arXiv subjects

R. Cosentino

Publications and source records attributed to R. Cosentino.

At least 55 records · Page 3Linked to original sources

arXiv2023

The commissioning phase

In May 1997 a consistent part of the services and structures committed to the industry had already been released to the commissioning group. The telescope itself was, with the exception of the Nasmyth derotators, motors and all the optics groups, basically ready in its mechanical parts to accept the integration of all services and control equipment. Also the verification of the cabling (interlocks, data-nets, power and controls) already mounted was started in the same period. Starting from June 1998 (telescope first-light date) the telescope went gradually in use, several nights per week, in order to test and tune the tracking and pointing system, the optics and the first derotator system (Nasmyth A station). At the end of the commissioning period and with the first scientific instruments mounted (April 1999) also the first routinely observations started. In this moment the telescope is doing astronomy 80% of time and the complete first-light instrumentation is mounted.

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arXiv2023

SARG control system

The control system and the entire architecture of the High Resolution Spectrograph (SARG) for the Italian National Telescope "Galileo" (TNG) are here described. The concept of SARG instrument controls is similar to that of the other TNG instruments, in particular the CCD detector driving and the image acquisition use the same TNG standard boards and the same selected bus: the VME. The link between the SARG VME and the other telescope components is based on the same GATE software that guarantees the compatibility with the entire distributed TNG software. The control of the moving parts as well as the other parts of instrument that is the lamp controller and the temperature sensors, is based on a commercial controller connected to the system through a serial link. Furthermore a specialized software running on a PC has been realized to test the rotating tables independently of the VME system. Test of accuracy and repeatability of the positioning were done and some results are presented.

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arXiv2023

CCDs for the instrumentation of the Telescopio Nazionale Galileo

Most of the scientific instrumentation as well as the tracking systems and the Shack- Hartmann wavefront analysers at the Italian National Telescope Galileo use CCDs as detectors. The characterization of detectors is of fundamental importance for their correct utilization in scientific instrumentation. We report on the measurement of the electro-optical characteristics of CCDs that will be used in the scientific instrumentation at the Italian National Telescope. In particular we will show and compare the quantum eÆciency, the charge transfer eÆciency, the dark current, the read out noise the uniformity and the linearity of two sets of CCDs manufactured by EEV and LORAL. Finally, we will show the preliminary tests done at the telescope with the optical imager that has a mosaic of two EEV chips.

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arXiv2022

Phosphine in the Venusian Atmosphere: A Strict Upper Limit from SOFIA GREAT Observations

The presence of phosphine (PH$_3$) in the atmosphere of Venus was reported by Greaves et al. (2021a), based on observations of the J=1-0 transition at 267 GHz using ground-based, millimeter-wave spectroscopy. This unexpected discovery presents a challenge for our understanding of Venus's atmosphere, and has led to a reappraisal of the possible sources and sinks of atmospheric phosphorous-bearing gases. Here we present results from a search for PH$_3$ on Venus using the GREAT instrument aboard the SOFIA aircraft, over three flights conducted in November 2021. Multiple PH$_3$ transitions were targeted at frequencies centered on 533 GHz and 1067 GHz, but no evidence for atmospheric PH$_3$ was detected. Through radiative transfer modeling, we derived a disk-averaged upper limit on the PH$_3$ abundance of 0.8 ppb in the altitude range 75-110 km, which is more stringent than previous ground-based studies.

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arXiv2022

Progress on the simulation tools for the SOXS spectrograph: Exposure time calculator and End-to-End simulator

We present the progresses of the simulation tools, the Exposure Time Calculator (ETC) and End-to-End simulator (E2E), for the Son Of X-Shooter (SOXS) instrument at the ESO-NTT 3.58-meter telescope. The SOXS will be a single object spectroscopic facility, made by a two-arms high-efficiency spectrograph, able to cover the spectral range 350-2000 nanometer with a mean resolving power R$\approx$4500. While the purpose of the ETC is the estimate, to the best possible accuracy, of the Signal-to-Noise ratio (SNR), the E2E model allows us to simulate the propagation of photons, starting from the scientific target of interest, up to the detectors. We detail the ETC and E2E architectures, computational models and functionalities. The interface of the E2E with external simulation modules and with the pipeline are described, too. Synthetic spectral formats, related to different seeing and observing conditions, and calibration frames to be ingested by the pipeline are also presented.

