Search

This paper reports on the detailed characterisation of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved ($\log g=4.17$), iron-poor ([Fe/H]$=-0.46$), but alpha-enhanced ([$\alpha$/Fe]$=0.27$), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT shows that the transiting planet, K2-111b, orbits with a period $P_b=5.3518\pm0.0004$ d, and has a planet radius of $1.82^{+0.11}_{-0.09}$ R$_\oplus$ and a mass of $5.29^{+0.76}_{-0.77}$ M$_\oplus$, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111c, with an orbital period of $15.6785\pm 0.0064$ days, orbiting in near-3:1 mean-motion resonance with the transiting planet, and a minimum planet mass of $11.3\pm1.1$ M$_\oplus$. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters., Comment: Accepted for publication in MNRAS on 28 Sept 2020. Paper is 18 pages with an additional 12 pages of supplementary material. Data is available at https://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/MNRAS/499/5004

Radial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the Solar System. Kepler-102, which consists of 5 tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using radial velocities. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets; however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and TNG/HARPS-N and modeled Kepler-102's activity using quasi-periodic Gaussian Process Regression. For Kepler-102d, we report a mass upper limit of M$_{d} < $5.3 M$_{\oplus}$ [95\% confidence], a best-fit mass of M$_{d}$=2.5 $\pm$ 1.4 M$_{\oplus}$, and a density of $\rho_{d}$=5.6 $\pm$ 3.2 g/cm$^{3}$ which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a mass of M$_{e}$=4.7 $\pm$ 1.7 M$_{\oplus}$ and a density of $\rho_{e}$=1.8 $\pm$ 0.7 g/cm$^{3}$. These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2-4% of the planet mass and 16-50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors., Comment: Accepted to AJ 11/08/2022

GIARPS (GIAno & haRPS) is an observing mode that allows having on the same focal station of the Telescopio Nazionale Galileo (TNG) both the high-resolution spectrographs, HARPS–N (visible, VIS) and GIANO–B (near-Infrared, NIR), working simultaneously. To date, GIARPS is the first and unique worldwide instrument providing cross-dispersed echelle spectroscopy at R= 50,000 in the NIR and 115,000 in the VIS over a wide spectral range (0.383−2.45 μm) in a single exposure. GIARPS is online since 2017 and it is used in a wide range of science cases, especially for the search of exoplanets around young and active stars and the characterization of their atmosphere. In the next future, it will be equipped with NIR absorbing cells to obtain high precision radial velocity (RV). Furthermore, a solar telescope (LOCNES, D=10 cm) will allow the use of GIANO-B to study NIR spectra of the Sun-like-a-star to have more hints on the influence of activity on RV and transmission spectroscopy. 1. GIARPS GIARPS (Claudi et al 2017) is a TNG observing allowing the simultaneous use of the HARPS-N and GIANO-B spectrographs, exploiting a wide wavelength range (0.383 - 2.45 µm) with high-resolution (115,000 in the visible, 50,000 in the NIR) in a single exposure. GIARPS is the result of the refurbishment of GIANO from a fiber-fed spectrograph to GIANO-B directly fed by the same Nasmyth-B focus feeding HARPS-N, by means of a preslit. The light coming from the Nasmyth-B focus meets a dichroic that reflects the visible toward HARPS-N and transmits the NIR to GIANO-B. The dichroic is mounted on a motorized slide to select the preferred observing mode. GIANO-B dewar is rigidly connected to the fork of the TNG and does not add vibration modes to those generated by the telescope (jitter, tracking etc.). For the time being, GIARPS uses both the instruments for high precision radial velocity measurements exploiting the simultaneous reference technique with HARPS-N (Th–lamps) and GIANO-B (telluric lines) reaching in the NIR about 10 m\s for bright stars (H≤5 mag) and 70 m\s (H~9 mag). In future, it will be equipped with absorption cells (acethylene, ammonia and methane) to reach the better precision of 3 m/s. 2. SCIENTIFIC RESULTS 2.1 EXOPLANETARY SCIENCE In the last few years, several works reported the contribution of GIARPS in the field of the search and characterization of extrasolar planets. The simultaneous RV collection in the VIS and NIR band allows discriminating between planetary and stellar signals, being the latter wavelength-dependent. Carleo et al. (2018) made use of several NIR RVs to rule-out the hot Jupiter around the 150 Myr old star BD+201790. With a similar method, in the framework of the GAPS2 program, Carleo et al. (2020) confirmed the presence of a hot Jupiter around the Hyades member HD285507 and demonstrated that the previously detected RV signal around AD Leo has stellar origin. GIARPS also provides suitable data for the atmospheric characterization of exoplanets. Guilluy et al. (2020) performed high-resolution transmission spectroscopy of the transiting hot Jupiter HD189733b aiming to detect the absorption signal of the helium triplet at 1083.3 nm, an useful diagnostic for extended and escaping atmospheres. They confirmed the result by comparing the helium feature with the one of the Halpha in the VIS to evaluate the stellar activity impact on the planetary absorption. Finally, Baratella et al. (2020) analysed a sample of intermediate-age stars ( 2.2 OTHER SCIENCE Massi et al. (2019) combining GIARPS spectra with the high spatial resolution of GRAVITY, obtained a view of the innermost regions of circumstellar discs in YSOs modelling the accretion and ejection mechanisms. The characterization of the star–disk interaction region of CTT in the Taurus-Auriga star-forming region is the main target of GHOsT project (Giannini et al 2019; Gangi et al. 2020). They analyzed the kinematic statistical properties of the [O I] 630 nm and H2 2.12 μm lines and their mutual relationship. The results suggest that molecular and neutral atomic emission in disk winds originate from regions that might overlap, with the survival of molecular winds in disks depending on the gas exposure to the star irradiation. SPA (Origlia et al 2019) is an ongoing GIARPS large program with the aim to perform an age-resolved chemical map of the solar neighborhood and the Galactic thin disk. More than 500 stars, covering different distances, ages and evolutionary stages, will be observed. Frasca et al. (2019) for the ASCC 123 cluster, and D’Orazi et al. (2020) for Hyades and Praesepe derived the stellar parameters, extinction, radial, and projected rotational velocities, and chemical abundances. They found that Praesepe ([Fe/H]=+0.21±0.01 dex ) is more metal-rich than the Hyades (Δ[Fe/H]=+0.05±0.01 dex). 3. CONCLUSION Since Fall 2017, GIARPS works routinely at the TNG. Thanks to its wide wavelength range it is unique in the northern hemisphere and up to the commissioning of NIRPS at the 3.6m ESO Telescope, the unique in this world. The search for extrasolar planets and the study of stellar populations are the major science cases. Furthermore, the range of GIARPS partially overlap the range of ARIEL suggesting a possible synergy with this space mission dedicated to the study of exoplanetary atmospheres. REFERENCES Baratella et al. 2020, A&A, 640, A123 Carleo et al. 2018, A&A, 613, A50 Carleo et al. 2020, A&A 638, A5 Claudi et al 2017, EPJP, 132, 364 D'Orazi et al., 2020, A&A, 633, A38 Frasca et al 2019, A&A, 632, A16 Gangi et al. 2020, A&A, 634, A32 Giannini et al., 2019, A&A, 631, A44 Guilluy et al. 2020, A&A, 639, A49 Massi et al. 2019 in “JET Simulations, Experiments, and Theory: Ten Years After JETSET. What Is Next?” Ed. C. Sauty, p.133, Doi: K55-7873 Origlia et al., 2019, A&A, 629, A117

