Observational Characterization of Main-belt Comet and Candidate Main-belt Comet Nuclei
Why this work is in the frame
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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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>g</mml:mi> <mml:mo accent="false">′</mml:mo> <mml:mo>−</mml:mo> <mml:mi>r</mml:mi> <mml:mo accent="false">′</mml:mo> <mml:mo>=</mml:mo> <mml:mn>0.52</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.05</mml:mn> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>r</mml:mi> <mml:mo accent="false">′</mml:mo> <mml:mo>−</mml:mo> <mml:mi>i</mml:mi> <mml:mo accent="false">′</mml:mo> <mml:mo>=</mml:mo> <mml:mn>0.22</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.07</mml:mn> </mml:math> , 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.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it