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arXiv2022

The vacuum and cryogenics system of the SOXS spectrograph

SOXS (Son Of X-Shooter) is a single object spectrograph built by an international consortium for the ESO NTT telescope. SOXS is based on the heritage of the X-Shooter at the ESO-VLT with two arms (UV-VIS and NIR) working in parallel, with a Resolution-Slit product of about 4500, capable of simultaneously observing over the entire band the complete spectral range from the U- to the H-band. SOXS will carry out rapid and long-term Target of Opportunity requests on a variety of astronomical objects. The SOXS vacuum and cryogenic control system has been designed to evacuate, cool down and maintain the UV-VIS detector and the entire NIR spectrograph to their operating temperatures. The design chosen allows the two arms to be operated independently. This paper describes the final design of the cryo-vacuum control system, its functionalities and the tests performed in the integration laboratories.

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arXiv2022

Progress on the SOXS transients chaser for the ESO-NTT

SOXS (Son Of X-Shooter) is a single object spectrograph offering a simultaneous spectral coverage from U- to H-band, built by an international consortium for the 3.58-m ESO New Technology Telescope at the La Silla Observatory. It is designed to observe all kind of transients and variable sources discovered by different surveys with a highly flexible schedule maintained by the consortium, based on the Target of Opportunity concept. SOXS is going to be a fundamental spectroscopic partner for any kind of imaging survey, becoming one of the premier transient follow-up instruments in the Southern hemisphere. This paper gives an updated status of the project, when the instrument is in the advanced phase of integration and testing in Europe, prior to the activities in Chile.

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arXiv2022

The internal alignment and validation of a powered ADC for SOXS

The Son Of X-Shooter (SOXS) is a two-channel spectrograph along with imaging capabilities, characterized by a wide spectral coverage (350nm to 2000nm), designed for the NTT telescope at the La Silla Observatory. Its main scientific goal is the spectroscopic follow-up of transients and variable objects. The UV-VIS arm, of the Common Path sub-system, is characterized by the presence of a powered Atmospheric Dispersion Corrector composed (ADC) by two counter-rotating quadruplets, two prisms, and two lenses each. The presence of powered optics in both the optical groups represents an additional challenge in the alignment procedures. We present the characteristics of the ADC, the analysis after receiving the optics from the manufacturer, the emerging issues, the alignment strategies we followed, and the final results of the ADC in dispersion and optical quality.

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arXiv2022

SOXS mechanical integration and verification in Italy

SOXS (SOn of X-Shooter) is a medium resolution (~4500) wide-band (0.35 - 2.0 μm) spectrograph which passed the Final Design Review in 2018. The instrument is in the final integration phase and it is planned to be installed at the NTT in La Silla by next year. It is mainly composed of five different optomechanical subsystems (Common Path, NIR spectrograph, UV-VIS spectrograph, Camera, and Calibration) and other mechanical subsystems (Interface flange, Platform, cable corotator, and cooling system). A brief overview of the optomechanical subsystems is presented here as more details can be found in the specific proceedings while a more comprehensive discussion is dedicated to the other mechanical subsystems and the tools needed for the integration of the instrument. Moreover, the results obtained during the acceptance of the various mechanical elements are presented together with the experiments performed to validate the functionality of the subsystems. Finally, the mechanical integration procedure is shown here, along with all the modifications applied to correct the typical problems happening in this phase.

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arXiv2022

From Assembly to the Complete Integration and Verification of the SOXS Common Path

The Son Of X-Shooter (SOXS) is a single object spectrograph offering simultaneous spectral coverage in UV-VIS (350-850 nm) and NIR (800-2000 nm) wavelength regimes with an average of R close to 4500 for a 1 slit. SOXS also has imaging capabilities in the visible wavelength regime. It is designed and optimized to observe all kinds of transients and variable sources. The final destination of SOXS is the Nasmyth platform of the ESO NTT at La Silla, Chile. The SOXS consortium has a relatively large geographic spread, and therefore the Assembly Integration and Verification (AIV) of this medium-class instrument follows a modular approach. Each of the five main sub-systems of SOXS, namely the Common Path, the Calibration Unit, the Acquisition Camera, the UV-VIS Spectrograph, and the NIR Spectrograph, are undergoing (or undergone) internal alignment and testing in the respective consortium institutes. INAF-Osservatorio Astronomico di Padova delivers the Common Path sub-system, the backbone of the entire instrument. We report the Common Path internal alignment starting from the assembly of the individual components to the final testing of the optical quality, and the efficiency of the complete sub-system.