Earth-like planets, dark energy and variability of fundamental physical constants can be discovered by observing wavelength shifts in the optical spectra of astronomical objects1–5. These wavelength shifts are so tiny that exquisitely accurate and precise wavelength calibration of astronomical spectrometers is required. Laser frequency combs, broadband spectra of laser lines with absolutely known optical frequencies, are uniquely suited for this purpose6–13, provided their lines are resolved by the spectrometer. Generating such astronomical laser frequency combs (‘astrocombs’) remains challenging. Here, a microphotonic astrocomb is demonstrated via temporal dissipative Kerr solitons14–16 in photonic-chip-based silicon nitride microresonators17, directly providing a spurious-free spectrum of resolvable calibration lines. Sub-harmonically driven by temporally structured light18, the astrocomb is stabilized to a frequency standard, resulting in absolute calibration with a precision of 25 cm s–1 (radial velocity equivalent), relevant for Earth-like planet detection and cosmological research. The microphotonic technology can be extended in spectral span17,19–24, further boosting the calibration precision. A microphotonic astrocomb is demonstrated via temporal dissipative Kerr solitons in photonic-chip-based silicon nitride microresonators with a precision of 25 cm s–1 (radial velocity equivalent), useful for Earth-like planet detection and cosmological research.

The atmospheres of gaseous giant exoplanets orbiting close to their parent stars (hot Jupiters) have been probed for nearly two decades. They allow us to investigate the chemical and physical properties of planetary atmospheres under extreme irradiation conditions. Previous observations of hot Jupiters as they transit in front of their host stars have revealed the frequent presence of water vapour and carbon monoxide in their atmospheres; this has been studied in terms of scaled solar composition under the usual assumption of chemical equilibrium. Both molecules as well as hydrogen cyanide were found in the atmosphere of HD 209458b, a well studied hot Jupiter (with equilibrium temperature around 1,500 kelvin), whereas ammonia was tentatively detected there and subsequently refuted. Here we report observations of HD 209458b that indicate the presence of water (H2O), carbon monoxide (CO), hydrogen cyanide (HCN), methane (CH4), ammonia (NH3) and acetylene (C2H2), with statistical significance of 5.3 to 9.9 standard deviations per molecule. Atmospheric models in radiative and chemical equilibrium that account for the detected species indicate a carbon-rich chemistry with a carbon-to-oxygen ratio close to or greater than 1, higher than the solar value (0.55). According to existing models relating the atmospheric chemistry to planet formation and migration scenarios, this would suggest that HD 209458b formed far from its present location and subsequently migrated inwards. Other hot Jupiters may also show a richer chemistry than has been previously found, which would bring into question the frequently made assumption that they have solar-like and oxygen-rich compositions., Comment: As part of the Springer Nature Content Sharing Initiative, it is possible to access a view-only version of this paper by using the following SharedIt link: https://rdcu.be/cifrz

Funding: A.C.C. acknowledges support from the Science and Technology Facilities Council (STFC) consolidated grant No. ST/R000824/1. Radial velocity (RV) searches for Earth-mass exoplanets in the habitable zone around Sun-like stars are limited by the effects of stellar variability on the host star. In particular, suppression of convective blueshift and brightness inhomogeneities due to photospheric faculae/plage and starspots are the dominant contribution to the variability of such stellar RVs. Gaussian process (GP) regression is a powerful tool for statistically modeling these quasi-periodic variations. We investigate the limits of this technique using 800 days of RVs from the solar telescope on the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph. These data provide a well-sampled time series of stellar RV variations. Into this data set, we inject Keplerian signals with periods between 100 and 500 days and amplitudes between 0.6 and 2.4 m s−1. We use GP regression to fit the resulting RVs and determine the statistical significance of recovered periods and amplitudes. We then generate synthetic RVs with the same covariance properties as the solar data to determine a lower bound on the observational baseline necessary to detect low-mass planets in Venus-like orbits around a Sun-like star. Our simulations show that discovering planets with a larger mass (~0.5 m s−1) using current-generation spectrographs and GP regression will require more than 12 yr of densely sampled RV observations. Furthermore, even with a perfect model of stellar variability, discovering a true exo-Venus (~0.1 m s−1) with current instruments would take over 15 yr. Therefore, next-generation spectrographs and better models of stellar variability are required for detection of such planets. Postprint

Ambrosino, F., et al., Millisecond spinning, low-magnetic-field neutron stars are believed to attain their fast rotation in a 0.1–1-Gyr-long phase during which they accrete matter endowed with angular momentum from a low-mass companion star. Despite extensive searches, coherent periodicities originating from accreting neutron star magnetospheres have been detected only at X-ray energies and in ~10% of the currently known systems. Here we report the detection of optical and ultraviolet coherent pulsations at the X-ray period of the transient low-mass X-ray binary system SAX J1808.4−3658, during an accretion outburst that occurred in August 2019. At the time of the observations, the pulsar was surrounded by an accretion disk, displayed X-ray pulsations and its luminosity was consistent with magnetically funnelled accretion onto the neutron star. Current accretion models fail to account for the luminosity of both optical and ultraviolet pulsations; these are instead more likely to be driven by synchro-curvature radiation in the pulsar magnetosphere or just outside of it. This interpretation would imply that particle acceleration can take place even when mass accretion is going on, and opens up new perspectives in the study of coherent optical/ultraviolet pulsations from fast-spinning accreting neutron stars in low-mass X-ray binary systems., A.M.Z. thanks the HST contact scientist, D. Welty (STScI), for constant support in the observation planning and T. Royle (STScI) for checking the scheduling processes. A.M.Z. thanks A. Riley (STIS Team) for the support in the scientific data analysis. A.M.Z. acknowledges the support of the PHAROS COST Action (CA16214) and A. Ridolfi for his help in data analysis. A.M.Z. would also like to thank G. Benevento for comments on draft. F.C.Z. is supported by a Juan de la Cierva fellowship. S.C. and P.D.A. acknowledge support from ASI grant I/004/11/3. D.d.M., A.P. and L.S. acknowledge financial support from the Italian Space Agency (ASI) and National Institute for Astrophysics (INAF) under agreements ASI-INAF I/037/12/0. L.B., D.d.M., T.D.S., A.P. and L.S. acknowledge financial contributions from ASI-INAF agreement no. 2017-14-H.0, INAF main-stream (principal investigator: T. Belloni; principal investigator: A. De Rosa). D.F.T. acknowledges support from grants PGC2018-095512-B-I00, SGR2017-1383 and AYA2017-92402-EXP. L.B and T.D.S. thank A. Marino for useful discussions and acknowledge financial contributions from the HERMES project financed by the Italian Space Agency (ASI) agreement no. 2016/13 U.O. T.D.S. and L.S. acknowledge the iPeska research grant (principal investigator: A. Possenti) funded under the INAF national call Prin-SKA/CTA approved with the Presidential Decree 70/2016. A.P., F.C.Z., and D.T. acknowledge the International Space Science Institute (ISSI-Beijing), which funded and hosted the international team ‘Understanding and Unifying the Gamma-rays Emitting Scenarios in High Mass and Low Mass X-ray Binaries’.

