Signatures of strong gravity with GRAVITY
Bibliographic record
Abstract
The dynamics of stars and gas undoubtedly shows the existence of a 4 million solar mass black hole at the center of the Milky Way: Sagittarius A* (SgrA*). Violent flare emission allows us to probe the immediate environment of the central mass. Near-infrared polarimetry now shows signatures of strong gravity that are statistically significant against randomly polarized red noise. Using these signatures we can derive spin and inclination information of SgrA*. A combined synchrotron self Compton (SSC) and adiabatic expansion model with source components peaking in the sub-mm domain can fully account for the observed flare flux densities and the time delays towards the (sub-)mm flares that have been reported in some cases. We discuss the expected centroid paths of the NIR images and summarize how the geometrical structure of the emitting region (i.e. spot shape, presence of a torus or spiral-arm pattern etc.) affects this centroid tracks. While most of the mentioned geometries are able to fit the observed fluxes, future NIR interferometry with GRAVITY at the VLT will break some of the degeneracies between different emission models. In this contribution we summarize several GRAVITY science cases for SgrA*. Our simulations propose that focusing GRAVITY observations on the polarimetry mode could reveal a clear centroid track of the spot(s). A non-detection of centroid shifts cannot rule out the multi-component model or spiral arms scenarios. However, a clear wander between alternating centroid positions during the flares will prove the idea of bright long-lived spots occasionally orbiting the central black hole.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".