Modern stellar spectroscopy caveats

Blanco-Cuaresma, S.

doi:10.1093/mnras/stz549

Cited by 246 publications

(151 citation statements)

References 53 publications

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“…The aforementioned relation was also used for the determination of the systemic velocity of the one RRd star in our sample. In order to determine the systemic velocity of RR Lyrae stars in our sample we extracted single-epoch spectra from the SDSS and measured the radial velocity for the Hα line by crosscorrelation with a synthetic template 14 using the iSpec package routines (Blanco-Cuaresma et al 2014;Blanco-Cuaresma 2019) and MOOG (Sneden 1973, February 2017. Individual radial velocity measurements were phased using the stars' ephemerids with MJDs centered in the middle of the exposure.…”

Section: Discussionmentioning

confidence: 99%

Purveyors of fine halos

Hanke

Koch

Prudil

et al. 2020

A&A

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A long-lasting open question in the field of Galactic archeology refers to the size of the contribution from former globular cluster (GC) stars to the formation of the stellar halo of the Milky Way. We contribute to answering this important question by establishing observational links between the present-day halo field star population and GCs. To this end, we combined astrometric information such as space motions and parallaxes from the second data release of the Gaia mission (Gaia DR2) with spectroscopic radial velocities and metallicities ([Fe/H]) from the Sloan Digital Sky Survey (SDSS-IV, DR14) to end up with a seven-dimensional chemodynamical information space for more than 3 · 10 5 stars. Moreover, from our previous study, we incorporated the sample of halo giant stars with a distinct chemical signature (strong CN bandheads) that resembles the light-elements anomaly otherwise only seen in the second generation of globular cluster stellar populations. Using three different tagging techniques -among which is the exploration of conservative integrals of motion -we are able to establish unique associations between 151 extratidal stars in the neighborhood of eight GCs, which coincide with earlier findings of stellar envelopes beyond the tidal radius and even beyond (out to several tens of tidal radii). In addition, we trace the possible origin of about 62% of the sample of CN-strong giants to their potential host clusters. We find a connection between several of the involved GCs and the Gaia-Enceladus and Sequoia merger events. By establishing kinematic and chemical connections between 17 CN-strong stars and their surrounding fields, we identify co-moving groups of stars at the same [Fe/H] with a possible cluster origin. Some of these associations contain RR Lyrae variables, which allows meaningful distance inferences to be made. From these, we find strong evidence that four CN-strong stars and their associates are connected to the Sagittarius stream whilst their tightly confined [Fe/H] may hint to a birth site in M 54, the massive cluster in Sagittarius' core remnant. Finally, by employing the counts of CN-strong and bona-fide CN-normal giants from our novel sample, we provide tentative estimates for the fraction of first-generation cluster stars among all stars lost to the halo. In the immediate cluster vicinity, this value amounts to 50.0 ± 16.7% while the associations in the halo field rather imply 80.2 +4.9 −5.2 %. We speculate that -if proven real by spectroscopic follow-up -the disparity between these numbers could indicate a major contribution of low-mass clusters to the overall number of stars escaped to the halo or could alternatively suggest strong mass loss from the first generation during early cluster dissolution.

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Section: Discussionmentioning

confidence: 99%

Purveyors of fine halos

Hanke

Koch

Prudil

et al. 2020

A&A

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“…We used the public spectroscopic software iSpec (Blanco-Cuaresma et al 2014a;Blanco-Cuaresma 2019) to analyze the 4 http://archive.eso.org/wdb/wdb/adp/phase3_spectral/ form 5 The archive (http://archives.ia2.inaf.it/tng/faces/ search.xhtml?dswid=-9619) does not allow an automatic search for a large number of stars, so we queried the stars of Rup 147 that we knew in advance had been observed by Bragaglia et al (2018). 6 http://atlas.obs-hp.fr/elodie/ Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The atmospheric parameters T eff , log g, [M/H], and [α/M], and the microturbulence parameter mic are inferred for each spectrum using spectral synthesis fitting, in a non-differential way. We used the master line list by Blanco-Cuaresma (2019) and also the wings of Hα, Hβ, and the Mg I b triplet lines.…”