Using radial velocity measurements from four instruments, we report the mass and density of a $2.043\pm0.069 ~\rm{R}_{\oplus}$ sub-Neptune orbiting the quiet K-dwarf Wolf 503 (HIP 67285). In addition, we present improved orbital and transit parameters by analyzing previously unused short-cadence $K2$ campaign 17 photometry and conduct a joint radial velocity-transit fit to constrain the eccentricity at $0.41\pm0.05$. The addition of a transit observation by $Spitzer$ also allows us to refine the orbital ephemeris in anticipation of further follow-up. Our mass determination, $6.26^{+0.69}_{-0.70}~\rm{M}_{\odot}$, in combination with the updated radius measurements, gives Wolf 503 b a bulk density of $\rho = 2.92\pm ^{+0.50}_{-0.44}$ $\rm{g}~\rm{cm}^{-3}$. Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial $\rm{H}_2\rm{O}$ mass fraction ($45^{+19.12}_{-16.15}\%$) or a modest H/He envelope ($0.5\pm0.28\%$). The low H/He mass fraction, along with the old age of Wolf 503 ($11\pm2$ Gyrs), makes this sub-Neptune an opportune subject for testing theories of XUV-driven mass loss while the brightness of its host ($J=8.3$ mag) makes it an attractive target for transmission spectroscopy., Comment: Accepted to ApJ 2021 July 15

LOCNES (LOw-Cost NIR Extended Solar telescope) is a solar telescope installed at the TNG (Telescopio Nazionale Galileo). It feeds the light of the Sun into the NIR spectrograph GIANO-B through a 40-m patch of optical fibers. LOCNES has been designed to obtain high signal-to-noise ratio spectra of the Sun as a star with an accurate wavelength calibration through molecular-band cells. This is an entirely new area of investigation that will provide timely results to improve the search of telluric planets with NIR spectrographs such as iSHELL, CARMENES, and GIANO-B. We will extract several disc-integrated activity indicators and average magnetic field measurements for the Sun in the NIR. Eventually, they will be correlated with both the RV of the Sun-as-a -star and the resolved images of the solar disc in visible and NIR. Such an approach will allow for a better understanding of the origin of activity-induced RV variations in the two spectral domains and will help in improving the techniques for their corrections. In this paper, we outline the science drivers for the LOCNES project and its first commissioning results.

During the last few years we have been working on a modernization plan for the Telescopio Nazionale Galileo (TNG) Control System1,2. On October 2019 we had the opportunity to execute the first step of this process. The telescope was going to be stopped for one month due to M1 mirror being aluminized, so we could change the azimuth control system, that had been thoroughly tested during the summer, with no additional observational time loss. In this paper we present the new control system based on the CompactRIO platform from National Instruments, the switching process between the old and the new control systems, and a performance comparison between them.

Ultra-short period (USP) planets are a class of exoplanets with periods shorter than one day. The origin of this sub-population of planets is still unclear, with different formation scenarios highly dependent on the composition of the USP planets. A better understanding of this class of exoplanets will, therefore, require an increase in the sample of such planets that have accurate and precise masses and radii, which also includes estimates of the level of irradiation and information about possible companions. Here we report a detailed characterization of a USP planet around the solar-type star HD 80653 $\equiv$ EP 251279430 using the K2 light curve and 108 precise radial velocities obtained with the HARPS-N spectrograph, installed on the Telescopio Nazionale Galileo. From the K2 C16 data, we found one super-Earth planet ($R_{b}=1.613\pm0.071 R_{\oplus}$) transiting the star on a short-period orbit ($P_{\rm b}=0.719573\pm0.000021$ d). From our radial velocity measurements, we constrained the mass of HD 80653 b to $M_{b}=5.60\pm0.43 M_{\oplus}$. We also detected a clear long-term trend in the radial velocity data. We derived the fundamental stellar parameters and determined a radius of $R_{\star}=1.22\pm0.01 R_{\odot}$ and mass of $M_{\star}=1.18\pm0.04 M_{\odot}$, suggesting that HD 80653, has an age of $2.7\pm1.2$ Gyr. The bulk density ($\rho_{b} = 7.4 \pm 1.1$ g cm$^{-3}$) of the planet is consistent with an Earth-like composition of rock and iron with no thick atmosphere. Our analysis of the K2 photometry also suggests hints of a shallow secondary eclipse with a depth of 8.1$\pm$3.7 ppm. Flux variations along the orbital phase are consistent with zero. The most important contribution might come from the day-side thermal emission from the surface of the planet at $T\sim3480$ K., Comment: 15 pages, 12 figures; accepted by A&A

Exoplanets orbiting very close to their host star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (HeI) triplet at 1083.3nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmosphere. We perform high-resolution transmission spectroscopy of the transiting hot Jupiter HD189733b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo, taking advantage of the simultaneous optical+near infrared spectral coverage to detect HeI in the planet's extended atmosphere and to gauge the impact of stellar magnetic activity on the planetary absorption signal. Observations were performed during five transit events of HD189733b. By comparison of the in- and out-of-transit GIANO-B observations we compute high-resolution transmission spectra, on which we perform equivalent width measurements and light-curves analyses to gauge the excess in-transit absorption in the HeI triplet. We detect an absorption signal during all five transits. The mean in-transit absorption depth amounts to 0.75+/-0.03%. We detect night-to-night variations in the HeI absorption signal likely due to the transit events occurring in presence of stellar surface inhomogeneities. We evaluate the impact of stellar-activity pseudo-signals on the true planetary absorption using a comparative analysis of the HeI and the H$\alpha$ lines. We interpret the time-series of the HeI absorption lines in the three nights not affected by stellar contamination -exhibiting a mean in-transit absorption depth of 0.77+/-0.04%- using a 3-d atmospheric code. Our simulations suggest that the helium layers only fill part of the Roche lobe. Observations can be explained with a thermosphere heated to $\sim$12000 K, expanding up to $\sim$1.2 planetary radii, and losing $\sim$1 g/s of metastable helium., Comment: 17 pages, 17 figures, accepted for publication in A&A

