SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages

This paper presents SOAP 2.0, a new version of the SOAP code that estimates in a simple way the photometric and radial velocity variations induced by active regions. The inhibition of the convective blueshift 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 convective blueshift 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 full width at half maximum (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 \vsini$\le8$\kms. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD189733, 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 $\alpha$ 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.Comment: 28 pages, 15 figures, accepted for publication in ApJ after minor revisions (taken into account in this version

A rotating cylinder in an asymptotically locally anti-de Sitter background

A family of exact solutions is presented which represents a rigidly rotating cylinder of dust in a background with a negative cosmological constant. The interior of the infinite cylinder is described by the Godel solution. An exact solution for the exterior solution is found which depends both on the rotation of the interior and on its radius. For values of these parameters less than a certain limit, the exterior solution is shown to be locally isomorphic to the Linet-Tian solution. For values larger than another limit, it is shown that the exterior solution extends into a region which contains closed timelike curves. At large distances from the source, the space-time is shown to be asymptotic locally to anti-de Sitter space.Comment: To appear in Classical and Quantum Gravit

SOAP-T: A tool to study the light-curve and radial velocity of a system with a transiting planet and a rotating spotted star

We present an improved version of SOAP (Boisse et al. 2012) named "SOAP-T", which can generate the radial velocity variations and light-curves for systems consisting of a rotating spotted star with a transiting planet. This tool can be used to study the anomalies inside transit light-curves and the Rossiter-McLaughlin effect, to better constrain the orbital configuration and properties of planetary systems and active zones of their host stars. Tests of the code are presented to illustrate its performance and to validate its capability when compared with analytical models and real data. Finally, we apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space telescope and use this system to discuss the capability of this tool in analyzing light-curves for the cases where the transiting planet overlaps with the star's spots.Comment: 9 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

Improvements on analytic modelling of stellar spots

In this work we present the solution of the stellar spot problem using the Kelvin-Stokes theorem. Our result is applicable for any given location and dimension of the spots on the stellar surface. We present explicitely the result up to the second degree in the limb darkening law. This technique can be used to calculate very efficiently mutual photometric effects produced by eclipsing bodies occulting stellar spots and to construct complex spot shapes.Comment: Resubmitted to MNRAS after accounting for minor comments of second review, 9 pages, 5 figures, software available at http://eduscisoft.com/KSINT

On the long-term correlation between the flux in the Ca II H & K and Halpha lines for FGK stars

The re-emission in the cores of the Ca II H & K and H$\alpha$ lines, are well known proxies of stellar activity. However, these activity indices probe different activity phenomena, the first being more sensitive to plage variation, while the other one being more sensitive to filaments. In this paper we study the long-term correlation between $\log R'_{HK}$ and $\log I_{H\alpha}$, two indices based on the Ca II H & K and H$\alpha$ lines respectively, for a sample of 271 FGK stars using measurements obtained over a $\sim$9 year time span. Because stellar activity is one of the main obstacles to the detection of low-mass and long-period planets, understanding further this activity index correlation can give us some hints about the optimal target to focus on, and ways to correct for these activity effects. We found a great variety of long-term correlations between $\log R'_{HK}$ and $\log I_{H\alpha}$. Around 20% of our sample has strong positive correlation between the indices while about 3% show strong negative correlation. These fractions are compatible with those found for the case of early-M dwarfs. Stars exhibiting a positive correlation have a tendency to be more active when compared to the median of the sample, while stars showing a negative correlation are more present among higher metallicity stars. There is also a tendency for the positively correlated stars to be more present among the coolest stars, a result which is probably due to the activity level effect on the correlation. Activity level and metallicity seem therefore to be playing a role on the correlation between $\log R'_{HK}$ and $\log I_{H\alpha}$. Possible explanations based on the influence of filaments for the diversity in the correlations between these indices are discussed in this paper.Comment: 18 pages, 13 figures, 4 tables, accepted for publication in Astronomy and Astrophysic

In vitro germination of zygotic embryos excised from cryopreserved endocarps of queen palm (Syagrus romanzoffiana (Cham.) Glassman).

Made available in DSpace on 2018-08-07T00:50:50Z (GMT). No. of bitstreams: 1 SantosSalomao2017ArticleInVitroGerminationOfZygoticEmb.pdf: 1026285 bytes, checksum: dfa02987e6b6d20d4777ced8145c7268 (MD5) Previous issue date: 2017-10-31bitstream/item/180975/1/Santos-Salomao2017-Article-InVitroGerminationOfZygoticEmb.pd

Light elements in stars with exoplanets

It is well known that stars orbited by giant planets have higher abundances of heavy elements when compared with average field dwarfs. A number of studies have also addressed the possibility that light element abundances are different in these stars. In this paper we will review the present status of these studies. The most significant trends will be discussed.Comment: 10 pages, 6 figures. Submitted to the proceedings of IAU symposium 268: Light elements in the universe

Chemical abundances of stars with brown-dwarf companions

It is well-known that stars with giant planets are on average more metal-rich than stars without giant planets, whereas stars with detected low-mass planets do not need to be metal-rich. With the aim of studying the weak boundary that separates giant planets and brown dwarfs (BDs) and their formation mechanism, we analyze the spectra of a sample of stars with already confirmed BD companions both by radial velocity and astrometry. We employ standard and automatic tools to perform an EW-based analysis and to derive chemical abundances from CORALIE spectra of stars with BD companions. We compare these abundances with those of stars without detected planets and with low-mass and giant-mass planets. We find that stars with BDs do not have metallicities and chemical abundances similar to those of giant-planet hosts but they resemble the composition of stars with low-mass planets. The distribution of mean abundances of $\alpha$-elements and iron peak elements of stars with BDs exhibit a peak at about solar abundance whereas for stars with low-mass and high-mass planets the [X$_\alpha$/H] and [X$_{\rm Fe}$/H] peak abundances remain at $\sim -0.1$~dex and $\sim +0.15$~dex, respectively. We display these element abundances for stars with low-mass and high-mass planets, and BDs versus the minimum mass, $m_C \sin i$, of the most-massive substellar companion in each system, and we find a maximum in $\alpha$-element as well as Fe-peak abundances at $m_C \sin i \sim 1.35\pm 0.20$ jupiter masses. We discuss the implication of these results in the context of the formation scenario of BDs in comparison with that of giant planets.Comment: Accepted for publication in Astronomy & Astrophysic