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A coordinated optical and X-ray spectroscopic campaign on HD 179949: Searching for planet-induced chromospheric and coronal activity

Citation

Scandariato, G and Maggio, A and Lanza, AF and Pagano, I and Fares, R and Shkolnik, EL and Bohlender, D and Cameron, AC and Dieters, S and Donati, J-F and Martinez Fiorenzano, AF and Jardine, M and Moutou, C, A coordinated optical and X-ray spectroscopic campaign on HD 179949: Searching for planet-induced chromospheric and coronal activity, Astronomy and Astrophysics, 552 Article A7. ISSN 0004-6361 (2013) [Refereed Article]


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Copyright Statement

Copyright 2013 Astronomy and Astrophysics

DOI: doi:10.1051/0004-6361/201219875

Abstract

Context: HD 179949 is an F8V star, orbited by a close-in giant planet with a period of ~3 days. Previous studies suggested that the planet enhances the magnetic activity of the parent star, producing a chromospheric hot spot which rotates in phase with the planet orbit. However, this phenomenon is intermittent since it was observed in several but not all seasons.

Aims: A long-term monitoring of the magnetic activity of HD 179949 is required to study the amplitude and time scales of star-planet interactions.

Methods: In 2009 we performed a simultaneous optical and X-ray spectroscopic campaign to monitor the magnetic activity of HD 179949 during ~5 orbital periods and ~2 stellar rotations. We analyzed the Ca II H&K lines as a proxy for chromospheric activity, and we studied the X-ray emission in search of flux modulations and to determine basic properties of the coronal plasma.

Results: A detailed analysis of the flux in the cores of the Ca II H&K lines and a similar study of the X-ray photometry shows evidence of source variability, including one flare. The analysis of the time series of chromospheric data indicates a modulation with a ~11 days period, compatible with the stellar rotation period at high latitudes. Instead, the X-ray light curve suggests a signal with a period of ~4 days, consistent with the presence of two active regions on opposite hemispheres.

Conclusions: The observed variability can be explained, most likely, as due to rotational modulation and to intrinsic evolution of chromospheric and coronal activity. There is no clear signature related to the orbital motion of the planet, but the possibility that just a fraction of the chromospheric and coronal variability is modulated with the orbital period of the planet, or the stellar-planet beat period, cannot be excluded. We conclude that any effect due to the presence of the planet is difficult to disentangle.

Item Details

Item Type:Refereed Article
Keywords:planet-star interactions – stars: activity – stars: magnetic field – stars: solar-type
Research Division:Physical Sciences
Research Group:Astronomical and Space Sciences
Research Field:Planetary Science (excl. Extraterrestrial Geology)
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Dieters, S (Dr Stefan Dieters)
ID Code:88385
Year Published:2013
Web of Science® Times Cited:13
Deposited By:Mathematics and Physics
Deposited On:2014-01-31
Last Modified:2014-05-26
Downloads:289 View Download Statistics

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