2MASS J18082002−5104378: The brightest (<i>V</i>= 11.9) ultra metal-poor star

Meléndez, Jorge; Placco, Vinicius M.; Tucci-Maia, Marcelo; Ramírez, Iván; Li, Ting S.; Perez, Gabriel Martins Palma

doi:10.1051/0004-6361/201527456

Cited by 29 publications

(42 citation statements)

References 51 publications

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“…The UMP nature of the primary in the 2MASS J18082002-5104378 system was discovered by Meléndez et al (2016). Those authors measured the spectroscopic stellar parameters we reproduce in Table 1.…”

Section: Observationsmentioning

confidence: 91%

“…Those authors measured the spectroscopic stellar parameters we reproduce in Table 1. Meléndez et al (2016) also noted that 2MASS J18082002-5104378 was a single-lined spectroscopic binary with radial velocity variations in the most luminous component on the order of 100 km s −1 over a five month period from 2014 October to 2015 March. In addition, Meléndez et al (2016) found no evidence for a second set of absorption lines in their high-resolution, high signal-to-noise ratio (S/N) spectra.…”

Section: Observationsmentioning

confidence: 92%

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An Ultra Metal-poor Star Near the Hydrogen-burning Limit*

Schlaufman

Thompson

Casey

2018

ApJ

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ApJ in pressABSTRACT It is unknown whether or not low-mass stars can form at low metallicity. While theoretical simulations of Population III (Pop III) star formation show that protostellar disks can fragment, it is impossible for those simulations to discern if those fragments survive as low-mass stars. We report the discovery of a low-mass star on a circular orbit with orbital period P = 34.757 ± 0.010 days in the ultra metalpoor (UMP) single-lined spectroscopic binary system 2MASS J18082002-5104378. The secondary star 2MASS J18082002-5104378 B has a mass M 2 = 0.14 +0.06 −0.01 M , placing it near the hydrogenburning limit for its composition. The 2MASS J18082002-5104378 system is on a thin disk orbit as well, making it the most metal-poor thin disk star system by a considerable margin. The discovery of 2MASS J18082002-5104378 B confirms the existence of low-mass UMP stars and its short orbital period shows that fragmentation in metal-poor protostellar disks can lead to the formation and survival of low-mass stars. We use scaling relations for the typical fragment mass and migration time along with published models of protostellar disks around both UMP and primordial composition stars to explore the formation of low-mass Pop III stars via disk fragmentation. We find evidence that the survival of low-mass secondaries around solar-mass UMP primaries implies the survival of solar-mass secondaries around Pop III primaries with masses 10 M M * 100 M . If true, this inference suggests that solar-mass Pop III stars formed via disk fragmentation could survive to the present day.

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Section: Observationsmentioning

confidence: 91%

Section: Observationsmentioning

confidence: 92%

An Ultra Metal-poor Star Near the Hydrogen-burning Limit*

Schlaufman

Thompson

Casey

2018

ApJ

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“…The root-mean-square deviation of our computed orbit from the observations is 0.52 km s −1 . Meléndez et al (2016) estimated the temperature of 2MASS J1808-5104 by imposing the excitation equilibrium of Fe i lines and adding an empirical correction described in Frebel et al (2013). Since 2MASS J1808-5104 was observed by Gaia, we used the Gaia photometry recently displayed in the Table 3.…”

Section: Binary Nature and Orbitmentioning

confidence: 99%

“…Thus measurements and upper limits of Be at the lowest abundances are of paramount importance to probe a primordial production of Be. The discovery of the bright extremely metalpoor star 2MASS J1808-5104 ([Fe/H]=-3.8) by Meléndez et al (2016) opens up the possibility to probe the Be abundance in stars at the lowest metallicities. In this paper we present the analysis of high signal-to-noise ratio (S/N) UV spectra of the star 2MASS J1808-5104 acquired with the specific aim of investigating its Be abundance.…”

