Distance to the 1.5 millisecond pulsar and other 4C 21.53 objects

Heiles, C.; Kulkarni, [No Value]; Stevens, M.; Backer, D.; Davis, Mm; Goss, Wm

doi:10.1086/184133

Cited by 11 publications

(2 citation statements)

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“…Figure 3 shows the measured anomalous dispersion delays averaged over all three observing runs together with the hydrogen emission and absorption spectra measured from the same data. Note that these emission and absorption spectra are consistent with previously published results by Heiles et al (1983). From the figure, it can been seen that the structure in the anomalous dispersion "delay spectrum" is consistent with the features seen in absorption.…”

Section: Observations and Analysissupporting

confidence: 90%

Apparent Faster-Than-Light Pulse Propagation in Interstellar Space: A New Probe of the Interstellar Medium

Jenet¹,

Fleckenstein²,

Ford³

et al. 2010

ApJ

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Radio pulsars emit regular bursts of radio radiation that propagate through the interstellar medium (ISM), the tenuous gas and plasma between the stars. Previously known dispersive properties of the ISM cause low frequency pulses to be delayed in time with respect to high frequency ones. This effect can be explained by the presence of free electrons in the medium. The ISM also contains neutral hydrogen which has a well known resonance at 1420.4 MHz. Electro-magnetic theory predicts that at such a resonance, the induced dispersive effects will be drastically different from those of the free electrons. Pulses traveling through a cloud of neutral hydrogen should undergo "anomalous dispersion," which causes the group velocity of the medium to be larger than the speed of light in vacuum. This superluminal group velocity causes pulses containing frequencies near the resonance to arrive earlier in time with respect to other pulses. Hence, these pulses appear to travel faster than light. This phenomenon is caused by an interplay between the time scales present in the pulse and the time scales present in the medium. Although counter-intuitive, it does not violate the laws of special relativity. Here, we present Arecibo observations of the radio pulsar PSR B1937+21 that show clear evidence of anomalous dispersion. Though this effect is known in laboratory physics, this is the first time it has been directly observed in an astrophysical context, and it has the potential to be a useful tool for studying the properties of neutral hydrogen in the Galaxy.

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Section: Observations and Analysissupporting

confidence: 90%

Apparent Faster-Than-Light Pulse Propagation in Interstellar Space: A New Probe of the Interstellar Medium

Jenet¹,

Fleckenstein²,

Ford³

et al. 2010

ApJ

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“…If these effects can be modeled, higher timing precision is obtainable in the future, possibly helping in setting tighter limits on the parallax measurements. Heiles et al (1983) studied the H i absorption spectra toward PSR B1937+21, 4C21.53W and another close-by source. By setting the Galactic tangent point to 5.4 kpc, a comparison of position and intensity of the lines for these three objects allowed them to conclude that 4C21.53W is at ≃ 10.7 kpc and the pulsar at ≃ 5 kpc from us.…”

Section: The Pulsar Distancementioning

confidence: 99%

BeppoSAX observation of PSR B1937+21

Cusumano¹,

Löhmer

Krämer

et al. 2004

A&A

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Abstract. We present the results of a BeppoSAX observation of the fastest rotating pulsar known: PSR B1937+21. The ∼200 ks observation (78.5 ks MECS/34 ks LECS on-source time) allowed us to investigate with high statistical significance both the spectral properties and the pulse profile shape. The pulse profile is clearly double peaked at energies 4 keV. Peak widths are compatible with the instrumental time resolution and the second pulse lags the main pulse 0.52 in phase, like is the case in the radio. In the 1.3-4 keV band we detect a ∼45% DC component; conversely the 4-10 keV pulsed fraction is consistent with 100%. The on-pulse spectrum is fitted with an absorbed power-law of spectral index ∼1.2, harder than that of the total flux which is ∼1.9. The total unabsorbed (2-10 keV) flux is F 2−10 = 4.1 × 10 −13 erg cm −2 s −1 , implying a luminosity of L X = 5.0 × 10 31 Θ (d/3.6 kpc) 2 erg s −1 and a X-ray efficiency of η = 4.5 × 10 −5 Θ, where Θ is the solid angle spanned by the emission beam. These results are in agreement with those obtained by ASCA and a more recent Rossi-XTE observation. The hydrogen column density N H ∼ 2 × 10 22 cm −2 is ∼10 times higher than expected from the radio dispersion measure and average Galactic density of e − . Though it is compatible (within 2σ) with the Galactic (H  derived) value of ∼ 1 × 10 22 cm −2 , inspection of dust extinction maps reveal that the pulsar falls in a highly absorbed region. In addition, 1.4 GHz radio map shows that the nearby (likely unrelated) H  source 4C21.53W is part of a circular emission region ∼4 across.

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Recombination Lines and Galactic Structure

Lockman

1990

Radio Recombination Lines: 25 Years of Investigation

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Distance to the 1.5 millisecond pulsar and other 4C 21.53 objects

Cited by 11 publications

References 0 publications

Apparent Faster-Than-Light Pulse Propagation in Interstellar Space: A New Probe of the Interstellar Medium

Apparent Faster-Than-Light Pulse Propagation in Interstellar Space: A New Probe of the Interstellar Medium

BeppoSAX observation of PSR B1937+21

Recombination Lines and Galactic Structure

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