No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals

Abstract

Two studies utilizing sparse aperture masking (SAM) interferometry and $H_{\alpha }$ differential imaging have reported multiple jovian companions around the young solar-mass star, LkCa 15 (LkCa 15 bcd): the first claimed direct detection of infant, newly-formed planets ("protoplanets"). We present new near-infrared direct imaging/spectroscopy from the SCExAO system coupled with the CHARIS integral field spectrograph and multi-epoch thermal infrared imaging from Keck/NIRC2 of LkCa 15 at high Strehl ratios. These data provide the first direct imaging look at the same wavelengths and in the same locations where previous studies identified the LkCa 15 protoplanets and thus offer the first decisive test of their existence. The data do not reveal these planets. Instead, we resolve extended emission tracing a dust disk with a brightness and location comparable to that claimed for LkCa 15 bcd. Forward-models attributing this signal to orbiting planets are inconsistent with the combined SCExAO/CHARIS and Keck/NIRC2 data. An inner disk provides a more compelling explanation for the SAM detections and perhaps also the claimed $H_{\alpha }$ detection of LkCa 15 b. We conclude that there is currently no clear, direct evidence for multiple protoplanets orbiting LkCa 15, although the system likely contains at least one unseen jovian companion. To identify jovian companions around LkCa 15 from future observations, the inner disk should be detected and its effect modeled, removed, and shown to be distinguishable from planets. Protoplanet candidates identified from similar systems should likewise be clearly distinguished from disk emission through modeling.

12 pages, 4 figures, 1 table; Astrophysical Journal Letters in press

References in corpus (16)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Fundamental limitations of high contrast imaging set by small sample statistics
• On the Diversity of the Taurus Transitional Disks: UX Tau A & Lk Ca 15
• Radiative transfer in very optically thick circumstellar disks
• Searching for circumplanetary disks around LkCa 15
• Confidence Level and Sensitivity Limits in High Contrast Imaging
• Resolving the planet-hosting inner regions of the LkCa 15 disk
• Investigation of the inner structures around HD169142 with VLT/SPHERE
• Deep Thermal Infrared Imaging of HR 8799 bcde: New Atmospheric Constraints and Limits on a Fifth Planet
• Far-infrared to millimeter data of protoplanetary disks: dust growth in the Taurus, Ophiuchus, and Chamaeleon I star-forming regions
• Separating extended disc features from the protoplanet in PDS 70 using VLT/SINFONI
• GPI PSF subtraction with TLOCI: the next evolution in exoplanet/disk high-contrast imaging
• Subaru/SCExAO First-Light Direct Imaging of a Young Debris Disk around HD 36546
• New Spatially Resolved Observations of the T Cha Transition Disk and Constraints on the Previously Claimed Substellar Companion
• A Resolved Near-Infrared Image of The Inner Cavity in The GM Aur Transitional Disk
• Imaging protoplanets: observing transition disks with non-redundant masking

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• High-Contrast Integral Field Spectrograph (HCIFS): multi-spectral wavefront control and reduced-dimensional system identification
• High-contrast integral field spectropolarimetry of planet-forming disks with SCExAO/CHARIS
• New constraints on the presence of debris disks around G 196-3 B and VHS J125601.92-125723.9 b
• SCExAO, a testbed for developing high-contrast imaging technologies for ELTs
• Performance and Early Science with the Subaru Coronagraphic Extreme Adaptive Optics Project
• Two Rings and a Marginally Resolved, 5 AU, Disk Around LkCa 15 Identified Via Near Infrared Sparse Aperture Masking Interferometry
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• Update on the Preliminary Design of SCALES: the Santa Cruz Array of Lenslets for Exoplanet Spectroscopy