First constraints on the magnetic field strength in extra-Galactic stars: FORS2 observations of Of?p stars in the Magellanic Clouds

Massive O-type stars play a dominant role in our Universe, but many of their properties remain poorly constrained. In the last decade magnetic fields have been detected in all Galactic members of the distinctive Of?p class, opening the door to a better knowledge of all O-type stars. With the aim of extending the study of magnetic massive stars to nearby galaxies, to better understand the role of metallicity in the formation of their magnetic fields and magnetospheres, and to broaden our knowledge of the role of magnetic fields in massive star evolution, we have carried out spectropolarimetry of five extra-Galactic Of?p stars, as well as a couple of dozen neighbouring stars. We have been able to measure magnetic fields with typical error bars from 0.2 to 1.0 kG, depending on the apparent magnitude and on weather conditions. No magnetic field has been firmly detected in any of our measurements, but we have been able to estimate upper limits to the field values of our target stars. One of our targets, 2dFS 936, exhibited an unexpected strengthening of emission lines. We confirm the unusual behaviour of BI 57, which exhibits a 787 d period with two photometric peaks and one spectroscopic maximum. The observed strengthening of the emission lines of 2dFS 936, and the lack of detection of a strong magnetic field in a star with such strong emission lines is at odd with expectations. Together with the unusual periodic behaviour of BI 57, it represents a challenge for the current models of Of?p stars. The limited precision that we obtained in our field measurements (in most cases as a consequence of poor weather) has led to field-strength upper limits that are substantially larger than those typically measured in Galactic magnetic O stars. Further higher precision observations and monitoring are clearly required.Comment: Accepted by A&

Is there a mass discrepancy in the Cepheid binary OGLE-LMC-CEP0227?

Context. The Cepheid mass discrepancy, the difference between masses predicted from stellar evolution and stellar pulsation calculations, is a challenge for the understanding of stellar astrophysics. Recent models of the eclipsing binary Cepheid OGLE-LMC-CEP-0227 have suggested that the discrepancy may be resolved. Aims. We explore for what physical parameters do stellar evolution models agree with the measured properties of OGLE-LMC-CEP0227 and compare to canonical stellar evolution models assuming no convective core overshooting. Methods. We construct state-of-the-art stellar evolution models for varying mass, metallicity, and convective core overshooting and compare the stellar evolution predictions with the observed properties. Results. The observed mass, effective temperature, and radius of the two stars in the binary system are well fit by numerous combinations of physical parameters, suggesting a Cepheid mass discrepancy of 10-20% relative to canonical stellar evolution models. Conclusions. The properties of the observed binary Cepheid suggest that the Cepheid mass discrepancy is still a challenge and requires more specific observations, such as the rate of period change, to better constrain and understand the necessary physics for stellar evolution models to resolve the discrepancy.Comment: 5 pages, 3 figures, A&A accepte

Numerical modeling of the rheological characteristic of olive paste under different conditioning treatments: Traditional malaxation, high-frequency ultrasound and microwave

Olive paste, a mixture of olive oil, vegetation water and solid particles, have a complex rheological behavior. Its viscosity (μ) cannot be considered as constant and depends on several parameters. The olive paste changes its rheological characteristics from the inlet to the outlet of the olive oil extraction line because of temperature increase and variation in fluid composition (i.e., solid-liquid m). A numerical analysis was carried out using different mathematical models to predict the apparent viscosity of olive paste as a function of the solids and olive oil volume fractions. Experimental trials were carried out processing the olive paste using different techniques: traditional malaxing (TM), the use of megasound (MS) and the use of microwaves (MW). The collected data consisted of apparent viscosity values, the related shear strain rates and the composition of the olive paste. These data were interpolated using a power law model whose parameters were determined by means of a linear regression in a bi-logarithmic scale at each step of the olive milling process. As a result of comparison with the experimental data, the different models were found to be quite effective for describing the relative viscosity behavior and the obtained solid volume fraction obtained after the three different processing methods confirms the best behavior of the MS technique. As a final consideration, the results of this work represent another step toward full comprehension of the physical characteristics of the olive paste finalizes to improve the solid-liquid separation in olive oil centrifugal decanters

On the distance of the Magellanic Clouds using Cepheid NIR and optical-NIR Period Wesenheit Relations

