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Habitable Planets Eclipsing Brown Dwarfs: Strategies for Detection and Characterization

A. R. Belu, F. Selsis, S. N. Raymond, E. PallÚ, R. A. Street, D. K. Sahu, K von Braun, E. Bolmont, P. Figueira, G. C. Anupama, I. Ribas

Abstract
Given the very close proximity of their habitable zones, brown dwarfs represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper we develop search strategies to find habitable planets transiting brown dwarfs depending on their maximum habitable orbital period (PHZ out). Habitable planets with PHZ out shorter than the useful duration of a night (e.g. 8-10 hrs) can be screened with 100% completeness from a single location and in a single night (near-IR). More luminous brown dwarfs require continuous monitoring for longer duration, e.g. from space or from a longitude-distributed network (one test scheduling achieved - 3 telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known brown dwarfs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between 4.5+5.6/-1.4 and 56+31/-13 %, depending on our assumptions. We calculate that brown dwarfs within 5-10 pc are characterizable for potential biosignatures with a 6.5 m space telescope using ~1% of a 5-year mission’s lifetime spread over a contiguous segment only 1/5th to 1/10th of this duration.

Keywords
astrobiology — brown dwarfs — eclipses — infrared: planetary systems — instrumentation: spectrographs — solar neighborhood

The Astrophysical Journal
Volume 768, Number 2, Page 125_1
2013 May

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Instituto de Astrof├şsica e Ci├¬ncias do Espa├žo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Funda├ž├úo para a Ci├¬ncia e a Tecnologia
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