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arXiv2022

The GAPS Programme at TNG: XXXVI. Measurement of the Rossiter-McLaughlin effect and revising the physical and orbital parameters of the HAT-P-15, HAT-P-17, HAT-P-21, HAT-P-26, HAT-P-29 eccentric planetary systems

Aim: We aim to refine the orbital and physical parameters and determine the sky-projected planet orbital obliquity of five eccentric transiting planetary systems: HAT-P-15, HAT-P-17, HAT-P-21, HAT-P-26, and HAT-P-29. Each of the systems hosts a hot Jupiter, except for HAT-P-26 which hosts a Neptune-mass planet. Methods: We observed transit events of these planets with the HARPS-N spectrograph, obtaining high-precision radial velocity measurements that allow us to measure the Rossiter-McLaughlin effect for each of the target systems. We used these new HARPS-N spectra and archival data, including those from Gaia, to better characterise the stellar atmospheric parameters. The photometric parameters for four of the hot Jupiters were recalculated using 17 new transit light curves, obtained with an array of medium-class telescopes, and data from the TESS space telescope. HATNet time-series photometric data were checked for the signatures of rotation periods of the target stars and their spin axis inclination. Results: From the analysis of the Rossiter-McLaughlin effect, we derived a sky-projected obliquity of 13, -26.3, -0.7, -26 degree for HAT-P-15b, HAT-P-17b, HAT-P-21b and HAT-P-29b, respectively. Due to the quality of the data, we were not able to well constrain the sky-projected obliquity for HAT-P-26b, although a prograde orbit is favoured. The stellar activity of HAT-P-21 indicates a rotation period of 15.88 days, which allowed us to determine its true misalignment angle (25 degree). Our new analysis of the physical parameters of the five exoplanetary systems returned values compatible with those existing in the literature. Using TESS and the available transit light curves, we reviewed the orbital ephemeris for the five systems and confirmed that the HAT-P-26 system shows transit timing variations, which may tentatively be attributed to the presence of a third body.

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arXiv2022

Twenty-year monitoring of the surface magnetic fields of chemically peculiar stars

Magnetic chemically peculiar stars of the main sequence can present rotational periods as long as many decades. Here we report the results of an observational campaign started in 2001 aimed at establishing these very long periods from the variability of the integrated magnetic field modulus, the so-called surface magnetic field $B_s$, as measured from the Zeeman splitting of the Fe{\sc ii}\,6149.258\,Å spectral line. Thirty-six stars have been monitored with various high-resolution spectrographs at different telescopes, totalling 412 newly collected spectra. To improve the phase coverage, we have also exploited all public archives containing high-resolution spectra, many not yet published. On the basis of these new $B_s$ variability curves, we 1) confirm or revisit the periods of 24 stars, 2) extend the lower limits to the periods of HD\,55719 ($P > 38$\,yr), HD\,165474 ($P > 27$\,yr), HD\,177765 ($P > 37$\,yr), 3) establish for the first time the periods of HD\,29578 ($P = 10.95$\,yr), HD\,47103 ($P = 17.683$\,d), HD\,150562 ($P = 5.7$\,yr), HD\,216018 ($P = 34.044$\,d), and 4) set lower limits to the periods of HD\,75445 ($P >> 14$\,yr), HD\,110066 ($P >> 29$\,yr), HD\,116114 ($P > 48$\,yr), and HD\,137949 ($P > 27$\,yr). As to $γ$\,Equ, whose period must exceed 90 years, we point out a clear decrease in the field modulus, the maximum of which coincides within the uncertainties with the minimum of the variation in the integrated longitudinal field.

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arXiv2022

The GAPS Programme at TNG XXXVIII. Five molecules in the atmosphere of the warm giant planet WASP-69b detected at high spectral resolution

The field of exo-atmospheric characterisation is progressing at an extraordinary pace. Atmospheric observations are now available for tens of exoplanets, mainly hot and warm inflated gas giants, and new molecular species continue to be detected revealing a richer atmospheric composition than previously expected. Thanks to its warm equilibrium temperature (963$\pm$18~K) and low-density (0.219$\pm$0.031~g cm$^{-3}$), the close-in gas giant WASP-69b represents a golden target for atmospheric characterization. With the aim of searching for molecules in the atmosphere of WASP-69b and investigating its properties, we performed high-resolution transmission spectroscopy with the GIANO-B near-infrared spectrograph at the Telescopio Nazionale Galileo. We observed three transit events of WASP-69b. During a transit, the planetary lines are Doppler-shifted due to the large change in the planet's radial velocity, allowing us to separate the planetary signal from the quasi-stationary telluric and stellar spectrum. Considering the three nights together, we report the detection of CH$_4$, NH$_3$, CO, C$_2$H$_2$, and H$_2$O, at more than $3.3σ$ level. We did not identify the presence of HCN and CO$_2$ with confidence level higher than 3$σ$. This is the first time that five molecules are simultaneously detected in the atmosphere of a warm giant planet. These results suggest that the atmosphere of WASP-69b is possibly carbon-rich and characterised by the presence of disequilibrium chemistry.

