References of "Valentini, Marica"
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See detailGalactic archaeology: mapping and dating stellar populations with asteroseismology of red-giant stars
Miglio, A.; Chiappini, C.; Morel, Thierry ULg et al

in Monthly Notices of the Royal Astronomical Society (2013), 429

Our understanding of how the Galaxy was formed and evolves is severely hampered by the lack of precise constraints on basic stellar properties such as distances, masses and ages. Here, we show that solar ... [more ▼]

Our understanding of how the Galaxy was formed and evolves is severely hampered by the lack of precise constraints on basic stellar properties such as distances, masses and ages. Here, we show that solar-like pulsating red giants represent a well-populated class of accurate distance indicators, spanning a large age range, which can be used to map and date the Galactic disc in the regions probed by observations made by the CoRoT and Kepler space telescopes. When combined with photometric constraints, the pulsation spectra of such evolved stars not only reveal their radii, and hence distances, but also provide well-constrained estimates of their masses, which are reliable proxies for the ages of the stars. As a first application, we consider red giants observed by CoRoT in two different parts of the Milky Way, and determine precise distances for ˜2000 stars spread across nearly 15 000 pc of the Galactic disc, exploring regions which are a long way from the solar neighbourhood. We find significant differences in the mass distributions of these two samples which, by comparison with predictions of synthetic models of the Milky Way, we interpret as mainly due to the vertical gradient in the distribution of stellar masses (hence ages) in the disc. In the future, the availability of spectroscopic constraints for this sample of stars will not only improve the age determination, but also provide crucial constraints on age-velocity and age-metallicity relations at different Galactocentric radii and heights from the plane. [less ▲]

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See detailGAUFRE: a tool for an automated determination of atmospheric parameters from spectroscopy
Valentini, Marica ULg; Morel, Thierry ULg; Miglio, Andrea et al

in 40th Liege International Astrophysical Colloquium 'Ageing low-mass stars: from red giants to white dwarfs' (2013, January 01)

We present an automated tool for measuring atmospheric parameters (T_eff, log(g), [Fe/H]) for F-G-K dwarf and giant stars. The tool, called GAUFRE, is written in C++ and composed of several routines ... [more ▼]

We present an automated tool for measuring atmospheric parameters (T_eff, log(g), [Fe/H]) for F-G-K dwarf and giant stars. The tool, called GAUFRE, is written in C++ and composed of several routines: GAUFRE-RV measures radial velocity from spectra via cross-correlation against a synthetic template, GAUFRE-EW measures atmospheric parameters through the classic line-by-line technique and GAUFRE-CHI2 performs a chi^2 fitting to a library of synthetic spectra. A set of F-G-K stars extensively studied in the literature were used as a benchmark for the program: their high signal-to-noise and high resolution spectra were analysed by using GAUFRE and results were compared with those present in literature. The tool is also implemented in order to perform the spectral analysis after fixing the surface gravity (log(g)) to the accurate value provided by asteroseismology. A set of CoRoT stars, belonging to LRc01 and LRa01 fields was used for first testing the performances and the behaviour of the program when using the seismic log(g). [less ▲]

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See detailFirst results for the solar neighborhood of the Asiago Red Clump Survey
Valentini, Marica ULg; Munari, U.; Saguner, T. et al

in European Physical Journal Web of Conferences (2012, February 01)

The Asiago Red Clump Spectroscopic Survey (ARCS) is an ongoing survey that provides atmospheric parameters, distances and space velocities of a well selected sample of Red Clump stars distributed along ... [more ▼]

The Asiago Red Clump Spectroscopic Survey (ARCS) is an ongoing survey that provides atmospheric parameters, distances and space velocities of a well selected sample of Red Clump stars distributed along the celestial equator. We used the ARCS catalog for a preliminary investigation of the Galactic disk in the Solar Neighborhood, in particular we focused on detection and characterization of moving groups. [less ▲]

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See detailSolar-like pulsating stars as distance indicators: G-K giants in the CoRoT and Kepler fields
Miglio, A.; Morel, Thierry ULg; Barbieri, M. et al

in European Physical Journal Web of Conferences (2012, February 01)

