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The EBLM project - IX. Five fully convective M-dwarfs, precisely measured with CHEOPS and TESS light curves
Get PDFEclipsing binaries are important benchmark objects to test and calibrate stellar structure and evolution models. This is especially true for binaries with a fully convective M-dwarf component for which direct measurements of these stars' masses and radii are difficult using other techniques. Within the potential of M-dwarfs to be exoplanet host stars, the accuracy of theoretical predictions of their radius and effective temperature as a function of their mass is an active topic of discussion. Not only the parameters of transiting exoplanets but also the success of future atmospheric characterization relies on accurate theoretical predictions. We present the analysis of five eclipsing binaries with low-mass stellar companions out of a subsample of 23, for which we obtained ultra-high-precision light curves using the CHEOPS satellite. The observation of their primary and secondary eclipses are combined with spectroscopic measurements to precisely model the primary parameters and derive the M-dwarfs mass, radius, surface gravity, and effective temperature estimates using the PYCHEOPS data analysis software. Combining these results to the same set of parameters derived from TESS light curves, we find very good agreement (better than 1 per cent for radius and better than 0.2 per cent for surface gravity). We also analyse the importance of precise orbits from radial velocity measurements and find them to be crucial to derive M-dwarf radii in a regime below 5 per cent accuracy. These results add five valuable data points to the mass-radius diagram of fully convective M-dwarfs
Definizione dei requisiti per l’esecuzione di Data Request su OPS4@DPCT per la Gaia Science Verification di Cycle 4 (DR4) e Cycle 5 (DR5)
Get PDFBeatrice Bucciarelli - INAF (Osservatorio Astrofisico di Torino) Debora Busonero - INAF (Osservatorio Astrofisico di Torino) Enrico Licata - INAF (Osservatorio Astrofisico di Torino) Alberto Riva - INAF (Osservatorio Astrofisico di Torino) Leonardo Tolomei - ALTEC@DPCT (ALTEC, Aerospace Logistics Technology Engineering Company - Torino) Alberto Vecchiato - INAF (Osservatorio Astrofisico di Torino)Si definiscono alcuni templates di queries “SQL like”, da fornire al DPCT@ALTEC di Gaia, da implementare su OPS4 in vista delle attività di analisi e verifica per il rilascio della DR4. In particolare, si forniscono informazioni necessarie alla definizione degli input e degli output attesi da un qualsiasi utilizzatore, membro del Consorzio DPAC, per tramite del Team INAF@DPCT, partecipante alla fase di verifica e validazione precedente le Gaia Data Releases (GDR) ad esito delle estrazioni dati (strutturati e non) condotte sul sistema OPS4
Gaia Data Release 3. Stellar chromospheric activity and mass accretion from Ca II IRT observed by the Radial Velocity Spectrometer
Get PDFContext. The Gaia Radial Velocity Spectrometer (RVS) provides the unique opportunity of a spectroscopic analysis of millions of stars at medium resolution (λ/Δλ ∼ 11 500) in the near-infrared (845−872 nm). This wavelength range includes the Ca II infrared triplet (IRT) at 850.03, 854.44, and 866.45 nm, which is a good indicator of magnetic activity in the chromosphere of late-type stars. Aims: Here we present the method devised for inferring the Gaia stellar activity index from the analysis of the Ca II IRT in the RVS spectrum, together with its scientific validation. Methods: The Gaia stellar activity index is derived from the Ca II IRT excess equivalent width with respect to a reference spectrum, taking the projected rotational velocity (vsini) into account. We performed scientific validation of the Gaia stellar activity index by deriving a R′IRT index, which is largely independent of the photospheric parameters, and considering the correlation with the R′HK index for a sample of stars. A sample of well-studied pre-main-sequence (PMS) stars is considered to identify the regime in which the Gaia stellar activity index may be affected by mass accretion. The position of these stars in the colour-magnitude diagram and the correlation with the amplitude of the photometric rotational modulation is also scrutinised. Results.Gaia DR3 contains a stellar activity index derived from the Ca II IRT for some 2 × 106 stars in the Galaxy. This represents a `gold mine' for studies on stellar magnetic activity and mass accretion in the solar vicinity. Three regimes of the chromospheric stellar activity are identified, confirming suggestions made by previous authors based on much smaller R′HK datasets. The highest stellar activity regime is associated with PMS stars and RS CVn systems, in which activity is enhanced by tidal interaction. Some evidence of a bimodal distribution in main sequence (MS) stars with Teff ≳ 5000 K is also found, which defines the two other regimes, without a clear gap in between. Stars with 3500 K ≲ Teff ≲ 5000 K are found to be either very active PMS stars or active MS stars with a unimodal distribution in chromospheric activity. A dramatic change in the activity distribution is found for Teff ≲ 3500 K, with a dominance of low activity stars close to the transition between partially- and fully convective stars and a rise in activity down into the fully convective regime
