Giovanni Catanzaro

Aims . In this work we present the results of our analysis of medium-resolution LAMOST spectra of candidate members of the cluster NGC 1647 with the aim of determining the stellar parameters, activity level, lithium abundance, and to study the cluster properties. Methods . We used the code ROTFIT to determine the atmospheric parameters ( T _eff , log g , and [Fe/H]), radial velocity ( V _r ), and projected rotation velocity ( v sin i ). Moreover, for solar-type and cooler stars ( T _eff ≤ 6500 K), we calculated the H α and Li I λ 6708 net equivalent width by means of the subtraction of non-active photospheric templates. We determined the rotation periods for 160 stars by analyzing the available TESS photometry. Results . We derived V _r , v sin i , and atmospheric parameters for 341 spectra of 155 stars, plus three additional bright targets with archival UVES spectra. Moreover, we found four double-lined spectroscopic systems for which we provide the radial velocities of the two components. The V _r distribution of the cluster members peaks at −5.3 km s ⁻¹ with a dispersion of 1.6 km s ⁻¹ , while the average metallicity is [Fe/H] = −0.08±0.08 dex, in line with previous determinations, which were based on only a handful stars. From the fitting of the spectral energy distribution of 160 likely members we infer the existence of a differential reddening across the cluster field with an average value of A _V = 1.1 mag. The A _V values show a distinct correlation with the color offset from the lower boundary of the main sequence, as observed in the Gaia color–magnitude diagram; conversely, this offset appears to be uncorrelated with v sin i . These two findings confirm that differential reddening is the primary driver behind the observed extended main-sequence turnoff (eMSTO) in this cluster. The age of NGC 1647, obtained from the lithium abundance, is 203±27 Myr, which is compatible with the values inferred from a gyrochronological approach and the isochrone fitting.

Context. The C-MetaLL project has provided homogeneous spectroscopic abundances of 290 Classical Cepheids (DCEPs) for which we have the intensity-averaged magnitudes in multiple optical and NIR bands, periods, pulsation modes, and Gaia parallaxes corrected for individual zero-point (ZP) biases. Aims. Our goal is to derive updated period–Wesenheit–metallicity (PWZ) relations using the largest and most homogeneous metallicity sample ever used for such analyses, covering a range of −1.3 < [Fe/H] < +0.3 dex, and to assess the metallicity dependence of these relations. Methods. We computed several optical and NIR Wesenheit magnitudes adopting both Cardelli et al. (1989, ApJ, 345, 245) and Fitzpatrick (1999, PASP, 111, 63) reddening laws, and transformed Johnson-Cousins Wesenheit magnitudes into their HST equivalents using empirical relations. Using 275 DCEPs with reliable parallaxes, we applied a robust photometric parallax technique, which simultaneously fits all parameters – including the global ZP counter-correction to Gaia parallaxes – and handles outliers via a Cauchy likelihood to account for the sample’s excess variance. Results. We find a stronger metallicity dependence ( γ ≈ −0.5 mag/dex in optical, −0.4 mag/dex in NIR) than recent literature reports. Gaia parallax ZP counter-correction ( ϵ ) varies moderately across bands, with an average value of ∼10 μas, aligning with previous determinations. Applying our PWZ relations to ∼4500 LMC Cepheids yields distances generally consistent within 1 σ with geometric estimates. The choice of reddening law has a small impact, while using only fundamental-mode pulsators significantly increases the uncertainties. Including α element corrections increases | γ | and reduces ϵ . However, we find 1 σ consistency γ values with the literature, particularly for the Wesenheit magnitude in the HST bands, by restricting the sample to brighter (i.e. closer) objects, or by including only pulsators with −0.7 < [Fe/H] < 0.2 dex. Our results hint at a large γ or a non-linear dependence on metallicity of DCEP luminosities at the metal-poor end, which is difficult to quantify with the precision of parallaxes of the present dataset.

