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We present a new method for the measurement of very small Γ γ partial width that is important for the synthesis of elements in astrophysics. The method is based on the simultaneous detection of scattered beam, residual nucleus and decay γ rays. This method is optimized for the use of the CHIMERA detector at LNS. Experimental details are described.

Context. The flux distribution of solar analogues is required for calculating the spectral albedo of solar system bodies such as asteroids and trans-Neptunian objects. Ideally a solar analogue should be comparatively faint as the target of interest, but very few analogues fainter than V = 9 mag have been identified so far. Only atmospheric parameters equal to solar guarantee a flux distribution equal to solar as well, while only photometric colours equal to solar do not. Reddening is also a factor to consider when selecting faint analogue candidates. Aims. Our aim is to implement the methodology for identifying faint analogues at the limit of precision allowed by the current spectroscopic surveys. We quantify the precision attainable for the atmospheric parameters of effective temperature (Teff), metallicity ([Fe/H]), and surface gravity (log g) when derived from moderately low-resolution (R = 8000) spectra with S∕N ~ 100. We estimate the significance of reddening at 100–300 pc from the Sun. Methods. We used the less precise photometry in the HIPPARCOS catalogue to select potential analogues with V ~ 10.5 mag (located at ~135 pc). We calibrated Teff and [Fe/H] as functions of equivalent widths of spectral indices by means of the principal component analysis regression. We derived log g, mass, radius, and age from the atmospheric parameters, Gaia parallaxes, and evolutionary tracks. We evaluated the presence of reddening for the candidates by underestimations of photometric Teff with respect to those derived by spectral indices. These determinations were validated with extinction maps. Results. We obtained the atmospheric parameters Teff, [Fe/H], and log g with precision of 97 K, 0.06 dex, 0.05 dex, respectively. From 21 candidates analysed, we identify five solar analogues: HIP 991, HIP 5811, and HIP 69477 have solar parameters within 1σ errors, and HIP 55619 and HIP 61835 within 2σ errors. Six other stars have Teff close to solar, but slightly lower [Fe/H]. Our analogues show no evidence of reddening except for four stars, that present E(B−V) ≥ 0.06 mag, translating to at least a 200 K decrease in photometric Teff.

Context. The determination of stellar effective temperature (Teff) in F, G, and K stars using Hα profile fitting is a quite remarkable and powerful tool because it does not depend on reddening and is only slightly sensitive to other atmospheric parameters. Nevertheless, this technique is not frequently used because of the complex procedure needed to recover the profile of broad lines in echelle spectra. As a consequence, tests performed on different models have sometimes provided ambiguous results. Aims. The main aim of this work is to test the ability of the Hα profile fitting technique to derive Teff. We also aim to improve the applicability of this technique to echelle spectra and to test how well 1D + LTE models perform on a variety of F–K stars. We also apply the technique to HARPS spectra and test the reliability and the stability of the HARPS response over several years using the Sun. Methods. We have developed a normalization method for recovering undistorted Hα profiles and we have first applied it to spectra acquired with the single-order Coudé instrument (resolution R = 45 000) at do Pico dos Dias Observatory to avoid the problem of blaze correction. The continuum location around Hα is optimised using an iterative procedure, where the identification of minute telluric features is performed. A set of spectra was acquired with the MUSICOS echelle spectrograph (R = 40 000) to independently validate the normalization method. The accuracy of the method and of the 1D + LTE model is determined using Coudé/HARPS/MUSICOS spectra of the Sun and Coudé-only spectra of a sample of ten Gaia Benchmark Stars with Teff determined from interferometric measurements. HARPS, Coudé, and MUSICOS spectra are used to determine Teff of 43 sample stars. Results. We find that a proper choice of spectral windows of fits plus the identification of telluric features allow for a very careful normalization of the spectra and produce reliable Hα profiles. We also find that the most used solar atlases cannot be used as templates for Hα temperature diagnostics without renormalization. The comparison with the Sun shows that Hα profiles from 1D + LTE models underestimate the solar Teff by 28 K. We find the same agreement between Hα and interferometry and between Hα and Infrared Flux Method: a shallow dependency on metallicity according to the relation Teff = TeffHα − 159[Fe/H] + 28 K within the metallicity range − 0.70 to + 0.40 dex. The comparison with the Infrared Flux Method shows a scatter of 59 K dominated by photometric errors (52 K). In order to investigate the origin of this dependency, we analyzed spectra from 3D models and found that they produce hotter temperatures, and that their use largely improves the agreement with the interferometric and Infrared Flux Method measurements. Finally, we find HARPS spectra to be fully suitable for Hα profile temperature diagnostics; they are perfectly compatible with the Coudé spectra, and lead to the same Teff for the Sun as that found when analysing HARPS spectra over a timespan of more than 7 yr.