Exoplanet detection with precise radial velocity (RV) observations is currently limited by spurious RV signals introduced by stellar activity. We show that machine learning techniques such as linear regression and neural networks can effectively remove the activity signals (due to starspots/faculae) from RV observations. Previous efforts focused on carefully filtering out activity signals in time using modeling techniques like Gaussian Process regression (e.g. Haywood et al. 2014). Instead, we systematically remove activity signals using only changes to the average shape of spectral lines, and no information about when the observations were collected. We trained our machine learning models on both simulated data (generated with the SOAP 2.0 software; Dumusque et al. 2014) and observations of the Sun from the HARPS-N Solar Telescope (Dumusque et al. 2015; Phillips et al. 2016; Collier Cameron et al. 2019). We find that these techniques can predict and remove stellar activity from both simulated data (improving RV scatter from 82 cm/s to 3 cm/s) and from more than 600 real observations taken nearly daily over three years with the HARPS-N Solar Telescope (improving the RV scatter from 1.753 m/s to 1.039 m/s, a factor of ~ 1.7 improvement). In the future, these or similar techniques could remove activity signals from observations of stars outside our solar system and eventually help detect habitable-zone Earth-mass exoplanets around Sun-like stars., Comment: 28 pages, 14 figures, Accepted for publication in the Astronomical Journal

Stellar activity is the major roadblock on the path to finding true Earth-analogue planets with the Doppler technique. Thus, identifying new indicators that better trace magnetic activity (i.e. faculae and spots) is crucial to aid in disentangling these signals from that of a planet's Doppler wobble. In this work, we investigate activity related features as seen in disk-integrated spectra from the HARPS-N solar telescope. We divide high-activity spectral echelle orders by low-activity master templates (as defined using both log R'HK and images from the Solar Dynamics Observatory, SDO), creating "relative spectra". With resolved images of the surface of the Sun (via SDO), the faculae and spot filling factors can be calculated, giving a measure of activity independent of, and in addition to, log R'HK. We find pseudo-emission (and pseudo-absorption) features in the relative spectra that are similar to those reported in our previous work on alpha Cen B. In alpha Cen B, the features are shown to correlate better to changes in faculae filling factor than spot filling factor. In this work we more confidently identify changes in faculae coverage of the visible hemisphere of the Sun as the source of features produced in the relative spectra. Finally, we produce trailed spectra to observe the RV component of the features, which show that the features move in a redward direction as one would expect when tracking active regions rotating on the surface of a star., Comment: 13 pages, 10 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

Laser frequency combs (LFC) have been shown to provide exquisite precision that can be used in astronomical spectrograph calibration [1–5], for research fields such as exoplanets, cosmology and fundamental physics.

The quest for extrasolar planets and their characterisation as well as studies of fundamental physics on cosmological scales rely on capabilities of high-resolution astronomical spectroscopy. A central requirement is a precise wavelength calibration of astronomical spectrographs allowing for extraction of subtle wavelength shifts from the spectra of stars and quasars. Here, we present an all-fibre, 400 nm wide near-infrared frequency comb based on electro-optic modulation with 14.5 GHz comb line spacing. Tests on the high-resolution, near-infrared spectrometer GIANO-B show a photon-noise limited calibration precision of

We present confirmation of the planetary nature of PH-2b, as well as the first mass estimates for the two planets in the Kepler-103 system. PH-2b and Kepler-103c are both long-period and transiting, a sparsely-populated category of exoplanet. We use {\it Kepler} light-curve data to estimate a radius, and then use HARPS-N radial velocities to determine the semi-amplitude of the stellar reflex motion and, hence, the planet mass. For PH-2b we recover a 3.5-$\sigma$ mass estimate of $M_p = 109^{+30}_{-32}$ M$_\oplus$ and a radius of $R_p = 9.49\pm0.16$ R$_\oplus$. This means that PH-2b has a Saturn-like bulk density and is the only planet of this type with an orbital period $P > 200$ days that orbits a single star. We find that Kepler-103b has a mass of $M_{\text{p,b}} = 11.7^{+4.31}_{-4.72}$ M$_{\oplus}$ and Kepler-103c has a mass of $M_{\text{p,c}} = 58.5^{+11.2}_{-11.4}$ M$_{\oplus}$. These are 2.5$\sigma$ and 5$\sigma$ results, respectively. With radii of $R_{\text{p,b}} = 3.49^{+0.06}_{-0.05}$ R$_\oplus$, and $R_{\text{p,c}} = 5.45^{+0.18}_{-0.17}$ R$_\oplus$, these results suggest that Kepler-103b has a Neptune-like density, while Kepler-103c is one of the highest density planets with a period $P > 100$ days. By providing high-precision estimates for the masses of the long-period, intermediate-mass planets PH-2b and Kepler-103c, we increase the sample of long-period planets with known masses and radii, which will improve our understanding of the mass-radius relation across the full range of exoplanet masses and radii., The HARPS-N project has been funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard University Origins of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), and the Italian National Astrophysical Institute (INAF), the University of St Andrews, Queen’s University Belfast, and the University of Edinburgh. AM acknowledges support from Senior Kavli Institute Fellowships at the University of Cambridge. ACC acknowledges support from the Science & Technology Facilities Council (STFC) consolidated grant number ST/R000824/1. AV’s and RDH’s work was performed under contract with the California Institute of Technology/Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. LM acknowledges support from PLATO ASI-INAF agreement n.2015-019-R.1-2018 This publication was made possible through the support of a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. This material is partly based upon work supported by the National Aeronautics and Space Administration under grants No. NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program. Some of this work has been carried out in the frame of the National Centre for Competence in Research ‘PlanetS’ supported by the Swiss National Science Foundation (SNSF).

Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally-driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/non-rocky transition in period-radius space. Here we present the confirmation of TOI-1235 b ($P=3.44$ days, $r_p=1.738^{+0.087}_{-0.076}$ R$_{\oplus}$), a planet whose size and period are intermediate between the competing model predictions thus making the system an important test case for emergence models of the rocky/non-rocky transition around early M dwarfs ($R_s=0.630\pm 0.015$ R$_{\odot}$, $M_s=0.640\pm 0.016$ M$_{\odot}$). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial-velocities from HARPS-N and HIRES. We measure a planet mass of $6.91^{+0.75}_{-0.85}$ M$_{\oplus}$, which implies an iron core mass fraction of $20^{+15}_{-12}$% in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like and we constrain a H/He envelope mass fraction to be $, Accepted to The Astronomical Journal. 8 figures & 5 tables. Table 2 is provided in the arXiv source code

Synchronous-driving of nonlinear optical microresonator offers robust, deterministic and ultra- efficient generation of ultra-short temporal soliton pulses as well as high-repetition rate frequency combs. The soliton pulses are all-optically controlled and provide resolvable lines for astronomical spectrometer calibration or optical telecommunications.

