Mr
Jian Li
(Institute of High Energy Physics, CAS)
LS I +61 303 is one of a handful of high-mass X-ray
binaries that have been detected at all frequencies
through radio to TeV. Its nature is still under debate,
with rotationally powered pulsar-composed systems and
microquasar jets being discussed. LS I +61 303 is a very
bright TeV source and one of the 15th brightest GeV
sources detected by Fermi. However, it enters a low TeV
state and its Fermi MeV-GeV emission has declined in
recent years for an unknown reason.
We found evidence from the longest monitoring of
LS I +61 303 done to date by RXTE for the 1667 days
super-orbital modulation in X-ray, which is probably
related to the recent low state of very high energy
emission. The 1667 days super-orbital period has already
been detected at non-contemporaneous radio and optical
measurements. We have found in phase super-orbital
variability between optical frequencies and X-ray.
However, the super-orbital variability at radio
frequencies and X-ray are not consistent in phase,
a 281.8 +/- 44.6 days shift are discovered.
The multi-wavelength phenomenology in super-orbital
modulation of LS I + 61 303 and in particular, the recent
low TeV emission, can be explained in the context of a
high magnetic field, slow period pulsar model. In that
case, LS I +61 303 system would most likely be subject to
a flip-flop behavior, from a rotationally powered ejector
regime in apastron to a propeller regime in periastron
along each of the system’s eccentric orbits. With long
term variation of the accreted mass, these observed multi-
wavelength behaviors are expected from LS I +61 303.
0
LS I +61 303 is one of a handful of high-mass X-ray
binaries that have been detected at all frequencies
through radio to TeV. Its nature is still under debate,
with rotationally powered pulsar-composed systems and
microquasar jets being discussed. LS I +61 303 is a very
bright TeV source and one of the 15th brightest GeV
sources detected by Fermi. However, it enters a low TeV
state and its Fermi MeV-GeV emission has declined in
recent years for an unknown reason.
We found evidence from the longest monitoring of
LS I +61 303 done to date by RXTE for the 1667 days
super-orbital modulation in X-ray, which is probably
related to the recent low state of very high energy
emission. The 1667 days super-orbital period has already
been detected at non-contemporaneous radio and optical
measurements. We have found in phase super-orbital
variability between optical frequencies and X-ray.
However, the super-orbital variability at radio
frequencies and X-ray are not consistent in phase,
a 281.8 +/- 44.6 days shift are discovered.
The multi-wavelength phenomenology in super-orbital
modulation of LS I + 61 303 and in particular, the recent
low TeV emission, can be explained in the context of a
high magnetic field, slow period pulsar model. In that
case, LS I +61 303 system would most likely be subject to
a flip-flop behavior, from a rotationally powered ejector
regime in apastron to a propeller regime in periastron
along each of the system’s eccentric orbits. With long
term variation of the accreted mass, these observed multi-
wavelength behaviors are expected from LS I +61 303.
Mr
Jian Li
(Institute of High Energy Physics, CAS)
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