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arXiv2022

The GAPS Programme at TNG XL: A puffy and warm Neptune-sized planet and an outer Neptune-mass candidate orbiting the solar-type star TOI-1422

We investigate the exoplanet candidate TOI-1422b, which was discovered by the TESS space telescope around the high proper-motion G2V star TOI-1422 ($V=10.6$ mag), 155pc away, with the primary goal of confirming its planetary nature and characterising its properties. We monitored TOI-1422 with the HARPS-N spectrograph for 1.5 years to precisely quantify its radial velocity variation. The radial velocity measurements are analyzed jointly with TESS photometry and we also check for blended companions through high-spatial resolution images using the AstraLux instrument. We estimate that the parent star has a radius and a mass of $R^*=1.019_{-0.013}^{+0.014} R_{\odot}$, $M^*=0.981_{-0.065}^{+0.062} M_{\odot}$, respectively. Our analysis confirms the planetary nature of TOI-1422b and also suggests the presence of a Neptune-mass planet on a more distant orbit, the candidate TOI-1422c, which is not detected in TESS light curves. The inner planet, TOI-1422b, orbits on a period $P_{\rm b}=12.9972\pm0.0006$ days and has an equilibrium temperature $T_{\rm eq, b}=867\pm17$ K. With a radius of $R_{\rm b}=3.96^{+0.13}_{-0.11} R_{\oplus}$, a mass of $M_{\rm b}=9.0^{+2.3}_{-2.0} M_{\oplus}$ and, consequently, a density of $ρ_{\rm b}=0.795^{+0.290}_{-0.235}$ g cm$^{-3}$, it can be considered a warm Neptune-size planet. Compared to other exoplanets of similar mass range, TOI-1422b is among the most inflated ones and we expect this planet to have an extensive gaseous envelope that surrounds a core with a mass fraction around $10\%-25\%$ of the total mass of the planet. The outer non-transiting planet candidate, TOI-1422c, has an orbital period of $P_{\rm c}=29.29^{+0.21}_{-0.20}$ days, a minimum mass, $M_{\rm c}\sin{i}$, of $11.1^{+2.6}_{-2.3} M_{\oplus}$, an equilibrium temperature of $T_{\rm eq, c}=661\pm13$ K and, therefore, if confirmed, it could be considered as another warm Neptune.

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arXiv2022

The GAPS programme at TNG XXXIV. Activity-rotation, flux-flux relationships, and active region evolution through stellar age

Active region evolution plays an important role in the generation and variability of magnetic fields on the surface of lower main-sequence stars. However, determining the lifetime of active region growth and decay as well as their evolution is a complex task. We aim to test whether the lifetime for active region evolution shows any dependency on the stellar parameters. We identify a sample of stars with well-defined ages via their kinematics. We made use of high-resolution spectra to compute rotational velocities, activity levels, and emission excesses. We use these data to revisit the activity-rotation-age relationship. The time-series of the main optical activity indicators were analysed together with the available photometry by using Gaussian processes to model the stellar activity of these stars. Autocorrelation functions of the available photometry were also analysed. We use the derived lifetimes for active region evolution to search for correlations with the stellar age, the spectral type, and the level of activity. We also use the pooled variance technique to characterise the activity behaviour of our targets. Our analysis confirms the decline of activity and rotation as the star ages. We also confirm that the rotation rate decays with age more slowly for cooler stars and that, for a given age, cooler stars show higher levels of activity. We show that F- and G-type young stars also depart from the inactive stars in the flux-flux relationship. The gaussian process analysis of the different activity indicators does not seem to provide any useful information on active region's lifetime and evolution. On the other hand, active region's lifetimes derived from the light-curve analysis might correlate with the stellar age and temperature. Although we caution the small number statistics, our results suggest that active regions seem to live longer on younger, cooler, and more active stars.