Section: Pipelinementioning

confidence: 99%

Differential abundances of open clusters and their tidal tails: Chemical tagging and chemical homogeneity

Casamiquela

Tarricq

Soubiran

et al. 2020

A&A

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Context. Well studied Open Clusters (OCs) of the Solar neighbourhood are frequently used as reference objects to test galactic and stellar theories. For that purpose their chemical composition needs to be known with a high level of confidence. It is also important to clarify if each OC is chemically homogeneous and if it has a unique chemical signature. Aims. The aims of this work are (1) to determine accurate and precise abundances of 22 chemical species (from Na to Eu) in the Hyades, Praesepe and Rupecht 147 using a large number of stars at different evolutionary states, (2) to evaluate the level of chemical homogeneity of these OCs, (3) to compare their chemical signatures. Methods. We gathered ∼800 high resolution and high signal-to-noise spectra of ∼100 members in the three clusters, obtained with the latest memberships based on Gaia DR2 data. We build a pipeline which computes atmospheric parameters and strictly line-by-line differential abundances among twin stars in our sample. With this method we are able to reach a very high precision in the abundances (0.01-0.02 dex in most of the elements). Results. We find large differences in the absolute abundances in some elements, which can be attributed to diffusion, NLTE effects or systematics in the analysis. For the three OCs, we find strong correlations in the differential abundances between different pairs of elements. According to our experiment with synthetic data, this can be explained by some level of chemical inhomogeneity. We compare differential abundances of several stars from the Hyades and Praesepe tails: the stars that differ more in chemical abundances also have distinct kinematics, even though they have been identified as members of the tail. Conclusions. It is possible to obtain high precision abundances using a differential analysis even when mixing spectra from different instruments. With this technique we find that the Hyades and Preasepe have the same chemical signature when G dwarfs and K giants are considered. Despite a certain level of inhomogeneity in each cluster, it is still possible to clearly distinguish the chemical signature of the older cluster Ruprecht 147 when compared to the Hyades and Praesepe.

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“…Valenti & Fischer 2005;Piskunov & Valenti 2017), one of the most widely-used spectroscopic techniques for determining stellar atmospheric parameters. A full account of the key caveats of these two methods can be found in Jofré et al (2019) and Blanco-Cuaresma (2019). The advent of high-resolution near-infrared (NIR) spectrographs such as CARMENES (Quirrenbach et al 2018), SPIRou (Artigau et al 2014), GIANO (Origlia et al 2014;Oliva et al 2018), CRIRES+ (Hatzes & CRIRES+ Team 2017), IRD (Kotani et al 2014), HPF (Wright et al 2018), and NIRPS (Wildi et al 2017) allows us to revisit these techniques, originally applied in the optical, in order to assess the impact of the NIR wavelength range on stellar parameter computations.…”

Section: Introductionmentioning

confidence: 99%

Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

Marfil

Tabernero

Montes

et al. 2020

Monthly Notices of the Royal Astronomical Society

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With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultrastable, double-channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar atmospheric parameters (T eff , log g, ξ, and [Fe/H]) by means of the StePar code, a Python implementation of the equivalent width method that employs the 2017 version of the MOOG code and a grid of MARCS model atmospheres. We compiled four Fe i and Fe ii line lists suited to metal-rich dwarfs, metal-poor dwarfs, metal-rich giants, and metal-poor giants that cover the wavelength range from 5 300 to 17 100Å, thus substantially increasing the number of identified Fe i and Fe ii lines up to 653 and 23, respectively. We examined the impact of the near-infrared Fe i and Fe ii lines upon our parameter determinations after an exhaustive literature search, placing special emphasis on the 14 Gaia benchmark stars contained in our sample. Even though our parameter determinations remain in good agreement with the literature values, the increase in the number of Fe i and Fe ii lines when the near-infrared region is taken into account reveals a deeper T eff scale that might stem from a higher sensitivity of the near-infrared lines to T eff .

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Modern stellar spectroscopy caveats

Cited by 246 publications

References 53 publications

Purveyors of fine halos

Purveyors of fine halos

Differential abundances of open clusters and their tidal tails: Chemical tagging and chemical homogeneity

Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

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