Using the Sun to estimate Earth-like planets detection capabilities. V. Parameterizing the impact of solar activity components on radial velocities

Stellar activity induced by active structures (eg, spots, faculae) is known to strongly impact the radial velocity time series. It then limits the detection of small planetary RV signals (eg, an Earth-mass planet in the habitable zone of a solar-like star). In previous papers, we studied the detectability of such planets around the Sun seen as an edge-on star. For that purpose, we computed the RV and photometric variations induced by solar magnetic activity, using all active structures observed over one entire cycle. Our goal is to perform similar studies on stars with different physical and geometrical properties. As a first step, we focus on Sun-like stars seen with various inclinations, and on estimating detection capabilities with forthcoming instruments. To do so, we first parameterize the solar active structures with the most realistic pattern so as to obtain results consistent with the observed ones. We simulate the growth, evolution and decay of solar spots, faculae and network, using parameters and empiric laws derived from solar observations and literature. We generate the corresponding structure lists over a full solar cycle. We then build the resulting spectra and deduce the RV and photometric variations for a `Sun' seen with various inclinations. The produced RV signal takes into account the photometric contribution of structures as well as the attenuation of the convective blueshift. The comparison between our simulated activity pattern and the observed one validates our model. We show that the inclination of the stellar rotation axis has a significant impact on the time series. RV long-term amplitudes as well as short-term jitters are significantly reduced when going from edge-on to pole-on configurations. Assuming spin-orbit alignment, the optimal configuration for planet detection is an inclined star (i~45{\deg}).Comment: Accepted to Astronomy and Astrophysics on May, 27th 2015. The manuscript includes 22 pages, 20 figure

Variability in stellar granulation and convective blueshift with spectral type and magnetic activity. II. From young to old main-sequence K-G-F stars

The inhibition of small-scale convection in the Sun dominates the long-term radial velocity (RV) variability: it therefore has a critical effect on light exoplanet detectability using RV techniques. We here extend our previous analysis of stellar convective blueshift and its dependence on magnetic activity to a larger sample of stars in order to extend the Teff range, to study the impact of other stellar properties, and finally to improve the comparison between observed RV jitter and expected RV variations. We estimate a differential velocity shift for Fe and Ti lines of different depths and derive an absolute convective blueshift using the Sun as a reference for a sample of 360 F7-K4 stars with different properties (age, Teff, metallicity). We confirm the strong variation in convective blueshift with Teff and its dependence on (as shown in the line list in Paper I) activity level. Although we do not observe a significant effect of age or cyclic activity, stars with a higher metallicity tend to have a lower convective blueshift, with a larger effect than expected from numerical simulations. Finally, we estimate that for 71% of the stars in our sample the RV and LogR'HK variations are compatible with the effect of activity on convection, as observed in the solar case, while for the other stars, other sources (such as binarity or companions) must be invoked to explain the large RV variations. We also confirm a relationship between LogR'HK and metallicity, which may affect discussions of the possible relationship between metallicity and exoplanets, as RV surveys are biased toward low LogR'HK and possibly toward high-metallicity stars. We conclude that activity and metallicity strongly affect the small-scale convection levels in stars in the F7-K4 range, with a lower amplitude for the lower mass stars and a larger amplitude for low-metallicity stars.Comment: 12 pages, 9 figures ; accepted in Astronomy and Astrophysic

Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample

Massive, Main-Sequence AF-type stars have so far remained unexplored in past radial velocity surveys, due to their small number of spectral lines and their high rotational velocities that prevent the classic RV computation method. Our aim was to search for giant planets around AF MS stars, to get first statistical information on their occurrence rate and to compare the results with evolved stars and lower-mass MS stars. We used the HARPS spectrograph located on the 3.6m telescope at ESO La Silla Observatory to observe 108 AF MS stars with B-V in the -0.04 to 0.58 range and masses in the range 1.1-3.6 Msun. We used our SAFIR software specifically developed to compute the radial velocities of these early-type stars. We report the new detection of a mpsini = 4.51 Mjup companion with a ~826-day period to the F6V dwarf HD111998. We present new data on the 2-planet system around the F6IV-V dwarf HD60532. We also report the detection of 14 binaries with long-term RV trends. 70% of our targets show detection limits between 0.1 and 10 Mjup in the 1 to 10^3-day range. We derive brown dwarf (13 < mpsini < 80 Mjup) occurrence rates in the 1 to 10^3-day range of $2_{-2}^{+5}$% and $2.6_{-2.6}^{+6.7}$% for stars with masses in the ranges 1.1-1.5 and 1.5-3 Msun, respectively. As for Jupiter-mass companions (1 < mpsini < 13 Mjup), we get occurrence rates in the 1 to 10^3-day range of $4_{-0.9}^{+5.9}$% and $6.3_{-6.3}^{+15.9}$% respectively for the same stellar mass ranges. When considering the same Jupiter-mass companions but periods in the 1 to 100-day range only, we get occurrence rates of $2_{-2}^{+5.2}$% and $3.9_{-3.9}^{+9.9}$%. Given the present error bars, these results do not show a significant difference with companion frequencies derived for solar-like stars.Comment: 23 pages (text), 15 figures, accepted in Astronomy and Astrophysic

