Exoplanet HD 209458b : Evaporation strengthened

Following re-analysis of Hubble Space Telescope observations of primary transits of the extrasolar planet HD209458b at Lyman-alpha, Ben-Jaffel (2007, BJ007) claims that no sign of evaporation is observed. Here we show that, in fact, this new analysis is consistent with the one of Vidal-Madjar et al. (2003, VM003) and supports the detection of evaporation. The apparent disagreement is mainly due to the disparate wavelength ranges that are used to derive the transit absorption depth. VM003 derives a (15+/-4)% absorption depth during transit over the core of the stellar Lyman-alpha line (from -130 km/s to +100 km/s), and this result agrees with the (8.9+/-2.1)% absorption depth reported by BJ007 from a slightly expanded dataset but over a larger wavelength range (+/-200 km/s). These measurements agree also with the (5+/-2)% absorption reported by Vidal-Madjar et al. (2004) over the whole Lyman-alpha line from independent, lower-resolution data. We show that stellar Lyman-alpha variability is unlikely to significantly affect those detections. The HI atoms must necessarily have velocities above the escape velocities and/or be outside the Roche lobe, given the lobe shape and orientation. Absorption by HI in HD209458b's atmosphere has thus been detected with different datasets, and now with independent analyses. All these results strengthen the concept of evaporating hot-Jupiters, as well as the modelization of this phenomenon.Comment: To be published in ApJ

The impact of atmospheric circulation on the chemistry of the hot Jupiter HD 209458b

This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.We investigate the effects of atmospheric circulation on the chemistry of the hot Jupiter HD 209458b. We use a simplified dynamical model and a robust chemical network, as opposed to previous studies which have used a three dimensional circulation model coupled to a simple chemical kinetics scheme. The temperature structure and distribution of the main atmospheric constituents are calculated in the limit of an atmosphere that rotates as a solid body with an equatorial rotation rate of 1 km/s. Such motion mimics a uniform zonal wind which resembles the equatorial superrotation structure found by three dimensional circulation models. The uneven heating of this tidally locked planet causes, even in the presence of such a strong zonal wind, large temperature contrasts between the dayside and nightside, of up to 800 K. This would result in important longitudinal variations of some molecular abundances if the atmosphere were at chemical equilibrium. The zonal wind, however, acts as a powerful disequilibrium process. We identify the existence of a pressure level of transition between two regimes, which may be located between 100 and 0.1 mbar depending on the molecule. Below this transition layer, chemical equilibrium holds, while above it, the zonal wind tends to homogenize the chemical composition of the atmosphere, bringing molecular abundances in the limb and nightside regions close to chemical equilibrium values characteristic of the dayside, i.e. producing an horizontal quenching effect in the abundances. Reasoning based on timescales arguments indicates that horizontal and vertical mixing are likely to compete in HD 209458b's atmosphere, producing a complex distribution where molecular abundances are quenched horizontally to dayside values and vertically to chemical equilibrium values characteristic of deep layers.M.A., O.V., F.S., and E.H. acknowledge support from the European Research Council (ERC Grant 209622: E3ARTHs). Computer time for this study was provided by the computing facilities MCIA (Mésocentre de Calcul Intensif Aquitain) of the Université de Bordeaux and of the Université de Pau et des Pays de l’Adour. We thank the anonymous referee for a constructive report that helped to improve this manuscript

The Deuterium, Oxygen, and Nitrogen Abundance Toward LSE 44

We present measurements of the column densities of interstellar DI, OI, NI, and H2 made with FUSE, and of HI made with IUE toward the sdO star LSE 44, at a distance of 554+/-66 pc. This target is among the seven most distant Galactic sight lines for which these abundance ratios have been measured. The column densities were estimated by profile fitting and curve of growth analyses. We find D/H = (2.24 +1.39 -1.32)E-5, D/O = (1.99 +1.30 -0.67)E-2, D/N = (2.75 +1.19 -0.89)E-1, and O/H = (1.13 +0.96 -0.71)E-3 (2 sigma). Of the most distant Galactic sight lines for which the deuterium abundance has been measured LSE 44 is one of the few with D/H higher than the Local Bubble value, but D/O toward all these targets is below the Local Bubble value and more uniform than the D/H distribution. (Abstract abridged.)Comment: 20 pages, including 9 figures. Accepted for publication in Ap

A Declarative Paradigm for Robust Cumulative Scheduling

International audienceThis paper investigates cumulative scheduling in uncertain environments, using constraint programming. We present a new declarative characterization of robustness, which preserves solution quality.We highlight the significance of our framework on a crane assignment problem with business constraints

Deuterium Toward WD1634-573: Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission

We use Far Ultraviolet Spectrocopic Explorer (FUSE) observations to study interstellar absorption along the line of sight to the white dwarf WD1634-573 (d=37.1+/-2.6 pc). Combining our measurement of D I with a measurement of H I from Extreme Ultraviolet Explorer data, we find a D/H ratio toward WD1634-573 of D/H=(1.6+/-0.5)e-5. In contrast, multiplying our measurements of D I/O I=0.035+/-0.006 and D I/N I=0.27+/-0.05 with published mean Galactic ISM gas phase O/H and N/H ratios yields D/H(O)=(1.2+/-0.2)e-5 and D/H(N)=(2.0+/-0.4)e-5, respectively. Note that all uncertainties quoted above are 2 sigma. The inconsistency between D/H(O) and D/H(N) suggests that either the O I/H I and/or the N I/H I ratio toward WD1634-573 must be different from the previously measured average ISM O/H and N/H values. The computation of D/H(N) from D I/N I is more suspect, since the relative N and H ionization states could conceivably vary within the LISM, while the O and H ionization states will be more tightly coupled by charge exchange.Comment: 23 pages, 5 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty; accepted by ApJ Supplemen

