential example of a pulsar, illustrating the interplay between stellar evolution and high-energy emissions. The discovery of pulsars in 1967, which was initially fortuitous, revolutionized the field of astrophysics, providing researchers with a novel instrument to investigate fundamental aspects of physics, including tests of general relativity and the behavior of matter in extreme environments. In contrast, magnetars constitute a subset of neutron stars characterized by their exceptionally strong magnetic fields, which can be a thousandfold greater than those of typical pulsars. The intense magnetic fields of magnetars can generate dramatic bursts of gamma-ray and X-ray emissions, making them among the most potent sources of energy in the universe. Their emissions can also have substantial implications for their surrounding environments, potentially influencing star formation and the evolution of nearby celestial bodies. Neutron stars can also produce phenomena akin to those observed in white dwarfs, albeit with significantly more extreme outcomes. For instance, the merging of two neutron stars can result in kilonovae, explosive events that arise from the rapid neutron capture process. Kilonovae possess the capability to produce heavy elements and release vast amounts of energy, contributing to the nucleosynthesis of elements within the universe. The study of kilonovae has yielded valuable insights into the origins of elements such as gold and platinum, thereby deepening our comprehension of cosmic chemical evolution. The Crab Nebula itself serves as a captivating illustration of the consequences of stellar evolution and the interactions between neutron stars and their environments. This supernova remnant, formed from the explosion of a colossal star, contains a pulsar at its center, which emits beams of radiation as it rotates. Observations across diverse wavelengths, including X-rays from the Chandra X-ray Observatory and optical data from the Hubble Space Telescope, have unveiled a wealth of information regarding the dynamics of the Crab Nebula and the processes transpiring within and surrounding the pulsar. Neutron stars can be involved in the process of X-ray bursts, which occur when material from a companion star is accreted onto the neutron star’s surface. This accretion can lead to sudden outbursts of X-ray radiation, resulting in substantial energy releases that can be detected from considerable distances.

0:00 Introduction
1:17 Pulsars: Accidental Discovery in 1967
6:57 Pulsar "Lighthouse" Model
12:04 Pulsar Evolution
17:48 The Crab Nebula in History
21:14 Many Wavelength Crab
22:22 The Crab by Chandra X-Ray Observatory
25:33 Recent Hubble image of M1
29:50 Vela Pulsar by Chandra
32:12 Binary Neutron Stars
35:03 X-Ray Binary spinning up a neutron star
38:11 Colliding Neutron Stars
39:50 Over the Top?
40:57 REVIEW QUESTIONS

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