Observational Characterization of Main-belt Comet and Candidate Main-belt Comet Nuclei
Bibliographic record
Abstract
Abstract We report observations of nine main-belt comets (MBCs) or candidate MBCs, most of which were obtained when the targets were apparently inactive. We find effective nucleus radii (assuming albedos of p V = 0.05 ± 0.02) of r n = (0.24 ± 0.05) km for 238P/Read, r n = (0.9 ± 0.2) km for 313P/Gibbs, r n = (0.6 ± 0.1) km for 324P/La Sagra, r n = (1.0 ± 0.2) km for 426P/PANSTARRS, r n = (0.5 ± 0.1) km for 427P/ATLAS, r n < (0.3 ± 0.1) km for P/2016 J1-A (PANSTARRS), r n < (0.17 ± 0.04) km for P/2016 J1-B (PANSTARRS), r n ≤ (0.5 ± 0.2) km for P/2017 S9 (PANSTARRS), recently redesignated 455P/PANSTARRS, and r n = (0.4 ± 0.1) km for P/2019 A3 (PANSTARRS). We identify evidence of activity in observations of 238P in 2021, and find similar inferred activity onset times and net initial mass-loss rates for 238P during perihelion approaches in 2010, 2016, and 2021. P/2016 J1-A and P/2016 J1-B are also found to be active in 2021 and 2022, making them collectively the tenth MBC confirmed to be recurrently active near perihelion and therefore likely to be exhibiting sublimation-driven activity. The nucleus of 313P is found to have colors of g ′ − r ′ = 0.52 ± 0.05 and r ′ − i ′ = 0.22 ± 0.07 , consistent with 313P being a Lixiaohua family member. We also report nondetections of P/2015 X6 (PANSTARRS), where we conclude that its current nucleus size is likely below our detection limits (r n ≲ 0.3 km). Lastly, we find that of 17 MBCs or candidate MBCs for which nucleus sizes (or inferred parent body sizes) have been estimated, >80% have r n ≤ 1.0 km, pointing to an apparent physical preference toward small MBCs, where we suggest that Yarkovsky–O’Keefe–Radzievskii–Paddack spin-up may play a significant role in triggering and/or facilitating MBC activity.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".