Mid-infrared photometry of the T Tauri triple system with kernel phase interferometry

Abstract

Context. T Tauri has long been the prototypical young pre-main-sequence star. However, with increasing resolution and sensitivity, T Tauri has now been decomposed into a triple system with a complex disk and outflow geometry. Aims. We aim to measure the brightness of all three components of the T Tauri system (T Tau N, T Tau Sa, and T Tau Sb) in the mid-infrared in order to obtain photometry around the ∼9.7 μm silicate feature. This allows us to study their variability and to investigate the distribution of dust and the geometry of circumstellar and circumbinary disks in this complex system. Methods. We observe the T Tauri system with the Very Large Telescope (VLT)/VISIR-NEAR instrument, performing diffraction-limited imaging in the mid-infrared. With kernel phase interferometry post-processing of the data, and using the astrometric positions of all three components from VLT/SPHERE, we measure the three components’ individual brightnesses (including the southern binary at an angular separation down to ∼0.2λ/D) and obtain their photometry. In order to validate our methods, we simulate and recover mock data of the T Tauri system using the observed reference point-spread function of HD 27639. Results. We find that T Tau N is rather stable and shows weak silicate emission, while T Tau Sa is highly variable and shows prominent silicate absorption. T Tau Sb became significantly fainter compared to data from 2004 and 2006, suggesting increased extinction by dust. The precision of our photometry is limited by systematic errors in kernel phase interferometry, which is consistent with previous studies using this technique. Conclusions. Our results confirm the complex scenario of misaligned disks in the T Tauri system that had been observed previously, and they are in agreement with the recently observed dimming of T Tau Sb in the near-infrared. Our mid-infrared photometry supports the interpretation that T Tau Sb has moved behind the dense region of the Sa-Sb circumbinary disk on its tight orbit around Sa, therefore suffering increased extinction.

Performance of near-infrared high-contrast imaging methods with JWST from commissioning

“…This pipeline is based on the XARA ‖ package [18,25,26] and performs bad pixel corrections, windowing, and subpixel re-centering prior to extracting the kernel phases. Finally, the kernel phases of the science target were calibrated with Karhunen-Loève decomposition [22,27,28,29] using the two point-source reference stars as calibrators and detection limits were computed with fouriever. We note that in principle, any of the three KPI targets could have been used as the science target here.…”

The Near Infrared Imager and Slitless Spectrograph for JWST -- V. Kernel Phase Imaging and Data Analysis

“…Both the bootstrapping and the MCMC method yield comparable results and an advantage of the latter is that it can also be used to fit more complex models such as multiple companions simultaneously or geometric disk and ring models to the data (see, e.g., Kammerer et al 2021;Blakely et al 2022).…”

“…Similar to angular differential imaging (Marois et al 2006) in classical high-contrast imaging, Laugier et al (2020) also derived self-calibrating angular differential kernel phase observables, but these are more suitable for datasets with larger field rotation than JWST can provide. To measure the photometry of the individual components of the T Tau triple star system at ∼ 10 µm, Kammerer et al (2021) applied KPI to VLT VISIR-NEAR observations in the mid-infrared, demonstrating the feasibility of KPI with instruments such as JWST MIRI. Recently, pioneering work from Pope et al (2021) has shown that automatic differentiation methods can be used to extract kernel phase observables from any differentiable optical system, such as a Lyot coronagraph for instance, which has previously been impossible given that focal plane masks destroy the linearity of the Fourier phase observables.…”

Image reconstruction for kernel phase interferometry with SCExAO/CHARIS using gradient descent

“…Such an image is processed as if it were taken by an interferometric array thereby computing an interferometric observable, the kernel phase, which can be used for subsequent model fitting. KPI has been successfully deployed in a number of contexts, including studying brown dwarfs 3 and the prototypical young pre-main sequence system T Tauri, 4 and is a useful way to extend the capability of existing instruments such as NIRISS on JWST. 5 It could also be applied to high-contrast imagers such as GPI 6 which sit behind extreme-AO systems.…”