Insight into topological and functional relationships of cytochrome c oxidase subunit I of Saccharomyces cerevisiae by means of intragenic complementation

AbstractIn yeast, revertants were selected from four respiratory deficient mutants carrying mutations in the cytochrome c oxidase subunit I gene. Intragenic second site mutations revealed amino acids which are functionally complementary to the original mutated position and may be in topological interaction with it. The results provide additional data in favour of the model proposed for the structure of the binuclear centre in proton-motive oxidases

piRNAs and Aubergine cooperate with Wispy poly(A) polymerase to stabilize mRNAs in the germ plasm

Piwi-interacting RNAs (piRNAs) and PIWI proteins play a crucial role in germ cells by repressing transposable elements and regulating gene expression. In Drosophila, maternal piRNAs are loaded into the embryo mostly bound to the PIWI protein Aubergine (Aub). Aub targets maternal mRNAs through incomplete base-pairing with piRNAs and can induce their destabilization in the somatic part of the embryo. Paradoxically, these Aub-dependent unstable mRNAs encode germ cell determinants that are selectively stabilized in the germ plasm. Here we show that piRNAs and Aub actively protect germ cell mRNAs in the germ plasm. Aub directly interacts with the germline-specific poly(A) polymerase Wispy, thus leading to mRNA polyadenylation and stabilization in the germ plasm. These results reveal a role for piRNAs in mRNA stabilization and identify Aub as an interactor of Wispy for mRNA polyadenylation. They further highlight the role of Aub and piRNAs in embryonic patterning through two opposite functions

Activity time series of old stars from late F to early K VI. Exoplanet mass characterisation and detectability in radial velocity

Stellar variability impacts radial velocities at various timescales and therefore the detectability of exoplanets and the mass determination based on this technique. It is necessary to implement systematic studies, to delineate the current limitations of RV techniques to detect Earth-like planets. This paper aims are to investigate whether the targeted 10% mass uncertainty from RV follow-up of transits detected by PLATO can be reached, and to analyse and quantify Earth-like planet detectability for various spectral types. We implemented blind tests based on a large data set of realistic synthetic time series reproducing different phenomena leading to stellar variability such as complex magnetic activity patterns as well as flows, covering F6-K4 stars and a wide range of activity levels. The 10% mass uncertainty for a 1 MEarth in the habitable zone of a G2 star cannot be reached, even with an improved version of a usual correction of stellar activity and even for long-duration (ten years) well-sampled observations. This level can be reached for masses above 3 MEarth or for K4 stars alone. We quantify the maximum dispersion of the RV residuals needed to reach this 10% level, assuming the correction method and models do not affect the planetary signal. Several other methods were tested and do not allow a significantly improvement of this limited performance. Similarly, such low-mass planets in the habitable zone cannot be detected with a similar correction: blind tests lead to very low detection rates for 1 MEarth and a very high level of false positives. Very significant and new improvements with respect to methods based on activity indicators to correct for stellar activity must be devised at all timescales to reach the objective of 10% uncertainty on the mass or to detect such planets in RV. Methods based on the correlation with activity indicators are unlikely to be sufficient.Comment: Paper accepted in Astronomy and Astrophysic

Beyond seek and destroy: How to generate allelic series using genome editing tools