We present the largest near-infrared (NIR) data sets, $JHKs$, ever collected for classical Cepheids in the Magellanic Clouds (MCs). We selected fundamental (FU) and first overtone (FO) pulsators, and found 4150 (2571 FU, 1579 FO) Cepheids for Small Magellanic Cloud (SMC) and 3042 (1840 FU, 1202 FO) for Large Magellanic Cloud (LMC). Current sample is 2--3 times larger than any sample used in previous investigations with NIR photometry. We also discuss optical $VI$ photometry from OGLE-III. NIR and optical--NIR Period-Wesenheit (PW) relations are linear over the entire period range ($0.0<\log P_{\rm FU} \le1.65$) and their slopes are, within the intrinsic dispersions, common between the MCs. These are consistent with recent results from pulsation models and observations suggesting that the PW relations are minimally affected by the metal content. The new FU and FO PW relations were calibrated using a sample of Galactic Cepheids with distances based on trigonometric parallaxes and Cepheid pulsation models. By using FU Cepheids we found a true distance moduli of $18.45\pm0.02{\rm(random)}\pm0.10{\rm(systematic)}$ mag (LMC) and $18.93\pm0.02{\rm(random)}\pm0.10{\rm(systematic)}$ mag (SMC). These estimates are the weighted mean over ten PW relations and the systematic errors account for uncertainties in the zero-point and in the reddening law. We found similar distances using FO Cepheids ($18.60\pm0.03{\rm(random)}\pm0.10{\rm(systematic)}$ mag [LMC] and $19.12\pm0.03{\rm(random)}\pm0.10{\rm(systematic)}$ mag [SMC]). These new MC distances lead to the relative distance, $\Delta\mu=0.48\pm0.03$ mag (FU, $\log P=1$) and $\Delta\mu=0.52\pm0.03$ mag (FO, $\log P=0.5$),which agrees quite well with previous estimates based on robust distance indicators.Comment: 17 pages, 7 figure

Performance of the Vignale-Kohn functional in the linear response of metals

Recently the linear response of metallic solids has been formulated within the time-dependent current-density-functional approach [Romaniello and de Boeij, Phys. Rev. B 71, 155108 (2005)]. The implementation, which originally used only the adiabatic local density approximation for the exchange-correlation kernel is extended in order to include also the Vignale-Kohn current functional. Within this approximation the exchange-correlation kernel is frequency dependent, thus relaxation effects due to electron-electron scattering can now be taken into account and some deficiencies of the adiabatic local density approximation (ALDA), as the absence of the low-frequency Drude-like tail in absorption spectra, can be cured. We strictly follow the previous formulation of the linear response of semiconductors by using the Vignale-Kohn functional [Berger, de Boeij, and van Leeuwen, Phys. Rev. B 71, 155104 (2005)]. The self-consistent equations for the interband and intraband contributions to the induced density and current density, which are completely decoupled within the ALDA and in the long-wavelength limit, now remain coupled. We present our results calculated for the optical properties of the noble metals Cu, Ag, and Au and we compare them with measurements found in literature. In the case of Au we treat the dominant scalar relativistic effects using the zeroth-order regular approximation in the ground-state density-functional-theory calculations, as well as in the time-dependent response calculations

On the metallicity distribution of classical Cepheids in the Galactic inner disk

We present homogeneous and accurate iron abundances for almost four dozen (47) of Galactic Cepheids using high-spectral resolution (R$\sim$40,000) high signal-to-noise ratio (S/N $\ge$ 100) optical spectra collected with UVES at VLT. A significant fraction of the sample (32) is located in the inner disk (RG $le$ 6.9 kpc) and for half of them we provide new iron abundances. Current findings indicate a steady increase in iron abundance when approaching the innermost regions of the thin disk. The metallicity is super-solar and ranges from 0.2 dex for RG $\sim$ 6.5 kpc to 0.4 dex for RG $\sim$ 5.5 kpc. Moreover, we do not find evidence of correlation between iron abundance and distance from the Galactic plane. We collected similar data available in the literature and ended up with a sample of 420 Cepheids. Current data suggest that the mean metallicity and the metallicity dispersion in the four quadrants of the Galactic disk attain similar values. The first-second quadrants show a more extended metal-poor tail, while the third-fourth quadrants show a more extended metal-rich tail, but the bulk of the sample is at solar iron abundance. Finally, we found a significant difference between the iron abundance of Cepheids located close to the edge of the inner disk ([Fe/H]$\sim$0.4) and young stars located either along the Galactic bar or in the nuclear bulge ([Fe/H]$\sim$0). Thus suggesting that the above regions have had different chemical enrichment histories. The same outcome applies to the metallicity gradient of the Galactic bulge, since mounting empirical evidence indicates that the mean metallicity increases when moving from the outer to the inner bulge regions.Comment: 10 pages, 5 figures; Corrected typos, corrected Table

The Carina Project. X. On the kinematics of old and intermediate-age stellar populations

