Multiwavelengh study of LMC Pulsar PSR B0540-69

The LMC Pulsar, PSR B0540-69, is the second youngest known isolated pulsar after the Crab. A multiwavelengh approach to simultaneously observe the LMC Pulsar in the radio, optical, X-ray, and soft gamma-ray regimes has begun. This is the first-ever attempt to simultaneously observe PSR B0540-69 in both optical (CTIO) and X-ray (RXTE) wavelengths and will determine if there exists phase difference of the pulse between two energy bands. This program will derive a precise rotational ephemeris to determine the phase relation of the pulse in different energy bands, characterize the pulse shape, investigate the high energy cut-off, and derive the braking index of the pulsar.

Phase shift between optical and X-ray pulses detected!
The simultaneous observations in optical (CTIO) and X-ray (RXTE) for the PSR B540-69 on November 12, 1996 reveal that there is a "shift" in the phase-folded light curves. The shift is ~15% of the pulsar period (50 msec) and the optical pulse arrives 7.5 msec earlier than the X-ray pulse. Panel (c) in below figure is a cross-check of our timing-analysis process using an optical observation of the Crab pulsar. The vertical dotted-lines are the predicted arrival time of the Crab pulse and the offset from the detected pulse is within 0.08% of the Crab period (33 msec) or ~0.25 msec. This uncertainty in our analysis proves that the detected 7.5 msec offset in optical pulse of PSR B0540-69 is for real.

Test of FTOOLS phase-binner (FASEBIN) with the RXTE Crab pulsar data.
The histograms are the RXTE Crab data produced with FASEBIN
and the vertical dotted line represents the absolute zero-phase
from the Crab pulsar radio ephemeris of the Princeton data base.

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