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We investigate the e ect of di erent star formation histories (SFHs) on the relation between stellar mass (M8 ) and star formation rate (SFR) using a sample of galaxies with reliable spectroscopic redshift zspec > 2 drawn from the VIMOS Ultra-Deep Survey (VUDS). We produce an extensive database of dusty model galaxies, calculated starting from a new library of single stellar population (SSPs) models, weighted by a set of 28 di erent star formation histories based on the Schmidt function, and characterized by di erent ratios of the gas infall timescale τinfall to the star formation effciency ν. Dust extinction and re-emission were treated by means of the radiative transfer calculation. The spectral energy distribution (SED) fitting technique was performed by using GOSSIP+, a tool able to combine both photometric and spectroscopic information to extract the best value of the physical quantities of interest, and to consider the intergalactic medium (IGM) attenuation as a free parameter. We find that the main contribution to the scatter observed in the SFR-M8 plane is the possibility of choosing between di erent families of SFHs in the SED fitting procedure, while the redshift range plays a minor role. The majority of the galaxies, at all cosmic times, are best fit by models with SFHs characterized by a high τinfall/ν ratio. We discuss the reliability of a low percentage of dusty and highly star-forming galaxies in the context of their detection in the far infrared (FIR). [ABSTRACT FROM AUTHOR]

Context. The scattering of light by an asteroid's surface depends on the properties of its particles, volume density, and roughness. It is described by the reflection coefficient which, upon integration over the illuminated and observed part of the surface, yields the disk-integrated photometric brightness of the asteroid. The Lommel-Seeliger reflection coefficient is applicable to dark, low-albedo C-class asteroids, with prospects for moderate-albedo S-class and M-class asteroids. Aims. We calculate the disk-integrated brightness for an ellipsoidal asteroid with a Lommel-Seeliger reflection coefficient (LS ellipsoid). Furthermore, we calculate the photocenter for the LS ellipsoid, that is, the distance of the center of light from the barycenter. Methods. Because of their analytical nature, the closed-form expressions can be readily utilized in numerical simulations. Results. We show lightcurves and photocenter variations for realistic examples of ellipsoidal shapes for a number of pole orientations. The results highlight the reciprocity principle of the radiative-transfer theory and suggest a nontrivial dependence of the photocenter on the pole orientation and viewing geometry. Conclusions. Finally, we outline a number of applications and future prospects. [ABSTRACT FROM AUTHOR]

Context. A member of the Local Group, IC 1613 is a gas rich irregular dwarf galaxy that appears to have formed stars continuously over the last 10 Gyr and is relatively independent of external influences from other galaxies. Aims. This paper aims to study the spatial distribution of the asymptotic giant branch (AGB) population in IC 1613 and its metallicity. Methods. Using WFCAM on UKIRT, high quality JHK photometry of an area of 0.8 deg² centered on IC 1613 was obtained. The data have been used to isolate the C- and M-type components of the AGB population and using their number ratio, C/M, a global mean metallicity has been derived. The metallicity and the tip of the red giant branch magnitude (TRGB) have been studied as a function of distance from the galactic centre and as a function of azimuthal angle. Results. The TRGB has been found to be at K0 = 18.25 ± 0.15 mag. The colour separation between the C- and M-type components of the AGB population has been located at (J - K)0 = 1.15 ± 0.05 mag, giving a global C/M ratio of 0.52 ± 0.04 and from this an iron abundance of [Fe/H] = -1.26 ± 0.07 dex has been calculated. Conclusions. The AGB population has been detected out to a radial distance of 4.5 kpc in the de-projected plane of the galaxy. The measured TRGB is consistent with previous measurements and no significant variation is detected in the TRGB or in metallicity either with galactocentric distance or azimuthal angle. [ABSTRACT FROM AUTHOR]

