Bibliographic record
Abstract
Multi-wavelength observations of supernovae (SN) not only probe the explosion mechanism, but also carry information about the configuration of the star at the moment of collapse and the mass-loss history of the progenitor system in the years immediately preceding its death. The study of supernovae therefore offers a rare observational view of the final stages of stellar evolution. As a result, the recent advent of wide-field SN searches---which are discovering new classes of astronomical transients at an ever-increasing rate---has both expanded the types of stellar systems that we can directly probe and challenged theoretical models of the late-stages of stellar evolution. This thesis explores several new regimes of transient space that have been opened by these modern, wide-field, time domain surveys. We present a series of observational studies which constrain the explosion properties, progenitor systems, and intrinsic rates for several classes of peculiar astronomical transients.\n\nFirst, we investigate the properties of transients that reach SN luminosities but evolve on rapid timescales. We present a detailed study of the rapidly-declining hydrogen-poor SN 2005ek, showing that it could be produced by the core-collapse of a stripped massive star with a very small ejecta mass. We then describe results from the first systematic search for rapidly-evolving and luminous transients in a wide-field survey with a rapid cadence. Using data from the PanSTARRS1 Medium-Deep Survey (PS1-MDS), we both identified a new class of rapidly-evolving transients and calculated their intrinsic rates---demonstrating that these explosions are not intrinsically rare. Second, we utilize very early UV/spectroscopic observations and detailed multi-wavelength follow-up of the stripped-envelope core-collapse SN 2013ge to place constraints on the final configuration of the progenitor system. Finally, we investigate the progenitor stars and mass-loss mechanism that operates in a class of luminous SN that explode within a dense circumstellar medium (Type IIn SN). This is accomplished through a joint analysis of the explosion properties and host galaxy environments for a large number of events, including the full sample of Type IIn SN discovered by the PS1-MDS. We find that luminous Type IIn SN explode in a wide range of galaxies which are are robustly distinguished from the host galaxies of hydrogen-poor super-luminous SN in being more luminous, massive, and metal-rich. Furthermore, we show that a significant fraction of luminous Type IIn SN explode in the bright central regions of their host galaxies, indicating that the physical conditions for star formation in these environments are conducive for the formation of luminous Type IIn progenitors.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".