SOAP 2.0: A TOOL TO ESTIMATE THE PHOTOMETRIC AND RADIAL VELOCITY VARIATIONS INDUCED BY STELLAR SPOTS AND PLAGES

By Xavier Dumusque, I. Boisse, Nuno C. Santos. 2014

156 citations recorded by the source corpus.

This paper presents SOAP 2.0, a new version of the Spot Oscillation And Planet (SOAP) code that estimates in a simple way the photometric and radial velocity (RV) variations induced by active regions. The inhibition of the convective blueshift (CB) inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the CB effect. For spots, this effect becomes significant only for slow rotators. In addition, in the case of a major active region dominating the activity-induced signal, the ratio between the FWHM and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with v sin i ⩽8 km s−1. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD 189733, we show that SOAP 2.0 manages to reproduce the activity variation as well as previous simulations when a spot is dominating the activity-induced variation. In addition, SOAP 2.0 also reproduces the activity variation induced by a plage on the slowly rotating star α Cen B, which is not possible using previous simulations. Following these results, SOAP 2.0 can be used to estimate the signal induced by spots and plages, but also to correct for it when a major active region is dominating the RV variation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3219f9af0571630926b0cb68642f65a01be2f95c

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In Astronomy and Astrophysics

1. J. Southworth
2. S. Udry
3. J. Johnson
4. C. Lovis
5. F. Pepe
6. F. Bouchy
7. R. Dawson
8. D. Queloz

In Instrumentation

1. J. Southworth
2. S. Udry
3. C. Lovis
4. R. Dawson
5. F. Pepe
6. Suzanne Aigrain
7. F. Bouchy
8. D. Queloz

Citations in the corpus

• WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, background): “As for the non-detections of out-of-eclipse variations or spot-crossing events in the photometry, they might be explained, at least to some extent, if the star is plagedominated, in opposition to spot-dominated (see Dumusque et al. 2014).”
• A Gaussian process framework for modelling stellar activity signals in radial velocity data (2015, methodology): “Moreover, Dumusque et al. (2014) showed that SOAP 2.0 manages to reproduce the activity-induced variation on the early-K dwarfs HD 189733 and α Cen B ; modelling the activity-induced variation on the latter star with our new GP framework is considered in Section 4.4.”
• State of the Field: Extreme Precision Radial Velocities (2016, methodology): “These diagnostics include measurements of emission in the cores of Ca II H&K spectral lines, changes in the spectral line bisector, or variability in the full width half maximum (FWHM) of the spectral cross correlation function (CCF; Dumusque et al. 2014).”