The kinematical coincidence method is used to extract angular distribution of elastic scattering and transfer reactions. The detected light particle energy spectra are used to extract the angular distribution with around 1° resolution in the Center of Mass (CM) system. Examples with 10Be beam are presented. In the case of proton scattering, γ-ray coincidences are used to discriminate excited levels population from elastic scattering. © Owned by the authors, published by EDP Sciences, 2014.

The elliptic-flow ratio of neutrons with respect to protons or light complex particles in reactions of heavy-ions at pre-relativistic energies has been proposed as an observable sensitive to the strength of the symmetry term of the nuclear equation of state at supra-saturation densities. The results obtained from the existing FOPI/LAND data for 197Au+197Au collisions at 400 MeV/nucleon in comparison with the UrQMD model simulations favoured a moderately soft symmetry term, but suffer from a considerable statistical uncertainty. These results have been confirmed by an independent analysis based on the Tübingen QMD simulations. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration. The present status of the data analysis is reported

The binary break-up of projectile-like fragments in non central heavy-ion collisions follows different decay patterns, from equilibrated emission towards dynamical (prompt) fission. Recently, comparing two systems with different N/Z in the entrance channel, it has been shown that the dynamical emission cross-section is enhanced for the most neutron rich system while the statistical emission cross-section is independent from the isotopic composition. In order to understand this dependence and disentangle it from the initial size of the nuclei, we have studied the two isobaric systems 124 Xe +64 Zn and 124 Xe +64 Ni at 35 A MeV (InKiIsSy experiment), in comparison with the previous studied reactions (124 Sn +64 Ni and 112 Sn +58 Ni ) at the same bombarding energy. We present the first results evidencing a striking similar effect in the dynamical decay as a function of the N/Z of the target for equal size systems.

International audience; The elliptic-flow ratio of neutrons with respect to protons or light complex particles in reactions of heavy ions at pre-relativistic energies has been proposed as an observable sensitive to the strength of the symmetry term of the nuclear equation of state at supra-saturation densities. In the ASY-EOS experiment at the GSI laboratory, flows of neutrons and light charged particles were measured for ^197Au+^197Au collisions at 400 MeV/nucleon. Flow results obtained for the Au+Au system, in comparison with predictions of the UrQMD transport model, confirm the moderately soft to linear density dependence of the symmetry energy deduced from the earlier FOPI-LAND data.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.ISBN: 978-88-7438-101-2; International audience; Two and multi particle correlations from the decay of sources produced in 12C+24Mg and 12C+208Pb collisions at E=35 AMeV have been studied by using the forward part (1° < θlab < 30°) of the CHIMERA multi-detector. Correlations and invariant mass spectroscopy are used to explore simultaneous and sequential decays of resonances in light isotopes with Z∼3-6, produced in peripheral collisions via the break-up of excited quasi-projectiles. Among them we mention 5Li, 6Li, 6Be, 8Be and the astrophysically important state in 12C decaying into three alpha particles. Results and future perspectives at the INFN-LNS will be presented.

High signal to noise, high resolution spectra were obtained for a sample of normal, mild barium, and barium giants. Atmospheric parameters were determined from the FeI and FeII lines. Abundances for Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, and Gd, were determined from equivalent widths and model atmospheres in a differential analysis, with the red giant Eps Vir as the standard star. The different levels of s-process overabundances of barium and mild barium stars were earlier suggested to be related to the stellar metallicity. Contrary to this suggestion, we found in this work no evidence of barium and mild barium to having different range in metallicity. However, comparing the ratio of abundances of heavy to light s-process elements, we found some evidence that they do not share the same neutron exposure parameter. The exact mechanism controlling this difference is still not clear. As a by-product of this analysis we identify two normal red giants misclassified as mild barium stars. The relevance of this finding is discussed. Concerning the suggested nucleosynthetic effects possibly related to the s-process, for elements like Cu, Mn, V and Sc, we found no evidence for an anomalous behavior in any of the s-process enriched stars analyzed here. However, further work is still needed since a clear [Cu/Fe] vs. [Ba/H] anticorrelation exists for other s-process enriched objects., 34 pages, 18 figures, A&A accepted (revised version)

International audience; The elliptic-flow ratio of neutrons with respect to protons or lightcomplex particles in reactions of heavy ions at pre-relativistic energieshas been proposed as an observable sensitive to the strength of thesymmetry term of the nuclear equation of state at supra-saturationdensities. In the ASY-EOS experiment at the GSI laboratory, flows ofneutrons and light charged particles were measured for 197Au+197Au,96Zr+96Zr and 96Ru+96Ru collisions at 400 MeV/nucleon with theLarge Area Neutron Detector LAND as part of a setup with severaladditional detection systems used for the event characterization. Flowresults obtained for the Au+Au system, in comparison with predictionsof the UrQMD transport model, confirm the moderately soft to lineardensity dependence of the symmetry energy deduced from the earlierFOPI-LAND data.