The search for telluric extrasolar planets with the Radial Velocity (RV) technique is intrinsically limited by the stellar jitter due to the activity of the star, because stellar surface inhomogeneities, including spots, plages and convective granules, induce perturbations hiding or even mimicking the planetary signal. This kind of noise is poorly understood in all the stars, but the Sun, due to their unresolved surfaces. For these reasons, the effects of the surface inhomogeneities on the measurement of the RV are very difficult to characterize. On the other hand, a better knowledge of these phenomena can allow us a step forward in our understanding of solar and stellar RV noise sources. This will allow to develop more tools for an optimal activity correction leading to more precise stellar RVs. Due to the high spatial resolution with which the Sun is observed, this noise is well known for it. Despite this, a link is lacking between the single observed photospheric phenomena and the behavior of the Sun observed as a star. LOCNES (Low Cost NIR Extended Solar Telescope) will allow to gather time series of RVs in order to disentangle the different contributions to the stellar (i.e., suns) RV jitter. Since July 2015, a Low Cost Solar Telescope (LCST) has been installed outside the TNG dome to feed solar light to the HARPS-N spectrograph (0.38-0.69 μm; R=115000). The refurbishment of the Near Infrared (NIR) High Resolution Spectrograph GIANO (now GIANO-B) and the new observing mode GIARPS at TNG (simultaneous observations in visible with HARPS-N and in NIR with GIANO-B) is a unique opportunity to extend the wavelength range up to 2.4 μm for measuring the RV time series of the Sun as a star. This paper outlines the LOCNES project and its scientific drivers.

We studied the polarised spectrum of the post-AGB binary system 89\,Herculis on the basis of data collected with the high resolution \emph{Catania Astrophysical Observatory Spectropolarimeter}, \emph{HArps-North POlarimeter} and \emph{Echelle SpectroPolarimetric Device for the Observation of Stars}. We find the existence of linear polarisation in the strongest metal lines in absorption and with low excitation potentials. Signals are characterized by complex Q and U morphologies varying with the orbital period. As possible origin of this "Second Solar Spectrum"-like behaviour, we rule out magnetic fields, continuum depolarisation due pulsations and hot spots. { The linear polarisation we detected also in the Ca{\sc ii}\,8662\AA\, line is a clear evidence of optical pumping polarisation and it rules out the scattering polarisation from free electrons of the circumbinary environment.} In the framework of optical pumping due to the secondary star, the observed periodic properties of the spectral line polarisation can be justied by two jets, flow velocity of few tens of km\,s$^{-1}$, at the basis of that hour-glass structure characterising 89\,Herculis. We also discovered linear polarisation across the emission profile of metal lines. Numerical simulations show that these polarised profiles could be formed in an undisrupted circumbinary disk rotating at $\le$10 km\,s$^{-1}$ and whose orientation in the sky is in agreement with optical and radio interferometric results. We conclude that the study of those aspherical enevlopes, whose origin is not yet completely understood, of PNe and already present in the post-AGB's, can benefit of high resolution spectropolarimetry and that this technique can shape envelopes still too far for interferometry., Comment: Submitted to MNRAS

GIARPS (GIAno & haRPS – n) is a project devoted to have on the same focal station of the Tele-scopio Nazionale Galileo (TNG) both the high resolution spectrographs HARPS-N in the visible and GIANO in the NIR working simultaneously. This allows to have such a unique facility in the north hemisphere on duty at the TNG that could be considered the first and unique worldwide instrument providing cross-dispersed echelle spectroscopy at a resolution of 50,000 and over a wide spectral range (0.390−2.45μm) in a single exposure. The science case is very broad, given the versatility of such an instrument and the large wavelength range. A number of outstanding science cases encompassing mainly extra-solar planet science starting from rocky planet search and hot Jupiters atmosphere characterization can be considered. Furthermore both instruments can measure high precision radial velocity by means the simultaneous calibration technique (HARPS – N) and absorption cell technique (GIANO) in a single exposure. Other science cases are also possible. Young stars and proto-planetary disks, cool stars and stellar populations, moving minor bodies in the solar system, bursting young stellar objects, cataclysmic variables and X–ray binary transients in our Galaxy, supernovae up to gamma-ray bursts in the very distant and young Universe, can take advantage of the unicity of this facility both in terms of contemporaneous wide wavelength range and high resolution spectroscopy.

Since 2012, thanks to the installation of the high-resolution echelle spectrograph in the optical range HARPS-N, the Italian telescope TNG (La Palma) became one of the key facilities for the study of the extrasolar planets. In 2014 TNG also offered GIANO to the scientific community, providing a near-infrared (NIR) cross-dispersed echelle spectroscopy covering 0.97-2.45μm at a resolution of 50000. GIANO, although designed for direct light-feed from the telescope at the Nasmyth-B focus, was provisionally mounted on the rotating building and connected via fibers to only available interface at the Nasmyth-A focal plane. The synergy between these two instruments is particularly appealing for a wide range of science cases, especially for the search of exoplanets around young and active stars and the characterisation of their atmosphere. Through the funding scheme "WOW" (a Way to Others Worlds), the Italian National Institute for Astrophysics (INAF) proposed to position GIANO at the focal station for which it was originally designed and the simultaneous use of these spectrographs with the aim to achieve high-resolution spectroscopy in a wide wavelength range (0.383-2.45μm) obtained in a single exposure, giving rise to the project called GIARPS (GIANO-B & HARPS-N). Because of its characteristics, GIARPS can be considered the first and unique worldwide instrument providing not only high resolution in a large wavelength band, but also a high-precision radial velocity measurement both in the visible and in the NIR arm, since in the next future GIANO-B will be equipped with gas absorption cells.

PSR J1023+0038 is the first millisecond pulsar discovered to pulsate in the visible band; such a detection took place when the pulsar was surrounded by an accretion disk and also showed X-ray pulsations. We report on the first high time resolution observational campaign of this transitional pulsar in the disk state, using simultaneous observations in the optical (TNG, NOT, TJO), X-ray (XMM-Newton, NuSTAR, NICER), infrared (GTC) and UV (Swift) bands. Optical and X-ray pulsations were detected simultaneously in the X-ray high intensity mode in which the source spends $\sim$ 70% of the time, and both disappeared in the low mode, indicating a common underlying physical mechanism. In addition, optical and X-ray pulses were emitted within a few km, had similar pulse shape and distribution of the pulsed flux density compatible with a power-law relation $F_{\nu} \propto \nu^{-0.7}$ connecting the optical and the 0.3-45 keV X-ray band. Optical pulses were detected also during flares with a pulsed flux reduced by one third with respect to the high mode; the lack of a simultaneous detection of X-ray pulses is compatible with the lower photon statistics. We show that magnetically channeled accretion of plasma onto the surface of the neutron star cannot account for the optical pulsed luminosity ($\sim 10^{31}$ erg/s). On the other hand, magnetospheric rotation-powered pulsar emission would require an extremely efficient conversion of spin-down power into pulsed optical and X-ray emission. We then propose that optical and X-ray pulses are instead produced by synchrotron emission from the intrabinary shock that forms where a striped pulsar wind meets the accretion disk, within a few light cylinder radii away, $\sim$ 100 km, from the pulsar., Comment: 26 pages, 14 figures, first submitted to ApJ on 2019, January 18

TNG is a 4m class active optics telescope at the Observatory of Roque de Los Muchachos. In the framework of keeping optimum performances during observation and continuous reliability the telescope control system (TCS) of the TNG is going through a deep upgrade after nearly 20 years of service. The original glass encoders and bulb lamp heads are substituted with modern steel scale drums and scanning units. The obsolete electronic racks and computers for the control loops are replaced with modern and compact commercial drivers with a net improvement in the motors torque ripple. In order to minimize the impact on the number of nights lost during the mechanical and electronic changes in the TCS the new TCS is developed and tested in parallel to the existing one and three steps will be taken to achieve the full upgrade. We describe here the second step that affected the main axes of the telescope, AZ and EL.

