Aims. The inner disk of the Galaxy has a number of young star clusters dominated by red supergiants that are heavily obscured by dust extinction and observable only at infrared wavelengths. These ...clusters are important tracers of the recent star formation and chemical enrichment history in the inner Galaxy. Methods. During the technical commissioning and as a first science verification of the GIANO spectrograph at the Telescopio Nazionale Galileo, we secured high-resolution (R ≃ 50 000) near-infrared spectra of three red supergiants in the young Scutum cluster RSGC2. Results. Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to identify several tens of atomic and molecular lines suitable for chemical abundance determinations. By means of spectral synthesis and line equivalent width measurements, we obtained abundances of Fe and other iron-peak elements such as V, Cr, Ni, of alpha (O, Mg, Si, Ca and Ti) and other light elements (C, N, Na, Al, K, Sc), and of some s-process elements (Y, Sr). We found iron abundances between half and one third solar and solar-scaled X/Fe abundance patterns of iron-peak, alpha and most of the light elements, consistent with a thin-disk chemistry. We found a depletion of C/Fe and enhancement of N/Fe, consistent with CN burning, and low 12C/13C abundance ratios (between 9 and 11), requiring extra-mixing processes in the stellar interiors during the post-main-sequence evolution. Finally, we found a slight Sr/Fe enhancement and a slight Y/Fe depletion (by a factor of ≤2), with respect to solar.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
We are completing the construction of GIANO, a high resolution near-infrared cryogenic spectrograph for the Telescopio Nazionale Galileo (TNG). Most of the optics are made of aluminium and operate at ...cryogenic temperature. We evaluated the optical degradation due to mis-matches between the thermal expansion coefficients of the different aluminium parts of the instrument. We performed accurate measurements of the relative thermal expansion coefficients (CTE) of Al-6061 and Al-6082 over the 300–77 K temperatures range. We find that the two alloys have identical thermal expansion coefficient within a maximum (3
σ
) uncertainty of Δ
α
/
α
< 0.28%. Our results show that it is possible to overcome the problem of the alignment of a cryogenic instrument, manufacturing the curved optics, the optics’ holders and the optical bench with different metallic alloys with small CTE mismatch (Al-6061 and Al-6082). This conclusion has also been confirmed by the results of the optical tests with the instrument cooled in the laboratory, showing no significant image quality degradation.
An important portion of the historical built environment, which is characterized by un-reinforced masonry, is particularly vulnerable to collapse in case of earthquakes, as demonstrated by recent ...events. Strategies to target the facades of the most vulnerable buildings need to be tailored for retrofitting and emergency planning. In this research, a novel expeditious vulnerability assessment method, particularly suitable for historical masonry aggregates, is proposed. The method allows assessing the vulnerability index based on information available from external surveys on the building, thus facilitating and speeding up the investigation. If other more precise information (e.g., curbs and tie rods effectiveness) is available, the vulnerability estimation can be improved. The method focuses on out-of-plane mechanisms of the facade, which cause debris to fall on adjacent streets, impeding emergency response. The expeditious method is tailored starting from analytical methods applied on a large sample of historical buildings hit by earthquakes, and validated by means of comparison with kinematic analysis and observed damage state on a relevant case study, Caldarola (Macerata, Central Italy, which was struck by the earthquake in 2016). Results show a good agreement between the proposed method, the kinematic analysis, and the observed damage state of the considered case study, with 75% and 87.5% correspondence, and the method is especially precise for evaluating highly damaged facades.
PDF
