1,309 research outputs found
Review of overall parameters of giant radio pulses from the Crab pulsar and B1937+21
We present a review of observed parameters of giant radio pulses, based on
the observations conducted by our group during recent years. The observations
cover a broad frequency range of about 3 octaves, concentrating between 600 and
4850 MHz. Giant pulses of both the Crab pulsar and the millisecond pulsar
B1937+21 were studied with the 70-m Tidbinbilla, the 100-m GBT, 64-m Kalyazin
and Westerbork radio telescopes. We discuss pulse energy distribution,
dependence of peak flux density from the pulse width, peculiarities of radio
spectra, and polarization properties of giant radio pulses.Comment: 3 pages, 4 figures, to be published in the Proceedings of the
conference "40 Years of Pulsars: Millisecond Pulsars, Magnetars, and More"
held on August 12-17, 2007, McGill University, Montreal, Canad
Pulsar Science with the Green Bank 43m Telescope
The 43m telescope at the NRAO site in Green Bank, WV has recently been
outfitted with a clone of the Green Bank Ultimate Pulsar Processing Instrument
(GUPPI \cite{Ransom:2009}) backend, making it very useful for a number of
pulsar related studies in frequency ranges 800-1600 MHz and 220-440 MHz. Some
of the recent science being done with it include: monitoring of the Crab
pulsar, a blind search for transient sources, pulsar searches of targets of
opportunity, and an all-sky mapping project. For the Crab monitoring project,
regular observations are searched for giant pulses (GPs), which are then
correlated with -ray photons from the \emph{Fermi} spacecraft. Data
from the all-sky mapping project are first run through a pipeline that does a
blind transient search, looking for single pulses over a DM range of 0-500
pc~cm. These projects are made possible by MIT Lincoln Labs.Comment: 2 pages, 1 figure, to appear in AIP Conference Proceedings of Pulsar
Conference 2010 "Radio Pulsars: a key to unlock the secrets of the Universe",
Sardinia, October 201
Correlation of Chandra photons with the radio giant pulses from the Crab pulsar
No apparent correlation was found between giant pulses (GPs) and X-ray
photons from the Crab pulsar during 5.4 hours of simultaneous observations with
the Green Bank Telescope at 1.5 GHz and Chandra X-Ray Observatory primarily in
the energy range 1.5-4.5 keV. During the Crab pulsar periods with GPs the X-ray
flux in radio emission phase windows does not change more than by +-10% for
main pulse (MP) GPs and +-30% for interpulse (IP) GPs. During giant pulses
themselves, the X-ray flux does not change more than by two times for MP GPs
and 5 times for IP GPs. All limits quoted are compatible with 2-sigma
fluctuations of the X-ray flux around the sets of false GPs with random arrival
times. The results speak in favor of changes in plasma coherence as the origin
of GPs. However, the results do not rule out variations in the rate of particle
creation if the particles that emit coherent radio emission are mostly at the
lowest Landau level.Comment: 7 pages, 5 figures; to appear in The Astrophysical Journal, 201
Instantaneous Radio Spectra of Giant Pulses from the Crab Pulsar from Decimeter to Decameter Wavelengths
The results of simultaneous multifrequency observations of giant radio pulses
from the Crab pulsar, PSR B0531+21, at 23, 111, and 600 MHz are presented and
analyzed. Giant pulses were detected at a frequency as low as 23 MHz for the
first time. Of the 45 giant pulses detected at 23 MHz, 12 were identified with
counterparts observed simultaneously at 600 MHz. Of the 128 giant pulses
detected at 111 MHz, 21 were identified with counterparts observed
simultaneously at 600 MHz. The spectral indices for the power-law frequency
dependence of the giant-pulse energies are from -3.1 to -1.6. The mean spectral
index is -2.7 +/- 0.1 and is the same for both frequency combinations (600-111
MHz and 600-23 MHz). The large scatter in the spectral indices of the
