On the binary nature of the progenitor of SN2015ap: insights from its light curve and spectral evolution
Bibliographic record
Abstract
ABSTRACT Stripped-envelope supernovae (SESNe) display a wide range of photometric and spectroscopic behaviours, often reflecting complex progenitor evolution. SN 2015ap is a type Ib event located in the nearby galaxy IC 1776, previously modelled as powered by radioactive decay and possibly a magnetar engine. In this work, we revisit its multiband photometry and spectroscopy, gathering all publicly available observational data for this source, to investigate the nature of its progenitor and power source. We use an innovative time analysis method based on Gaussian process, leveraging its ability to model both noise and periodic components in unevenly sampled data without requiring regular sampling. We detect significant periodic modulations in the post-peak light curve, with a characteristic time-scale of $\sim$8.4 d. These modulations are also seen in the H α line velocity, suggesting a structured circumstellar medium (CSM) shaped by binary interaction. We model the light curve with semi-analytical prescriptions (mosfit), including CSM and central engine components, and derive an ejecta mass of $\sim$2.2–2.4 $\mathrm{M}_\odot$, explosion energy of $\sim 3.4\times 10^{51}$ erg, and a $^{56}$Ni mass of $\sim$0.11 $\mathrm{M}_\odot$. The colour evolution indicates an additional energy injection, consistent with either prolonged breakout or delayed central powering. While the data are compatible with a weak magnetar contribution, the overall evidence favours a binary progenitor system, with non-conservative mass transfer shaping the observed CSM. SN 2015ap thus adds to the growing sample of SESNe where binarity plays a central role in driving both the explosion and its observables.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| 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".