The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available ... [more ▼]

The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available average seismic constraints allow a precise and largely model-independent determination of stellar radii (hence distances) and masses. We here briefly report on the distance determination of thousands of giants in the CoRoT and Kepler fields of view. [less ▲]

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See detailFast core rotation in red-giant stars as revealed by gravity-dominated mixed modes
Beck, Paul G; Montalban Iglesias, Josefa ULg; Kallinger, Thomas et al

in Nature (2012), 481

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much ... [more ▼]

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected `mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior. [less ▲]

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See detailUsing seismic targets as benchmarks for spectroscopic analyses of cool stars
Morel, Thierry ULg; Miglio, Andrea ULg; Valentini, Marica ULg

in Journal of Physics: Conference Series (2011), 328

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An ... [more ▼]

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An extensive comparison for about 40 well-studied pulsating stars with gravities derived by traditional means (ionization balance, pressure-sensitive spectral features or location with respect to evolutionary tracks) supports the validity of this technique and reveals an overall remarkable agreement with mean differences not exceeding 0.05 dex (although with a dispersion of up to ~0.2 dex). It is argued that interpolation in theoretical isochrones may be the most precise way of estimating the gravity by traditional means in nearby dwarfs. The use of seismic targets as benchmarks in the context of forthcoming large-scale surveys (such as the follow up of the Gaia mission) is briefly discussed. [less ▲]

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See detailA spectroscopic survey of faint, high-Galactic-latitude red clump stars. I. The high resolution sample
Valentini, Marica ULg; Munari, U.

in Astronomy and Astrophysics (2010), 522

Context. Their high intrinsic brightness and small dispersion in absolute magnitude make red clump (RC) stars a prime tracer of Galactic structure and kinematics. <BR /> Aims: We aim to derive accurate ... [more ▼]

Context. Their high intrinsic brightness and small dispersion in absolute magnitude make red clump (RC) stars a prime tracer of Galactic structure and kinematics. <BR /> Aims: We aim to derive accurate, multi-epoch radial velocities and atmospheric parameters (T[SUB]eff[/SUB], log g, [M/H], V[SUB]rot[/SUB] sin i) of a large sample of carefully selected RC stars, fainter than those present in other spectroscopic surveys and located over a great circle at high Galactic latitudes. <BR /> Methods: We acquired data of the program stars of high signal-to-noise ratio (S/N) and high resolution with the Asiago Echelle spectrograph. Radial velocities were obtained by applying cross-correlation and atmospheric parameters via χ^2 fit to a synthetic spectral library. Extensive tests were carried out by re-observing with the same instrument a large number of standard stars taken from a variety of sources in the literature. During these tests, we found that the absolute Tycho V[SUB]T[/SUB] magnitude of local red clump stars is not dependent on metallicity <BR /> Results: A total of 277 red clump stars (101 of them with a second epoch observation) of the extended solar neighborhood and 55 calibration stars were observed and included in an output catalog that contains (in addition to relevant support astrometric and photometric data taken from literature) the main output of our survey: accurate multi-epoch radial velocities (σ(RV)_&sun; ≤ 0.4 km s[SUP]-1[/SUP]), accurate atmospheric parameters (σ(T[SUB]eff[/SUB]) = 68 K, σ(log g) = 0.11 dex, σ([M/H]) = 0.10 dex, σ(V[SUB]rot[/SUB] sin i) = 1.1 km s[SUP]-1[/SUP]), distances, and space velocities (U, V, W). [less ▲]

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See detailIPHAS and the symbiotic stars . II. New discoveries and a sample of the most common mimics
Corradi, R. L. M.; Valentini, Marica ULg; Munari, U. et al

in Astronomy and Astrophysics (2010), 509

Context. Knowledge of the total population of symbiotic stars in the Galaxy is important for understanding basic aspects of stellar evolution in interacting binaries and the relevance of this class of ... [more ▼]

