A Thorne–Żytkow object, also known as a hybrid star, is a conjectured type of star wherein a red giant or red supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. Such objects were hypothesized by Kip Thorne and Anna Żytkow in 1977. In 2014, it was discovered that the star HV 2112, located in the Small Magellanic Cloud (SMC), was a strong candidate. Another possible candidate is the star HV 11417, also located in the SMC.
X-ray bursters are one class of X-ray binary stars exhibiting X-ray bursts, periodic and rapid increases in luminosity that peak in the X-ray region of the electromagnetic spectrum. These astrophysical systems are composed of an accreting neutron star and a main sequence companion 'donor' star. There are two types of X-ray bursts, designated I and II. Type I bursts are caused by thermonuclear runaway, while type II arise from the release of gravitational (potential) energy liberated through accretion. For type I (thermonuclear) bursts, the mass transferred from the donor star accumulates on the surface of the neutron star until it ignites and fuses in a burst, producing X-rays. The behaviour of X-ray bursters is similar to the behaviour of recurrent novae. In the latter case the compact object is a white dwarf that accretes hydrogen that finally undergoes explosive burning.
Bohdan Paczyński or Bohdan Paczynski was a Polish astronomer notable for his theories and work in the fields of stellar evolution, accretion discs, and gamma ray bursts. He is the recipient of the Eddington Medal (1987), the Henry Draper Medal (1997), the Gold Medal of the Royal Astronomical Society (1999), and the Order of Polonia Restituta (2007).
A stellar black hole is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. The process is observed as a hypernova explosion or as a gamma ray burst. These black holes are also referred to as collapsars.
Richard Klein is an Adjunct Professor of Astronomy at the University of California, Berkeley and a Scientific Staff Member at the Lawrence Livermore National Laboratory (LLNL). Klein received his bachelor's degree in physics from Rensselaer Polytechnic Institute in 1966 and his PhD in physics from Brandeis University in 1973.
Michiel Baldur Maximiliaan van der Klis is a Dutch astronomer best known for his work on extreme 'pairings' of stars called X-ray binaries, more particularly his explanation of the occurrence of quasi-periodic oscillations (QPOs) in these systems and his co-discovery of the first millisecond X-ray pulsar. In the 1980s he gained worldwide fame with his investigation of QPOs. His revolutionary discoveries have had an enormous impact in his field of research; in effect, they have made it what it is today. Van der Klis pioneered special mathematical analysis techniques that are now regarded as the “gold standard” within his discipline.
The Heidelberg Institute for Theoretical Studies is a non-profit research institution founded in 2010 by Klaus Tschira, co-founder of SAP, through the Klaus Tschira Stiftung foundation. Situated at the intersection of the natural sciences, mathematics, and computer science, it is dedicated to the exploration of fundamental research, with its core focus being in the realm of processing, structuring, and analysis of datasets, encompassing a diverse array of research fields, from molecular biology to astrophysics.
Dmitry Valerevich Bisikalo is a Russian astrophysicist and an expert in the interaction of binary stars. He is a member of the Russian Academy of Sciences, the IAU, Acting Chief of the Scientific Secretary of the Russian Academy of Sciences and Chief Researcher of the Institute of Astronomy of the Russian Academy of Sciences (RAS).
Chryssa Kouveliotou is a Greek astrophysicist. She is a professor at George Washington University and a retired senior technologist in high-energy astrophysics at NASA's Marshall Space Flight Center in Huntsville, Alabama.
Vassiliki Kalogera is a Greek astrophysicist. She is a professor at Northwestern University and the Director of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). She is a leading member of the LIGO Collaboration that observed gravitational waves in 2015.
Andrew Robert King, is a British astrophysicist and Professor of Astrophysics in the Department of Physics and Astronomy at the University of Leicester. His previous institutions include University College London and the Institute for Theoretical Physics at the University of Hamburg and a visiting position at the Observatoire de Paris. He currently holds visiting positions at the Astronomical Institute of the University of Amsterdam, and he is a visiting professor at Leiden University. He has served as Editor and now is Deputy Editor-in-Chief of the international astronomy journal Monthly Notices of the Royal Astronomical Society.
BP Crucis is an X-ray binary system containing a blue hypergiant and a pulsar.
Anna Louise Watts is a Professor of Astrophysics at the University of Amsterdam. She studies neutron stars and their thermonuclear explosions.
Luciano Rezzolla is an Italian professor of relativistic astrophysics and numerical relativity at the Goethe University Frankfurt. His main field of study is the physics and astrophysics of compact objects such as black holes and neutron stars. It was announced in 2019 that he had been appointed honorary Andrews Professor of Astronomy at Trinity College Dublin (TCD).
Rudy Wijnands is a Dutch astrophysicist. He is professor of Observational High-Energy Astrophysics at the University of Amsterdam.
Irene Tamborra is the Italian particle astrophysicist, specializing in the areas of neutrino astrophysics and cosmology as well as multi-messenger astronomy. She is professor of particle astrophysics at the Niels Bohr Institute, University of Copenhagen.
Ken'ichi Nomoto is a Japanese astrophysicist and astronomer, known for his research on stellar evolution, supernovae, and the origin of heavy elements.
Pycnonuclear fusion is a type of nuclear fusion reaction which occurs due to zero-point oscillations of nuclei around their equilibrium point bound in their crystal lattice. In quantum physics, the phenomenon can be interpreted as overlap of the wave functions of neighboring ions, and is proportional to the overlapping amplitude. Under the conditions of above-threshold ionization, the reactions of neutronization and pycnonuclear fusion can lead to the creation of absolutely stable environments in superdense substances.
Common envelope jets supernova (CEJSN) is a type of supernova, where the explosion is caused by the merger of a giant or supergiant star with a compact star such as a neutron star or a black hole. As the compact star plunges into the envelope of the giant/supergiant, it begins to accrete matter from the envelope and launches jets that can disrupt the envelope. Often, the compact star eventually merges with the core of the giant/supergiant; other times the infall stops before core merger.
You-Hua Chu is a Taiwanese astronomer. She has served as the director of the Institute of Astronomy and Astrophysics, Academia Sinica and the chair of the Department of Astronomy at the University of Illinois at Urbana-Champaign. Her main research areas are interactions between the interstellar medium and stars and observations of planetary systems in the post main sequence stages.