We present an analysis of the atmospheric content of aerosols measured at Observatorio del Roque de los Muchachos (ORM; Canary Islands). Using a laser diode particle counter located at the Telescopio Nazionale Galileo (TNG) we have detected particles of 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 um size. The seasonal behavior of the dust content in the atmosphere is calculated. The Spring has been found to be dustier than the Summer, but dusty conditions may also occur in Winter. A method to estimate the contribution of the aerosols emissivity to the sky brightness in the near-infrared (NIR) is presented. The contribution of dust emission to the sky background in the NIR has been found to be negligible comparable to the airglow, with a maximum contribution of about 8-10% in the Ks band in the dusty days.

Aims: The Scutum complex in 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 five red supergiants in the young Scutum cluster RSGC3. Results: Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to measure several tens of atomic and molecular lines that were suitable for determining chemical abundances. By means of spectral synthesis and line equivalent width measurements, we obtained abundances of Fe and iron-peak elements such as Ni, Cr, and Cu, alpha (O, Mg, Si, Ca, Ti), other light elements (C, N, F, Na, Al, and Sc), and some s-process elements (Y, Sr). We found average half-solar iron abundances and solar-scaled [X/Fe] abundance patterns for most of the elements, consistent with a thin-disk chemistry. We found depletion of [C/Fe] and enhancement of [N/Fe], consistent with standard CN burning, and low 12C /13C abundance ratios (between 9 and 11), which require extra-mixing processes in the stellar interiors during the post-main sequence evolution. We also found local standard of rest VLSR = 106 km s-1 and heliocentric Vhel = 90 km s-1 radial velocities with a dispersion of 2.3 km s-1. Conclusions: The inferred radial velocities, abundances, and abundance patterns of RSGC3 are very similar to those previously measured in the other two young clusters of the Scutum complex, RSGC1 and RSGC2, suggesting a common kinematics and chemistry within the Scutum complex.

Multi-Object Spectrographs (MOS) are the major instruments for studying primary galaxies and remote and faint objects. Current object selection systems are limited and/or difficult to implement in next generation MOS for space and groundbased telescopes. A promising solution is the use of MOEMS devices such as micromirror arrays which allow the remote control of the multi-slit configuration in real time. We are developing a Digital Micromirror Device (DMD) - based spectrograph demonstrator called BATMAN. We want to access the largest FOV with the highest contrast. The selected component is a DMD chip from Texas Instruments in 2048 x 1080 mirrors format, with a pitch of 13.68μm. Our optical design is an all-reflective spectrograph design with F/4 on the DMD component. This demonstrator permits the study of key parameters such as throughput, contrast and ability to remove unwanted sources in the FOV (background, spoiler sources), PSF effect, new observational modes. This study will be conducted in the visible with possible extension in the IR. A breadboard on an optical bench, ROBIN, has been developed for a preliminary determination of these parameters. The demonstrator on the sky is then of prime importance for characterizing the actual performance of this new family of instruments, as well as investigating the operational procedures on astronomical objects. BATMAN will be placed on the Nasmyth focus of Telescopio Nazionale Galileo (TNG) during next year.

The Telescopio Nazionale Galileo (TNG)[9] hosts, starting in April 2012, the visible spectrograph HARPS-N. It is based on the design of its predecessor working at ESO's 3.6m telescope, achieving unprecedented results on radial velocity measurements of extrasolar planetary systems. The spectrograph's ultra-stable environment, in a temperature-controlled vacuum chamber, will allow measurements under 1 m/s which will enable the characterization of rocky, Earth-like planets. Enhancements from the original HARPS include better scrambling using octagonal section fibers with a shorter length, as well as a native tip-tilt system to increase image sharpness, and an integrated pipeline providing a complete set of parameters. Observations in the Kepler field will be the main goal of HARPS-N, and a substantial fraction of TNG observing time will be devoted to this follow-up. The operation process of the observatory has been updated, from scheduling constraints to telescope control system. Here we describe the entire instrument, along with the results from the first technical commissioning.

The performances of a modern telescope and its safety are dependent on the presence of atmospheric dust. The TNG telescope at ORM (Canary Islands) was one of the first sites monitored on a continuous basis by an automatic dust monitor. This paper presents the analysis of about 10 years of atmospheric dust content collected at the ORM using the TNG facilities. We have detected particles of 0.3, 0.5, 1.0, 3.0, 5.0 and 10.0 μm size. In this study particles of 0.5 and 5.0 μm measured at Paranal Observatory (Chile) are also compared to those similar at TNG. The seasonal behavior of the particles content in the atmosphere is compared between the two sites. The contribution of the dust emissivity to the sky brightness in the NIR is computed for the first time. To complete this study we defined the aerosol mass critical limit to be used as a safety limit for the observations. We found a limit of 12 μg m -3 as total mass of (0.5 + 5.0) μm particles.

We present an analysis of the atmospheric dust content and its effects on astronomical observations at Observatorio del Roque de Los Muchachos (ORM), in La Palma Island (Canaries). We have detected atmospheric particles having size 0.3, 0.5, 1.0 and 5.0 μm, closer to Telescopio Nazionale Galileo (TNG) dome and using a power law we have derived the content of 10.0 µm particles. Using a model we have calculated the contribute of aerosols to astronomical extinction in B, V and I from a 5 years series database in two typical conditions: clear and dusty days. A correlation is also analysed comparing the aerosol extinction and total astronomical extinction using the Carlsberg Automatic Meridian Circle (CAMC) extinction database in V. We have estimated that the dust reach an altitude of about 5 km above the sea level during the sand storms. Finally we have concluded that in the visible band extension is dominated by particles at 1.0, 5.0, and 10.0 μm.

Because of the finite speed of light, a laser guide Star that is seen from the side is not exactly a straight line. When such a laser guide star is used to sense tip-tilt with some of the perspective-based techniques that are used to retrieve an absolute tip-tilt laser, such nonstraightness introduces an error. We estimate this effect for various diameters of a laser projector, assuming a Kolmogorov turbulence spectrum and figuring the maximum achievable Strehl ratio. We found that under poor seeing conditions the effect is not negligible and that laser projectors larger than those currently used are required.