Context. Knowledge of the total population of symbiotic stars in the Galaxy is important for understanding basic aspects of stellar evolution in interacting binaries and the relevance of this class of objects in the formation of supernovae of type Ia. <BR /> Aims: In a previous paper, we presented the selection criteria needed to search for symbiotic stars in IPHAS, the INT Hα survey of the Northern Galactic plane. IPHAS gives us the opportunity to make a systematic, complete search for symbiotic stars in a magnitude-limited volume. <BR /> Methods: Follow-up spectroscopy at different telescopes worldwide of a sample of sixty two symbiotic star candidates is presented. <BR /> Results: Seven out of nineteen S-type candidates observed spectroscopically are confirmed to be genuine symbiotic stars. The spectral type of their red giant components, as well as reddening and distance, were computed by modelling the spectra. Only one new D-type symbiotic system, out of forty-three candidates observed, was found. This was as expected (see discussion in our paper on the selection criteria). The object shows evidence for a high density outflow expanding at a speed ≥65 km s[SUP]-1[/SUP]. Most of the other candidates are lightly reddened classical T Tauri stars and more highly reddened young stellar objects that may be either more massive young stars of HAeBe type or classical Be stars. In addition, a few notable objects have been found, such as three new Wolf-Rayet stars and two relatively high-luminosity evolved massive stars. We also found a helium-rich source, possibly a dense ejecta hiding a WR star, which is surrounded by a large ionized nebula. <BR /> Conclusions: These spectroscopic data allow us to refine the selection criteria for symbiotic stars in the IPHAS survey and, more generally, to better understand the behaviour of different Hα emitters in the IPHAS and 2MASS colour-colour diagrams. Based on observations obtained at; the 2.6 m Nordic Optical Telescope operated by NOTSA; the 2.5 m INT and 4.2 m WHT telescopes of the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias; the 2.3 m ANU telescope at Siding Spring Observatory, Australia; the Asiago 1.82 m telescope of the INAF Astronomical Observatory of Padova, Italy; and the 2.1 m telescope at San Pedro Martir, Mexico. Some of the INT spectra incorporated into this paper were obtained as part of a CCI International Time Programme awarded to the IPHAS collaboration. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has also made use of the SIMBAD database, operated at CDS, Strasbourg, France. [less ▲]

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See detailOptical evolution of Nova Ophiuchi 2007 = V2615 Oph
Munari, U.; Henden, A.; Valentini, Marica ULg et al

in Monthly Notices of the Royal Astronomical Society (2008), 387

The moderately fast Nova Oph 2007 reached maximum brightness on 2007 March 28 at V = 8.52, B - V = +1.12, V - R[SUB]C[/SUB] = +0.76, V - I[SUB]C[/SUB] = +1.59 and R[SUB]C[/SUB] - I[SUB]C[/SUB] = +0.83 ... [more ▼]

The moderately fast Nova Oph 2007 reached maximum brightness on 2007 March 28 at V = 8.52, B - V = +1.12, V - R[SUB]C[/SUB] = +0.76, V - I[SUB]C[/SUB] = +1.59 and R[SUB]C[/SUB] - I[SUB]C[/SUB] = +0.83, after fast initial rise and a pre-maximum halt lasting a week. Decline times were t[SUP]V[/SUP][SUB]2[/SUB] = 26.5, t[SUP]B[/SUP][SUB]2[/SUB] = 30, t[SUP]V[/SUP][SUB]3[/SUB] = 48.5 and t[SUP]B[/SUP][SUB]3[/SUB] = 56.5 d. The distance to the nova is d = 3.7 +/- 0.2 kpc, the height above the Galactic plane is z = 215 pc, the reddening is E(B - V) = 0.90 and the absolute magnitude at maximum is M[SUP]max[/SUP][SUB]V[/SUB] = -7.2 and M[SUP]max[/SUP][SUB]B[/SUB] = -7.0. The spectrum four days before maximum resembled a F6 supergiant, in an agreement with broad-band colours. It later developed into that of a standard `FeII'-class nova. Nine days past maximum, the expansion velocity estimated from the width of Hα emission component was ~730 km s[SUP]-1[/SUP], and the displacement from it of the principal and diffuse-enhanced absorption systems was ~650 and 1380 km s[SUP]-1[/SUP], respectively. Dust probably formed and disappeared during the period from 82 to 100 d past maximum, causing (at peak dust concentration) an extinction of ΔB = 1.8 mag and an extra ΔE(B - V) = 0.44 reddening. [less ▲]

