Planet search with the Keck/NIRC2 vortex coronagraph in the M_s band for Vega^★

¹ Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, 06304 Nice, France
e-mail: bin.ren@oca.eu
² Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³ Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena CA 91125, USA
⁴ Earth and Planets Laboratory, Carnegie Institution for Science, Washington DC 20015, USA
⁵ Division of Geological & Planetary Sciences, California Institute of Technology, MC 150-21, 1200 East California Boulevard, Pasadena CA 91125, USA
⁶ Department of Earth Sciences, University of Oregon, Eugene OR 97403, USA
⁷ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA 91109, USA
⁸ Department of Astronomy & Astrophysics, University of California, Santa Cruz, 1156 High St, Santa Cruz CA 95064, USA
⁹ Infrared Processing and Analysis Center (IPAC), California Institute of Technology, MC 100-22, 1200 East California Boulevard, Pasadena CA 91125, USA
¹⁰ American Museum of Natural History, New York NY 12345, USA
¹¹ Space Telescope Science Institute (STScI), 3700 San Martin Drive, Baltimore MD 21218, USA
¹² Aix-Marseille Univ., CNRS, CNES, LAM, Marseille, France

Received: 12 July 2022
Accepted: 18 January 2023

Abstract

Context. Gaps in circumstellar disks can signal the existence of planetary perturbers, making such systems preferred targets for direct imaging observations of exoplanets.

Aims. Being one of the brightest and closest stars to the Sun, the photometric standard star Vega hosts a two-belt debris disk structure. Together with the fact that its planetary system is being viewed nearly face-on, Vega has been one of the prime targets for planet imaging efforts.

Methods. Using the vector vortex coronagraph on Keck/NIRC2 in the M_s band at 4.67 μm, we report the planet detection limits from 1 au to 22 au for Vega with an on-target time of 1.8 h.

Results. We reach a 3 M_Jupiter limit outward of 12 au, which is nearly an order of magnitude deeper than for other existing studies. Combining our observations with existing radial velocity studies, we can confidently rule out the existence of companions more than ~8 M_Jupiter from 22 au down to 0.1 au for Vega. Interior and exterior to ~4 au, this combined approach reaches planet detection limits down to ~2–3 M_Jupiter using radial velocity and direct imaging, respectively.

Conclusions. By reaching multi-Jupiter mass detection limits, our results are expected to be complemented by the planet imaging of Vega in the upcoming observations using the James Webb Space Telescope to obtain a more holistic understanding of the planetary system configuration around Vega.