Constraining accretion signatures of exoplanets in the TW Hya transitional disk

TL;DR

This study used near-infrared spectroscopy to search for accretion signatures of potential protoplanets in the TW Hya disk, setting limits on their masses and informing future direct imaging efforts.

Contribution

It provides new detection limits for accreting protoplanets in TW Hya using Paβ line observations, improving constraints on planet masses in the disk.

Findings

No accretion signatures detected in the observed region.

Detection limits allow identification of protoplanets as small as ~1 Jupiter mass.

Mass estimates for potential planets are consistent with previous imaging constraints.

Abstract

We present a near-infrared direct imaging search for accretion signatures of possible protoplanets around the young stellar object (YSO) TW Hya, a multi-ring disk exhibiting evidence of planet formation. The Pa$\beta$ line (1.282 $\mu$m) is an indication of accretion onto a protoplanet, and its intensity is much higher than that of blackbody radiation from the protoplanet. We focused on the Pa$\beta$ line and performed Keck/OSIRIS spectroscopic observations. Although spectral differential imaging (SDI) reduction detected no accretion signatures, the results of the present study allowed us to set 5$\sigma$ detection limits for Pa$\beta$ emission of $5.8\times10^{-18}$ and $1.5\times10^{-18}$ erg/s/cm$^2$ at 0\farcs4 and 1\farcs6, respectively. We considered the mass of potential planets using theoretical simulations of circumplanetary disks and hydrogen emission. The resulting masses were $1.45\pm 0.04$ M$_{\rm J}$ and $2.29 ^{+0.03}_{-0.04}$ M$_{\rm J}$ at 25 and 95 AU, respectively, which agree with the detection limits obtained from previous broadband imaging. The detection limits should allow the identification of protoplanets as small as $\sim$1 M$_{\rm J}$, which may assist in direct imaging searches around faint YSOs for which extreme adaptive optics instruments are unavailable.