Detecting planetary mass companions near the water frost-line using JWST interferometry

Abstract

JWST promises to be the most versatile infrared observatory for the next two decades. The Near Infrared and Slitless Spectrograph (NIRISS) instrument, when used in the Aperture Masking Interferometry (AMI) mode, will provide an unparalleled combination of angular resolution and sensitivity compared to any existing observatory at mid-infrared wavelengths. Using simulated observations in conjunction with evolutionary models, we present the capability of this mode to image planetary mass companions around nearby stars at small orbital separations near the circumstellar water frost-line for members of the young, kinematic moving groups β Pictoris, TW Hydrae, as well as the Taurus-Auriga association. We show that for appropriately chosen stars, JWST/NIRISS operating in the AMI mode can image sub-Jupiter companions near the water frost-lines with ${\sim }68{{\%}}$ confidence. Among these, M-type stars are the most promising. We also show that this JWST mode will improve the minimum inner working angle by as much as ${\sim }50{{\%}}$ in most cases when compared to the survey results from the best ground-based exoplanet direct imaging facilities (e.g. VLT/SPHERE). We also discuss how the NIRISS/AMI mode will be especially powerful for the mid-infrared characterization of the numerous exoplanets expected to be revealed by Gaia. When combined with dynamical masses from Gaia, such measurements will provide a much more robust characterization of the initial entropies of these young planets, thereby placing powerful constraints on their early thermal histories.

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems I: High-contrast Imaging of the Exoplanet HIP 65426 b from 2 to 16 μm

“…In anticipation of the range of capabilities that JWST would provide, a similar range of predictions and simulations were constructed in an effort to forecast its potential for exoplanet imaging science. With JWSTʼs extraordinary sensitivity across 4−15μm (where cooler planets are more luminous; Morley et al 2014), the first direct detections of sub-Jupiter, and even sub-Saturn, mass planets will be within reach (Beichman et al 2020;Brande et al 2020;Carter et al 2021a;Ray et al 2023).…”

“…Millar-Blanchaer et al 2023, in preparation;E. Choquet et al 2023, in preparation), spectroscopy from 1 to 28 μm of the PMC VHS J125601.92-125723.9 AB b (VHS 1256b; Gauza et al 2015;Miles et al 2023), and AMI observations of HIP 65426 at 3.8 μm (S. Sallum et al 2023, in preparation; S. Ray et al 2023, in preparation). This program is rapidly disseminating these crucial initial data, and it is demonstrating the true capabilities of JWST for high-contrast imaging and spectroscopy for the first time.…”

Direct discovery of the inner exoplanet in the HD 206893 system

“…Secondly, recent exoplanet direct imaging surveys have had limited sensitivity (e.g., Nielsen et al 2019;Vigan et al 2021) to the peak of the orbital distribution of giant exoplanets that coincides with the location of the water ice line at 2−3 au for solar-type stars (e.g., Fernandes et al 2019;Frelikh et al 2019;Fulton et al 2021). However, upcoming interferometric observations using JWST (Ray et al 2023;Hinkley et al 2022) are likely to have the combination of sufficient sensitivity and resolution to reach these orbital zones, providing complementary characterization at 3−5 µm. Until then, this discovery of an exoplanet at 3.5 au, along with the discovery of β Pic c (Lagrange et al 2019;Nowak et al 2020), is more evidence that optical interferometry now enables direct characterization of these planets at the ice-line orbital separations of 2−4 au, where they form.…”

The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems

“…Using AMI to expand the parameter space inwards will hence enable the community to provide a more robust characterization of the orbital architectures of planetary systems. In addition to this, the mode is also predicted to access Jupiter mass companions at water frost-line separations around stars in nearby young moving groups/associations (Sallum et al 2019;Ray et al 2023). Going forward, this will be a promising technique for placing constraints on initial entropies (by using in conjunction, planetary mass estimates from e.g.…”

“…Going forward, this will be a promising technique for placing constraints on initial entropies (by using in conjunction, planetary mass estimates from e.g. Gaia) of planets for at least the next decade (Spiegel & Burrows 2012;Ray et al 2023).…”