We present a new comprehensive study of HD 81809, a nearby binary system of two solar-like stars showing high-amplitude X-ray emission and a well-defined 8 yr solar-like magnetic cycle. By analyzing high-resolution spectroscopy, alongside Gaia Data Release 3 (DR3) astrometry and bolometric fluxes, we derive updated fundamental parameters for both components. In particular, we uncover a significant chemical difference: the primary is metal poor ([Fe/H] ≃ −0.57), while the secondary shows solar-like metallicity ([Fe/H] ≃ 0.00). This suggests that the system originated in a mildly metal-poor environment, consistent with the Galactic thick disk population, and that the secondary’s surface composition has been altered by a recent accretion event. Using multisector TESS photometry, we detected solar-like oscillations in both components, deriving global asteroseismic parameters Δ ν = 43.32 ± 3.91 μ Hz and ν max = 708.7 4 − 3.74 + 3.23 μ Hz for HD 81809 A, and Δ ν = 97.75 ± 4.49 μ Hz and ν max = 2098.0 7 − 2.83 + 3.07 μ Hz for HD 81809 B. By combining all the observational constraints with stellar evolutionary models computed using the CLES and MESA codes, we reconstructed the evolutionary scenario of the system. Our results indicate that HD 81809 is an old system with an age of ∼10 Gyr, composed of a subgiant primary with mass M ∼ 0.87 _⊙ and radius R ∼ 1.96 R _⊙ —likely responsible for the reactivated dynamo cycle—and a main-sequence secondary with mass M ∼ 0.85 M _⊙ and radius R ∼ R 1.10 R _⊙ . This system represents a benchmark for studying stellar evolution, magnetic activity, and the physics of old, metal-poor stars in the Galactic thick disk.

Context . Classical Cepheids (DCEPs) are among the most important distance calibrators thanks to the correlation between their period and luminosity (PL relation), and play a crucial role in the calibration as the first rung of the extragalactic distance ladder. Given their typical age, they also constitute an optimal tracer of the young population in the Galactic disc. Aims . We aim to increase the number of available DCEPs with high-resolution spectroscopic metallicities, study the galactocentric radial gradients of several chemical elements, and analyse the spatial distribution of the Galactic young population of stars in the Milky Way disc. Methods . We performed a complete spectroscopical analysis of 136 spectra obtained from three different high-resolution spectrographs, for a total of 60 DCEPs. More than half have pulsational periods longer than 15 days, up to 70 days, doubling the number of stars in our sample with P > 15 d . We derived radial velocities, atmospheric parameters, and chemical abundances for up to 33 different species. Results . We present an updated list of trusted spectroscopic lines for the detection and estimation of chemical abundances. We used this new set to revisit the abundances already published in the context of the C-MetaLL (Cepheids-Metallicity in the Leavitt Law) survey and increase the number of available chemical species. For the first time (to our knowledge), we present the estimation of abundances for Cepheids for dysprosium (Dy, Z = 66), as well as a systematic estimation of erbium (Er, Z Z = 68), lutetium (Lu, Z = 71), and thorium (Th, Z = 90) abundances. Conclusions . We calculated a galactic radial gradient for [ Fe/H ] with a slope of −0.064 ± 0.002 dex kpc ⁻¹ , in good agreement with recent literature estimation. The other elements also exhibit a clear negative radial trend, with this effect diminishing and eventually disappearing for heavier neutron-capture elements. Depending on the proposed spiral arms model present in several literature sources, our most external stars agree on tracing either the Perseus, the Norma-Outer, or both the Outer and the association Outer-Scutum-Centaurus arms.

Context. Classical Cepheids are fundamental primary distance indicators and crucial tracers of the young stellar population in the Milky Way and nearby galaxies. While most chemical abundance studies of Cepheids have been carried out in the optical domain, near-infrared (NIR) spectroscopy offers unique advantages in terms of reduced extinction and access to new elemental tracers. Aims. Our goal is to validate NIR abundance determinations against well-established optical results and to explore the diagnostic power of previously unexplored NIR lines. NIR spectroscopy is far less hampered by interstellar extinction than optical observations, which allows us to probe Cepheids at larger distances and in highly obscured regions of the Galaxy. Moreover, the H and K bands provide access to diagnostic lines of elements (e.g., P, K, and Yb) that are not available in the optical domain. Methods. We acquired high-resolution ( R ≈ 45 000) spectra of 21 Galactic and 2 Large Magellanic Cloud (LMC) classical Cepheids with the high-resolution Immersion Grating Infrared Spectrometer (IGRINS) in the H and K bands. Effective temperatures were derived from a photometric approach and line-depth ratios, and the gravities and microturbulent velocities were estimated using empirical calibrations and statistical constraints. The abundances of 16 elements were determined through a full spectral synthesis in local thermodynamic equilibrium. We performed an extensive error analysis and compared our results with previous optical studies of the same stars. Results. Our NIR abundances and the optical literature values agree very well (Δ[Fe/H] ≤ 0.02 dex and σ ≈ 0.07 dex), which confirms the reliability of IGRINS-based measurements. The derived abundance gradients in the Galactic disk are fully consistent with previous optical determinations, with slopes of −0.06, −0.05, and −0.05 dex kpc ⁻¹ for Fe, Mg, and Si, respectively. We provide homogeneous determinations of P, K, and Yb abundances from NIR lines for classical Cepheids for the first time, and we report trends that are consistent with Galactic chemical evolution models. Moreover, the two LMC Cepheids included in our sample that were previously analyzed in the optical provide a direct benchmark that confirms the accuracy of NIR abundance determinations in extragalactic metal-poor environments. Conclusions. Our study demonstrates that high-resolution NIR spectroscopy of Cepheids yields robust abundances that are fully compatible with optical results and provides access to additional elements of nucleosynthetic interest. These results pave the way for future large-scale NIR surveys of Cepheids with facilities such as MOONS, ELT, and JWST, which are crucial for tracing the chemical evolution of the Milky Way and nearby galaxies in heavily obscured regions.

