(a) Centaurus X-3 is an x-ray pulsar with a pulse period of 4.84 seconds. Optica
ID: 2304146 • Letter: #
Question
(a) Centaurus X-3 is an x-ray pulsar with a pulse period of 4.84 seconds. Optically, an O-type supergiant is seen at the source of the x-rays. The x-ray pulses stop for a period of time every 2.1 days. Describe the Cen X-3 system, paying particular 3 attention to the source of the x-ray pulses. b) Consider this plot relating to another x-ray pulsar, Hercules X-1 HER X-I PULSE PERICO .23782 Describe what is shown in the plot, and discuss the mechanism for this behaviour How do measurements such as these rule out a certain scenario for the nature of the compact object in such systems? 2378 23780 .23779 3 974 976 YEAR (c) Imagine a close binary star system consisting of a low-mass main sequence star and a high-mass main sequence star. Briefly describe the likely evolution of this system, and indicate why it is unlikely that the system will become a low-mass 3 x-ray binary (d) Why is it thought that globular clusters contain an over-abundance of low-mass x-ray binary systems?Explanation / Answer
(a) Centaurus X-3 is an x-ray pulsar so it must be a neutron star, but as in optical wavelength an O-type supergiant star is seen at that point, it must be a binary system of one neutron star and one O-type supergiant star. The x-ray pulses stop for a period of 2.1 days means the neutron star orbit around the supergiant and for 2.1 days it hides behind the supergiant. The x-ray emission is due to the accretion of the matter from the supergiant star to the neutron star through the magnetic field in relativistic speed. This type of radiation is called synchrotron radiation.
(b) From the plot we can see that the pulse period has been decreased in year 1978 as compare to year 1972. It means the rotation speed of the pulsar has been increased over time. It is called spin-up trend of x-ray pulsar. The origin of this effect is the result of torque exerted on the neutron star by the accreting material. In other words over time the two systems come close to each other due to the accretion process and to make the angular momentum conserved the rotation speed increased.
(c) In a system of a low mass main sequence star and a high mass main sequence star the high mass star burns its mass in a very high rate through CNO cycle and ends up into a neutron star or a blackhole much more faster than the low mass star which will turned into a white dwarf in the end. Most probably after the high mass star becoming a black hole or neutron star the merging occurs and it does not get enough time to become a low-mass x-ray binary system.
(d) In globular clusters the systems are more likely to be binary due to the large numbers of stars present much closer to each other. The age of all the stars in the cluster are nearly same and the gas, dust left in the globular clusters after the formation of these stars are used as the accreting materials in the binary systems. Hence these clusters are likely to be over-populated with x-ray binary systems.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.