Evidence for enhanced chromospheric Ca II H & K emission in stars with close-in extrasolar planets

Abstract

The planet-star interaction is manifested in many ways. It was found out that a close-in exoplanet causes small but measurable variability in the cores of a few lines in the spectra of several stars which corresponds to the orbital period of the exoplanet. Stars with and without exoplanets may have different properties. The main goal of our study is to search for influence which exoplanets might have on atmospheres of their host stars. Unlike the previous studies, we do not study changes in the spectrum of a host star or differences between stars with and without exoplanets. We aim to study a large number of stars with exoplanets, current level of their chromospheric activity and look for a possible correlation with the exoplanetary properties. To analyse the chromospheric activity of stars we exploit our own (2.2m ESO/MPG telescope) and publicly available archival spectra (Keck Observatory Archive), measure the equivalent widths of the cores of Ca II H and K lines and use them as a tracer of their activity. Subsequently, we search for their dependence on the orbital parameters and mass of the exoplanet. We found a statistically significant evidence that the equivalent width of the Ca II K line emission and log R'_{HK} activity parameter of the host star varies with the semi-major axis and mass of the exoplanet. Stars with T_eff <= 5500 K having exoplanets with semi-major axis a <= 0.15 AU (P_orb <= 20 days) have a broad range of Ca II K emissions and much stronger emission in general than stars at similar temperatures but with higher values of semi-major axes. Ca II K emission of cold stars (T_eff <= 5500 K) with close-in exoplanets (a <= 0.15 AU) is also more pronounced for more massive exoplanets. The overall level of the chromospheric activity of stars may be affected by their close-in exoplanets. Stars with massive close-in exoplanets may be more active.

9 pages, 8 figures, 1 table

References in corpus (9)

• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• The On/Off Nature of Star-Planet Interactions
• Extrasolar Giant Planets and X-ray Activity
• Hot Jupiters and stellar magnetic activity
• Observability of the General Relativistic Precession of Periastra in Exoplanets
• A correlation between host star activity and planet mass for close-in extrasolar planets?
• On the chromospheric activity of stars with planets
• Parent Stars of Extrasolar Planets. XII. Additional evidence for trends with vsini, condensation temperature, and chromospheric activity
• First Observation of Planet-Induced X-ray Emission: The System HD 179949

Cited by in corpus (18)

• The GAPS programme with HARPS-N at TNG. I: Observations of the Rossiter-McLaughlin effect and characterisation of the transiting system Qatar-1
• H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood
• The corona of HD 189733 and its X-ray activity
• Modelling the light-curve of KIC 12557548b: an extrasolar planet with a comet like tail
• A comprehensive statistical assessment of star-planet interaction
• An Ultraviolet Investigation of Activity on Exoplanet Host Stars
• On the detectability of star-planet interaction
• The GAPS Programme with HARPS-N at TNG. XIII. The orbital obliquity of three close-in massive planets hosted by dwarf K-type stars: WASP-43, HAT-P-20 and Qatar-2
• Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin
• No X-rays from WASP-18. Implications for its age, activity, and the influence of its massive hot Jupiter
• SALT observations of the Chromospheric Activity of Transiting Planet Hosts: Mass Loss and Star Planet Interactions
• Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companion
• A possible long-term activity cycle for ι Horologii: First results from the HKα & SPI-HKα projects
• A BCool survey of the magnetic fields of planet-hosting solar-type stars
• The evolution of lithium in FGK dwarf stars: The Li rotation connection and the Li desert
• A statistical search for Star-Planet Interaction in the UltraViolet using GALEX
• ${\zeta }^1+{\zeta }^2$ Reticuli binary system: A puzzling chromospheric activity pattern
• Chromospheric emission of planet candidate systems - a way to identify false positives