Constraints on the nearby exoplanet Eps Ind Ab from deep near/mid-infrared imaging limits

Gayathri Viswanath, Markus Janson, Carl-Henrik Dahlqvist, Dominique Petit dit de la Roche, Matthias Samland, Julien Girard, Prashant Pathak, Markus Kasper, Fabo Feng, Michael Meyer, Anna Boehle, Sascha P. Quanz, Hugh R. A. Jones, Olivier Absil, Wolfgang Brandner, Anne-Lise Maire, Ralf Siebenmorgen, Michael Sterzik, Eric Pantin

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The past decade has seen increasing efforts in detecting and characterising exoplanets by high contrast imaging in the near/mid-infrared, which is the optimal wavelength domain for studying old, cold planets. In this work, we present deep AO imaging observations of the nearby Sun-like star $\epsilon$ Ind A with NaCo ($L^{\prime}$) and NEAR (10-12.5 microns) instruments at VLT, in an attempt to directly detect its planetary companion whose presence has been indicated from radial velocity (RV) and astrometric trends. We derive brightness limits from the non-detection of the companion with both instruments, and interpret the corresponding sensitivity in mass based on both cloudy and cloud-free atmospheric and evolutionary models. For an assumed age of 5 Gyr for the system, we get detectable mass limits as low as 4.4 $M_{\rm J}$ in NaCo $L^{\prime}$ and 8.2 $M_{\rm J}$ in NEAR bands at 1.5$\arcsec$ from the central star. If the age assumed is 1 Gyr, we reach even lower mass limits of 1.7 $M_{\rm J}$ in NaCo $L^{\prime}$ and 3.5 $M_{\rm J}$ in NEAR bands, at the same separation. However, based on the dynamical mass estimate (3.25 $M_{\rm J}$) and ephemerides from astrometry and RV, we find that the non-detection of the planet in these observations puts a constraint of 2 Gyr on the lower age limit of the system. NaCo offers the highest sensitivity to the planetary companion in these observations, but the combination with the NEAR wavelength range adds a considerable degree of robustness against uncertainties in the atmospheric models. This underlines the benefits of including a broad set of wavelengths for detection and characterisation of exoplanets in direct imaging studies.
Original languageEnglish
Article numberA89
Number of pages11
JournalAstronomy & Astrophysics
Early online date21 Jul 2021
Publication statusE-pub ahead of print - 21 Jul 2021


  • astro-ph.EP


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