Aims. We present the results of the combined photometric and spectroscopic analysis of a bright (V = 9.14), close (d = 31 pc), late-type detached eclipsing binary, AK Fornacis. This P = 3.981 d system has not been previously recognised as a double-lined spectroscopic binary, and this is the first full physical model of this unique target. Methods. With the FEROS, CORALIE, and HARPS spectrographs, we collected a number of high-resolution spectra to calculate radial velocities of both components of the binary. Measurements were done with our own disentangling procedure and the TODCOR technique, and were later combined with the photometry from the ASAS and SuperWASP archives.We also performed an atmospheric analysis of the component spectra with the Spectroscopy Made Easy package. Results. Our analysis shows that AK For consists of two active, cool dwarfs having masses of M1 = 0.6958 ± 0.0010 and M2 = 0.6355 ± 0.0007 M⊙ and radii of R1 = 0.687 ± 0.020 and R2 = 0.609 ± 0.016 R⊙, respectively, which are slightly less metal-abundant than the Sun. Parameters of both components are well reproduced by the models. Conclusions. AK For is the brightest system among the known eclipsing binaries with K- or M-type stars. Its orbital period is one of the longest, and its rotational velocities is one of the lowest, which allows us to obtain very precise radial velocity measurements. The precision in physical parameters that we obtained places AK For among the binaries with the best mass measurements in the literature. It also fills the gap in our knowledge of stars in the range of 0.5-0.8 M⊙ and between short and long-period systems. All this makes AK For a unique benchmark for understanding the properties of low-mass stars. [ABSTRACT FROM AUTHOR]

Context. In some recent works, the C/O abundance ratio in high-metallicity stars with planets is found to vary by more than a factor of two, i.e. from ~0.4 to C/O ≳ 1. This has led to discussions about the existence of terrestrial planets with a carbon-dominated composition that is very different from the composition of the Earth. Aims. The mentioned C/O values were obtained by determining carbon abundances from high-excitation C i lines and oxygen abundances from the forbidden [Oi] line at 6300 Å. This weak line is, however, strongly affected by a nickel blend at high metallicities. Aiming for more precise C/O ratios, oxygen abundances in this paper are derived from the high-excitation Oi triplet at 7774 Å. Methods. The C i lines at 5052 and 5380 Å in HARPS spectra were applied to determine carbon abundances of 33 solar-type stars for which FEROS spectra are available for determining oxygen abundances from the Oi λ7774 triplet. Differential abundances with respect to the Sun were derived from equivalent widths using MARCS model atmospheres. Non-LTE corrections were included, and the analysis was carried out with both spectroscopic and photometric estimates of stellar effective temperatures and surface gravities. Results. The results do not confirm the high C/O ratios previously found. C/O shows a tight, slightly increasing dependence on metallicity, i.e. from C/O ≳ 0.58 at [Fe/H] = 0.0 to C/O ≳ 0.70 at [Fe/H] = 0.4 with an rms scatter of only 0.06. Conclusions. Recent findings of C/O ratios higher than 0.8 in high-metallicity stars seem to be spurious due to statistical errors in estimating the strength of the weak [Oi] line in the Ni i blended λ6300 feature. Assuming that the composition of a proto-planetary disk is the same as that of the host star, the C/O values found in this paper lend no support to the existence of carbon-rich planets. The small scatter of C/O among thin-disk stars suggests that the nucleosynthesis products of Type II supernovae and low- to intermediate-mass stars are well mixed in the interstellar medium. [ABSTRACT FROM AUTHOR]

Context. The sample of hot Jupiters that have been studied in great detail is still growing. In particular, when the planet transits its host star, it is possible to measure the planetary radius and the planet mass (with radial velocity data). For the study of planetary atmospheres, it is essential to obtain transit and occultation measurements at multiple wavelengths. Aims. We aim to characterize the transiting hot Jupiter WASP-19b by deriving accurate and precise planetary parameters from a dedicated observing campaign of transits and occultations. Methods. We have obtained a total of 14 transit lightcurves in the r'-Gunn, I-Cousins, z'-Gunn, and I + z' filters and 1' occultation lightcurves in z'-Gunn using EulerCam on the Euler-Swiss telescope and TRAPPIST. We also obtained one lightcurve through the narrow-band NB119' filter of HAWK-I on the VLT measuring an occultation at 1.19 ±m. We performed a global MCMC analysis of all new data, together with some archive data in order to refine the planetary parameters and to measure the occultation depths in z'-band and at 1.19 ±m. Results. We measure a planetary radius of Rp = 1:376 ± 0.46 RJ, a planetary mass of Mp = 1:165 ± 0.068 MJ, and find a very low eccentricity of e = :0.0077+0.0068 -0.0032, compatible with a circular orbit. We have detected the z'-band occultation at 3σ significance and measure it to be ±Foccz' = 352 ± 116 ppm, more than a factor of 2 smaller than previously published. The occultation at 1.19 ±m is only marginally constrained at ±Focc, NB119' = 1711+745726 ppm. Conclusions. We show that the detection of occultations in the visible range is within reach, even for 1 m class telescopes if a considerable number of individual events are observed. Our results suggest an oxygen-dominated atmosphere of WASP-19b, making the planet an interesting test case for oxygen-rich planets without temperature inversion. [ABSTRACT FROM AUTHOR]