individual pulses and the large number of unidentified giant pulses suggest
that the spectra of the individual giant pulses do not actually follow a simple
power law. The observed shapes of the giant pulses at all three frequencies are
determined by scattering on interstellar plasma irregularities. The scatter
broadening of the pulses and its frequency dependence were determined as
tau_sc=20*(f/100)^(-3.5 +/- 0.1) ms, where the frequency f is in MHz.Comment: 13 pages, 1 figure, 1 table (originally published in Russian in
Astronomicheskii Zhurnal, 2006, vol. 83, No. 7, pp. 630-637), translated by
Georgii Rudnitski
Correlation of Fermi photons with high-frequency radio giant pulses from the Crab pulsar
To constrain the giant pulse (GP) emission mechanism and test the model of
Lyutikov (2007) for GP emission, we have carried out a campaign of simultaneous
observations of the Crab pulsar at gamma-ray (Fermi) and radio (Green Bank
Telescope) wavelengths. Over 10 hours of simultaneous observations we obtained
a sample of 2.1x10^4 giant pulses, observed at a radio frequency of 9 GHz, and
77 Fermi photons, with energies between 100 MeV and 5 GeV. The majority of GPs
came from the interpulse (IP) phase window. We found no change in the GP
generation rate within 10-120 s windows at lags of up to +-40 min of observed
gamma-ray photons. The 95% upper limit for a gamma-ray flux enhancement in
pulsed emission phase window around all GPs is 4 times the average pulsed
gamma-ray flux from the Crab. For the subset of IP GPs, the enhancement upper
limit, within the IP emission window, is 12 times the average pulsed gamma-ray
flux. These results suggest that GPs, at least high-frequency IP GPs, are due
to changes in coherence of radio emission rather than an overall increase in
the magnetospheric particle density.Comment: 9 pages, 6 figures; to appear in The Astrophysical Journal, February
201
A Giant Sample of Giant Pulses from the Crab Pulsar
We observed the Crab pulsar with the 43-m telescope in Green Bank, WV over a
timespan of 15 months. In total we obtained 100 hours of data at 1.2 GHz and
seven hours at 330 MHz, resulting in a sample of about 95000 giant pulses
(GPs). This is the largest sample, to date, of GPs from the Crab pulsar taken
with the same telescope and backend and analyzed as one data set. We calculated
power-law fits to amplitude distributions for main pulse (MP) and interpulse
(IP) GPs, resulting in indices in the range of 2.1-3.1 for MP GPs at 1.2 GHz
and in the range of 2.5-3.0 and 2.4-3.1 for MP and IP GPs at 330 MHz. We also
correlated the GPs at 1.2 GHz with GPs from the Robert C. Byrd Green Bank
Telescope (GBT), which were obtained simultaneously at a higher frequency (8.9
GHz) over a span of 26 hours. In total, 7933 GPs from the 43-m telescope at 1.2
GHz and 39900 GPs from the GBT were recorded during these contemporaneous
observations. At 1.2 GHz, 236 (3%) MP GPs and 23 (5%) IP GPs were detected at
8.9 GHz, both with zero chance probability. Another 15 (4%) low-frequency IP
GPs were detected within one spin period of high-frequency IP GPs, with a
chance probability of 9%. This indicates that the emission processes at high
and low radio frequencies are related, despite significant pulse profile shape
differences. The 43-m GPs were also correlated with Fermi gamma-ray photons to
see if increased pair production in the magnetosphere is the mechanism
responsible for GP emission. A total of 92022 GPs and 393 gamma-ray photons
were used in this correlation analysis. No significant correlations were found
between GPs and gamma-ray photons. This indicates that increased pair
production in the magnetosphere is likely not the dominant cause of GPs.
Possible methods of GP production may be increased coherence of synchrotron
emission or changes in beaming direction.Comment: 33 pages, 10 figures, 6 tables, accepted for publication in Ap
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