Deep infrared imaging of close companions to austral A- and F-type stars
Bibliographic record
Abstract
The search for substellar companions around stars with different masses along the main sequence is critical to understanding the different processes leading to the formation of low-mass stars, brown dwarfs, and planets. In particular, the existence of a large population of low-mass stars and brown dwarfs physically bound to early-type main-sequence stars could imply that the massive planets recently imaged at wide separations (10–100 AU) around A-type stars are disc-born objects in the low-mass tail of the binary distribution and are thus formed via gravitational instability rather than by core accretion. Our aim is to characterize the environment of early-type main-sequence stars by detecting substellar companions between 10 and 500 AU. The sample stars are also surveyed with radial velocimetry, providing a way to determine the impact of the imaged companions on planets at ≲10 AU. High-contrast and high angular resolution near-infrared images of a sample of 38 southern A- and F-type stars were obtained between 2005 and 2009 with the instruments NaCo on the Very Large Telescope and PUEO on the Canada-France-Hawaii Telescope. Direct and saturated imaging were used in the J to Ks bands to probe the faint circumstellar environments with contrasts of ~5 × 10-2 to 10-4 at separations of $0\farcs2$ and 1″, respectively. Using coronagraphic imaging, we achieved contrasts between 10-5 and 10-6 at separations >5″̣ Multi-epoch observations were performed to distinguish comoving companions from background contaminants. This survey is sensitive to companions of A and F stars in the brown dwarf to low-mass star mass regime. About 41 companion candidates were imaged around 23 stars. Follow-up observations for 83% of these stars allowed us to identify a large number of background contaminants. We report detection of 7 low-mass stars with masses between 0.1 and 0.8 M⊙ in 6 multiple systems: the discovery of an M2 companion around the A5V star <ns0:ext-link ext-link-type="aoi">HD 14943</ns0:ext-link> and detection of <ns0:ext-link ext-link-type="aoi">HD 41742B</ns0:ext-link> around the F4V star <ns0:ext-link ext-link-type="aoi">HD 41742</ns0:ext-link> in a quadruple system. We resolve the known companion of the F6.5V star <ns0:ext-link ext-link-type="aoi">HD 49095</ns0:ext-link> as a short-period binary system composed of 2 M/L dwarfs. We also resolve the companions to the astrometric binaries <ns0:ext-link ext-link-type="aoi">ι Crt</ns0:ext-link> (F6.5V) and <ns0:ext-link ext-link-type="aoi">26 Oph</ns0:ext-link> (F3V), and identify an M3/M4 companion to the F4V star <ns0:ext-link ext-link-type="aoi">o Gru</ns0:ext-link>, associated with an X-ray source. The global multiplicity fraction measured in our sample of A and F stars is ≥ 16%. This has a probable impact on the radial velocity measurements performed on the sample stars.
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How this classification was reachedexpand
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 | 0.000 | 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) | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".