Prefazione
Get PDFPrefazione al libro "Urania Panormita" nella quale si descrive brevemente il patrimonio storico astronomico della Specola e il suo rapporto col territorio
Three Eruptions Observed by Remote Sensing Instruments Onboard Solar Orbiter
Get PDFSolar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA. The EUI instrument was built by CSL, IAS, MPS, MSSL/UCL, PMOD/WRC, ROB, LCF/IO with funding from the Belgian Federal Science Policy Office (BELSPO/PRODEX PEA 4000134088); the Centre National d’Etudes Spatiales (CNES); the UK Space Agency (UKSA); the Bundesministerium für Wirtschaft und Energie (BMWi) through the Deutsches Zentrum für Luft- und Raumfahrt (DLR); and the Swiss Space Office (SSO). The Metis programme is supported by the Italian Space Agency (ASI) under the contracts to the co-financing National Institute of Astrophysics (INAF): Accordi ASI-INAF N. I-043-10-0 and Addendum N. I-013-12-0/1, Accordo ASI-INAF N.2018-30-HH.0 and under the contracts to the industrial partners OHB Italia SpA, Thales Alenia Space Italia SpA and ALTEC: ASI-TASI N. I-037-11-0 and ASI-ATI N. 2013-057-I.0. Metis was built with hardware contributions from Germany (Bundesministerium für Wirtschaft und Energie (BMWi) through the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)), from the Academy of Sciences of the Czech Republic (Czech PRODEX) and from ESA. We acknowledge the use of Solar Orbiter/EUI, Solar Orbiter/Metis, PROBA2/SWAP, SDO/AIA, SOHO/LASCO, and STEREO/EUVI, COR2 data. The LASCO CME catalogue used in this study is generated and maintained at the CDAW Data Center by NASA and The Catholic University of America in cooperation with the Naval Research Laboratory. SOHO is a project of international cooperation between ESA and NASA.On February 21 and March 21 - 22, 2021, the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter observed three prominence eruptions. The eruptions were associated with coronal mass ejections (CMEs) observed by Metis, Solar Orbiter's coronagraph. All three eruptions were also observed by instruments onboard the Solar-TErrestrial RElations Observatory (Ahead; STEREO-A), the Solar Dynamics Observatory (SDO), and the Solar and Heliospheric Observatory (SOHO). Here we present an analysis of these eruptions. We investigate their morphology, direction of propagation, and 3D properties. We demonstrate the success of applying two 3D reconstruction methods to three CMEs and their corresponding prominences observed from three perspectives and different distances from the Sun. This allows us to analyze the evolution of the events, from the erupting prominences low in the corona to the corresponding CMEs high in the corona. We also study the changes in the global magnetic field before and after the eruptions and the magnetic field configuration at the site of the eruptions using magnetic field extrapolation methods. This work highlights the importance of multi-perspective observations in studying the morphology of the erupting prominences, their source regions, and associated CMEs. The upcoming Solar Orbiter observations from higher latitudes will help to constrain this kind of study better
IXPE Observations of the Quintessential Wind-accreting X-Ray Pulsar Vela X-1
No full textThe radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up to 80%. However, phase-resolved and energy-resolved polarimetry of X-ray pulsars is required in order to test different models and to shed light on the emission processes and the geometry of the emission region. Here we present the first results of the observations of the accreting X-ray pulsar Vela X-1 performed with the Imaging X-ray Polarimetry Explorer. Vela X-1 is considered to be the archetypal example of a wind-accreting, high-mass X-ray binary system, consisting of a highly magnetized neutron star accreting matter from its supergiant stellar companion. The spectropolarimetric analysis of the phase-averaged data for Vela X-1 reveals a polarization degree (PD) of 2.3% ± 0.4% at the polarization angle (PA) of -47.°3 ± 5.°4. A low PD is consistent with the results obtained for other X-ray pulsars and is likely related to the inverse temperature structure of the neutron star atmosphere. The energy-resolved analysis shows the PD above 5 keV reaching 6%-10% and a ~90° difference in the PA compared to the data in the 2-3 keV range. The phase-resolved spectropolarimetric analysis finds a PD in the range 0%-9% with the PA varying between -80° and 40°
The photochemical evolution of polycyclic aromatic hydrocarbons and nontronite clay on early Earth and Mars
