Astronomers have detected two gas giant exoplanets designated K2-60b and EPIC 216468514b and characterized their fundamental parameters. The planets were first spotted by NASA’s Kepler space telescope and their planetary nature was confirmed by follow-up spectroscopic observations. The findings were presented in a paper published in November on arXiv.org.
The discovery was made by an international team of researchers led by Philipp Eigmüller of the German Aerospace Center’s (DLR) Institute of Planetary Research. They have combined data from Kepler’s prolonged mission known as K2 and spectroscopic observations provided by the FIbrefed Echelle Spectrograph (FIES) mounted at the Nordic Optical Telescope (NOT) and the HARPS-N spectrograph at the Telescopio Nazionale Galileo (TNG). Both telescopes are part of the Roque de los Muchachos Observatory located on the island of La Palma in the Canary Islands.
“FIES and HARPS-N are two very prominent instruments for radial velocity follow up on the northern hemisphere, which allow us to determine the speed of a star to a precision of only a few meters per second. For the confirmation of transiting planets and to determine their mass such instrument are of utter importance,” Eigmüller told Astrowatch.net.
He added that without radial velocity measurements it is quite difficult to verify the planetary nature of a planetary candidate. In combination with the radius (from the transit depth) radial velocity follow-up allows researchers to determine the mean planetary density.
“This gives us first insights into the nature of the planet,” Eigmüller said.
According to the research, K2-60b is a sub-Jovian exoworld with a radius of about 0.68 Jupiter radii and 58 percent less massive than our solar system’s biggest planet. EPIC 216468514b has a radius 44 percent larger than Jupiter’s and a mass of 0.84 Jupiter masses. What is noteworthy, both planets have short orbital periods - 3 and 3.31 days respectively.
The scientists underline that K2-60b is among the few planets at the edge of the so-called “desert” of short-period sub-Jovian planets, while EPIC 216468514b is a highly inflated Jovian planet orbiting an evolved star about to leave the main sequence.
“K2-60b is a very dense sub-Jovian planet. With is high effective temperature given by its close-in orbit K2-60b is one of only few planets near the so called ‘sub-Jovian desert’ which describes the dearth hot sub-Jovians and super-earth planets. EPIC 216468514b on the other hand is a highly inflated hot Jupiter, in orbit around a sub-giant star,” Eigmüller said.
He noted that K2-60b will in future be useful for understanding the sub-Jovian “desert” and to define its borders. This is related to planetary formation theories and thus will allow the researchers to extend our understanding of how planet systems are formed and evolve over time. When it comes to EPIC 216468514b, a statistical sample of planets around evolved stars could give us the chance to understand the evolution of planetary systems in regards to the evolution of their host stars.