Coronagraphic near-IR photometry of AB Dor C

TL;DR

This study uses coronagraphic near-infrared photometry at the VLT to accurately measure the properties of the low-mass companion AB Dor C, refining its photometry and age estimate, and demonstrating the technique's effectiveness for exoplanet studies.

Contribution

The paper presents new coronagraphic photometry of AB Dor C, improving the accuracy of its measurements and age estimation, and showcases the technique's advantages over direct imaging.

Findings

AB Dor C detected at 0.185" with consistent H and Ks magnitudes

Refined age estimate of (75±25) Myr for AB Dor C

Coronagraphy enhances photometric accuracy and efficiency

Abstract

Observations of low-mass companions for which the dynamical masses are well constrained help to improve the calibration of evolutionary models. Such observations thereby provide more confidence in the estimation of the mass of a companion using the photometric methods expected for the next generation of planet finder instruments. The commissioning of a new coronagraph at the Very Large Telescope (VLT) was the occasion to test the performance of this technique on the well-known object AB Dor A and its 0.09$M_\odot$ companion AB Dor C. The purpose of this paper is to refine the photometric analysis on this object and to provide an accurate photometric error budget. In addition to coronagraphy, we calibrated the residual stellar halo with a reference star. We used standard techniques for photometric extraction. The companion AB Dor C is easily detected at 0.185" from the primary star, and its magnitudes in H and Ks are in agreement with an M5.5 object, as already known from spectroscopic observations. However, these new measurements make the earlier J-band photometry less reliable. Finally, the comparison with evolutionary models supports an age of (75\pm 25) Myr, contrary to previous analyses. These observations demonstrate that coronagraphic observations can be more efficient than direct imaging, not only to improve contrast, but also to provide a better photometric estimation as long as a good calibration of the stellar halo is achieved.