The Adaptive Optics Module of the Telescopio Nazionale Galileo (AdOpt@TNG) has enjoyed a huge refurbishment. A new WaveFront Sensing CCD (EEV39 80x80pixels by SciMeasure) has been mounted, allowing for up to 1KHz frame rate. Thanks to the versatility of the pyramid wavefront sensor, the fast changing of the 4x4 and 8x8 pupil sampling has been easily and successfully implemented. A dual pentium processor PC with Real-Time Linux has substituted the old VME as Real Time Computer. The implementation of the new Deformable Mirror by Xinetics will be also discussed. A new Graphical User Interface has been built to allow for user-friendly utilization of the module by astronomers. On-sky observations will be presented in terms of FWHM and Strehl Ratio for different values of guiding star magnitudes and seeing conditions. The encouraging on-sky results and overall system stability pushed to offer AdOpt@TNG to the international astronomical community.

Adaptive Optics Systems for Extremely Large Telescopes (ELT) will need new wavefront sensing concepts to deploy their full capabilities. In this paper we exemplify the necessity of new wavefront sensing ideas by discussing briefly some major problems and present as a possible solution the pseudo infinite guide star sensor (PIGS). A prototype of a PIGS sensor was already built in the laboratory, which could demonstrate its feasibility.

In order to get a better understanding of the optical turbulence at the free atmosphere we present a statistical analysis of the wind and temperature profiles at different heights measured by balloon-born sonde during the years 2003,2004 and until mid 2005, and the stellar image twinkling measurements from a DIMM. The data from the balloon-borne measurements shows the variation of the strength of the jet stream and temperature gradient that are related to formation of turbulent layers in the upper air which contribute to the degradation of the optical images or to laser propagation through the atmosphere. The use of standard radiosonde data compared with the seeing can be used as a tool to define the vertical distribution of the strength of the turbulence in the atmosphere and that will contribute to better optimization of the performance of Adaptative Optics systems.

The Adaptive Optics System of the Galileo Telescope (AdOpt@TNG) is the only adaptive optics system mounted on a telescope which uses a pyramid wavefront snesor and it has already shown on sky its potentiality. Recently AdOpt@TNG has undergone deep changes at the level of its higher orders control system. The CCD and the Real Time Computer (RTC) have been substituted as a whole. Instead of the VME based RTC, due to its frequent breakdowns, a dual pentium processor PC with Real-Time-Linux has been chosen. The WFS CCD, that feeds the images to the RTC, was changed to an off-the-shelf camera system from SciMeasure with an EEV39 80x80 pixels as detector. While the APD based Tip/Tilt loop has shown the quality on the sky at the TNG site and the ability of TNG to take advantage of this quality, up to the diffraction limit, the High-Order system has been fully re-developed and the performance of the closed loop is under evaluation to offer the system with the best performance to the astronomical community.

The next generation ground based telescopes deploy their full potential in terms of resolution only with Adaptive Optics (AO). A limiting factor for such systems is the sky coverage with natural guide stars. A way to overcome this problem is a artificial star, i.e. laser guide star (LGS) generated in the sodium layer of the mesosphere at an height of approximately 90km-100km. Sensing the wave front of such a LGS, whose photons are collected by a next generation ground based telescope up to 100m pupil diameter leads to new problems. They are related to the finite distance of the altitude where the artificial star forms with respect to the telescope entrance pupil. We present a new wave front sensing concept to overcome this problem and we show first results of an open loop experiment done on sky. Measurements have been carried out November 2003 with the Rayleigh laser of the University of Durham at the WHT in La Palma as a result of collaboration between MPIA and the AO group of the University of Durham. The geometry of the LGS created in 4km altitude with respect to the 4m aperture of the WHT scales by a factor 1:25 with a sodium LGS at 100km and a telescope with 100m entrance pupil diameter.

Since summer 2001, dust pollution of the air is regularly measured through a particle counter at the Telescopio Nazionale Galileo (TNG) located at the Roque de los Muchachos Observatory (La Palma - Canary Islands). Canary Islands are normally interested by a dominant atmospheric circulation with NE winds. Depending on their strenght, and their exact direction, winds may bring with themselves small to large amount of dust from the Sahara desert, with important consequences on the transparency of the sky. Meteorological satellites gave us some impressive examples of such these phenomenon. We show here the results of trying a correlation between dust-pollution data and the nightly atmospheric extinction measured at other telescopes. While the transparency is mostly affecting the astronomical work, other effects like changes of air temperature and humidity are clearly visible; for this reason dust-pollution data are also compared with the weather data recorded at the TNG meteo tower.

Since 1999 the National Telescope Galileo (TNG) is offering observative nights to the astronomical community. With the aim of increase the efficiency of the telescope and minimize downtime many changes have been done from the original project. Recently it has been taken the decision to completely renew the electronic hardware and software of the active optics system, essencially based on VMEs and on the obsolete transputers processors. From the optical point of view some important modifications have also been implemented in order to allow the off-axis Shack-Hartmann analisys. Also the CCD cameras and their controllers have been redeveloped and the whole control software has been ported to a new architecture to by-pass the VMEs system and directly interact with the actuators and the CCD controllers.

Since several problems of Laser Guide Stars, like conical anisoplanatism, perspective elongation, etc., scales with the telescope diameter, the use of artificial stars will become more difficult with apertures in the range of ELTs. Problems with Laser Guide Stars are reviewed and a way is shown how to overcome most of these difficulties with the concept of Pseudo Infinity Guide Stars (PIGS). A new kind of wavefront sensor is introduced taking advantage of the concept by the means of two optical devices, a reflecting rod and a mask. We explain this novel wavefront sensor, show results of a laboratory experiment, and conclude in further steps to apply the concept with full MCAO capability.

Layer Oriented represented in the last few years a new and promising aproach to solve the problems related to the limited field of view achieved by classical Adaptive Optics systems. It is basically a different approach to multi conjugate adaptive optics, in which pupil plane wavefront sensors (like the pyramid one) are conjugated to the same altitudes as the deformable mirrors. Each wavefront sensor is independently driving its conjugated deformable mirror thus simplifying strongly the complexity of the wavefront computers used to reconstruct the deformations and drive the mirror themselves, fact that can become very important in the case of extremely large telescopes where the complexity is a serious issue. The fact of using pupil plane wavefront sensors allow for optical co-addition of the light at the level of the detector thus increasing the SNR of the system and permitting the usage of faint stars, improving the efficiency of the wavefront sensor. Furthermore if coupled to the Pyramid wavefront sensor (because of its high sensitivity), this technique is actually peforming a very efficient usage of the light leading to the expectation that, even by using only natural guide stars, a good sky coverage can be achieved, above all in the case of giant telescopes. These are the main reasons for which in the last two years several projects decided to make MCAO systems based on the Layer Oriented technique. This is the case of MAD (an MCAO demonstrator that ESO is building with one wavefront sensing channel based on the Layer Oriented concept) and NIRVANA (an instrument for LBT). Few months ago we built and successfully tested a first prototype of a layer oriented wavefront sensor and experiments and demonstrations on the sky are foreseen even before the effective first light of the above mentioned instruments. The current situation of all these projects is presented, including the extensive laboratory testing and the on-going experiments on the sky.