Genome editing tools have greatly facilitated the functional analysis of genes of interest by targeted mutagenesis. Many usable genome editing tools, including different site-specific nucleases and editor databases that allow single-nucleotide polymorphisms (SNPs) to be introduced at a given site, are now available. These tools can be used to generate high allelic diversity at a given locus to facilitate gene function studies, including examining the role of a specific protein domain or a single amino acid. We compared the effects, efficiencies and mutation types generated by our LbCPF1, SpCAS9 and base editor (BECAS9) constructs for the OsCAO1 gene. SpCAS9 and LbCPF1 have similar efficiencies in generating mutations but differ in the types of mutations induced, with the majority of changes being single-nucleotide insertions and short deletions for SpCAS9 and LbCPF1, respectively. The proportions of heterozygotes also differed, representing a majority in our LbCPF1, while with SpCAS9, we obtained a large number of biallelic mutants. Finally, we demonstrated that it is possible to specifically introduce stop codons using the BECAS9 with an acceptable efficiency of approximately 20%. Based on these results, a rational choice among these three alternatives may be made depending on the type of mutation that one wishes to introduce, the three systems being complementary. SpCAS9 remains the best choice to generate KO mutations in primary transformants, while if the desired gene mutation interferes with regeneration or viability, the use of our LbCPF1 construction will be preferred, because it produces mainly heterozygotes. LbCPF1 has been described in other studies as being as effective as SpCAS9 in generating homozygous and biallelic mutations. It will remain to be clarified in the future, whether the different LbCFP1 constructions have different efficiencies and determine the origin of these differences. Finally, if one wishes to specifically introduce stop codons, BECAS9 is a viable and efficient alternative, although it has a lower efficiency than SpCAS9 and LbCPF1 for creating KO mutations

Environmental risk mapping of canine leishmaniasis in France

<p>Abstract</p> <p>Background</p> <p>Canine leishmaniasis (CanL) is a zoonotic disease caused by <it>Leishmania infantum</it>, a Trypanosomatid protozoan transmitted by phlebotomine sandflies. Leishmaniasis is endemic in southern France, but the influences of environmental and climatic factors on its maintenance and emergence remain poorly understood. From a retrospective database, including all the studies reporting prevalence or incidence of CanL in France between 1965 and 2007, we performed a spatial analysis in order to i) map the reported cases in France, and ii) produce an environment-based map of the areas at risk for CanL. We performed a Principal Component Analysis (PCA) followed by a Hierarchical Ascendant Classification (HAC) to assess if the locations of CanL could be grouped according to environmental variables related to climate, forest cover, and human and dog densities. For each group, the potential distribution of CanL in France was mapped using a species niche modelling approach (Maxent model).</p> <p>Results</p> <p>Results revealed the existence of two spatial groups of CanL cases. The first group is located in the Cévennes region (southern Massif Central), at altitudes of 200-1000 m above sea level, characterized by relatively low winter temperatures (1.9°C average), 1042 mm average annual rainfall and much forest cover. The second group is located on the Mediterranean coastal plain, characterized by higher temperatures, lower rainfall and less forest cover. These two groups may correspond to the environments favoured by the two sandfly vectors in France, <it>Phlebotomus ariasi </it>and <it>Phlebotomus perniciosus </it>respectively. Our niche modelling of these two eco-epidemiological patterns was based on environmental variables and led to the first risk map for CanL in France.</p> <p>Conclusion</p> <p>Results show how an ecological approach can help to improve our understanding of the spatial distribution of CanL in France.</p

Le "De bello ciuili" de Lucain, une parole en mutation (de la rhétorique républicaine à une poétique de la guerre civile)

