The Gj1214 Super-Earth System: Stellar Variability, New Transits, and a Search for Additional Planets

Berta, Zachory K.; Charbonneau, David; Bean, Jacob L.; Irwin, Jonathan; Burke, Christopher J.; Désert, Jean-Michel; Nutzman, P.; Falco, E.

doi:10.1088/0004-637x/736/1/12

Cited by 164 publications

(189 citation statements)

References 94 publications

(157 reference statements)

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“…Considering the error bars, the planet-to star radius ratio measurements through optical and near-infrared observations (Sada et al 2010;Berta et al 2011;Carter et al 2011) are all consistent with the results of Charbonneau et al 2009Charbonneau et al (0.1162) obtained in the optical bands. Furthermore, Berta et al (2011) detected variations in the planet-to-star radius ratio at different epochs and assessed the expected variation in this ratio due to stellar variability at optical wavelengths (see their Fig. 8).…”

Section: Introductionsupporting

confidence: 89%

“…Similar approaches may be found in Désert et al (2011a), Berta et al (2011), andCarter et al (2011). In the computation of the stellar flux, we assume that the stellar and the spot intensities vary according to the same quadratic limb-darkening law, namely…”

Section: Modelling Stellar Activitymentioning

confidence: 98%

“…11, Seager & Mallén-Ornelas 2003;Richardson et al 2006) that can improve the determination of the transit parameters. Thus, even if we consider limb darkening in the derivation of the transit profiles, taking into account that it decreases towards longer wavelengths (see Table 1 in electronic form, Claret et al 1995), its impact will not be so crucial, since our study is focused primarily on infrared passbands (see Deming et al 2007;Carter et al 2008;Berta et al 2011).…”

Section: Modelling Stellar Activitymentioning

confidence: 99%

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Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits

Ballerini

Micela

Lanza

et al. 2012

A&A

102

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Stellar magnetic activity is a source of noise in the study of the transits of extrasolar planets. It induces flux variations that significantly affect the transit depth determination and the derivations of planetary and stellar parameters. Furthermore, the colour dependence of stellar activity may significantly influence the characterization of planetary atmospheres. Here we present a systematic approach to quantify the corresponding stellar flux variations as a function of wavelength bands. We consider a star with spots covering a given fraction of its disc and model the variability in both the UBVRIJHK photometric system and the Spitzer/IRAC wavebands for dwarf stars from G to M spectral types. We compare activity-induced flux variations in different passbands with planetary transits and quantify how they affect the determination of the planetary radius and the analysis of the transmission spectroscopy in the study of planetary atmospheres. We suggest that the monitoring of the systems by using broad-band photometry, from visible to infrared, helps us to constrain activity effects. The ratio of the relative variations in the stellar fluxes at short wavelength optical bands (e.g., U or B) to near-infrared ones (e.g., J or K) can be used to distinguish starspot brightness dips from planetary transits in a stellar light curve. In addition to the perturbations in the measurement of the planetary radius, we find that starspots can affect the determinations of both the relative semimajor axis and the inclination of the planetary orbit, which have a significant impact on the derivation of the stellar density from the transit light curves.

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Section: Introductionsupporting

confidence: 89%

Section: Modelling Stellar Activitymentioning

confidence: 98%

Section: Modelling Stellar Activitymentioning

confidence: 99%

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Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits

Ballerini

Micela

Lanza

et al. 2012

A&A

102

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“…There is a priori no reason to assume that the only spots present on the stellar surface are those responsible for the variability. This would result in flat regions in the light curve when no spots are visible on the stellar hemisphere pointed toward Earth, which is not seen in the light curve by Berta et al (2011).…”

Section: The Impact Of Unocculted Starspotsmentioning

confidence: 98%

“…We linked the stellar brightness during the night of the GROND observations to that during the INT r-band observations using the data from Berta et al (2011). Subsequently, this was linked to our INT I-band observations using the offset found above.…”

Section: Correcting For the Stellar Variabilitymentioning

confidence: 99%

Optical to near-infrared transit observations of super-Earth GJ 1214b: water-world or mini-Neptune?

Mooij

Brogi

Kok

et al. 2012

A&A

103

127

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Context. GJ 1214b, the 6.55 Earth-mass transiting planet recently discovered by the MEarth team, has a mean density of ∼35% of that of the Earth. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Aims. In the case of a hydrogen-rich atmosphere, molecular absorption and scattering processes may result in detectable radius variations as a function of wavelength. The aim of this paper is to measure these variations. Methods. We have obtained observations of the transit of GJ 1214b in the r-and I-band with the Isaac Newton Telescope (INT), in the g-, r-, i-and z-bands with the 2.2 m MPI/ESO telescope, in the K s -band with the Nordic Optical Telescope (NOT), and in the K c -band with the William Herschel Telescope (WHT). By comparing the transit depth between the the different bands, which is a measure for the planet-to-star size ratio, the atmosphere is investigated. Results. We do not detect clearly significant variations in the planet-to-star size ratio as function of wavelength. Although the ratio at the shortest measured wavelength, in g-band, is 2σ larger than in the other bands. The uncertainties in the K s and K c bands are large, due to systematic features in the light curves. Conclusions. The tentative increase in the planet-to-star size ratio at the shortest wavelength could be a sign of an increase in the effective planet-size due to Rayleigh scattering, which would require GJ 1214b to have a hydrogen-rich atmosphere. If true, then the atmosphere has to have both clouds, to suppress planet-size variations at red optical wavelengths, as well as a sub-solar metallicity, to suppress strong molecular features in the near-and mid-infrared. However, star spots, which are known to be present on the hoststar's surface, can (partly) cancel out the expected variations in planet-to-star size ratio, because the lower surface temperature of the spots causes the effective size of the star to vary with wavelength. A hypothetical spot-fraction of ∼10%, corresponding to an average stellar dimming of ∼5% in the i-band, would be able to raise the near-and mid-infrared points sufficiently with respect to the optical measurements to be inconsistent with a water-dominated atmosphere. Modulation of the spot fraction due to the stellar rotation would in such case cause the observed flux variations of GJ 1214.

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SPECULOOS Exoplanet Search and Its Prototype on TRAPPIST

Burdanov¹,

Delrez²,

Gillon³

et al. 2018

Handbook of Exoplanets

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The Gj1214 Super-Earth System: Stellar Variability, New Transits, and a Search for Additional Planets

Cited by 164 publications

References 94 publications

Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits

Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits

Optical to near-infrared transit observations of super-Earth GJ 1214b: water-world or mini-Neptune?

SPECULOOS Exoplanet Search and Its Prototype on TRAPPIST

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