The Measurement of Thermal Radiation at Microwave Frequencies

The Crab pulsar is well-known for its anomalous giant radio pulse emission. Past studies have concentrated only on the very bright pulses or were insensitive to the faint end of the giant pulse luminosity distribution. With our new instrumentation offering a large bandwidth and high time resolution combined with the narrow radio beam of the Westerbork Synthesis Radio Telescope (WSRT), we seek to probe the weak giant pulse emission regime. The WSRT was used in a phased array mode, resolving a large fraction of the Crab nebula. The resulting pulsar signal was recorded using the PuMa II pulsar backend and then coherently dedispersed and searched for giant pulse emission. After careful flux calibration, the data were analysed to study the giant pulse properties. The analysis includes the distributions of the measured pulse widths, intensities, energies, and scattering times. The weak giant pulses are shown to form a separate part of the intensity distribution. The large number of giant pulses detected were used to analyse scattering and scintillation in giant pulses. We report for the first time the detection of giant pulse emission at both the main-and interpulse phases within a single rotation period. The rate of detection is consistent with the appearance of pulses at either pulse phase as being independent. These pulse pairs were used to examine the scintillation timescales within a single pulse period.

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“…proportional to the rms noise variations at the telescope output and can be expressed by the radiometer equation (Dicke 1946),…”

Section: Flux Calibrationmentioning

confidence: 99%

Giant pulses from the Crab pulsar

Karuppusamy

Stappers

Straten³

2010

A&A

108

111

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“…Once the telescope gain and system temperature had been established, the off-pulse noise in flux units was computed using the radiometer equation (Dicke 1946) that can be expressed as…”

Section: Flux Calibrationmentioning

confidence: 99%

A low frequency study of PSRs B1133+16, B1112+50, and B0031−07

Karuppusamy

Stappers

Serylak

2010

A&A

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We use the low frequency (110-180 MHz) capabilities of the Westerbork Synthesis Radio Telescope (WSRT) to characterise a large collection of single pulses from three low magnetic field pulsars. Using the Pulsar Machine II (PuMa-II) to acquire and coherently dedisperse the pulsar signals, we examine whether the bright pulses observed in these pulsars are related to the classical giant pulse emission. Giant pulses are reported from PSR B1112+50 and bright pulses from the PSRs B1133+16 and B0031−07. These pulsars also exhibit large intensity modulations observed as rapid changes in the single pulse intensity. Evidence of global magnetospheric effects is provided by our detection of bright double pulses in PSRs B0031−07 and B1133+16. Using the multi-frequency observations, we accurately determine the dispersion measures (4.844 ± 0.002 for B1133+16 and 9.1750 ± 0.0001 for B1112+50), derive the radio emission height in PSR B1133+16 and report on the properties of subpulse drift modes in these pulsars. We also find that these pulsars show a much larger intensity modulation at low sky frequencies resulting in narrow and bright emissions.

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“…T " (6) Thus, the minimum detectable temperature change is In order to use this small NEP, room temperature blackbody radiation, which introduces noise as well as heat, must be rigorously avoided. This can be conveniently be done with low-pass cooled filters in the far infrared, but very narrow-band cooled filters would be required for near infrared systems which have room temperature background.…”

Section: Ml-mentioning

confidence: 99%