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On the Detection of Exomoons Transiting Isolated Planetary-mass Objects

Limbach, Mary Anne and Vos, Johanna M. and Winn, Joshua N. and Heller, René and Mason, Jeffrey C. and Schneider, Adam C. and Dai, Fei (2021) On the Detection of Exomoons Transiting Isolated Planetary-mass Objects. Astrophysical Journal Letters, 918 (2). Art. No. L25. ISSN 2041-8205. doi:10.3847/2041-8213/ac1e2d.

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All-sky imaging surveys have identified several dozen isolated planetary-mass objects (IPMOs) far away from any star. Here we examine the prospects for detecting transiting moons around these objects. We expect transiting moons to be common, occurring around 10%–15% of IPMOs, given that close-orbiting moons have a high geometric transit probability and are expected to be a common outcome of giant planet formation. The IPMOs offer an advantage over other directly imaged planets in that high-contrast imaging is not necessary to detect the photometric transit signal. For at least 30 (>50%) of the currently known IPMOs, observations of a single transit with the James Webb Space Telescope would have low enough forecast noise levels to allow for the detection of an Io- or Titan-like moon. The intrinsic variability of the IPMOs will be an obstacle. Using archival time-series photometry of IPMOs with the Spitzer Space Telescope as a proof of concept, we found evidence for a fading event of 2MASS J1119–1137 AB that might have been caused by intrinsic variability but is also consistent with a single transit of a habitable-zone 1.7 R_⊕ exomoon. Although the interpretation of this particular event is inconclusive, the characteristics of the data and the candidate signal suggest that Earth-sized habitable-zone exomoons around IPMOs are detectable with existing instrumentation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Limbach, Mary Anne0000-0002-9521-9798
Vos, Johanna M.0000-0003-0489-1528
Winn, Joshua N.0000-0002-4265-047X
Heller, René0000-0002-9831-0984
Mason, Jeffrey C.0000-0003-0035-598X
Schneider, Adam C.0000-0002-6294-5937
Dai, Fei0000-0002-8958-0683
Additional Information:© 2021. The American Astronomical Society. Received 2021 June 8; revised 2021 August 9; accepted 2021 August 17; published 2021 September 7. We are grateful to Darren L. DePoy for many useful discussions while preparing this manuscript. We thank an anonymous referee for a helpful and thorough review. M.A.L. acknowledges support from the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University. JMV acknowledges support by NSF Award Number 1614527 and Spitzer Cycle 14 JPL Research Support Agreement 1627378. RH acknowledges support from the German Aerospace Agency (Deutsches Zentrum für Luft- und Raumfahrt) under PLATO Data Center grant 50OO1501. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of the UltracoolSheet, maintained by Will Best, Trent Dupuy, Michael Liu, Rob Siverd, and Zhoujian Zhang and developed from compilations by Dupuy & Liu (2012), Dupuy & Kraus (2013), Liu et al. (2016), and Best et al. (2017b, 2020b). Software: (Foreman-Mackey et al. 2013), (, LombScargle (VanderPlas 2017), ELCA (Pearson 2019), Starry (Luger et al. 2019), (Foreman-Mackey 2016), (van der Walt et al. 2011), and (Speagle 2020).
Funding AgencyGrant Number
George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy (MIFPA)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)50OO1501
Subject Keywords:Natural satellites (Extrasolar); Free floating planets; Transits; Exoplanets; Habitable zone
Issue or Number:2
Classification Code:Unifed Astronomy Thesaurus concepts: Natural satellites (Extrasolar) (483); Free floating planets (549); Transits (1711); Exoplanets (498); Habitable zone (696)
Record Number:CaltechAUTHORS:20210914-225406812
Persistent URL:
Official Citation:Mary Anne Limbach et al 2021 ApJL 918 L25
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110900
Deposited By: George Porter
Deposited On:16 Sep 2021 21:58
Last Modified:16 Sep 2021 21:58

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