Context. We have obtained BVRI photometry for 21 stellar fields located in directions towards the central $3.5^\circ$ of the Galaxy. Each field is $10\times 10$ arcmin in size, and a total of ~$2 \times 10^5$ stars were measured. Aims. Previous analyses based on 2 Micron All Sky Survey (2MASS) data have shown that these directions have a relatively low extinction ($A_K \simeq 0.25{-}0.30$). The combined optical-infrared sample contains about $3.5 \times 10^4$ stars. This large dataset provides a more detailed extinction map within these surveyed areas than previously derived. The large number of colour indexes available also yielded estimates of effective temperatures and metallicities for the inner bulge stars. Methods. Extinction and effective temperature were estimated for each star based on comparing the observed colours to model predictions. The extinction-corrected colour magnitude diagrams indicate the presence of a broad red giant branch of inner bulge stars detached from the helium-burning red clump of both bulge and disc stars. The red giant stars belonging to the bulge form a wide sequence mostly due to variable metallicity. As previously done by other authors, we derived photometric metallicities by comparing the position of each bulge red giant to a set of templates based on Galactic globular clusters. Results. We confirm the existence of regions with $A_K < 0.30$ in these fields, as attested by analysis of the stellar colours. The resulting metallicity distribution function is peaked at $\rm [Fe/H] \simeq -0.25$ and extends to supersolar values up to $\rm [Fe/H] \simeq 0.3$. This distribution is similar among the 4 regions, with relatively small field-to-field variations within the central 1kpc. Our results are also in good agreement with the metallicity distributions from other authors, both photometric and spectroscopic. Put together, this result strongly limits the existence of an abundance gradient in the inner bulge.

A calibration of H-alpha as both a chromospheric diagnostic and an age indicator is presented, complementing the works previously done on this subject (Herbig 1985, Pasquini & Pallavicini 1991. The chromospheric diagnostic was built with a statistically significant sample, covering nine years of observations, and including 175 solar neighborhood stars. Regarding the age indicator, the presence of stars for which very accurate ages are determined, such as those belonging to clusters and kinematic groups, lends confidence to our analysis. We also investigate the possibility that stars of the same age might have gone through different tracks of chromospheric decay, identifying - within the same age range - effects of metallicity and mass. These parameters, however, as well as age, seem to be significant only for dwarf stars, losing their meaning when we analyze stars in the subgiant branch. This result suggests that, in these evolved stars, the emission mechanism cannot be magnetohydrodynamical in nature, in agreement with recent models (Fawzy et al. 2002c, and references therein). The Sun is found to be a typical star in its H-alpha chromospheric flux, for its age, mass and metallicity. As a byproduct of this work, we developed an automatic method to determine temperatures from the wings of H-alpha, which means the suppression of the error inherent to the visual procedure used in the literature., 10 pages, 10 figures, accepted for publication in Astronomy & Astrophysics. Nature of replacement: match astro-ph and ADS title (greek letter)

The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich Heavy-Ion at intermediate energies has been recently proposed as an observable sensitive to the strength of the symmetry term in the nuclear equation of state (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for 197Au+197Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011. © Owned by the authors, 2012.

The connection rotation-CaII emission flux-lithium abundance is analyzed for a sample of bona fide subgiant stars, with evolutionary status determined from HIPPARCOS trigonometric parallax measurements and from the Toulouse-Geneva code., Comment: 9 pages, 8 figures

OPEN ACCESS; International audience; Latest results concerning the study of central collisions in 58Ni+48Ca reactions at Elab(Ni)=25 AMeV are presented. The experimental data, collected with the CHIMERA 4π device, have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain. The method adopted to perform the centrality selection refers to the global variable "flow angle", that is related to the event shape in momentum space, as it is determined by the eigenvectors of the experimental kinetic-energy tensor. The main features of the reaction products were explored by using different constraints on some of the relevant observables, such as mass and velocity distributions and their correlations. Much emphasis was devoted to the competition between fusion-evaporation processes with subsequent identification of a heavy residue and a prompt multifragmentation mechanism. The reaction mechanism was simulated in the framework of transport theories (dynamical stochastic BNV calculations, followed by sequential SIMON code) and further comparison with dynamical calculations from transport model (QMD, CoMD) are in progress. Moreover, an extension of this study taking into account for the light particles has been envisaged.

