An international team of astronomers has announced the discovery of a transiting hot Jupiter in a rare triple-star system.
This artist’s impression shows the view from a terrestrial exoplanet towards the planet’s host star in a triple stellar system. Image credit: M. Kornmesser / ESO.
The newfound gas giant, designated KELT-4Ab, was discovered by the astronomers using data from the Kilodegree Extremely Little Telescope (KELT).
The team, led by Dr. Jason Eastman from the Harvard-Smithsonian Center for Astrophysics, found that the planet has a mass of 0.9 Jupiter and a diameter of 1.7 Jupiter.
“In terms of size, KELT-4Ab is qualitatively similar to WASP-79b and WASP-94Ab, which have slightly larger planets around slightly fainter stars,” they said.
KELT-4Ab, according to the team, is located 685 light-years away.
The planet orbits KELT-4A – the brightest star of the hierarchical triple stellar system KELT-4 (otherwise known as HIP 51260, TYC 1973 954 1 and WISE J102815.04+253423.7) – every 3 days.
“KELT-4Ab is only the fourth known transiting planet in a hierarchical triple stellar system, along with WASP-12b, HAT-P-8b, and Kepler-444b,” Dr. Eastman and co-authors said.
“KELT-4A is second brightest host of all these systems, the brightest host of a hot Jupiter, and therefore a valuable find for extensive follow-up of inflated planets, hierarchical architectures, and hot Jupiter migration.”
The triple-star system KELT-4 also includes two fainter stars: KELT-4B and KELT-4C, collectively known as KELT-4BC.
The twin stars KELT-4B and KELT-4C orbit one another every 29 years. The pair then orbit KELT-4A once every 3,780 years.
The projected separation between KELT-4A and KELT-4BC is approximately 328 astronomical units (AU), and the separation between KELT-4B and KELT-4C is only 10 AU.
“KELT-4Ab’s existence within a hierarchical triple and its proximity to Earth provide a unique opportunity for dynamical studies with continued monitoring with high resolution imaging and precision radial velocities,” the astronomers said.
The discovery is reported in the February 2016 issue of the Astronomical Journal.
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Jason D. Eastman et al. 2016. KELT-4Ab: An Inflated Hot Jupiter Transiting the Bright (V ~ 10) Component of a Hierarchical Triple. Astronomical Journal 151, 45; doi: 10.3847/0004-6256/151/2/45
