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X-ray pulsar-based navigation and timing (XNAV) or simply pulsar navigation is a navigation technique whereby the periodic X-ray signals emitted from pulsars are used to determine the location of a vehicle, such as a spacecraft in deep space. A vehicle using XNAV would compare received X-ray signals with a database of known pulsar frequencies ...
An intermediate-mass binary pulsar (IMBP) is a pulsar-white dwarf binary system with a relatively long spin period of around 10–200 ms consisting of a white dwarf with a relatively high mass of approximately . [7] The spin periods, magnetic field strengths, and orbital eccentricities of IMBPs are significantly larger than those of low mass binary pulsars (LMBPs). [7]
For example, as pulsars gradually lose energy, they approach what is called the pulsar "death valley," a theoretical area in pulsar pulsar period—period derivative space, where the pulsar emission mechanism is thought to fail but may become sporadic as pulsars approach this region.
An X-ray pulsar is a type of binary star system consisting of a typical star (stellar companion) in orbit around a magnetized neutron star.The magnetic field strength at the surface of the neutron star is typically about 10 8 Tesla, over a trillion times stronger than the strength of the magnetic field measured at the surface of the Earth (60 μT).
The pulsar and its neutron star companion both follow elliptical orbits around their common center of mass. The period of the orbital motion is 7.75 hours, and the two neutron stars are believed to be nearly equal in mass, about 1.4 solar masses.
Millisecond pulsars have been detected in radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The leading hypothesis for the origin of millisecond pulsars is that they are old, rapidly rotating neutron stars that have been spun up or "recycled" through accretion of matter from a companion star in a close binary system.
The equations above have fixed point solutions with constant amplitudes, corresponding to single-mode (A 1 0, A 2 = 0) or (A 1 = 0, A 2 0) and double-mode (A 1 0, A 2 0) solutions. These correspond to singly periodic and doubly periodic pulsations of the star.
The pulsar provides a strong periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, "crab" and "millicrab" are sometimes used as units of flux density. A millicrab corresponds to a flux density of about 2.4 × 10 −11 erg s −1 cm −2 ( 2.4 × 10 −14 W/m 2 ) in the 2–10 keV X-ray band, for a "crab ...