We present new radial velocity (RV) measurements of old (horizontal branch) and intermediate-age (red clump) stellar tracers in the Carina dwarf spheroidal. They are based on more than 2,200 low-resolution spectra collected with VIMOS at VLT. The targets are faint (20<V<21.5 mag), but the accuracy at the faintest limit is <9 kms-1. These data were complemented with RV measurements either based on spectra collected with FORS2 and FLAMES/GIRAFFE at VLT or available in the literature. We ended up with a sample of 2748 stars and among them 1389 are candidate Carina stars. We found that the intermediate-age stellar component shows a well defined rotational pattern around the minor axis. The western and the eastern side of the galaxy differ by +5 and -4 km s-1 when compared with the main RV peak. The old stellar component is characterized by a larger RV dispersion and does not show evidence of RV pattern. We compared the observed RV distribution with N-body simulations for a former disky dwarf galaxy orbiting a giant MilkyWay-like galaxy (Lokas et al. 2015). We rotated the simulated galaxy by 60 degrees with respect to the major axis, we kept the observer on orbital plane of the dwarf and extracted a sample of stars similar to the observed one. Observed and predicted Vrot/{\sigma} ratios across the central regions are in remarkable agreement. This evidence indicates that Carina was a disky dwarf galaxy that experienced several strong tidal interactions with the Milky Way. Owing to these interactions, Carina transformed from a disky to a prolate spheroid and the rotational velocity transformed into random motions.Comment: 21 pages, 16 figures, 4 tables. Accepted for publication in Ap

Composting of olive mill pomace, agro‐industrial sewage sludge and other residues: Process monitoring and agronomic use of the resulting composts

The viability of co‐composting of olive mill pomace added to sewage sludge with other organic residues was evaluated and the agronomic use of the final composts was investigated. Two composting piles at different carbon‐nitrogen ratios were performed, in which olive mill pomace (OMP), sewage sludge from vegetable processing (SS), fresh residues from artichoke processing residues (AR), and wheat straw (WS) were used. The two composting piles were placed inside a spe-cially built greenhouse and a turning machine pulled by a tractor was used for turning and shred-ding the organic matrix (every 6 days) during the process. The humidity and temperature of organic matrices have been monitored and controlled during the entire composting process, which lasted 90 days. The process was also monitored to evaluate the microbiological safety of the final compost. The humidity of both piles was always kept just above 50% until the end of the thermophilic phase and the maximum temperature was about 50 °C during the thermophilic phase. The carbon‐nitro-gen ratio decreased from 21.4 and 28.2, respectively (initial value at day 1 in Pile A and B), to values ranging from 12.9 to 15.1, both composts that originated from the two different piles were microbi-ologically safe. During a two‐year period, the effects of different types of compost on the main qualitative parameters of processing tomato and durum wheat was evaluated. Five fertilization treatments were evaluated for tomato and durum wheat crops: unfertilized control (TR1); compost A (TR2); compost B (TR3); ½ mineral and ½ compost A (TR4); and mineral fertilizer commonly used for the two crops (TR5). Concerning the processing tomato yield, TR5 and TR4 showed the best results (2.73 and 2.51 kg, respectively). The same trend was observed considering the marketable yield per plant. The only difference was related to the treatments that included the compost (2.32, 1.77, and 1.73 kg/plant for TR4, TR3, and TR2, respectively). As regards the qualitative parameters of to-mato, the highest average weight of the fruits was found in the TR5, TR4, and TR3 treatments (re-spectively, 73.67 g, 70.34 g, and 68.10 g). For durum wheat, only the protein component was differ-entiated between treatments. Furthermore, wheat grain yield parameters generally increased by combined application of mineral fertilizer and compost

The Carina Project. VIII. The {\alpha}-element abundances

We have performed a new abundance analysis of Carina Red Giant (RG) stars from spectroscopic data collected with UVES (high resolution) and FLAMES/GIRAFFE (high and medium resolution) at ESO/VLT. The former sample includes 44 RGs, while the latter consists of 65 (high) and ~800 (medium resolution) RGs, covering a significant fraction of the galaxy's RG branch (RGB), and red clump stars. To improve the abundance analysis at the faint magnitude limit, the FLAMES/GIRAFFE data were divided into ten surface gravity and effective temperature bins. The spectra of the stars belonging to the same gravity/temperature bin were stacked. This approach allowed us to increase by at least a factor of five the signal-to-noise ratio in the faint limit (V>20.5mag). We took advantage of the new photometry index cU,B,I introduced by Monelli et al. (2014), as an age and probably a metallicity indicator, to split stars along the RGB. These two stellar populations display distinct [Fe/H] and [Mg/H] distributions: their mean Fe abundances are -2.15$\pm$0.06dex (sig=0.28), and -1.75$\pm$0.03dex (sig=0.21), respectively. The two iron distributions differ at the 75% level. This supports preliminary results by Lemasle et al. (2012) and by Monelli et al. (2014). Moreover, we found that the old and intermediate-age stellar populations have mean [Mg/H] abundances of -1.91$\pm$0.05dex (sig=0.22) and -1.35$\pm$0.03dex (sig=0.22); these differ at the 83% level. Carina's {\alpha}-element abundances agree, within 1sigma, with similar abundances for field Halo stars and for cluster (Galactic, Magellanic) stars. The same outcome applies to nearby dwarf spheroidals and ultra-faint dwarf galaxies, in the iron range covered by Carina stars. Finally, we found evidence of a clear correlation between Na and O abundances, thus suggesting that Carina's chemical enrichment history is quite different than in the globular clusters.Comment: 21 pages, 19 figures, 11 tables, accepted for publication in A&