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See detailARCS: the Asiago Red Clump Spectroscopic Survey
Valentini, Marica ULg; Barbon, R.; Munari, U. et al

in From Stars to Galaxies: Building the Pieces to Build Up the Universe (2007, December 01)

The Asiago Red Clump Spectroscopic survey derives from high resolution optical spectra accurate multi-epoch radial velocities and atmospheric parameters (T_{eff}, log g, [M/H], V_{rot}sin i, [α/Fe], ξ ... [more ▼]

The Asiago Red Clump Spectroscopic survey derives from high resolution optical spectra accurate multi-epoch radial velocities and atmospheric parameters (T_{eff}, log g, [M/H], V_{rot}sin i, [α/Fe], ξ) for a well selected sample of ˜500 equatorial Red Clump stars belonging to the solar neighborhood. These results coupled with astrometric and photometric external data are used in investigation of galactic structure and dynamics. [less ▲]

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See detailRadial Velocities and Atmospheric Parameters of Field Stars Suitable for RAVE Tests
Valentini, Marica ULg; Munari, U.; Tantalo, R. et al

in From Stars to Galaxies: Building the Pieces to Build Up the Universe (2007, December 01)

With the Asiago 1.82m telescope + Echelle spectrograph we have obtained high resolution spectra of 25 RAVE targets well distributed in atmospheric parameters. From them we have derived radial velocities ... [more ▼]

With the Asiago 1.82m telescope + Echelle spectrograph we have obtained high resolution spectra of 25 RAVE targets well distributed in atmospheric parameters. From them we have derived radial velocities and T_{eff}, log g, [M/H], V_{rot} sin i to the aim of serving as an external test for corresponding values derived from RAVE spectra. [less ▲]

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See detailEclipse of the B3V companion and flaring of emission lines in V838 Monocerotis
Munari, U.; Corradi, R. L. M.; Henden, A. et al

in Astronomy and Astrophysics (2007), 474

After four years during which only the spectacular light echo was showing continuous and rapid evolution while the central star was nearly constant, in autumn 2006 V838 Mon began a sequence of events ... [more ▼]

After four years during which only the spectacular light echo was showing continuous and rapid evolution while the central star was nearly constant, in autumn 2006 V838 Mon began a sequence of events which profoundly altered its spectroscopic and photometric behavior: (a) an eclipse of the B3V companion, characterized by the disappearance and reappearance of the B3V companion from optical spectra, and an eclipse-like lightcurve of ~70 day duration and Δ B ˜ 1.15 mag, Δ V ˜ 0.55 mag, Δ R[SUB]C[/SUB] ˜ 0.10 mag maximum depth; (b) a large increase in intensity of the [FeII] and FeII emission lines, and the appearance in emission for the first time since the 2002 outburst of Hα and higher Balmer series lines. While the [FeII] and FeII lines maintained a very sharp and unresolved profile, the Hα developed into a wide and structured profile, characterized by a sharp central reversal at the same velocity as one of the CO radio emission components. The disappearance of the B3V companion is equally well explained by a grazing eclipse from the outbursting L-type supergiant or by an eclipse from a dust cloud characterized by E[SUB]B-V[/SUB]=0.55 and R[SUB]V[/SUB]=3.1. We believe the flaring of the emission lines occurred at a similar time as the B3V eclipse just by chance. Tables 2-4 are only available in electronic form at http://www.aanda.org Based on observations made with the Asiago 1.82 m of the INAF Astronomical Observatory of Padova, and with 4.2 m WHT and 2.5 m INT operated by the Isaac Newton Group of Telescopes, and with the 2.6 m NOT operated jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias. [less ▲]

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