Coronagraphic near-IR photometry of AB Dor C

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.

Research Note to appear in Astronomy and Astrophysics

References in corpus (6)

• The nearest young moving groups
• Discovery of a Young Substellar Companion in Chamaeleon
• Very high contrast IFU spectroscopy of AB Doradus C: 9 mag contrast at 0.2" without a coronagraph using spectral deconvolution
• Accurate Astrometry and Photometry of Saturated and Coronagraphic Point Spread Functions
• On the common origin of the AB Dor moving group and the Pleiades cluster
• Improved age constraints for the AB Dor quadruple system - The binary nature of AB Dor B

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• Dynamical masses of the low-mass stellar binary ABDoradusB
• The milliarcsecond-scale radio structure of AB Dor A
• Evidence of a substellar companion to AB Dor C
• First light from the Dome C (Antarctica) of a phase knife stellar coronagraph