Get PDFThe photochemical evolution of polycyclic aromatic hydrocarbons (PAHs), an abundant form of meteoritic organic carbon, is of great interest to early Earth and Mars origin-of-life studies and current organic molecule detection efforts on Mars. Fe-rich clay environments were abundant on early Earth and Mars, and may have played a role in prebiotic chemistry, catalyzing the breakdown of PAHs and freeing up carbon for subsequent chemical complexification. Current Mars is abundant in clay-rich environments, which are most promising for harboring organic molecules and have comprised the main studied features by the Curiosity rover in search of them. In this work we studied the photocatalytic effects of the Fe-rich clay nontronite on adsorbed PAHs. We tested the effect of ultraviolet radiation on pyrene, fluoranthene, perylene, triphenylene, and coronene adsorbed to nontronite using the spike technique, and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in a Mars simulation chamber. We studied the infrared vibrational PAH bands with first order reaction kinetics and observed an extensive decrease of bands of pyrene, fluoranthene, and perylene, accompanied by the formation of PAH cations, while triphenylene and coronene remained preserved. We further analyzed our irradiated samples with nuclear magnetic resonance (NMR). Our study showed certain PAHs to be degraded via the (photo)Fenton mechanism, even under a dry, hypoxic atmosphere. Using solar spectra representative of early Earth, early Mars, and current Mars surface illumination up to 400 nm, the processes occurring in our set up are indicative of the UV-induced photochemistry taking place in Fe-rich clay environments on early Earth and Mars
DeepGraviLens: a multi-modal architecture for classifying gravitational lensing data
Get PDFGravitational lensing is the relativistic effect generated by massive bodies, which bend the space-time surrounding them. It is a deeply investigated topic in astrophysics and allows validating theoretical relativistic results and studying faint astrophysical objects that would not be visible otherwise. In recent years, machine learning methods have been applied to support the analysis of the gravitational lensing phenomena by detecting lensing effects in datasets consisting of images associated with brightness variation time series. However, the state-of-the-art approaches either consider only images and neglect time-series data or achieve relatively low accuracy on the most difficult datasets. This paper introduces DeepGraviLens, a novel multi-modal network that classifies spatio-temporal data belonging to one non-lensed system type and three lensed system types. It surpasses the current state-of-the-art accuracy results by 3% to 11%, depending on the considered data set. Such an improvement will enable the acceleration of the analysis of lensed objects in upcoming astrophysical surveys, which will exploit the petabytes of data collected, e.g., from the Vera C. Rubin Observatory
Virgo detector characterization and data quality: results from the O3 run
Get PDFThe Advanced Virgo detector has contributed with its data to the rapid growth of the number of detected GW signals in the past few years, alongside the two Advanced LIGO instruments. First during the last month of the Observation Run 2 (O2) in August 2017 (with, most notably, the compact binary mergers GW170814 and GW170817), and then during the full Observation Run 3 (O3): an 11 months data taking period, between April 2019 and March 2020, that led to the addition of 79 events to the catalog of transient GW sources maintained by LIGO, Virgo and now KAGRA. These discoveries and the manifold exploitation of the detected waveforms benefit from an accurate characterization of the quality of the data, such as continuous study and monitoring of the detector noise sources. These activities, collectively named detector characterization and data quality or DetChar, span the whole workflow of the Virgo data, from the instrument front-end hardware to the final analyses. They are described in detail in the following article, with a focus on the results achieved by the Virgo DetChar group during the O3 run. Concurrently, a companion article describes the tools that have been used by the Virgo DetChar group to perform this work
Einstein Telescope, the future generation of ground based gravitational wave detectors
Get PDFThe second-generation gravitational wave detectors Advanced LIGO and Advanced Virgo have shown their breakthrough capability to shed light on our understanding of the Universe. Although the steady increase in sensitivity, these detectors will hit in the future limitations due to their hosting infrastructures. This is the reason why a new generation of gravitational wave detectors are under studies. The Einstein Telescope (ET) is a planned European 3 rd generation gravitational Wave (GW) Observatory, a new research infrastructure designed to host a detector capable to observe the entire Universe using gravitational waves. ET will be a multi-interferometer observatory aiming to increase a factor ten the sensitivity of previous generation detectors. We will give an overview of the project, describe the main scientific goals and the technological challenges that must be overcome to reach the expected sensitivity