A Neptune-mass Planet Orbiting the Nearby G Dwarf HD16417

TL;DR

This paper reports the discovery of a Neptune-mass exoplanet orbiting the nearby G dwarf HD16417, confirmed through intensive Doppler measurements, highlighting the importance of extended observing campaigns for detecting low-mass planets.

Contribution

It presents the detection and detailed orbital characterization of a low-mass exoplanet, emphasizing the need for prolonged and continuous observations in Doppler planet searches.

Findings

Discovery of a 22.1 Earth-mass planet orbiting HD16417

Confirmation of the planet through independent observations

Demonstrates the necessity of extended campaigns for low-mass planet detection

Abstract

Precision Doppler measurements from an intensive 48 night "Rocky Planet Search" observing campaign on the Anglo-Australian Telescope (AAT) have revealed the presence of a low-mass exoplanet orbiting the G1 dwarf HD16417. Subsequent Doppler observations with the AAT, as well as independent observations obtained by the Keck Planet Search, have confirmed this initial detection and refine the orbital parameters to period 17.24+/-0.01 d, eccentricity 0.20+/-0.09, orbital semi-major axis 0.14+/-0.01 AU and minimum planet mass 22.1+/-2.0 Mearth. HD 16417 raises the number of published exoplanets with minimum masses of less than 25 Mearth to eighteen. Interestingly, the distribution of detected sub-25 Mearth planets over the spectral types G, K and M is almost uniform. The detection of HD 16417b by an intensive observing campaign clearly demonstrates the need for extended and contiguous observing campaigns when aiming to detect low-amplitude Doppler planets in short period orbits. Perhaps most critically it demonstrates that the search for low-mass Doppler planets will eventually require these traditional "bright-time" projects to extend throughout dark lunations.