A compact multi-planet system around a bright nearby star from the Dispersed Matter Planet Project

TL;DR

This study reports the discovery of four short-period, compact planets around a bright star, using high-precision radial velocity measurements, highlighting a potential link to circumstellar gas and planetary evolution.

Contribution

First detection of a multi-planet system around a star with low chromospheric activity using the Dispersed Matter Planet Project.

Findings

Four short-period planets identified around HD 38677

Planets range from super-Earth to Neptune mass

Potentially remnant cores of former giant planets

Abstract

The Dispersed Matter Planet Project targets stars with anomalously low Ca II H&K chromospheric emission. High precision, high cadence radial velocity measurements of the F8V star HD 38677 / DMPP-1 reveal four short period planets. DMPP-1 has log(R'HK) = -5.16 which probably indicates the presence of circumstellar absorbing gas arising from an ablating hot planet. The planets have P$_{\rm orb}$ ~ 2.9 - 19 d, i.e., a compact planetary system with super-Earth (~3 M$_\oplus$) to Neptune-mass (~24 M$_\oplus$) planets. These irradiated planets may be chthonian: remnant cores of giant planets after mass-loss while crossing the Neptune desert. Modelling the possible long-term activity indicators while searching for Keplerian signals modifies the recovered planetary signals. A priori inferences about the presence of short period planets allowed the efficient discovery of the DMPP-1 planets. They have great potential for novel and informative follow-up characterisation studies.