Validating Monotransits from Space Missions

Observed during Campaign 14 by the K2 mission, an object transited once across its star, lasting 59 hours at a depth of 17ppt.

Following its unearthing in the light curve, the likelihood of a false signal due to the photometry, telescope performance and other astrophysical sources was established; as well as performing immediate follow-up using Coralie on the Swiss-Euler telescope in La Silla, Chile. This provided initial stellar parameters from the spectra and radial velocity measurements for eliminating any possible binary systems.

Between the spectra and the second Gaia data release, a lot was learnt about the host star, as well as beginning planetary mass determinations with the radial velocity data.

Additionally, more system parameters can be gathered by fitting the transit with Namaste (Osborn et al., 2016), a mono-transit fitting software which can estimate orbital period and other key planetary parameters.

We will present the discovery and validation process of this planet-like candidate from K2’s Campaign 14 (Giles et al., in prep), and how this can be applied to other space-based missions such as TESS, CHEOPS and PLATO — particularly for TESS who will only observe large sections of the sky for short periods of time.

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