310 research outputs found
Absolute timing of the Crab pulsar with the INTEGRAL/SPI telescope
We have investigated the pulse shape evolution of the Crab pulsar emission in
the hard X-ray domain of the electromagnetic spectrum. In particular, we have
studied the alignment of the Crab pulsar phase profiles measured in the hard
X-rays and in other wavebands. To obtain the hard X-ray pulse profiles, we have
used six year (2003-2009, with a total exposure of about 4 Ms) of publicly
available data of the SPI telescope on-board of the INTEGRAL observatory,
folded with the pulsar time solution derived from the Jodrell Bank Crab Pulsar
Monthly Ephemeris. We found that the main pulse in the hard X-ray 20-100 keV
energy band is leading the radio one by milliperiods in phase, or
in time. Quoted errors represent only statistical
uncertainties.Our systematic error is estimated to be and is
mainly caused by the radio measurement uncertainties. In hard X-rays, the
average distance between the main pulse and interpulse on the phase plane is
. To compare our findings in hard X-rays with the soft 2-20
keV X-ray band, we have used data of quasi-simultaneous Crab observations with
the PCA monitor on-board the Rossi X-Ray Timing Explorer (RXTE) mission. The
time lag and the pulses separation values measured in the 3-20 keV band are
(corresponding to ) and
parts of the cycle, respectively. While the pulse separation values measured in
soft X-rays and hard X-rays agree, the time lags are statistically different.
Additional analysis show that the delay between the radio and X-ray signals
varies with energy in the 2 - 300 keV energy range. We explain such a behaviour
as due to the superposition of two independent components responsible for the
Crab pulsed emission in this energy band
IGR J17098-3628: an X-ray Nova discovered by INTEGRAL
We report the discovery with INTEGRAL on March 24, 2005, and follow-up
observations of the distant Galactic X-ray nova IGR J17098-3628.Comment: 4 pages, Proceedings of the 6th INTEGRAL Workshop "The Obscured
Universe" (July 2-8, 2006, Moscow), ESA SP-62
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