Free Access
Volume 563, March 2014
Article Number A72
Number of page(s) 19
Section Planets and planetary systems
Published online 12 March 2014

Online material

Appendix C: Constraints on ζ2 Ret set by direct imaging

VLT/NaCo (Lenzen et al. 2003; Rousset et al. 2003) Ks-band data were retrieved from the ESO archive (ID 086.C-0732(A); PI: Löhne, 71574). Two epochs were available in August 2010 and November 2010, the former missing photometric calibration therefore only the latter was used to set detection limits on the presence of bound companions. Nevertheless, both data sets were reduced and no companion was detected. The data from November 11, 2010 were obtained in field stabilized-mode with five manual offsets of the derotator to simulate field rotation, with the S27 camera providing a pixel scale of 27 mas/pixel. Twenty image cubes with a DITxNDIT of 1.5 s × 42 were obtained for a total observing time on target of 21 min. The semi-transparent mask C_0.7_sep_10 with a diameter of 0.7′′ and a central transmission of 3.5 × 10-3 was used. Each individual image was bad pixel-corrected and flat-fielded. Background subtraction was made for each cube using the closest sky images. The images were rencentred using a Gaussian fit of the attenuated central star. The data were selected within each data cube using criteria based on the attenuated central star flux and the encircled energy between 0.4′′ and 0.55′′. The images were then binned every 6 s and derotated into a reference frame where the pupil was stabilized in order to simulate angular differential imaging (ADI, Marois et al. 2006). In this reference frame, the total field rotation provided by the manual offsets plus the natural pupi/field rotation is 17°. This data cube was then reduced using principal components analysis (PCA, Soummer et al. 2012), retaining four components out of 105.

The noise in the final reduced image was estimated using a sliding nine pixel-wide box to obtain a preliminary map of detection limits in magnitude. We corrected this map by computing the flux losses due to the PCA reduction. They were estimated by injecting fake planets into the data cube at a 10-σ level and processing the data again. Last, these detection limits in magnitude were converted into detection limits in masses, using the COND (Baraffe et al. 2003) or BT-settl models (Allard et al. 2011), assuming an age of 2 Gyr. The 2D-detection limits derived with the COND evolutionary models are presented in Fig. C.1.

thumbnail Fig. C.1

Map of the detection limits in Jupiter masses set by the COND evolutionary models. The contours range from 60 to 150 MJup with a step of 10 MJup.

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© ESO, 2014

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