The systems 124 Sn+64 Ni and 112 Sn+58 Ni at 35 AMeV were analyzed in previous experiments, by using the 4π multi-detector CHIMERA in order to investigate the time-scale and mechanisms of fragments formation. By comparing the two systems, effects that have been correlated to Isospin transport in reaction dynamics and symmetry energy term of nuclear equation of state at sub-saturation density were found. Recently, in order to disentangle the Isospin effects from size effects the 124 Xe+64 Ni reaction was investigated at the same beam energy of 35 AMeV.

Effects related to the neutron to proton ratio (N/Z) degree of freedom in 40, 48Ca+40, 48Ca reactions at 25 MeV/nucleon have been investigated. Isotopic effect and even-odd staggering characterize the emission of light fragments at forward angles. The study of isobaric ratio 7Li/7Be for quasi-projectile source in semi-peripheral event of reactions allows moreover to investigate isospin diffusion effects in heavy ion collisions. © Owned by the authors, 2012.

Solar twins and analogs are fundamental in the characterization of the Sun's place in the context of stellar measurements, as they are in understanding how typical the solar properties are in its neighborhood. They are also important for representing sunlight observable in the night sky for diverse photometric and spectroscopic tasks, besides being natural candidates for harboring planetary systems similar to ours and possibly even life-bearing environments. We report a photometric and spectroscopic survey of solar twin stars within 50 pc of the Sun. Hipparcos absolute magnitudes and (B-V)_Tycho colors were used to define a 2 sigma box around the solar values, where 133 stars were considered. Additional stars resembling the solar UBV colors in a broad sense, plus stars present in the lists of Hardorp, were also selected. All objects were ranked by a color-similarity index with respect to the Sun, defined by uvby and BV photometry. Moderately high-resolution, high-S/N spectra were used for a subsample of equatorial-southern stars to derive Teff, log g, and [Fe/H] with average internal errors better than 50 K, 0.20 dex, and 0.08 dex, respectively. Ages and masses were estimated from theoretical HR diagrams. The color-similarity index proved very successful. We identify and rank new excellent solar analogs, which are fit to represent the Sun in the night sky. Some of them are faint enough to be of interest for moderately large telescopes. We also identify two stars with near-UV spectra indistinguishable from the Sun's. We present five new "probable" solar twin stars, besides five new "possible" twins. Masses and ages for the best solar twin candidates lie very close to the solar values, but chromospheric activity levels range somewhat. We propose that the solar twins be emphasized in the ongoing searches for extra-solar planets and SETI searches., 25 pages, 15 figures, 14 tables

The Mount Wilson Ca II index log$(R'_{\rm HK})$ is the accepted standard metric of calibration for the chromospheric activity versus age relation of FGK stars. Recent results claim its inability to discern activity levels, and thus ages, for stars older than $\sim$2 Gyr, which would severely hamper its application to date disk stars older than the Sun. We present a new activity-age calibration of the Mt. Wilson index explicitly taking into account mass and $[$Fe/H$]$ biases, implicit in samples of stars selected to have precise ages, that have so far gone unappreciated. We show that these selection biases tend to blur the activity-age relation for large age ranges. We calibrate the Mt. Wilson index for a sample of field FGK stars with precise ages, covering a wide range of mass and $[$Fe/H$]$, augmented with data from the Pleiades, Hyades, M67 clusters, and the Ursa Major moving group. We further test the calibration with extensive new Gemini/GMOS log$(R'_{\rm HK})$ data of the old, solar $[$Fe/H$]$ clusters M67 and NGC 188. The observed NGC 188 activity level is clearly lower than M67. We correctly recover the isochronal age of both clusters and establish the viability of deriving usable chromospheric ages for solar-type stars up to at least $\sim$6 Gyr, average errors being $\sim$0.14 dex provided that the mass and $[$Fe/H$]$ dimensions are explicitly accounted for. We test our calibration against asteroseismological ages, finding excellent correlation ($\rho$ = +0.89). We show that our calibration improves the chromospheric age determination for a wide range of ages, masses, and metallicities in comparison to previous age-activity relations., Comment: 4 pages, 3 figures, accepted for publication in A&A letters