Les deux premiers chants de Lucain témoignent d une utilisation novatrice des discours directs dans l épopée. Présentés sous forme de triades de paroles juxtaposées le dialogue n est plus possible dans le monde du De bello ciuili- dont l objectif et le genre sont similaires, ils incitent le lecteur-auditeur de l Antiquité, rompu aux joutes oratoires des concours de déclamation, à les comparer. L examen de deux de ces groupes de discours sert de préliminaire à une enquête plus large sur la parole rhétorique, puis sur la parole poétique.Dans la confrontation des discours de la première triade (Curion / César /Laelius, au chant I) se lit la condamnation de l éloquence traditionnelle fondée sur des valeurs éthiques universellement partagées. Elle est supplantée par une rhétorique sophistique qui redéfinit, exclusivement en fonction des intérêts personnels de l orateur, tout ce qui a trait au droit, au juste ou à la citoyenneté, notions problématiques dans le contexte de perversion morale du bellum ciuile. L efficacité de cette nouvelle éloquence est signalée par le succès des trois suasoires qui sont à l origine des grands tournants narratifs de l œuvre : Curion décide César à entrer définitivement dans l affrontement civil (Chant I), Cicéron pousse Pompée à donner le signal du début du combat à Pharsale (Chant VII) et Pothin persuade Ptolémée d assassiner Magnus (Chant VIII).Dans la comparaison des trois paroles prophétiques de la fin du livre I auxquelles répondent les trois discours du début du chant suivant, effusions angoissées de Romains anonymes (les femmes, les hommes et le vieillard), se dessine un art poétique destiné à justifier les choix génériques du poète pour traiter son sujet. Conformant son œuvre à la médiocrité humaine des masses, il doit renoncer au genre tragique (discours des femmes) ainsi qu à la célébration épique des héros (discours des hommes) et s efforcer de proposer, à l instar du vieillard qui se remémore le passé pour anticiper le futur (le plus long discours de l épopée, rappelant, par sa place et son sujet, l ilioupersis d Enée), une épopée historique qui cherche à percer l opacité du monde de la guerre civile, dans lequel les dieux ne sont plus anthropomorphes. Empruntant leur esthétique du déchiffrement du réel aux Piérides ovidiennes, ces poétesses humaines, rivales des divines Muses (Métamorphoses V), Lucain refonde alors la persona de son uates. Chantre d un genre nouveau, pour une épopée renouvelée, le piéridique uates du De bello ciuili qui ne peut plus être omniscient puisque les pensées et les actions des superi lui sont inconnaissables- refuse le patronage des divinités traditionnelles de la poésie, promet à son héros César, non la gloire mais l exécration éternelle et proclame avec défi, qu il ne devra lui-même l éternité qu à la seule puissance de son talent personnel, divines Muses et grands guerriers héroïques des œuvres du passé ayant été congédiés par la guerre civile.The first two books of Lucan reveal an innovative use of direct speech in epic. Presented as contiguous speech triads dialogs being impossible in the realm of De bello ciuili whose purpose and genre are similar, they lead the ancient reader-listener, used to oral debates typical of declamation contests, to compare them. The investigation of two of these speech groups is our first step to a larger inquiry on rhetoric speech, then on poetic speech.Confronting the speech of the first triad (Curion/Caesar/Laelius in book I) reveals the end of traditional eloquence based on universal ethic values. It is superseded by a sophistic rhetoric that redefines (exclusively according to the speaker's private interests) whatever relates to law, justice or citizenship problematic concepts in the perverse moral context of bellum ciuile. The efficiency of this new eloquence is highlighted by the success of the three suasory performances which cause the work's main narrative turns: Curion convinces Caesar to definitely take part to the civil war (book I), Cicero leads Pompeus to launch the battle at Pharsalia (book VII) and Pothinus persuades Ptolemy to murder Magnus (book VIII).Comparing the three prophetic speeches at the end of book I (which mirror the three speeches at the beginning of the following book), anxious complains of anonimous Romans (the women, the men and the elderly), we identify an art of poetry aimed at motivating the generic choices made by the poet to handle his subject. Working along the lines of the human depravity of masses, he may not employ neither the tragic style (the speech of women) nor the epic celebration of heroes (the speech of men), but must suggest as the old man remembers the past to anticipate the future (the longest speech of the epic reminds Eneas Ilioupersis by means of its place and subject) an historical epic aiming at enlightening the opaque world of civil war, in which the gods are no longer anthropomorphic. Borrowing their deciphering aesthetic to Ovids Pierides, human female poets rivaling the godly Muses (Metamorphosis V), Lucan reinvents the persona of his uates. Promoting a new genre, for a renewed epic, the 'pieridic' uates of De Bello Ciuili, which can no longer be omniscient since the superi's thoughts and deeds are out of his reach refuses to worship the traditional poetry deities, swears to his 'hero' Caesar not the glory but the eternal hatred and defiantly proclaims that he himself will deserve eternity only through his own talent, the godly Muses and great heroic warriors of ancient works having been dismissed by civil war.PARIS-EST-Université (770839901) / SudocPARIS12-Bib. électronique (940280011) / SudocSudocFranceF