Systematic Multi-Epoch Monitoring of LkCa 15: Dynamic Dust Structures on Solar-System Scales

Abstract

We present the highest angular resolution infrared monitoring of LkCa 15, a young solar analog hosting a transition disk. This system has been the subject of a number of direct imaging studies from the millimeter through the optical, which have revealed multiple protoplanetary disk rings as well as three orbiting protoplanet candidates detected in infrared continuum (one of which was simultaneously seen at H$\alpha$). We use high-angular-resolution infrared imaging from 2014-2020 to systematically monitor these infrared signals and determine their physical origin. We find that three self-luminous protoplanets cannot explain the positional evolution of the infrared sources, since the longer time baseline images lack the coherent orbital motion that would be expected for companions. However, the data still strongly prefer a time-variable morphology that cannot be reproduced by static scattered-light disk models. The multi-epoch observations suggest the presence of complex and dynamic substructures moving through the forward-scattering side of the disk at $\sim 20$ AU, or quickly-varying shadowing by closer-in material. We explore whether the previous H$\alpha$ detection of one candidate would be inconsistent with this scenario, and in the process develop an analytical signal-to-noise penalty for H$\alpha$ excesses detected near forward-scattered light. Under these new noise considerations, the H$\alpha$ detection is not strongly inconsistent with forward scattering, making the dynamic LkCa 15 disk a natural explanation for both the infrared and H$\alpha$ data.

24 pages, 11 figures, accepted for publication in ApJ

References in corpus (25)

• Bayes in the sky: Bayesian inference and model selection in cosmology
• Two accreting protoplanets around the young star PDS 70
• On the Diversity of the Taurus Transitional Disks: UX Tau A & Lk Ca 15
• The Disk Around CoKu Tau/4: Circumbinary, not Transitional
• Dust flow in gas disks in the presence of embedded planets
• The newborn planet population emerging from ring-like structures in discs
• No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals
• Demographics of Transition Discs in Ophiuchus and Taurus
• Resolving the planet-hosting inner regions of the LkCa 15 disk
• Reference star differential imaging of close-in companions and circumstellar disks with the NIRC2 vortex coronagraph at W.M. Keck Observatory
• Annular substructures in the transition disks around LkCa 15 and J1610
• The LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system
• The widest H$\alpha$ survey of accreting protoplanets around nearby transition disks
• Principles of image reconstruction in optical interferometry: tutorial
• Comparison of planetary Hα-emission models: A new correlation with accretion luminosity
• ALMA Detection of Dust Trapping around Lagrangian Points in the LkCa 15 Disk
• Comparing Non-Redundant Masking and Filled-Aperture Kernel Phase for Exoplanet Detection and Characterization
• The Giant Accreting Protoplanet Survey (GAPlanetS) -- Results from a Six Year Campaign to Image Accreting Protoplanets
• Large Binocular Telescope Interferometer Adaptive Optics: On-sky performance and lessons learned
• New Spatially Resolved Observations of the T Cha Transition Disk and Constraints on the Previously Claimed Substellar Companion
• Data Reduction and Image Reconstruction Techniques for Non-Redundant Masking
• Imaging protoplanets: observing transition disks with non-redundant masking
• ELT Imaging of MWC 297 from the 23-m LBTI: Complex Disk Structure and a Companion Candidate
• Planetary line-to-accretion luminosity scaling relations: Extrapolating to higher-order hydrogen lines
• $\mathtt{PlanetEvidence}$: Planet or Noise?

Cited by in corpus (2)

• Searching for Protoplanets around MWC 758 and MWC 480 in Br-$\gamma$ using Kernel Phase and SCExAO/CHARIS
• Recovering simulated planet and disk signals using SCALES aperture masking