A5084408872- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astronomical and nuclear sciences
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Geomagnetism and Paleomagnetism Studies
- Adaptive optics and wavefront sensing
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Earth Systems and Cosmic Evolution
- Chemical Thermodynamics and Molecular Structure
- Astrophysical Phenomena and Observations
- Plant and animal studies
- High-pressure geophysics and materials
- Historical and Architectural Studies
- Space Science and Extraterrestrial Life
- Spacecraft and Cryogenic Technologies
- Regional Economic and Spatial Analysis
- Advanced Statistical Methods and Models
- Scientific Measurement and Uncertainty Evaluation
Astronomical Observatory of Capodimonte
2015-2024
National Institute for Astrophysics
2005-2022
CTA Observatory
2021
Max Planck Society
2018
Italian Institute of Technology
2017
University of Florida
2009
Global Social Observatory
2009
University of Geneva
2009
Telescopio Nazionale Galileo
2009
Osservatorio astronomico di Bologna
2009
We present new nonlinear, time-dependent convective hydrodynamical models of RR Lyrae stars computed assuming a constant helium-to-metal enrichment ratio and broad range in metal abundances (Z=0.0001--0.02). The stellar masses luminosities adopted to construct the pulsation were fixed according detailed central He burning Horizontal Branch evolutionary models. cover luminosity effective temperatures modal stability is investigated for both fundamental first overtones. predict topology...
The Gaia second Data Release (DR2) presents a first mapping of full-sky RR Lyrae stars and Cepheids observed by the spacecraft during initial 22 months science operations. Specific Object Study (SOS) pipeline, developed to validate fully characterise (SOS Cep&RRL) Gaia, has been presented in documentation papers accompanying Release. Here we describe how SOS pipeline was modified allow for processing multiband (G, G_BP G_RP) time series photometry all-sky candidate variables produce specific...
Context. Gaia has been in operations since 2014. The third data release expands from the early (EDR3) 2020 by providing 34 months of multi-epoch observations that allowed us to probe, characterise and classify systematically celestial variable phenomena. Aims. We present a summary variability processing analysis photometric spectroscopic time series 1.8 billion sources done for DR3. Methods. used statistical Machine Learning methods sources. Training sets were built global revision major...
The Gaia second Data Release (DR2) presents a first mapping of full-sky RR Lyrae stars and Cepheids observed by the spacecraft during initial 22 months science operations. Specific Object Study (SOS) pipeline, developed to validate fully characterise (SOS Cep&RRL) Gaia, has been presented in documentation papers accompanying Release. Here we describe how SOS pipeline was modified allow for processing multiband (G, G_BP G_RP) time series photometry all-sky candidate variables produce...
Parallaxes for 331 classical Cepheids, 31 Type II Cepheids and 364 RR Lyrae stars in common between Gaia the Hipparcos Tycho-2 catalogues are published Data Release 1 (DR1) as part of Tycho-Gaia Astrometric Solution (TGAS). In order to test these first parallax measurements primary standard candles cosmological distance ladder, that involve astrometry collected by during initial 14 months science operation, we compared them with literature estimates derived new period-luminosity ($PL$),...
Classical Cepheids are the most important primary indicators for extragalactic distance scale. Establishing precise zero points of their Period-Luminosity and Period-Wesenheit (PL/PW) relations has profound consequences on estimate $\rm H_0$. Type II also indicator tracers old stellar populations. The recent Data Release 2 (DR2) {\it Gaia} Spacecraft includes photometry parallaxes thousands classical type cepheids. We aim at reviewing classification DR2 to derive PL/PW Magellanic Cloud (MCs)...
The Gaia Data Release 2 (DR2): we summarise the processing and results of identification variable source candidates RR Lyrae stars, Cepheids, long period variables (LPVs), rotation modulation (BY Dra-type) delta Scuti & SX Phoenicis short-timescale variables. In this release aim to provide useful but not necessarily complete samples candidates. processed data consist G, BP, RP photometry during first 22 months operations as well positions parallaxes. Various methods from classical...
Gaia DR3 publishes a catalogue of full-sky RR Lyrae stars (RRLs) observed during the initial 34 months science operations, that were processed through Specific Object Study (SOS) pipeline for Cepheids and RRLs (SOS Cep&RRL) by Gaia. The SOS Cep&RRL validation candidate relies on tools include Period (P) G-amplitude diagram P-phi21 -phi31 parameters G light curve Fourier decomposition, based sample bona fide known (Gold Sample). processing led to 271779 listed in vari_rrlyrae table DR3. By...
Context. Cepheids are pulsating stars that play a crucial role in several astrophysical contexts. Among the different types, Classical fundamental tools for calibration of extragalactic distance ladder. They also powerful stellar population tracers context Galactic studies. The Gaia Third Data Release (DR3) publishes improved data on collected during initial 34 months operations. Aims. We present DR3 catalogue all obtained through analysis carried out with Specific Object Study (SOS) Cep&RRL...
We present new V- and I-band HST ACS photometry of I Zw 18, the most metal-poor blue compact dwarf (BCD) galaxy in nearby universe. It has been argued past that 18 is a very young system started forming stars only ≲500 Myr ago, but other work hinted older (≳1 Gyr) red giant branch (RGB) may also exist. Our data, once combined with archival provide deep uncontaminated optical color-magnitude diagram (CMD) now strongly indicates an RGB. The RGB tip (TRGB) magnitude yields distance modulus (m -...
