OA@INAF - Istituto Nazionale di Astrofisica
Not a member yet
15494 research outputs found
Sort by
The GAPS Programme at TNG LV. Multiple molecular species in the atmosphere of HAT-P-11 b and review of the HAT-P-11 planetary system
Get PDFThe atmospheric characterisation of hot and warm Neptune-size exoplanets is
challenging due to their small radius and atmospheric scale height. The
warm-Neptune HAT-P-11b is a remarkable target for such characterisation due to
the large brightness of its host star (V=9.46 mag; H=7.13 mag). The aims of
this work are to review the main physical and architectural properties of the
HAT-P-11 planetary system, and to probe the presence of 8 molecular species in
the atmosphere of HAT-P-11b at high spectral resolution in the near-infrared.
The planetary system was reviewed by analysing transits and occultations of
HAT-P-11b from the Kepler data set as well as HIRES at Keck archival
radial-velocity (RV) data. We modelled the latter with Gaussian-process
regression and a combined quasi-periodic and squared-exponential kernel to
account for stellar variations on both (short-term) rotation and (long-term)
activity-cycle timescales. In order to probe the atmospheric composition of
HAT-P-11b, we observed 4 transits of this target with GIANO-B at TNG. We find
that the long-period ( years) RV signal previously attributed to
planet HAT-P-11c is more likely due to the stellar magnetic activity cycle.
Nonetheless, the Hipparcos-Gaia difference in the proper-motion anomaly
suggests that an outer-bound companion might still exist. For HAT-P-11b, we
measure a radius , a mass , and an eccentricity
, in accordance with values in the literature.
Probing its atmosphere, we detect (S/N, significance)
and confirm the presence of (S/N, significance). We
also tentatively detect the signal of (S/N,
significance) and (S/N, significance),
whose presence need to be confirmed by further observations
The tidal deformation and atmosphere of WASP-12 b from its phase curve
Get PDFContext. Ultra-hot Jupiters present a unique opportunity to understand the physics and chemistry of planets, their atmospheres, and interiors at extreme conditions. WASP-12 b stands out as an archetype of this class of exoplanets, with a close-in orbit around its star that results in intense stellar irradiation and tidal effects. Aims. The goals are to measure the planet's tidal deformation, atmospheric properties, and also to refine its orbital decay rate. Methods. We performed comprehensive analyses of the transits, occultations, and phase curves of WASP-12b by combining new CHEOPS observations with previous TESS and Spitzer data. The planet was modeled as a triaxial ellipsoid parameterized by the second-order fluid Love number of the planet, h2, which quantifies its radial deformation and provides insight into the interior structure. Results. We measured the tidal deformation of WASP-12b and estimated a Love number of h2 = 1.55- 0.49+0.45 (at 3.2σ) from its phase curve. We measured occultation depths of 333 ± 24 ppm and 493 ± 29 ppm in the CHEOPS and TESS bands, respectively, while the nightside fluxes are consistent with zero, and also marginal eastward phase offsets. Our modeling of the dayside emission spectrum indicates that CHEOPS and TESS probe similar pressure levels in the atmosphere at a temperature of ~2900 K. We also estimated low geometric albedos of Ag = 0.086 ± 0.017 and Ag = 0.01 ± 0.023 in the CHEOPS and TESS passbands, respectively, suggesting the absence of reflective clouds in the high-temperature dayside of the planet. The CHEOPS occultations do not show strong evidence for variability in the dayside atmosphere of the planet at the median occultation depth precision of 120 ppm attained. Finally, combining the new CHEOPS timings with previous measurements refines the precision of the orbital decay rate by 12% to a value of - 30.23 ± 0.82 ms yr- 1, resulting in a modified stellar tidal quality factor of Q′∗ = 1.70 ± 0.14 × 105. Conclusions. WASP-12 b becomes the second exoplanet, after WASP-103b, for which the Love number has been measured from the effect of tidal deformation in the light curve. However, constraining the core mass fraction of the planet requires measuring h2 with a higher precision. This can be achieved with high signal-to-noise observations with JWST since the phase curve amplitude, and consequently the induced tidal deformation effect, is higher in the infrared
MAGIC detection of GRB 201216C at z = 1.1
