Asteroid (3200) Phaethon: Colors, Phase Curve, Limits on Cometary Activity, and Fragmentation
Bibliographic record
Abstract
Abstract We report on a multiobservatory campaign to examine asteroid 3200 Phaethon during its 2017 December close approach to Earth, in order to improve our measurements of its fundamental parameters, and to search for surface variations, cometary activity, and fragmentation. The mean colors of Phaethon are B – V = 0.702 ± 0.004, V – R = 0.309 ± 0.003, and R – I = 0.266 ± 0.004, neutral to slightly blue, consistent with previous classifications of Phaethon as a F-type or B-type asteroid. Variations in Phaethon’s B – V colors (but not V – R or R – I) with observer sublatitude are seen and may be associated with craters observed by the Arecibo radar. High-cadence photometry over phases from 20° to 100° allows a fit to the values of the HG photometric parameters; H = 14.57 ± 0.02, 13.63 ± 0.02, 13.28 ± 0.02, 13.07 ± 0.02; G = 0.00 ± 0.01, −0.09 ± 0.01, −0.10 ± 0.01, −0.08 ± 0.01 in the BVRI filters respectively; the negative G values are consistent with other observations of F-type asteroids. Light-curve variations were seen that are also consistent with concavities reported by Arecibo, indicative of large craters on Phaethon’s surface whose ejecta may be the source of the Geminid meteoroid stream. A search for gas/dust production sets an upper limit of 0.06 ± 0.02 kg s−1 when Phaethon was 1.449 au from the Sun, and 0.2 ± 0.1 kg s−1 at 1.067 au. A search for meter-class fragments accompanying Phaethon did not find any whose on-sky motion was not also consistent with background main-belt asteroids.
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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".