Query : 2014A&A...568A..99O

2014A&A...568A..99O - Astronomy and Astrophysics, volume 568A, 99-99 (2014/8-1)

Impact of occultations of stellar active regions on transmission spectra. Can occultation of a plage mimic the signature of a blue sky?


Abstract (from CDS):

Transmission spectroscopy during planetary transits, which is based on the measurements of the variations of the planet-to-star radius ratio as a function of wavelength, is a powerful technique to study the atmospheric properties of transiting planets. One of the main limitations of this technique is the effects of stellar activity, which up until now, have been taken into account only by assessing the effect of non-occulted stellar spots on the estimates of the planet-to-star radius ratio. In this paper, we study the impact of the occultation of a stellar spot and plage on the transmission spectra of transiting exoplanets for the first time. We simulated this effect by generating a large number of transit light curves for different transiting planets, stellar spectral types, and different wavelengths.
Result. of our simulations indicate that the anomalies inside the transit light curve can lead to a significant underestimation or overestimation of the planet-to-star radius ratio as a function of wavelength. At short wavelengths, the effect can reach to a difference of up to 10% in the planet-to-star radius ratio, mimicking the signature of light scattering in the planetary atmosphere. Atmospheric scattering has been proposed to interpret the increasing slopes of transmission spectra toward blue for exoplanets HD 189733b and GJ 3470b. Here, we show that these signatures can be alternatively interpreted by the occultation of stellar plages. Results also suggest that the best strategy to identify and quantify the effects of stellar activities on the transmission spectrum of a planet is to perform several observations during the transit epoch at the same wavelength. This will allow for identifying the possible variations in transit depth as a function of time due to stellar activity variability.

Abstract Copyright:

Journal keyword(s): planets and satellites: atmospheres - techniques: photometric - methods: data analysis - methods: numerical - stars: activity

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 LP 424-4 PM* 07 59 05.8395356736 +15 23 29.236065000   13.5   11.934   M2.0V 104 1
2 NAME LP 424-4b Pl 07 59 05.8395618539 +15 23 29.240025256           ~ 262 1
3 Ross 905 PM* 11 42 11.0933350978 +26 42 23.650782778   12.06 10.613 10.272 8.24 M3V 598 1
4 NAME G 139-21b Pl 17 15 18.9337265994 +04 57 50.064695682           ~ 663 1
5 HD 189733 BY* 20 00 43.7129433648 +22 42 39.073143456 9.241 8.578 7.648 7.126 6.68 K2V 841 1
6 HD 189733b Pl 20 00 43.7130382888 +22 42 39.071811263           ~ 1332 1
7 HD 209458b Pl 22 03 10.7729598762 +18 53 03.548248479           ~ 1756 1

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