Context. We present a combined photometric calibration of the Supernova Legacy Survey (SNLS) and the SDSS supernova survey, which results from a joint effort of the SDSS and the SNLS collaborations. Aims. Our primary motivation is to eventually sharpen cosmological constraints derived from type Ia supernova measurements by improving the accuracy of the photometric calibration. We deliver fluxes calibrated to the HST spectrophotometric star network for large sets of tertiary stars that cover the science fields of both surveys in all photometric bands. We also cross-calibrate directly the two surveys and demonstrate their consistency. Methods. For each survey the flat-fielding is revised based on the analysis of dithered star observations. The calibration transfer from the HST spectrophotometric standard stars to the multi-epoch tertiary standard star catalogs in the science fields follows three different paths: observations of primary standard stars with the SDSS PT telescope; observations of Landolt secondary standard stars with SNLS MegaCam instrument at CFHT; and direct observation of faint HST standard stars with MegaCam. In addition, the tertiary stars for the two surveys are cross-calibrated using dedicated MegaCam observations of stripe 82. This overlap enables the comparison of these three calibration paths and justifies using their combination to improve the calibration accuracy. Results. Flat-field corrections have improved the uniformity of each survey as demonstrated by the comparison of photometry in overlapping fields: the rms of the difference between the two surveys is 3 mmag in gri, 4 mmag in z and 8 mmag in u. We also find a remarkable agreement (better than 1%) between the SDSS and the SNLS calibration in griz. The cross-calibration and the introduction of direct calibration observations bring redundancy and strengthen the confidence in the resulting calibration. We conclude that the surveys are calibrated to the HST with a precision of about 0.4% in griz. This precision is comparable to the external uncertainty affecting the color of the HST primary standard stars. [ABSTRACT FROM AUTHOR]

Context. Monitoring of the photometric and chromospheric HK emission data series of stars similar to the Sun in age and average activity level showed that there is an empirical correlation between the average stellar chromospheric activity level and the photometric variability. In general, more active stars show larger photometric variability. Interestingly, the measurements and reconstructions of the solar irradiance show that the Sun is significantly less variable than indicated by the empirical relationship. Aims. We aim to identify possible reasons for the Sun to be currently outside of this relationship. Methods. We employed different scenarios of solar HK emission and irradiance variability and compared them with available time series of Sun-like stars. Results. We show that the position of the Sun on the diagram of photometric variability versus chromospheric activity changes with time. The present solar position is different from its temporal mean position as the satellite era of continuous solar irradiance measurements has accidentally coincided with a period of unusually high and stable solar activity. Our analysis suggests that although present solar variability is significantly smaller than indicated by the stellar data, the temporal mean solar variability might be in agreement with the stellar data. We propose that the continuation of the photometric program and its expansion to a larger stellar sample will ultimately allow us to constrain the historical solar variability. [ABSTRACT FROM AUTHOR]

Aims. We investigate the large-scale metallicity distribution in the Galactic bulge using large spatial coverage to constrain the bulge formation scenario. Methods. We use the VISTA variables in the Via Lactea (VVV) survey data and 2MASS photometry, which cover 320 sqdeg of the Galactic bulge, to derive photometric metallicities by interpolating the (J - Ks)0 colors of individual red giant branch stars based on a set of globular cluster ridge lines. We then use this information to construct the first global metallicity map of the bulge with a resolution of 30' × 45'. Results. The metallicity map of the bulge revealed a clear vertical metallicity gradient of ~0.04 dex/deg (~0.28 dex/kpc), with metalrich stars ([Fe/H] ~ 0) dominating the inner bulge in regions closer to the Galactic plane (∣b∣ < 5). At larger scale heights, the mean metallicity of the bulge population becomes significantly more metal poor. Conclusions. This fits in the scenario of a boxy bulge originating from the vertical instability of the Galactic bar, formed early via secular evolution of a two-component stellar disk. Older metal-poor stars dominate at higher scale heights due to the non-mixed orbits of originally hotter thick disk stars. [ABSTRACT FROM AUTHOR]