Context. The rotation periods of Ap stars range over five to six orders of magnitude. The origin of their differentiation remains unknown. Aims. We carry out a systematic study of the longest period Ap stars to gain insight into their properties. Methods. We analysed newly obtained spectra of a sample of super-slowly rotating Ap (ssrAp) star candidates identified by a TESS photometric survey to confirm that their projected equatorial velocity, v sin i , is consistent with (very) long rotation periods; to obtain a first determination of their magnetic fields; and to test their binarity. Results. The value of v sin i in 16 of the 18 studied stars is low enough for them to have moderately to extremely long rotation periods. All stars but one are definitely magnetic; for five of them, the magnetic field was detected for the first time. Another set of five new stars with resolved magnetically split lines were discovered. Five of the stars that were not previously known to be spectroscopic binaries were found to show radial velocity variations, and in one of them, lines from both components were observed.

Context. While most chemical abundance studies of Cepheids rely on optical spectroscopy, near-infrared (NIR) observations offer advantages in terms of reduced extinction and access to new elemental tracers. Aims. We aim to validate NIR-based abundance determinations against optical results and to explore the diagnostic power of spectral lines inaccessible in the optical domain. The H and K bands allow us to trace elements such as P, K, and Yb, while also probing obscured Galactic regions and more distant Cepheids. Methods. We obtained high-resolution (R=45000) H- and K-band spectra for 21 Galactic and 2 LMC Classical Cepheids using IGRINS. Atmospheric parameters were derived from photometry and line-depth ratios (Teff), empirical calibrations (log g), and spectral fitting. Abundances of 16 elements were determined via LTE full spectral synthesis and compared with optical literature values. Results. We find excellent agreement between NIR and optical abundances, confirming the reliability of IGRINS-based measurements. The Fe, Mg, and Si gradients match previous optical determinations. We provide the first homogeneous NIR-based measurements of P, K, and Yb in Cepheids, consistent with chemical evolution models. The two LMC Cepheids in our sample, also studied optically, serve as extragalactic benchmarks for validating NIR abundances in low-metallicity regimes. Conclusions. High-resolution NIR spectroscopy yields accurate chemical abundances in Cepheids, consistent with optical results, and grants access to additional nucleosynthetic tracers. These results support future large NIR spectroscopic surveys with instruments such as MOONS, ELT, and JWST for Galactic and extragalactic archaeology.

Pulsating detached eclipsing binary systems are crucial for studying the internal structure of oscillating stars. These systems are advantageous because binary effects on pulsations are minimal, allowing for more accurate determinations of fundamental stellar parameters such as mass and radius. They serve as unique laboratories for detailed investigations of pulsating stars. In this study, we focused on four detached eclipsing binaries exhibiting δ Scuti−type oscillations: HD 117476, 205 Dra, HY Vir, and V1031 Ori. Our preliminary investigation showed that all binary components of these targets lie within the δ Scuti instability strip. Therefore, we aimed to determine which components are pulsating and which are not and to explore the differences between them. To achieve this, we analyzed TESS photometric data and high-resolution spectra of the targets. Radial velocity (RV) variations were measured, and atmospheric parameters for each component were derived using spectral disentangling or synthetic composite spectra. We also modeled the binary light and RV curves to determine the fundamental physical parameters of the components. Furthermore, we examined pulsation properties using three different approaches to identify the pulsating components. The evolutionary status of the targets was also assessed. Our analysis revealed that, in each system, only one component exhibits δ Scuti−type pulsations, while the others are nonpulsating. Interestingly, we found that the key difference between pulsating and nonpulsating components within the same binary is metallicity: the metal-rich components were found to be nonpulsators, supporting theoretical studies on the effect of metallicity on δ Scuti−type pulsations.