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

Thayne Currie, Christian Marois, Lucas Cieza, Gijs D. Mulders, Kellen Lawson, Claudio Caceres, Dary Rodriguez-Ruiz, John Wisniewski, Olivier Guyon, Timothy D. Brandt, N. Jeremy Kasdin, Tyler D. Groff, Julien Lozi, Jeffrey Chilcote, Klaus Hodapp, Nemanja Jovanovic, Frantz Martinache, Nour Skaf, Wladimir Lyra, Motohide TamuraRuben Asensio-Torres, Ruobing Dong, Carol Grady, Benjamin Gerard, Misato Fukagawa, Derek Hand, Masahiko Hayashi, Thomas Henning, Tomoyuki Kudo, Masayuki Kuzuhara, Jungmi Kwon, Michael W. McElwain, Taichi Uyama

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

Two studies utilizing sparse aperture-masking (SAM) interferometry and Hα 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 Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with Coronagraphic High Angular Resolution Imaging Spectrograph (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 Hα 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.

Original languageEnglish (US)
Article numberL3
JournalAstrophysical Journal Letters
Volume877
Issue number1
DOIs
StatePublished - May 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Herbig Ae/Be
  • Herbig Ae/Be
  • instrumentation: high angular resolution
  • planetary systems
  • stars: individual (LkCa 15)
  • stars: variables: T Tauri
  • techniques: image processing
  • techniques: image processing: variables: T Tauri

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    Currie, T., Marois, C., Cieza, L., Mulders, G. D., Lawson, K., Caceres, C., Rodriguez-Ruiz, D., Wisniewski, J., Guyon, O., Brandt, T. D., Kasdin, N. J., Groff, T. D., Lozi, J., Chilcote, J., Hodapp, K., Jovanovic, N., Martinache, F., Skaf, N., Lyra, W., ... Uyama, T. (2019). No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals. Astrophysical Journal Letters, 877(1), [L3]. https://doi.org/10.3847/2041-8213/ab1b42