In this paper we present an extended set of nonlinear convective pulsation models at varying metallicity and ΔY/ΔZ ratio. The predicted instability strip bolometric light curves are discussed by comparing the new with our previous ones. particular, dependence on both metal helium abundances is investigated. By transforming into observational bands, able to derive period-color-luminosity Wesenheit relations for each selected chemical composition. Synthetic period-luminosity obtained...
We present a detailed investigation of the Cepheid distance scale by using both theory and observations. Through use pulsation models for fundamental mode Cepheids, we found that slope period–luminosity (P–L) relation covering entire period range (0.40 ⩽ log P 2.0) becomes steeper when moving from optical to near-infrared (NIR) bands, metallicity dependence decreases B- K band. The sign slopes P–LV P–LI is at odds with some recent empirical estimates. determined new homogeneous estimates V-...
Context. The European Space Agency spacecraft Gaia is expected to observe about 10 000 Galactic Cepheids and over 100 Milky Way RR Lyrae stars (a large fraction of which will be new discoveries), during the five-year nominal lifetime spent scanning whole sky a faint limit G = 20.7 mag, sampling their light variation on average 70 times.
Context. Classical Cepheids (DCEPs) represent a fundamental tool to calibrate the extragalactic distance scale. However, they are also powerful stellar population tracers in context of Galactic studies. The forthcoming Data Release 3 Gaia mission will allow us study, with unprecedented detail, structure, dynamics, and chemical properties disc, particular spiral arms, where most DCEPs reside. Aims. In this paper we aim quantify metallicity dependence DCEPs’ period-Wesenheit (PWZ) relation...
Abstract The Vera C. Rubin Legacy Survey of Space and Time (LSST) holds the potential to revolutionize time domain astrophysics, reaching completely unexplored areas Universe mapping variability scales from minutes a decade. To prepare maximize LSST data for exploration transient variable Universe, one four pillars science, Transient Variable Stars Science Collaboration, eight Collaborations, has identified research interest requirements, paths enable them. While our roadmap is...
We investigate how a different calibration of the Cepheid period–luminosity (PL) relation, taking into account metallicity corrections, affects absolute magnitude Type Ia supernovae (SNe Ia) and, in turn, determination Hubble constant H0. use SN light curves from literature and previously unpublished data to establish MB–Δm15(B) calibrate zero point by means nine SNe with Cepheid-measured distances. This relation is then used diagram, turn derive In attempt correct for host-galaxy...
We present new multiband (UBVI) time-series data of helium burning variables in the Carina dwarf spheroidal galaxy. The current sample includes 92 RR Lyrae—six them are identifications—and 20 Anomalous Cepheids, one which is identification. analysis Bailey diagram shows that luminosity amplitude first overtone component double-mode located along long-period tail regular variables, while fundamental short-period variables. This evidence further supports transitional nature these objects....
We present new FLAMES@VLT spectroscopic observations of 30 stars in the field Large Magellanic Cloud (LMC) stellar cluster NGC 1866. 1866 is one few young and massive globular clusters that close enough so its can be individually studied detail. Radial velocities have been used to separate belonging LMC field, same spectra derive chemical abundances for a variety elements, from [Fe/H] light (i.e. Na, O, Mg, etc.) heavy ones. The average iron abundance turns out [Fe/H]=−0.43 ± 0.01 dex (with...
We present a complete theoretical scenario for classical Cepheids in the most commonly used HST/WFC3 filters, going from optical (F555W, F606W and F814W) to near-infrared (F160W) bands. The importance of such study is related recent release new observed with 8 distant galaxies where SNIa are hosted. These observations have posed sound constraints current distance scale uncertainties on Hubble constant Ho smaller than 3%. Our models explore large range metallicity Helium content, thus...
We present a B, V color–magnitude diagram (CMD) of the Milky Way dwarf satellite Ursa Major II (UMa II), spanning magnitude range from ∼ 15 to 23.5 mag and extending over an 18 × arcmin2 area centered on Galaxy. Our photometry goes down about 2 below Galaxy's main-sequence turnoff that we detected at 21.5 mag. have discovered bona fide RR Lyrae variable star in UMa II, which use estimate conservative dereddened distance modulus for galaxy (m − M)0 = 17.70 ± 0.04 0.12 mag, where first error...
Abstract To properly quantify the possible residual systematic errors affecting classical Cepheid distance scale, a detailed theoretical scenario is recommended. By extending set of nonlinear, convective pulsation models published for Z = 0.02 to 0.004, 0.008, and 0.03, we provide homogeneous, nonlinear model grid taking into account simultaneous variations mass–luminosity relation, efficiency superadiabatic convection, chemical composition. The dependence inferred period–radius,...
We perform a detailed analysis of Cepheids in NGC 4258, Magellanic Clouds and Milky Way order to verify the reliability theoretical scenario based on large set nonlinear convective pulsation models. derive Wesenheit functions from synthetic BVI magnitudes pulsators we show that sign extent metallicity effect predicted Period-Wesenheit (P-W) relations change according adopted passbands. These P-W are applied measured Galactic available literature. find agree with dependence relations....
We present the first V, B − V color–magnitude diagram of Leo IV dwarf spheroidal galaxy, a faint Milky Way satellite recently discovered by Sloan Digital Sky Survey. have obtained B, time-series photometry reaching about half magnitude below turnoff, which we detect at = 24.7 mag, and performed study variable star population. identified three RR Lyrae stars (all fundamental-mode pulsators, RRab) one SX Phoenicis in galaxy. In period–amplitude are located close to loci Oosterhoff type I...