Pulsating X-Ray Sources Are Believed to Be

question 89

Multiple Choice

Pulsating X-ray sources are believed to be

• A) white dwarf stars with intense magnetic fields; the X-rays are generated by flares like those on the Sun but much stronger.
• B) spinning neutron stars in binary systems, emitting X-rays because of mass transfer onto the neutron star from its normal companion.
• C) the same as regular (optical) pulsars but observed in X-rays.
• D) black holes in binary systems, with an accretion disk around the black hole emitting X-rays.

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A steroid hormone produced in the ovaries, placenta, and adrenal glands, playing a key role in the menstrual cycle, pregnancy, and embryogenesis.