The need for a public forecast of stellar activity to optimise exoplanet radial velocity detections & transmission spectroscopy

Abstract

Advances in high-precision spectrographs have paved the way for the search for an Earth analogue orbiting a Sun-like star within its habitable zone. However, the research community remains limited by the presence of stellar noise produced by stellar magnetic activity. These activity phenomena can obscure the detection of Earth-mass exoplanets and can create parasitic signals in transmission spectra. In this paper, we outline the need for a public forecast of stellar activity, and produce a proof of principle. Using publicly available spectra we are able to forecast stellar minima several years ahead and reach a typical uncertainty on the timing of these minima of ~0.5 year, similar to the precision reached on our own Sun's magnetic cycle. Furthermore, we use our toy model to show that knowing when to observe can improve the sensitivity of HARPS-North's Solar telescope to low mass planets by up to an order of magnitude, and we show that the majority of exoplanets selected for Early Release Science and Guaranteed Time Observations on the James Webb will be observed close or during stellar maxima, incurring a higher risk of stellar contamination. We finish our paper by outlining a number of next steps to create a public forecast usable by teams around the globe, by telescope time allocation committees, and in preparation for spacecrafts such as Ariel.

10 pages, 12 figures, accepted for publication in MNRAS

References in corpus (22)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters
• Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity
• The unusual minimum of sunspot cycle 23 a consequence of Sun's meridional plasma flow variations
• Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum
• The Mount Wilson Observatory S-index of the Sun
• Impact of occultations of stellar active regions on transmission spectra: Can occultation of a plage mimic the signature of a blue sky?
• Transit spectroscopy with JWST: Systematics, starspots and stitching
• A candidate short-period sub-Earth orbiting Proxima Centauri
• Revisiting Proxima with ESPRESSO
• Two planets around Kapteyn's star : a cold and a temperate super-Earth orbiting the nearest halo red-dwarf
• Stellar activity mimics a habitable-zone planet around Kapteyn's star
• Filtering solar-like oscillations for exoplanet detection in radial velocity observations
• WASP-78b and WASP-79b: Two highly-bloated hot Jupiter-mass exoplanets orbiting F-type stars in Eridanus
• Fast Bayesian Inference for Exoplanet Discovery in Radial Velocity Data
• Analysis of full disc Ca II K spectroheliograms III. Plage area composite series covering 1892-2019
• Stellar surface inhomogeneities as a potential source of the atmospheric signal detected in the K2-18 b transmission spectrum
• A new method of correcting radial velocity time series for inhomogeneous convection
• SALT observations of the Chromospheric Activity of Transiting Planet Hosts: Mass Loss and Star Planet Interactions
• The CARMENES search for exoplanets around M dwarfs Detection of a mini-Neptune around LSPM J2116+0234 and refinement of orbital parameters of a super-Earth around GJ 686 (BD+18 3421)

Cited by in corpus (5)

• Monitoring the large-scale magnetic field of AD~Leo with SPIRou, ESPaDOnS and Narval. Toward a magnetic polarity reversal?
• Sub-m s${}^{-1}$ upper limits from a deep HARPS-N radial-velocity search for planets orbiting HD 166620 and HD 144579
• DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections
• Two neighbours of the ultra-short-period Earth-sized planet K2-157 b in the warm Neptunian savanna
• Revisiting $\epsilon$ Eridani with NEID: Identifying New Activity-Sensitive Lines in a Young K Dwarf Star