SEEDS Adaptive Optics Imaging of the Asymmetric Transition Disk Oph IRS 48 in Scattered Light

TL;DR

This study provides the first high-resolution near-infrared images of the Oph IRS 48 transition disk, revealing complex asymmetric structures, a spiral arm, and updated stellar properties through multi-wavelength observations.

Contribution

First resolved near-infrared imaging of Oph IRS 48 revealing detailed disk morphology and updated stellar parameters, including a new interpretation of the disk's asymmetries and structure.

Findings

Detected a 60 AU scattered light cavity with asymmetric arcs.

Identified a possible spiral arm or surface brightness deficit.

Constrained stellar spectral type to A0±1 with low accretion rate.

Abstract

We present the first resolved near infrared imagery of the transition disk Oph IRS 48 (WLY 2-48), which was recently observed with ALMA to have a strongly asymmetric sub-millimeter flux distribution. H-band polarized intensity images show a $\sim$60AU radius scattered light cavity with two pronounced arcs of emission, one from Northeast to Southeast and one smaller, fainter and more distant arc in the Northwest. K-band scattered light imagery reveals a similar morphology, but with a clear third arc along the Southwestern rim of the disk cavity. This arc meets the Northwestern arc at nearly a right angle, revealing the presence of a spiral arm or local surface brightness deficit in the disk, and explaining the East-West brightness asymmetry in the H-band data. We also present 0.8-5.4$\mu$m IRTF SpeX spectra of this object, which allow us to constrain the spectral class to A0$\pm$1 and measure a low mass accretion rate of 10$^{-8.5}$M$_{\odot}$/yr, both consistent with previous estimates. We investigate a variety of reddening laws in order to fit the mutliwavelength SED of Oph IRS 48 and find a best fit consistent with a younger, higher luminosity star than previous estimates.