Get PDFGamma-ray bursts (GRBs) are explosive transient events occurring at cosmological distances, releasing a large amount of energy as electromagnetic radiation over several energy bands. We report the detection of the long GRB 201216C by the MAGIC telescopes. The source is located at z = 1.1 and thus it is the farthest one detected at very high energies. The emission above 70 GeV of GRB 201216C is modelled together with multiwavelength data within a synchrotron and synchrotron self-Compton (SSC) scenario. We find that SSC can explain the broad-band data well from the optical to the very-high-energy band. For the late-time radio data, a different component is needed to account for the observed emission. Differently from previous GRBs detected in the very-high-energy range, the model for GRB 201216C strongly favours a wind-like medium. The model parameters have values similar to those found in past studies of the afterglows of GRBs detected up to GeV energies
CUBES, the Cassegrain U-Band Efficient Spectrograph: towards final design review
Get PDFIn the era of Extremely Large Telescopes, the current generation of 8-10m facilities are likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high instrumental efficiency (> 37%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R > 20, 000 (with a lower-resolution, sky-limited mode of R ∼ 7, 000). With the design focusing on maximizing the instrument throughput (ensuring a Signal to Noise Ratio - SNR- ∼ 20 per spectral resolution element at 313 nm for U ∼ 17.5 mag objects in 1h of observations), it will offer new possibilities in many fields of astrophysics: i) access to key lines of stellar spectra (e.g. lighter elements, in particular Beryllium), extragalactic studies (e.g. circumgalactic medium of distant galaxies, cosmic UV background) and follow-up of explosive transients. We present the CUBES instrument design, currently in Phase-C and approaching the final design review, summarizing the hardware architecture and interfaces between the different subsystems as well as the relevant technical requirements. We describe the optical, mechanical, electrical design of the different subsystems (from the telescope adapter and support structure, through the main opto-mechanical path, including calibration unit, detector devices and cryostat control, main control electronics), detailing peculiar instrument functions like the Active Flexure Compensation (AFC). Furthermore, we outline the AIT/V concept and the main instrument operations giving an overview of its software ecosystem. Installation at the VLT is planned for 2028/2029 and first science operations in late 2029
The nature of medium-period variables on the extreme horizontal branch. I. X-shooter study of variable stars in the globular cluster ω Cen★
Get PDFA fraction of the extreme horizontal branch stars of globular clusters exhibit a periodic light variability that has been attributed to rotational modulation caused by surface spots. These spots are believed to be connected to inhomogeneous surface distribution of elements. However, the presence of such spots has not been tested against spectroscopic data. We analyzed the phase-resolved ESO X-shooter spectroscopy of three extreme horizontal branch stars that are members of the globular cluster ω Cen and also display periodic light variations. The aim of our study is to understand the nature of the light variability of these stars and to test whether the spots can reproduce the observed variability. Our spectroscopic analysis of these stars did not detect any phase-locked abundance variations that are able to reproduce the light variability. Instead, we revealed the phase variability of effective temperature and surface gravity. In particular, the stars show the highest temperature around the light maximum. This points to pulsations as a possible cause of the observed spectroscopic and photometric variations. However, such an interpretation is in a strong conflict with Ritter’s law, which relates the pulsational period to the mean stellar density. The location of the ω Cen variable extreme horizontal branch stars in HR diagram corresponds to an extension of PG 1716 stars toward lower temperatures or blue, low-gravity, large-amplitude pulsators toward lower luminosities, albeit with much longer periods. Other models of light variability, namely, related to temperature spots, should also be tested further. The estimated masses of these stars in the range of 0.2−0.3 M are too low for helium-burning objects
ANDES, the high resolution spectrograph for the ELT: science goals, project overview, and future developments
Get PDFThe first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 μm with the goal of extending it to 0.35-2.4 μm with the addition of an U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allows ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states
Is GN-z11 powered by a super-Eddington massive black hole?
