Rall

Medeiros, Vinícius Nunes; Brito, Paulo César G. de; Silvestre, Bruno; Borges, Vinicius C. M.

doi:10.1145/3019612.3019730

Cited by 13 publications

(16 citation statements)

References 23 publications

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“…(km s some degree by incompleteness, the observed behavior of the v sin (i) distribution in particular does follow the behavior expected for FGK stars (Soderblom 1983;De Medeiros et al 1996;Nordström et al 2004). In fact, as we can see from Fig.…”

Section: Reddening Values E(b − V)supporting

confidence: 74%

Stellar parameters for stars of the CoRoT exoplanet field

Cortés

Maciel

Vieǐra

et al. 2015

A&A

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Context. Spectroscopic observations represent a fundamental step in the physical characterization of stars and, in particular, in the precise location of stars in the HR diagram. Rotation is also a key parameter, impacting stellar properties and evolution, which modulates the interior and manifests itself on the surface of stars. To date, the lack of analysis based on large samples has prevented our understanding of the real impact of stellar parameters and rotation on the stellar evolution as well as on the behavior of surface abundances. The space missions, CoRoT and Kepler, are providing us with rotation periods for thousands of stars, thus enabling a robust assessment of the behavior of rotation for different populations and evolutionary stages. For these reasons, the followup programs are fundamental to increasing the returns of these space missions. An analysis that combines spectroscopic data and rotation/modulation periods obtained from these space missions provides the basis for establishing the evolutionary behavior of the angular momentum of solar-like stars at different evolutionary stages, and the relation of rotation with other relevant physical and chemical parameters. Aims. To support the computation and evolutionary interpretation of periods associated with the rotational modulation, oscillations, and variability of stars located in the CoRoT fields, we are conducting a spectroscopic survey for stars located in the fields already observed by the satellite. These observations allow us to compute physical and chemical parameters for our stellar sample. Methods. Using spectroscopic observations obtained with UVES/VLT and Hydra/Blanco, and based on standard analysis techniques, we computed physical and chemical parameters (T eff , log (g), [Fe/H], v mic , v rad , v sin (i), and A(Li)) for a large sample of CoRoT targets. Results. We provide physical and chemical parameters for a sample comprised of 138 CoRoT targets. Our analysis shows the stars in our sample are located in different evolutionary stages, ranging from the main sequence to the red giant branch, and range in spectral type from F to K. The physical and chemical properties for the stellar sample are in agreement with typical values reported for FGK stars. However, we report three stars presenting abnormal lithium behavior in the CoRoT fields. These parameters allow us to properly characterize the intrinsic properties of the stars in these fields. Our results reveal important differences in the distributions of metallicity, T eff , and evolutionary status for stars belonging to different CoRoT fields, in agreement with results obtained independently from ground-based photometric surveys. Conclusions. Our spectroscopic catalog, by providing much-needed spectroscopic information for a large sample of CoRoT targets, will be of key importance for the successful accomplishment of several different programs related to the CoRoT mission, thus it will help further boost the scientific return associated with this space mission.

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Section: Reddening Values E(b − V)supporting

confidence: 74%

Stellar parameters for stars of the CoRoT exoplanet field

Cortés

Maciel

Vieǐra

et al. 2015

A&A

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“…Fewer than 2% of red giants rotate at speeds detectable at the APOGEE spectrograph resolution (de Medeiros et al 1996;Carlberg et al 2011). Therefore, the first versions of ASPCAP did not include rotational broadening as a dimension in the synthetic spectral grid, which substantially reduced the computing time.…”

Section: Synthetic Spectral Grids At T Eff mentioning

confidence: 99%

The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory

Albareti

Prieto

Almeida

et al. 2017

ApJS

500

281

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“…Contrarily to MS SL stars (e.g., García et al 2014a), only a few percent of the RGs show a pseudo-periodic photometric variability likely originating from surface spots (Ceillier et al 2017), which we hereafter call "rotational modulation". The most commonly adopted explanation is that RGs are slow rotators (e.g., Gray 1981;de Medeiros et al 1996) where no significant dynamo-driven magnetic fields are generated in their large convective envelope, implying no detectable surface spots. In this respect, it is worth noticing that no direct detection of magnetic field has been reported so far for stars on the red giant branch (RGB) with masses below 1.5 M (Charbonnel et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Active red giants: Close binaries versus single rapid rotators

Gaulme

Jackiewicz

Spada

et al. 2020

A&A

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Oscillating red-giant stars have provided a wealth of asteroseismic information regarding their interiors and evolutionary states, which enables detailed studies of the Milky Way. The objective of this work is to determine what fraction of red-giant stars shows photometric rotational modulation, and understand its origin. One of the underlying questions is the role of close binarity in this population, which relies on the fact that red giants in short-period binary systems (less than 150 days or so) have been observed to display strong rotational modulation. We selected a sample of about 4500 relatively bright red giants observed by Kepler, and show that about 370 of them (∼8%) display rotational modulation. Almost all have oscillation amplitudes below the median of the sample, while 30 of them are not oscillating at all. Of the 85 of these red giants with rotational modulation chosen for follow-up radial-velocity observation and analysis, 34 show clear evidence of spectroscopic binarity. Surprisingly, 26 of the 30 nonoscillators are in this group of binaries. On the contrary, about 85% of the active red giants with detectable oscillations are not part of close binaries. With the help of the stellar masses and evolutionary states computed from the oscillation properties, we shed light on the origin of their activity. It appears that low-mass red-giant branch stars tend to be magnetically inactive, while intermediate-mass ones tend to be highly active. The opposite trends are true for helium-core burning (red clump) stars, whereby the lower-mass clump stars are comparatively more active and the higher-mass ones are less active. In other words, we find that low-mass red-giant branch stars gain angular momentum as they evolve to clump stars, while higher-mass ones lose angular momentum. The trend observed with low-mass stars leads to possible scenarios of planet engulfment or other merging events during the shell-burning phase. Regarding intermediate-mass stars, the rotation periods that we measured are long with respect to theoretical expectations reported in the literature, which reinforces the existence of an unidentified sink of angular momentum after the main sequence. This article establishes strong links between rotational modulation, tidal interactions, (surface) magnetic fields, and oscillation suppression. There is a wealth of physics to be studied in these targets that is not available in the Sun.

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Rall

Cited by 13 publications

References 23 publications

Stellar parameters for stars of the CoRoT exoplanet field

Stellar parameters for stars of the CoRoT exoplanet field

The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory

Active red giants: Close binaries versus single rapid rotators

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