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arXiv2022

The GAPS Programme with HARPS-N at TNG. XXXVII. A precise density measurement of the young ultra-short period planet TOI-1807 b

Great strides have been made in recent years in the understanding of the mechanisms involved in the formation and evolution of planetary systems; despite this, many observational facts still do not have an explanation. A great contribution to the study of planetary formation processes comes from the study of young, low-mass planets, with short orbital periods. In the last years, the TESS satellite has identified many planets of this kind, and their characterization is mandatory to understand how they formed and evolved. Within the framework of the GAPS project, we performed the validation and characterization of the ultra-short period planet (USPP) TOI-1807b, orbiting its young host star BD+39 2643 (~300 Myr) in only 13 hours. This is the youngest USPP discovered so far. Thanks to a joint modeling of the stellar activity and planetary signals in the TESS light curve and in HARPS-N radial-velocity measurements, combined with accurate estimation of stellar parameters, we validated the planetary nature of TOI-1807b and measured its orbital and physical parameters. By using astrometric, photometric, and spectroscopic observations we found that BD+39 2643 is a young, active K dwarf star, member of a 300+/-80 Myr old moving group and that it rotates in Prot=8.8+/-0.1 days. This star hosts an USPP with an orbital period of only P_b=0.54937+/-0.00001 d. Thanks to the exquisite photometric and spectroscopic series, and the accurate information on the stellar activity, we measured both the radius and the mass of TOI-1807b with high precision, obtaining R_b=1.37+/-0.09 R_Earth and M_b=2.57+/-0.50 M_Earth. These planet parameters correspond to a rocky planet with an Earth-like density and no extended H/He envelope. From the analysis of the age-R_P distribution for planets with well measured ages, we inferred that TOI-1807b may have already lost a large part of its atmosphere during its 300 Myr life.

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arXiv2022

The GAPS Programme with HARPS-N at TNG. XXXV. Fundamental properties of transiting exoplanet host stars

Exoplanetary properties depend on stellar properties: to know the planet with accuracy and precision it is necessary to know the star as accurately and precisely as possible. Our immediate aim is to characterize in a homogeneous and accurate way a sample of 27 transiting planet-hosting stars observed within the GAPS program. We determined stellar parameters (effective temperature, surface gravity, rotational velocity) and abundances of 26 elements (Li,C,N,O,Na,Mg,Al,Si,S,Ca,Sc,Ti,V,Cr,Fe,Mn,Co,Ni,Cu,Zn,Y,Zr,Ba,La,Nd,Eu). Our study is based on high-resolution HARPS-N@TNG and FEROS@ESO spectra and uniform techniques. We derived kinematic properties from Gaia data and estimated for the first time in exoplanet host stars ages using elemental ratios as chemical clocks. Teff of our stars is of 4400-6700 K, while [Fe/H] is within -0.3 and 0.4 dex. Lithium is present in 7 stars. [X/H] and [X/Fe] abundances vs [Fe/H] are consistent with the Galactic Chemical Evolution. The dependence of [X/Fe] with the condensation temperature is critically analyzed with respect to stellar and kinematic properties. All targets with measured C and O abundances show C/O<0.8, compatible with Si present in rock-forming minerals. Most of targets show 1.0<Mg/Si<1.5, compatible with Mg distributed between olivine and pyroxene. HAT-P-26, the target hosting the lowest-mass planet, shows the highest Mg/Si ratio. From our chemo-dinamical analysis we find agreement between ages and position within the Galactic disk. We note a tendency for higher density planets to be around metal-rich stars and hints of higher stellar abundances of some volatiles for lower mass planets. We cannot exclude that part of our results could be also related to the location of the stars within the Galactic disk. We trace the planetary migration scenario from the composition of the planets related to the chemical composition of the hosting stars

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arXiv2022

Multi-Mask Least-Squares Deconvolution: Extracting RVs using tailored masks

To push the radial velocity (RV) exoplanet detection threshold, it is crucial to find more reliable radial velocity extraction methods. The Least-Squares Deconvolution (LSD) technique has been used to infer the stellar magnetic flux from spectropolarimetric data for the past two decades. It relies on the assumption that stellar absorption lines are similar in shape. Although this assumption is simplistic, LSD provides a good model for intensity spectra and likewise an estimate for their Doppler shift. We present the Multi-Mask Least-Squares Deconvolution (MM-LSD) RV extraction pipeline which extracts the radial velocity from two-dimensional echelle-order spectra using LSD with multiple tailored masks after continuum normalisation and telluric absorption line correction. The flexibility of LSD allows to exclude spectral lines or pixels at will, providing a means to exclude variable lines or pixels affected by instrumental problems. The MM-LSD pipeline was tested on HARPS-N data for the Sun and selected well-observed stars with 5.7 < Vmag < 12.6. For FGK-type stars with median signal-to-noise above 100, the pipeline delivered RV time series with on average 12 per cent lower scatter as compared to the HARPS-N RV extraction pipeline based on the Cross-Correlation Function technique. The MM-LSD pipeline may be used as a standalone RV code, or modified and extended to extract a proxy for the magnetic field strength.

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