In order to get first-hand results in the laboratory and possibly on the sky with the Layer-Oriented approach we designed, built, and tested a bread-board for this type of wavefront sensor. This device consists of a single wavefront sensor able to look simultaneously at four references. The positioning of three of the four reference stars with respect to the central one is made by the means of manually adjustable positioning units. A few additional degrees of freedom have been intentionally placed in the system in a way to test the sensitivity of the unit to misplacement and/or misalignment of some optical components. The laboratory set-up includes a crude system to mimic a telecentric F/32 focal plane illuminated by a number of fiber sources that can be placed in several different configurations. Wavefront deformation can be accomplished by placing some fixed deformating plates optically conjugated to several altitudes on the atmosphere. The system is designed in a way to be easily fitted to the existing AdOpt@TNG system, allowing for multiple references, one DM, closed loop operations. Any preliminar result from this activity will be reported. Laboratory experiments includes checking of the theoretical predictions, especially the effectiveness in sensing up to a certain spatial frequency the layers not specifically conjugated to the detector. The results of a demonstrative experiment, showing how the wavefront sensor is able to disentangle layers contribution, are also reported.

In the pyramid wavefront sensor some dynamic range is accomplished by modulating the optical signal across the four faces of the pyramid before the dissection and detection of the light. Although this can be realized in different ways, including systems which do not require any moving part, we question and discuss the real needs for such a modulation. In fact, when the closed-loop performance is not perfect, some residual errors on the wavefront sensor are expected and one should take care to allow for enough dynamic range to get a linear response within such a residual range. However, the non-corrected aberrations themselves can be considered as a form of modulation. Higher order uncompensated residuals are equivalent to a modulation for the lower compensated modes. We present a preliminary study showing that this sort of 'natural' modulation could be, at least under certain conditions, enough to reach comparable results with respect to dynamical modulation during correction, hence rising the question of the need of a modulation in the realization of the pyramid wavefront sensor.

The Adaptive Optics for the Telescopio Nazionale Galileo module (namely AdOpt@TNG) implements the pyramid wavefront sensor as a unique feature. This allows to get valuable information on its performance on the sky. An updated overview of the results obtained so far is shown, including a discussion on the sources of errors in the closed loop operation, distinguishing them between the ones specific of the pyramid wavefront sensor and the one more related to the system as a whole. This system allows also for a number of experiments and check of the sensitivity of such a wavefront sensor, especially in comparison with other types of sensing units. The ways to accomplish such an experiment in a convincing way are shown along with the first results obtained so far. Finally, we describe how and up to which extent a number of practical problems encountered in the near past can be solved implementing the recent new ideas on the pyramid theme, many of which popped up from our "lessons learned".

We describe some novel technical approaches to implement multi-pyramid wavefront sensing, partially extendable to single pyramid and to any MCAO system. First we introduce an achromatic version of the pyramid, which allows for a much better spatial resolution on the pupil and also relaxes the specifications in term of turned edges. Another item that we discuss is the distribution of tolerances in a layer-oriented AO system which makes attractive, at least in some cases, the usage of pairs of lenslet arrays, leaving only the pyramids free to move over the Field of View, hence relaxing the requirements in terms of roll and yaw in their positioning. Then we discuss the effect of pupil distortion occurring in the layers above the ground during the open loop phases of a MCAO system. Finally we discuss a possible usage of the Modulation Transfer Function as a valuable tool to estimate the correction of a certain Zernike polynomial, achievable with a pyramid wavefront sensor. These items are sketched along with a status of their practical implementation and possible future extensions.

The concept of Pyramid Wavefront sensor has been introduced as a more compact and flexible alternative to Shack--Hartmann wavefront sensing. In the past five years, however, such a novel concept promised a much larger sensitivity and an inherent easiness to be implemented in a multiple reference wavefront sensor. AdOptTNG, a natural guide star based adaptive optics module implemented at the 3.5m TNG telescope is equipped with such a sensor. We report here on the updated status, including on-sky experimental verification of various of the several features of such a sensor. We discuss the results obtained, their scalability and the lessons learned in building, aligning and operating it. Some comparison with theoretical and laboratory-based result, is also tentatively reported.

The Galileo Telescope is a Ritchey-Chretienne telescope with an aperture of 3.58 meters and is located in La Palma Island. Since the first light in June 1998, several nights have been used to calibrate and to test the active optics systems, an operation involving also the control and reduction software and the optics of the de-rotator system. At the moment the active optics system routinely works at the beginning of the nights to support both technical and scientific observations. The ultimate tests on the control system are here reported and its performances are analyzed in order to quantify the final optical quality. Also a brief report on the effects of the serrourier temperature is reported. A comparison between Shack-Hartmann analysis performed on the rotator adapter bench and wavefront analysis on the instrument focal plane (at Nasmith station) is also reported. Some images taken in the visible and near infrared ranges during the same night are shown.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The pyramid wavefront sensor is a novel concept device whose features are attractive for adaptive optics for several reasons. We show here the first loop closure of an AO system using this kind of sensor at the focal plane of a 4m-class telescope. One of the critical optical elements of our wavefront sensor is the pyramid that splits the light from the star used for the wavefront correction. This component is essentially a four faces prism having actually a full vertex angle of 7 degrees with specifications on its edges and roof of 4 - 5 microns or better. The best turned edges obtained on the prototypes already built have shown values of the order of 6 microns, with roofs of the same order, not far from the required tolerances. In this article we describe the techniques and the system used for the construction of this optical component and the improvements to the polishing procedure that we plan to adopt in order to increase the quality of its edges and optical surfaces. Pixel processing is suitable to fit with existing Shack-Hartmann systems, making this device an attractive add-on option for existing SH-based AO systems. The plans for future developments in order to firmly establish the performances of the pyramid wavefront sensor are briefed out.

The AdOptTNG module is an adaptive optics facility permanently mounted at the Nasmyth focus of the 4m-class Telescopio Nazionale Galileo (TNG). Its integration on the telescope started in late November 1998 and first-light of the speckle and tip-tilt modes took place shortly after. Both modes have been offered to the astronomical community and turned out to provide performances close to the expectations. Double stars with separation below 0.1 arcsec have been resolved by the speckle facility. Improvement of the Strehl ratio of a factor two and enhancement in the FWHM from 0.65 arcsec to 0.35 arcsec have been obtained on relatively faint reference stars. The high-speed low noise CCD, namely an 80 X 80 pixel read from the four corners, has been mounted and aligned with the Shack-Hartmann wavefront sensor. A Xinetics mirror with 96 actuators has been calibrated against the wavefront sensor with on-board alignment fibers. This has been done using a modal approach and using Singular Value Decomposition in order to get a reliable interaction matrix. Filtering can be modal too, using a default integrative filter coupled with a limited FIR-fashioned technique. Open loop measurements on the sky provide data to establish open loop transfer functions and realistic estimates of limiting magnitude. High-order wavefront correction loop has been successfully tested on the sky. In this paper we give a description of the overall functionality of the module and of the procedure required to acquire targets to be used as reference in the correction. A brief overview of the very first astronomical results obtained so far on angular size and shape measurements of a few asteroids and sub-arcsec imaging of Planetary Nebulae and Herbig Haro objects is also given.