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Be–white Dwarf X-ray Binary System
Be–white dwarf X-ray binary systems (BeWDs) are a rare type of X-ray binary consisting of a white dwarf that accretes matter from a rapidly-rotating Be star. These systems form through binary evolution where mass transfer spins up the accretor to become a Be star while the donor evolves into a white dwarf. BeWDs probably originate from a Be star and a Subdwarf O star, subdwarf O or Subdwarf B star, B star binaries. Population synthesis models indicate these systems can evolve through two primary pathways: * Approximately 60-70% merge into red giants that observationally look like luminous red novae. * About 30-40% evolve into double white dwarf systems that may be detectable as gravitational wave sources by Laser Interferometer Space Antenna (LISA), and will be its "most likely gravitational wave source". The formation requires specific initial conditions: the primary must transfer sufficient mass to spin up the secondary to Be star velocities without triggering common envelope e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Tale Of Two Stars ESA506449
A, or a, is the first Letter (alphabet), letter and the first vowel letter of the Latin alphabet, used in the modern English alphabet, and others worldwide. Its name in English is ''English alphabet#Letter names, a'' (pronounced ), plural ''aes''. It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version is often written in one of two forms: the double-storey and single-storey . The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children, and is also found in italic type. In English, ''English articles, a'' is the indefinite article, with the alternative form ''an''. Name In English, the name of the letter is the ''long A'' sound, pronounced . Its name in most other languages matches the letter's pronunciation in open syllables. History The earliest know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
