Transiting the sun

The impact of stellar activity on X-ray and ultraviolet transits

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Transits of hot Jupiters in X-rays and the ultraviolet have been shown to be both deeper and more variable than the corresponding optical transits. This variability has been attributed to hot Jupiters having extended atmospheres at these wavelengths. Using resolved images of the Sun from NASA's Solar Dynamics Observatory spanning 3.5 yr of Solar Cycle 24 we simulate transit light curves of a hot Jupiter to investigate the impact of Solar-like activity on our ability to reliably recover properties of the planet's atmosphere in soft X-rays (94), the UV (131-1700), and the optical (4500). We find that for stars with activity levels similar to those of the Sun, the impact of stellar activity results in underestimating the derived radius of the planet in soft X-ray/EUV by up-to 25% or overestimating it by up to 50% depending on whether the planet occults active regions. We also find that in up to 70% of the X-ray light curves the planet transits over bright starspots. In the far-ultraviolet (1600 and 1700), we find the mean recovered value of to be over-estimated by up to 20%. For optical transits we are able to consistently recover the correct planetary radius. We also address the implications of our results for transits of WASP-12 b and HD 189733b at short wavelengths.

Original languageEnglish (US)
Article number41
JournalAstrophysical Journal
Volume802
Issue number1
DOIs
StatePublished - Mar 20 2015
Externally publishedYes

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stellar activity
transit
sun
planet
Jupiter
planets
Jupiter (planet)
x rays
wavelength
light curve
atmosphere
solar cycle
starspots
atmospheres
helioseismology
radii
observatory
solar cycles
solar activity
wavelengths

Keywords

  • planets and satellites: atmospheres
  • planets and satellites: individual (HD 189733b, WASP-12b)
  • stars: activity
  • stars: coronae
  • starspots

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Transiting the sun : The impact of stellar activity on X-ray and ultraviolet transits. / Llama, J.; Shkolnik, Evgenya.

In: Astrophysical Journal, Vol. 802, No. 1, 41, 20.03.2015.

Research output: Contribution to journalArticle

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