The D/H Ratio in the Interstellar Medium toward the White Dwarf PG0038+199

We determine the D/H ratio in the interstellar medium toward the DO white dwarf PG0038+199 using spectra from the Far Ultraviolet Spectroscopic Explorer (FUSE), with ground-based support from Keck HIRES. We employ curve of growth, apparent optical depth and profile fitting techniques to measure column densities and limits of many other species (H2, NaI, CI, CII, CIII, NI, NII, OI, SiII, PII, SIII, ArI and FeII) which allow us to determine related ratios such as D/O, D/N and the H2 fraction. Our efforts are concentrated on measuring gas-phase D/H, which is key to understanding Galactic chemical evolution and comparing it to predictions from Big Bang nucleosynthesis. We find column densities log N(HI) = 20.41+-0.08, log N(DI)=15.75+-0.08 and log N(H2) = 19.33+-0.04, yielding a molecular hydrogen fraction of 0.14+-0.02 (2 sigma errors), with an excitation temperature of 143+-5K. The high HI column density implies that PG0038+199 lies outside of the Local Bubble; we estimate its distance to be 297 (+164,-104)pc (1 sigma). D/[HI+2H2] toward PG0038+199 is 1.91(+0.52,-0.42) e-5 (2 sigma). There is no evidence of component structure on the scale of Delta v > 8 km/s based on NaI, but there is marginal evidence for structure on smaller scales. The D/H value is high compared to the majority of recent D/H measurements, but consistent with the values for two other measurements at similar distances. D/O is in agreement with other distant measurements. The scatter in D/H values beyond ~100pc remains a challenge for Galactic chemical evolution.Comment: 59 pages, 7 tables, 18 figures (1 standalone), accepted by ApJ v2 minor typos correcte

The Velocity Distribution of the Nearest Interstellar Gas

The bulk flow velocity for the cluster of interstellar cloudlets within about 30 pc of the Sun is determined from optical and ultraviolet absorption line data, after omitting from the sample stars with circumstellar disks or variable emission lines and the active variable HR 1099. Ninety-six velocity components towards the remaining 60 stars yield a streaming velocity through the local standard of rest of -17.0+/-4.6 km/s, with an upstream direction of l=2.3 deg, b=-5.2 deg (using Hipparcos values for the solar apex motion). The velocity dispersion of the interstellar matter (ISM) within 30 pc is consistent with that of nearby diffuse clouds, but present statistics are inadequate to distinguish between a Gaussian or exponential distribution about the bulk flow velocity. The upstream direction of the bulk flow vector suggests an origin associated with the Loop I supernova remnant. Groupings of component velocities by region are seen, indicating regional departures from the bulk flow velocity or possibly separate clouds. The absorption components from the cloudlet feeding ISM into the solar system form one of the regional features. The nominal gradient between the velocities of upstream and downstream gas may be an artifact of the Sun's location near the edge of the local cloud complex. The Sun may emerge from the surrounding gas-patch within several thousand years.Comment: Typographical errors corrected; Five tables, seven figures; Astrophysical Journal, in pres

Variations in the D/H ratio of extended sightlines from FUSE observations

We use new FUSE data to determine the column densities of interstellar DI, NI, OI, FeII, and H2 along the HD41161 and HD53975 sightlines. Together with N(HI) from the literature (derived from Copernicus and IUE data) we derive D/H, N/H, and O/H ratios. These high column density sightlines have both log H(HI)>21.00 and allow us to probe gas up to 1300 pc. In particular these sightlines allow us to determine the gas phase D/H ratio in a hydrogen column density range, log N(H)>20.70, where the only five measurements available in the literature yield a weighted average of D/H = (0.86 +/- 0.08)E-5. We find D/H=(2.14+ 0.51 - 0.43)E-5 along the HD41161 sightline. This ratio is 3sigma higher than the weighted mean D/H ratio quoted above, for sightlines with log N(H)>20.70, while the D/H ratio for the HD53975 line of sight, D/H = (1.02 +0.23 -0.20)E-5, agrees within the 1sigma uncertainties. Our D/H measurement along the HD 41161 sightline presents the first evidence of variations of D/H at high N(H). Our result seems to indicate that either the long sightlines that according to the deuterium depletion model are dominated by cold undisturbed gas where deuterium would be depleted onto carbonaceous grains occur at higher N(H) than previously thought or that the clumping of low D/H values in the literature for the long sightlines has another explanation. In addition, the relatively high signal-to-noise ratio of the HD41161 data allows us to place constraints on the f-values of some neutral chlorine transitions, present in the FUSE bandpass, for which only theoretical values are available.Comment: Accepted for publication on the Dec 10 2006 issue of the Ap