Direct detection and characterization of M-dwarf planets using light echoes
arXiv:1801.01144 · doi:10.3847/1538-4357/aaa549
Abstract
Exoplanets orbiting M dwarf stars are a prime target in the search for life in the Universe. M dwarf stars are active, with powerful flares that could adversely impact prospects for life, though there are counter-arguments. Here, we turn flaring to advantage and describe ways in which it can be used to enhance the detectability of planets, in the absence of transits or a coronagraph, significantly expanding the accessible discovery and characterization space. Flares produce brief bursts of intense luminosity, after which the star dims. Due to the light travel time between the star and planet, the planet receives the high intensity pulse, which it re-emits through scattering (a light echo) or intrinsic emission when the star is much fainter, thereby increasing the planet's detectability. The planet's light echo emission can potentially be discriminated from that of the host star by means of a time delay, Doppler shift, spatial shift, and polarization, each of which can improve the contrast of the planet to the star. Scattered light can reveal the albedo spectrum of the planet to within a size scale factor, and is likely to be polarized. Intrinsic emission mechanisms include fluorescent pumping of multiple molecular hydrogen and neutral oxygen lines by intense LyAlpha and LyBeta flare emission, recombination radiation of ionized and photodissociated species, and atmospheric processes such as terrestrial upper atmosphere airglow and near infrared hydroxyl emission. We discuss the feasibility of detecting light echoes and find that under favorable circumstances, echo detection is possible.
References in corpus (23)
- Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
- A terrestrial planet candidate in a temperate orbit around Proxima Centauri
- Atmospheric Retrieval for Super-Earths: Uniquely Constraining the Atmospheric Composition with Transmission Spectroscopy
- Kepler Flares I. Active and Inactive M dwarfs
- A temperate rocky super-Earth transiting a nearby cool star
- The habitability of Proxima Centauri b II. Possible climates and Observability
- Combining high-dispersion spectroscopy (HDS) with high contrast imaging (HCI): Probing rocky planets around our nearest neighbors
- Atmospheric characterization of Proxima b by coupling the Sphere high-contrast imager to the Espresso spectrograph
- Spectropolarimetric signatures of Earth-like extrasolar planets
- HAZMAT I: The Evolution of Far-UV and Near-UV Emission from Early M Stars
- Detection of circular polarization in light scattered from photosynthetic microbes
- HATS-6b: A Warm Saturn Transiting an Early M Dwarf Star, and a Set of Empirical Relations for Characterizing K and M Dwarf Planet Hosts
- Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman- line
- MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri
- The full spectral radiative properties of Proxima Centauri
- The HARPS search for southern extra-solar planets XLII. A system of Earth-mass planets around the nearby M dwarf YZ Ceti
- Near-Ultraviolet Spectra of Flares on YZ CMi
- ALMA Discovery of Dust Belts Around Proxima Centauri
- The Pale Green Dot: A Method to Characterize Proxima Centauri b using Exo-Aurorae
- Probabilistic Constraints on the Mass and Composition of Proxima b
- Strong HI Lyman- variations from the 11 Gyr-old host star Kepler-444: a planetary origin ?
- On the Orbital Inclination of Proxima Centauri b
- Predicting exoplanet observability in time, contrast, separation and polarization, in scattered light