Method for Spot Detection on Solar-like Stars

Silva, Adriana V. R.

doi:10.1086/374324

Cited by 136 publications

(159 citation statements)

References 14 publications

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“…The resulting light curves SYNTH-4a to SYNTH-4d show the same occulted starspot. We calculate the wavelength dependent spot contrasts using equation (1) of Silva (2003), using a blackbody approximation, a solar-like effective temperature for the host star of T eff = 5772 K, and a spot temperature of T spot = 4772 K. We generate all simulated TLCs using PyTranSpot and add Gaussian noise to the calculated flux.…”

Section: Synthetic Data Setsmentioning

confidence: 99%

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

Juvan

Lendl

Cubillos

et al. 2018

A&A

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Several studies have shown that stellar activity features, such as occulted and non-occulted starspots, can affect the measurement of transit parameters biasing studies of transit timing variations and transmission spectra. We present PyTranSpot, which we designed to model multiband transit light curves showing starspot anomalies, inferring both transit and spot parameters. The code follows a pixellation approach to model the star with its corresponding limb darkening, spots, and transiting planet on a two dimensional Cartesian coordinate grid. We combine PyTranSpot with an MCMC framework to study and derive exoplanet transmission spectra, which provides statistically robust values for the physical properties and uncertainties of a transiting star-planet system. We validate PyTranSpot's performance by analyzing eleven synthetic light curves of four different star-planet systems and 20 transit light curves of the well-studied WASP-41b system. We also investigate the impact of starspots on transit parameters and derive wavelength dependent transit depth values for WASP-41b covering a range of 6200-9200 Å, indicating a flat transmission spectrum.

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Section: Synthetic Data Setsmentioning

confidence: 99%

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

Juvan

Lendl

Cubillos

et al. 2018

A&A

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“…From Table 5, it is clear that the star-spots are brighter in the redder passbands than in the bluer passbands, for all four simultaneous multiband observations. Modelling both the photosphere and the star-spot as black bodies (Rabus et al 2009;Sanchis-Ojeda et al 2011;Mancini et al 2013b;Mohler-Fischer et al 2013) and using equation (1) of Silva (2003) and T eff = 4645 ± 50 (Bryan et al 2012), we estimated the temperature of the star-spots at different bands and reported them in the last column of Table 5. The values of the temperature estimated for each transit are in good agreement between each other within the experimental uncertainties and point to star-spots with temperature between 4100 and 4200 K. This can be also noted in Fig.…”

Section: S Ta R -S P Ot M O D E L L I N Gmentioning

confidence: 99%

Erratum: Physical properties, star-spot activity, orbital obliquity and transmission spectrum of the Qatar-2 planetary system from multicolour photometry

Mancini

Southworth

Ciceri

et al. 2016

Mon. Not. R. Astron. Soc.

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We present 17 high-precision light curves of five transits of the planet Qatar-2 b, obtained from four defocused 2 m-class telescopes. Three of the transits were observed simultaneously in the Sloan g r i z passbands using the seven-beam Gamma Ray Burst Optical and Near-Infrared Detector imager on the MPG/ESO 2.2-m telescope. A fourth was observed simultaneously in Gunn grz using the Centro Astronómico Hispano Alemán 2.2-m telescope with Bonn University Simultaneous Camera, and in r using the Cassini 1.52-m telescope. Every light curve shows small anomalies due to the passage of the planetary shadow over a cool spot on the surface of the host star. We fit the light curves with the PRISM+GEMC model to obtain the photometric parameters of the system and the position, size and contrast of each spot. We use these photometric parameters and published spectroscopic measurements to obtain the physical properties of the system to high precision, finding a larger radius and lower density for both star and planet than previously thought. By tracking the change in position of one star-spot between two transit observations, we measure the orbital obliquity of Qatar-2 b to be λ = 4.• 3 ± 4.• 5, strongly indicating an alignment of the stellar spin with the orbit of the planet. We calculate the rotation period and velocity of the cool host star to be 11.5 ± 0.2 d and 3.28 ± 0.04 km s −1 at a colatitude of 74 • . We assemble the planet's transmission spectrum over the 386-976 nm wavelength range and search for variations of the measured radius of Qatar-2 b as a function of wavelength. Our analysis highlights a possible H 2 /He Rayleigh scattering in the blue.

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“…To analyze and characterize the physical parameters of the spots in these stars, we applied the transit model proposed by Silva (2003). This model simulates the passage of a planet in front of its host star.…”

Section: Spot Modelmentioning

confidence: 99%

“…Stellar activity is also present in other stars, that show remarkable lightcurve variations due to starspots and other magnetic phenomena. Skumanich (1972) first suggested that the activity of the star was associated with its rotation rate, and consequently with its age. Therefore, young rapidly rotating stars show higher level of activity and can produce larger spots and energetic flares.…”

Section: Introductionmentioning

confidence: 99%

Using planetary transits to estimate magnetic cycles lengths in Kepler stars

Estrela

Válio

2016

Proc. IAU

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Abstract. Observations of various solar-type stars along decades revealed that they can have magnetic cycles, just like our Sun. An investigation of the relation between their cycle length and rotation period can shed light on the dynamo mechanisms operating in these stars. Previous works on this relation suggested that the stars could be separated into active and inactive branches, with the Sun falling between them. In this work, we determined short magnetic activity cycles for 6 active solar-type stars observed by the Kepler telescope. The method adopted here estimates the activity from the excess in the residuals of the transitlight curves. This excess is obtained by subtracting a spotless model transit from the light curve, and then integrating over all the residuals during the transit. The presence of long term periodicity is estimated from the analysis of a Lomb-Scargle periodogram of the complete time series. Finally, we investigate the rotation-cycle period relation for the stars analysed here and find that some active stars do not follow the behaviour proposed earlier, falling in the inactive branch. In addition, we also notice a considerable spread from other stars in the literature in the active/inactive branches.

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Method for Spot Detection on Solar-like Stars

Cited by 136 publications

References 14 publications

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

PyTranSpot: A tool for multiband light curve modeling of planetary transits and stellar spots

Erratum: Physical properties, star-spot activity, orbital obliquity and transmission spectrum of the Qatar-2 planetary system from multicolour photometry

Using planetary transits to estimate magnetic cycles lengths in Kepler stars

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