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Register a new userDetection of Giant Pulses in pulsar PSR J1752+2359
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Added by
Alexander A. Ershov
Publication date
2005
fields
Physics
and research's language is
English
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We report the detection of Giant Pulses (GPs) in the pulsar PSR J1752+2359. About one pulse in 270 has a peak flux density more than 40 times the peak flux density of an average pulse (AP), and the strongest GP is as large as 260. The energy of the strongest GP exceeds the energy of the average pulse by a factor of 200 which is greater than in other known pulsars with GPs. PSR J1752+2359 as well as the previously detected pulsars PSR B0031-07 and PSR B1112+50, belong to the first group of pulsars found to have GPs without a strong magnetic field at the light cylinder.
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We report the emission variations in PSR J1047$-$6709 observed at 1369 MHz using the Parkes 64 m radio telescope. This pulsar shows two distinct emission states: a weak state and a bright emission state. We detected giant pulses (GPs) in the bright state for the first time. We found 75 GPs with pulse width ranging from 0.6 to 2.6 ms. The energy of GPs follows a power-law distribution with the index $alpha=-3.26pm0.22$. The peak flux density of the brightest GP is 19 Jy which is 110 times stronger than the mean pulse profile. The polarization properties of the average profile of GPs are similar to that of the pulses with energy less than 10 times average pulse energy in the bright state. This indicates that the emission mechanism is basically the same for them. Our results provide a new insight into the origin of the GPs in pulsars.
We report the detection of giant pulse emission from PSR B0950+08 in 24 hours of observations made at 39.4 MHz, with a bandwidth of 16 MHz, using the first station of the Long Wavelength Array, LWA1. We detected 119 giant pulses from PSR B0950+08 (at its dispersion measure), which we define as having SNRs at least 10 times larger than for the mean pulse in our data set. These 119 pulses are 0.035% of the total number of pulse periods in the 24 hours of observations. The rate of giant pulses is about 5.0 per hour. The cumulative distribution of pulse strength $S$ is a steep power law, $N(>S)propto S^{-4.7}$, but much less steep than would be expected if we were observing the tail of a Gaussian distribution of normal pulses. We detected no other transient pulses in a dispersion measure range from 1 to 90 pc cm$^{-3}$, in the beam tracking PSR B0950+08. The giant pulses have a narrower temporal width than the mean pulse (17.8 ms, on average, vs. 30.5 ms). The pulse widths are consistent with a previously observed weak dependence on observing frequency, which may be indicative of a deviation from a Kolmogorov spectrum of electron density irregularities along the line of sight. The rate and strength of these giant pulses is less than has been observed at $sim$100 MHz. Additionally, the mean (normal) pulse flux density we observed is less than at $sim$100 MHz. These results suggest this pulsar is weaker and produces less frequent giant pulses at 39 MHz than at 100 MHz.
We report the detection of giant pulse emission from PSR~B0950+08 in 12 hours of observations made simultaneously at 42~MHz and 74~MHz, using the first station of the Long Wavelength Array, LWA1. We detected 275 giant pulses (in 0.16% of the pulse periods) and 465 giant pulses (0.27%) at 42 and 74~MHz, respectively. The pulsar is weaker and produces less frequent giant pulses than at 100~MHz. Here, giant pulses are taken as having $geq$ 10 times the flux density of an average pulse; their cumulative distribution of pulse strength follows a power law, with a index of $-$4.1 at 42~MHz and $-$5.1 at 74~MHz, which is much less steep than would be expected if we were observing the tail of a Gaussian distribution of normal pulses. We detected no other transient pulses in a wide dispersion measure range from 1 to 5000~pc~cm$^{-3}$. There were 128 giant pulses detected within in the same periods from both 42 and 74~MHz, which means more than half of them are not generated in a wide band. We use CLEAN-based algorithm to analyze the temporal broadening and conclude that the scattering effect from the interstellar medium can not be observed. We calculated the altitude $r$ of the emission region using the dipolar magnetic field model. We found $r$(42~MHz) = 29.27~km ($0.242%$ of $R_{LC}$) and $r$(74~MHz) = 29.01~km ($0.240%$ of $R_{LC}$) for the average pulse, while for giant pulses, $r$(42~MHz) = 29.10~km ($0.241%$ of $R_{LC}$) and $r$(74~MHz) = 28.95~km ($0.240%$ of $R_{LC}$). Giant pulses, which have a double-peak structure, have a smaller mean peak-to-peak separation compared to the average pulse.
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We have detected occasional, short-lived ``echoes of giant pulses from the Crab pulsar. These echo events remind us of previously reported echoes from this pulsar, but they differ significantly in detail. Our echo events last at most only a few days; the echo emission lags the primary emission by only 40-100 musec. The echoes are consistently weaker and broader than the primary emission, and appear only at the lower of our two simultaneous observing frequencies. We suggest that these echoes are created by refraction in small plasma structures -- plasma clouds or magnetic flux ropes -- deep within the Crab nebula. If this is true, our echoes provide a new probe of small-scale structures within the inner synchrotron nebula.
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