440 research outputs found
RXTE observations of single pulses of PSR B0531+21: II Test for radio behavior
This article is the second in the series that analyze about 1.87 million
periods of Crab pulsar, observed by the PCA detector aboard the RXTE x-ray
observatory. At these energies the pulsar displays none of the three phenomena
that are often seen in normal radio pulsars -- ``pulse nulling'', ``systematic
sub pulse drifting'' and ``mode changing''. Presence or absence of these three
behavior in the Crab pulsar, at radio wavelengths, something that has not been
rigorously established yet, might be important for a satisfactory understanding
of the above three phenomena.Comment: 6 pages, 4 figure
A non-glitch speed-up event in the Crab Pulsar
Context: The rotation history of the Crab Pulsar is well described by (1) a
rotation frequency and a slowdown model that is specified by its first
two time derivatives and , known as the secular slowdown
model, (2) occasional (once in years) significant and abrupt
increases in the magnitude of and (occurring on timescales of
minutes), known as glitches, and (3) much slower increases and decreases in
and (occurring over months and years) that are an order of
magnitude smaller, known as timing noise.
Aims: This work reports a speed-up event in the Crab Pulsar that occurred
around February that is distinct from glitches and timing noise.
Methods: Monthly s and s of the Crab Pulsar, obtained at radio
frequencies and published by Jodrell Bank Observatory (JBO), are used to
demonstrate the speed-up event. Monthly arrival times of the Crab Pulsar's
pulse, also published by JBO, combined with X-ray data from the RXTE, SWIFT,
and NUSTAR observatories are used to verify the result.
Results: The speed-up event is caused by a persistent increase in ,
which results in a monotonic increase in . Over the last
days, has increased monotonically by an amount that is times
larger than the timing noise level.
Conclusions: This is a unique event in the Crab Pulsar. This is probably due
to a small increase in the Crab Pulsar's internal temperature. In its absence,
the next large glitch in the Crab Pulsar is expected to occur around
March. However, this event could have an important bearing on its occurrence.Comment: Accepted for publication as a Letter in Astronomy and Astrophysic
A review of x-ray spectral evolution in Crab pulsar
Pravdo et al (1997) claimed that the phase resolved x-ray spectrum in Crab
pulsar (PSR B0531+21) shows a spectral hardening at the leading edge of the
first peak of its integrated profile; this was a new and unexpected result.
This article reanalyzes their data, as well as some other related data, and
argues that the spectrum is as likely to be unvarying (i.e., neither hardening
nor softening).Comment: 12 pages, 4 figures, accepted for publication in A&
Time-scales of Radio Emission in PSR J0437-4715 at 327 MHz
Time-scales of radio emission are studied in PSR J0437-4715 at 327 MHz using
almost half a million periods of high quality data from Ooty Radio Telescope.
The radio emission in this milli second pulsar occurs on a short (s) time-scale
of approximately 0.026 +- 0.001 periods, and on a (l) time-scale that is much
longer than the widths of the components of the integrated profile
(approximately 0.05 periods). The width of the s emission increases with its
increasing relative contribution to the total radio emission. This may provide
constraints for the details of discharge of vacuum gaps above pulsar polar
caps. The s emission occasionally takes place in the form of intense spikes,
which are confined to the main component of the integrated profile for 90 per
cent of the time. The positions of spikes within a component of the integrated
profile have no simple relation to the shape of that component. This may have
impact on the interpretation of the integrated profile components in terms of
independent regions of emission on the polar cap.Comment: Accepted for publication in Vol 543 (1 Nov 2000) of The Astrophysical
Journa
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