Section: Introductionmentioning

confidence: 99%

Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation

Spite

Bonifacio

Spite

et al. 2019

A&A

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Context. Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. Aims. We investigate the Be abundance in the extremely metal-poor star 2MASS J1808-5104 ([Fe/H]=-3.84) with the aim of constraining inhomogeneities or the presence of late decaying particles. Methods. High resolution, high signal-to-noise ratio UV spectra were acquired at ESO with the Kueyen 8.2 m telescope and the UVES spectrograph. Abundances were derived using several model atmospheres and spectral synthesis code. Results. We measured log(Be/H) = −14.3 from a spectrum synthesis of the region of the Be line. Using a conservative approach, however we adopted an upper limit two times higher, i.e. log(Be/H) < −14.0. We measured the O abundance from UV OH lines and find [O/H]=-3.46 after a 3D correction. Conclusions. Our observation reinforces the existing upper limit on primordial Be. There is no observational indication for a primordial production of 9 Be. This places strong constraints on the properties of putative relic particles. This result also supports the hypothesis of a homogeneous Universe, at the time of nucleosynthesis. Surprisingly, our upper limit of the Be abundance is well below the Be measurements in stars of similar [O/H]. This may be evidence that the Be-O relation breaks down in the early Galaxy, perhaps due to the escape of spallation products from the gas clouds in which stars such as 2MASS J1808-5104 have formed.

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“…Until recently, the numbers of stars with confirmed metallicities of [Fe/H] < −3.0 was relatively small, making it difficult to infer the global characteristics of EMP stars. Since 2005, more than 200 stars with [Fe/H] < −3.0 have been confirmed, based on high-resolution spectroscopic analyses (e.g., Barklem et al 2005;Caffau et al 2013a,b;Yong et al 2013), including more than 50 stars with [Fe/H] < −3.5, and over 20 with [Fe/H] < −4.0 (Barklem et al 2005;Frebel et al 2005Frebel et al , 2015Cohen et al 2008;Caffau et al 2011aCaffau et al ,b, 2012Bonifacio et al 2012;Aoki et al 2013;Caffau et al 2013b;Spite et al 2013;Yong et al 2013;Keller et al 2014;Allende Prieto et al 2015;Li et al 2015;Placco et al 2015;Meléndez et al 2016).…”

Section: Introductionmentioning

confidence: 90%

Deep SDSS optical spectroscopy of distant halo stars

Fernández-Alvar

Prieto

Masseron

et al. 2016

A&A

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Aims. We present the results of an analysis for 107 extremely metal-poor (EMP) stars with metallicities less than [Fe/H] = −3.0, identified from medium-resolution spectra in the Sloan Digital Sky Survey (SDSS). Our analysis provides estimates of the stellar effective temperatures and surface gravities, as well as iron, calcium, and magnesium abundances. Methods. We follow the same methodology as in previous papers of this series, based on comparisons of the observed spectra with synthetic spectra. The abundances of Fe, Ca, and Mg are determined by fitting spectral regions dominated by lines of each element. In addition, we present a technique to determine upper limits for elements whose features are not detected in a given spectrum. We also analyse our sample with the SEGUE Stellar Parameter Pipeline, in order to obtain additional determinations of the atmospheric parameters, iron and alpha-element abundances, to compare with ours, and to infer [C/Fe] ratios. Results. We find that, in these moderate to low signal-to-noise and medium-resolution spectra in this metallicity regime, Ca is usually the only element that exhibits lines that are sufficiently strong to reliably measure its abundance. Fe and Mg exhibit weaker features that, in most cases, only provide upper limits. We measure [Ca/Fe] and [Mg/Fe] for EMP stars in the SDSS spectra, and conclude that most of the stars exhibit the usual level of enhancement for α-elements, ∼+0.4, although a number of stars for which only [Fe/H] upper limits could be estimated point to higher [α/Fe] ratios. We also find that 26% of the stars in our sample can be classified as carbon-enhanced metal-poor (CEMP) stars, and that the frequency of CEMP stars also increases with decreasing metallicity, as has been reported for previous samples. We identity a rare, bright (g = 11.90) EMP star, SDSS J134144.61+474128.6, with [Fe/H] = −3.27, [C/Fe] = +0.95, and elevated magnesium ([Mg/Fe] = +0.62), an abundance pattern typical of CEMP-no stars.

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2MASS J18082002−5104378: The brightest (V= 11.9) ultra metal-poor star

Cited by 29 publications

References 51 publications

An Ultra Metal-poor Star Near the Hydrogen-burning Limit*

An Ultra Metal-poor Star Near the Hydrogen-burning Limit*

Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation

Deep SDSS optical spectroscopy of distant halo stars

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