Searching for chemical classes among metal-poor stars using medium-resolution spectroscopy

Cruz, M. A.; Cogo‐Moreira, Hugo; Rossi, Silvia

doi:10.1093/mnras/stx3330

Cited by 6 publications

(5 citation statements)

References 65 publications

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“…Besides the [Fe/H] < −1.0 and [C/Fe] c > +0.7 conditions, we consider CEMP stars to be members of the so-called Group I if A(C) c 7.25. Since the carbon enrichment of these stars' atmospheres are usually accompanied by enhancement in their abundances of slow neutron-capture (s-process) elements (Spite et al 2013;Bonifacio et al 2015;Hansen et al 2015;Cruz et al 2018), they are generally associated with the CEMP-s ([Ba/Fe] > +1.0 and [Ba/Eu] > +0.5; Beers & Christlieb 2005) subclass of CEMP stars. Such a chemical profile is thought to be the result of mass transfer from a binary companion in the asymptotic giant branch (AGB) phase (Suda et al 2004;Ryan et al 2005;Lucatello et al 2005;Bisterzo et al 2011;Allen et al 2012;Placco et al 2013;Starkenburg et al 2014;Hansen et al 2016).…”

Section: Carbon and α−Elementsmentioning

confidence: 99%

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

Abbott¹,

Abbott²,

Abbott³

et al. 2017

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Gravitationswellen -ein leichtes Zittern der raumzeitVor 1,3 Milliarden Jahren: Seit langer Zeit schon haben sich in einer fernen Galaxie zwei schwarze Löcher umkreist, Gebilde von so ungeheurer Dichte, das selbst Licht ihrer Schwerkraft nicht mehr entweichen kann und von ihnen eingefangen wird. Seit Jahrmillionen haben sie bei ihrem Tanz umeinander mit ihrer masse die Raumzeit verformt und dabei Gravitationswellen abgestrahlt. ihr Abstand wurde dabei immer kleiner, ihre Geschwindigkeit immer höher, bis sie schließlich unter einem gewaltigen Ausbruch von Gravitationswellen zu einem einzelnen schwarzen Loch verschmelzen. Später werden wir diese Wellen GW150914 nennen. Für einen kurzen Augenblick wird durch sie mehr Leistung abgestrahlt als von allen Sternen im gesamten sichtbaren Universum in Form von elektromagnetischer Strahlung zusammen. Diese Gravitationswellen rasen mit Lichtgeschwindigkeit durch das Weltall und lassen auf ihrem Weg die Raumzeit erzittern.25. November 1915: GW150914 ist schon längst in unserer milchstra-

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Section: Carbon and α−Elementsmentioning

confidence: 99%

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

Abbott¹,

Abbott²,

Abbott³

et al. 2017

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“…A number of previous observational studies have indicated that carbon is omnipresent in the early universe (Beers & Christlieb 2005;Aoki et al 2007;Hansen et al 2016a;Placco et al 2016;Cruz et al 2018;Caffau et al 2018). Hence, the discovery and analysis of carbon-enhanced metal-poor stars ([C/Fe] 0.7 1 hereafter CEMP), suggest that this substantial enhancement could be closely linked to their formation.…”

Section: Corresponding Authormentioning

confidence: 99%

Metal-poor Stars Observed with the Automated Planet Finder Telescope. II. Chemodynamical Analysis of Six Low-metallicity Stars in the Halo System of the Milky Way

Mardini

Placco

Taani

et al. 2019

ApJ

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In this work, we study the chemical compositions and kinematic properties of six metal-poor stars with [Fe/H] < −2.5 in the Galactic halo. From high-resolution (R ∼ 110,000) spectroscopic observations obtained with the Lick/APF, we determined individual abundances for up to 23 elements, to quantitatively evaluate our sample. We identify two carbon-enhanced metal-poor stars (J1630+0953 and J2216+0246) without enhancement in neutron-capture elements (CEMP-no stars), while the rest of our sample stars are carbon-intermediate. By comparing the light-element abundances of the CEMP stars with predicted yields from non-rotating zero-metallicity massive-star models, we find that possible the progenitors of J1630+0953 and J2216+0246 could be in the 13-25 M ⊙ mass range, with explosion energies 0.3-1.8×10 51 erg. In addition, the detectable abundance ratios of light and heavy elements suggest that our sample stars are likely formed from a well-mixed gas cloud, which is consistent with previous studies. We also present a kinematic analysis, which suggests that most of our program stars likely belong to the inner-halo population, with orbits passing as close as ∼ 2.9 kpc from the Galactic center. We discuss the implications of these results on the critical constraints on the origin and evolution of CEMP stars, as well as the nature of the Population III progenitors of the lowest metallicity stars in our Galaxy.

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“…Many studies have indicated that metal-poor stars may show high carbon-to-iron ratios, and thus classified as carbon-enhanced metal-poor stars (Beers & Christlieb 2005;Aoki et al 2007;Hansen et al 2016a;Placco et al 2016;Kielty et al 2017;Roriz et al 2017;Cruz et al 2018;Caffau et al 2018). Furthermore, CEMP stars can be divided into four sub-classes, according to their neutron-capture elements nature.…”

Section: Introductionmentioning

confidence: 99%

Metal-poor Stars Observed with the Automated Planet Finder Telescope. I. Discovery of Five Carbon-enhanced Metal-poor Stars from LAMOST

Mardini¹,

Li²,

Placco³

et al. 2019

ApJ

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We report on the discovery of five carbon-enhanced metal-poor (CEMP) stars in the metallicity range of −3.3 < [Fe/H] < −2.4. These stars were selected from the LAMOST DR3 low-resolution (R∼ 2,000) spectroscopic database as metal-poor candidates and followed-up with high-resolution spectroscopy (R∼110,000) with the LICK/APF. Stellar parameters and individual abundances for 25 chemical elements (from Li to Eu) are presented for the first time. These stars exhibit chemical abundance patterns that are similar to those reported in other literature studies of very and extremely metal-poor stars. One of our targets, J2114−0616, shows high enhancement in carbon ([C/Fe]=1.37), nitrogen ([N/Fe]= 1.88), barium ([Ba/Fe]=1.00), and europium ([Eu/Fe]=0.84). Such chemical abundance pattern suggests that J2114−0616 can be classified as CEMP-r/s star. In addition, the star J1054+0528 can be classified as a CEMP-rI star, with [Eu/Fe]=0.44 and [Ba/Fe]=−0.52. The other stars in our sample show no enhancements in neutron-capture elements and can be classified as CEMP-no stars. We also performed a kinematic and dynamical analysis of the sample stars based on Gaia DR2 data. The kinematic parameters, orbits, and binding energy of these stars, show that J2114−0616 is member of the outer halo population, while the remaining stars belong to the inner halo population but with an accreted origin. Collectively, these results add important constraints on the origin and evolution of CEMP stars as well as on their possible formation scenarios.

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Searching for chemical classes among metal-poor stars using medium-resolution spectroscopy

Cited by 6 publications

References 65 publications

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

Metal-poor Stars Observed with the Automated Planet Finder Telescope. II. Chemodynamical Analysis of Six Low-metallicity Stars in the Halo System of the Milky Way

Metal-poor Stars Observed with the Automated Planet Finder Telescope. I. Discovery of Five Carbon-enhanced Metal-poor Stars from LAMOST

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