Beyond the dips of V807 Tau, a spectropolarimetric study of a dipper’s magnetosphere
Bibliographic record
Abstract
Context. The so-called dippers are pre-main-sequence objects that accrete material from their circumstellar disks through the stellar magnetosphere. Their unique type of variability allows us to probe the magnetic star-disk interaction processes in young stellar objects. Aims. We aim to characterize the magnetospheric accretion process in the young stellar object V807 Tau, one of the most stable dippers revealed by K2 in the Taurus star forming region. Methods. We performed photometric and spectropolarimetric follow-up observations of this system with CFHT/ESPaDOnS in order to investigate the variability of the system over several rotational periods. Results. We derive a 4.38 day period from the K2 dipper light curve. This period is also seen in the radial velocity variations, which we ascribe to spot modulation. The slightly redshifted narrow component of the He I 5876 Å line as well as the high velocity red wing of the Hβ and Hγ emission line profiles also vary in intensity with the same periodicity. The former traces the accretion shock at the stellar surface, and the latter is a signature of an accretion funnel flow crossing the line of sight. We derive a surface brightness map and the topology of the surface magnetic field from the modeling of Stokes I and V profiles, respectively, for photospheric lines and for the He I emission line. The latter reveals a bright spot at the stellar surface, located at a latitude of 60°, and a maximum field strength of ∼2 kG at this location. The topology of the magnetic field at the stellar surface is dominated by a dipolar component inclined by about 40° onto the spin axis. Variable blueshifted absorption components seen in the Balmer line profiles suggest episodic outflows. Despite of its clear and stable dipper behavior, we derive a relatively low inclination of 40° to 50° for this system, which calls question the origin of the dips. The low inclination we infer is also consistent with the absence of deep inverse P Cygni components in the line profiles. Conclusions. We conclude that magnetospheric accretion is ongoing in V807 Tau, taking place through non-axisymmetric accretion funnel flows controlled by a strong, tilted, and mainly dipolar magnetic topology. Whether an inner disk warp resulting from this process can account for the dipper character of this source remains to be seen, given the low inclination of the system.
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 | 0.001 | 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) | 0.001 | 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".