Further observations of VHE gamma rays from Vela X-1
C C G Bowden; S M Bradbury; P M Chadwick; J E Dickinson; N A Dipper; P J Edwards; E W Lincoln; T J L McComb; K J Orford; S M Rayner; K E Turver; C C G Bowden; Dept. of Phys., Durham Univ., UK; S M Bradbury; Dept. of Phys., Durham Univ., UK; P M Chadwick; Dept. of Phys., Durham Univ., UK; J E Dickinson; Dept. of Phys., Durham Univ., UK; N A Dipper; Dept. of Phys., Durham Univ., UK; P J Edwards; Dept. of Phys., Durham Univ., UK; E W Lincoln; Dept. of Phys., Durham Univ., UK; T J L McComb; Dept. of Phys., Durham Univ., UK; K J Orford; Dept. of Phys., Durham Univ., UK; S M Rayner; Dept. of Phys., Durham Univ., UK; K E Turver; Dept. of Phys., Durham Univ., UK
Журнал:
Journal of Physics G: Nuclear and Particle Physics
Дата:
1992-07-01
Аннотация:
Observations of Vel X-1 were made in February 1991 using the University of Durham Mark III and IV VHE gamma-ray telescopes at Narrabri, New South Wales, Australia. The complete data-set shows evidence for weak but apparently constant periodicity at the X-ray pulsar period with a signal strength compatible with the authors' earlier measurements. In addition, on two occasions (February 13 and February 22 1991) they have evidence for short (1800 s) outbursts of emission of gamma rays modulated with the pulsar period. These outbursts occur at the same orbital phase (0.68), and the periodic effects noted during the outbursts have probabilities of change occurrence of 5.9*10<sup>-4</sup> and 4.4*10<sup>-7</sup>.
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