Disappearing pulses in Vela X-1

Kretschmar, P.; Kreykenbohm, I.; Wilms, J.; Staubert, R.; Heindl, W. A.; Gruber, D. E.; Rothschild, R. E.
April 2000
AIP Conference Proceedings;2000, Vol. 510 Issue 1, p163
Academic Journal
We present results from a 20 h RXTE observation of Vela X-1, including a peculiar low state of a few hours duration, during which the pulsation of the X-ray emission ceased, while significant non-pulsed emission remained. This “quiescent state” was preceded by a “normal state” without any unusual signs and followed by a “high state” of several hours of increased activity with strong, flaring pulsations. While there is clear spectral evolution from the normal state to the low state, the spectra of the following high state are surprisingly similar to those of the low state. © 2000 American Institute of Physics.


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