VLBI Studies of the Crab Pulsar: Scintillation, Astrometry, and Emission
Bibliographic record
Abstract
The Crab Pulsar is one of the youngest and best-observed pulsars, and, with its interesting emission properties, one of the key testbeds for pulsar emission theories. Its radio pulse profile shows multiple pulse components with very different characteristics, including short and bright "giant pulses", which make up most of the emission from its two dominant components, the main pulse and interpulse. Detecting the fainter emission from the Crab Pulsar poses a challenge due to its location within the radio-bright Crab Nebula. Consequently, this thesis employs very long baseline techniques, combining data from multiple telescopes to synthesize an aperture much larger than a single dish. This approach improves both the angular resolution and sensitivity, enabling new studies of the Crab Pulsar in three different ways. In this thesis, I use the bending of light in the nebula, which causes scintillation and scattering due to the interference of pulsar emission that arrives via differently delayed paths, as a interstellar interferometer to constrain the emission regions associated with the Crab Pulsar's giant pulses. I find that the giant pulse emission occurs over an extended region, and infer that relativistic motion plays an important role in producing these pulses. Furthermore, I develop a novel calibration technique using the Crab Pulsar's giant pulses to precisely measure the parallax and proper motion of the pulsar, down to sub-milliarcsecond precision. Finally, I investigate the statistical properties of giant pulses and show the weaker radio emission of the Crab Pulsar and scattering effects, notably "echoes" of the pulsar emission, by leveraging the high sensitivity I obtained through coherent combination of signals from individual telescopes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".