Get PDFContext. Observations of z ∼ 6 quasars powered by supermassive black holes (SMBHs; MBH ∼ 108 − 10 M⊙) challenge our current understanding of early black hole (BH) formation and evolution. The advent of the James Webb Space Telescope (JWST) has enabled the study of massive BHs (MBHs; MBH ∼ 106 − 7 M⊙) up to z ∼ 11, thus bridging the properties of z ∼ 6 quasars to their ancestors. Aims: The JWST spectroscopic observations of GN-z11, a well-known z = 10.6 star-forming galaxy, have been interpreted with the presence of a super-Eddington (Eddington ratio ≡ λEdd ∼ 5.5) accreting MBH. To test this hypothesis, we used a zoom-in cosmological simulation of galaxy formation and BH co-evolution. Methods: We first tested the simulation results against the observed probability distribution function (PDF) of λEdd found in z ∼ 6 quasars. Then, in the simulation we selected the BHs that satisfy the following criteria: (a) 10 BH > 106 M⊙. Next, we applied the extreme value statistics to the PDF of λEdd resulting from the simulation. Results: We find that the probability of observing a z ∼ 10 − 11 MBH accreting with λEdd ∼ 5.5 in the volume surveyed by JWST is very low ( Conclusions: Our simulation cannot explain the JWST observations of GN-z11. This might be due to: (i) poor resolution and statistics in simulations, (ii) simplistic sub-grid models (e.g. BH accretion and seeding), (iii) uncertainties in the data analysis and interpretation
IGM damping wing constraints on the tail end of reionization from the enlarged XQR-30 sample
Get PDFThe attenuation of Lyα photons by neutral hydrogen in the intergalactic medium (IGM) at z ≳ 5 continues to be a powerful probe for studying the epoch of reionization. Given a framework to estimate the intrinsic (true) Lyα emission of high-z sources, one can infer the ionization state of the IGM during reionization. In this work, we use the enlarged XQR-30 sample of 42 high-resolution and high signal-to-noise quasar spectra between obtained with VLT/X-shooter to place constraints on the IGM neutral fraction. This is achieved using our existing Bayesian QSO reconstruction framework which accounts for uncertainties such as the: (i) posterior distribution of predicted intrinsic Lyα emission profiles (obtained via covariance matrix reconstruction of the Lyα and N V emission lines from unattenuated high-ionization emission line profiles; C IV, Si IV + O IV], and C III]) and (ii) distribution of ionized regions within the IGM using synthetic damping wing profiles drawn from a 1.63 Gpc3 reionization simulation. Following careful quality control, we used 23 of the 42 available QSOs to obtain constraints/limits on the IGM neutral fraction during the tail-end of reionization. Our median and 68th percentile constraints on the IGM neutral fraction are: and at z = 6.15 and 6.35. Further, we also report 68th percentile upper limits of , 0.20, 0.21, and 0.18 at z = 5.8, 5.95, 6.05, and 6.55. These results imply reionization is still ongoing at , consistent with previous results from XQR-30 (dark fraction and Lyα forest) along with other observational probes considered in the literature
The MUSE Ultra Deep Field (MUDF). V. Characterizing the Mass-Metallicity Relation for Low-mass Galaxies at z ∼ 1-2
Get PDFUsing more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope’s (HST) Wide Field Camera 3 and the Very Large Telescope’s Multi Unit Spectroscopic Explorer, we extend the gas-phase mass-metallicity relation (MZR) at z ≈ 1-2 down to stellar masses of M⋆ ≈ 107.5 M⊙. The sample reaches 6 times lower in stellar mass and star formation rate (SFR) than previous HST studies at these redshifts, and we find that galaxy metallicities decrease to log(O/H) + 12 ≈ 7.8 ± 0.1 (15% solar) at log(M⋆/M⊙) ≈ 7.5, without evidence of a turnover in the shape of the MZR at low masses. We validate our strong-line metallicities using the direct method for sources with [O iii] λ4363 and [O iii] λ1666 detections, and find excellent agreement between the techniques. The [O iii] λ1666-based metallicities double existing measurements with a signal-to-noise ratio ≥ 5 for unlensed sources at z > 1, validating the strong-line calibrations up to z ∼ 2.5. We confirm that the MZR resides ∼0.3 dex lower in metallicity than local galaxies and is consistent with the fundamental metallicity relation if the low-mass slope varies with SFR. At lower redshifts (z ∼ 0.5) our sample reaches ∼0.5 dex lower in SFR than current calibrations and we find enhanced metallicities that are consistent with extrapolating the MZR to lower SFRs. Finally, we detect only an ∼0.1 dex difference in the metallicities of galaxies in groups versus isolated environments. These results are based on robust calibrations and reach the lowest masses and SFRs that are accessible with HST, providing a critical foundation for studies with the Webb and Roman Space Telescopes
Gas, not dust: Migration of TESS/Gaia hot Jupiters possibly halted by the magnetospheres of protoplanetary disks
Get PDFContext. The presence of short-period ( 3-4 M⊙) may be the most efficient in swallowing their newborn planets