Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I.

Gray, R. O.; Corbally, Christopher J.; Garrison, R. F.; McFadden, M. T.; Robinson, Piers

doi:10.1086/378365

Cited by 429 publications

(297 citation statements)

References 30 publications

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“…14 Aur C is located 14.6 arcsec from A, at a distance of 104 ± 32 pc from the Sun (van Leeuwen 2007). Spectral types F2V+DA (Vennes et al 1998) or F5V (Gray et al 2003) have been proposed. It appears to be a fast rotator.…”

Section: Samplementioning

confidence: 99%

To Ba or not to Ba: Enrichment ins-process elements in binary systems with WD companions of various masses

Merle

Jorissen

Eck

et al. 2016

A&A

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Context. The enrichment in s-process elements of barium stars is known to be due to pollution by mass transfer from a companion formerly on the thermally pulsing asymptotic giant branch (AGB), now a carbon-oxygen white-dwarf (WD). Aims. We are investigating the relationship between the s-process enrichment in the barium star and the mass of its WD companion. It is expected that helium WDs, which have masses lower than about 0.5 M and never reached the AGB phase, should not pollute their giant companion with s-process elements. Therefore the companion should never turn into a barium star. Methods. Spectra with a resolution of R ∼ 86 000 were obtained with the HERMES spectrograph on the 1.2 m Mercator telescope for a sample of 11 binary systems involving WD companions of various masses. We used standard 1D local thermodynamical equilibrium MARCS model atmospheres coupled with the Turbospectrum radiative-transfer code that is embedded in the BACCHUS pipeline to derive the atmospheric parameters through equivalent widths of Fe i and Fe ii lines. Least-squares minimization between the observed and synthetic line shape was used to derive the detailed chemical abundances of CNO and s-process elements.Results. The abundances of s-process elements for the entire sample of 11 binary stars were derived homogeneously. The sample encompasses all levels of overabundances: from solar [s/Fe] = 0 to 1.5 dex in the two binary systems with S-star primaries (for which dedicated MARCS model atmospheres were used). The primary components of binary systems with a WD more massive than 0.5 M are enriched in s-process elements. We also found a trend of increasing [s/Fe] with [C/Fe] or [(C+N)/Fe]. Conclusions. Our results confirm the expectation that binary systems with WD companions less massive than 0.5 M do not host barium stars.

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Section: Samplementioning

confidence: 99%

To Ba or not to Ba: Enrichment ins-process elements in binary systems with WD companions of various masses

Merle

Jorissen

Eck

et al. 2016

A&A

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“…We assume a measurement error of 5% in the case of LOPeg since Gray et al (2003) do not report one. Nine objects have no available ¢ R log HK index but have a measurement for the alternative S HK index that also traces chromospheric activity.…”

Section: The Nearby Samplementioning

confidence: 99%

“…In a few cases where the B−V color of a target is redder than the color range where the relation has been tested (0.45 B−V 1.5), we display the value between parentheses in Table 1. We use the classification of Gray et al (2003) …”

Section: The Nearby Samplementioning

confidence: 99%

A High-Precision Near-Infrared Survey for Radial Velocity Variable Low-Mass Stars Using Cshell and a Methane Gas Cell

Gagné

Plavchan

Gao

et al. 2016

ApJ

233

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We present the results of a precise near-infrared (NIR) radial velocity (RV) survey of 32 low-mass stars with spectral types K2-M4 using CSHELL at the NASA InfraRed Telescope Facility in the K band with an isotopologue methane gas cell to achieve wavelength calibration and a novel, iterative RV extraction method. We surveyed 14 members of young (≈25-150 Myr) moving groups, the young field star εEridani, and 18 nearby (<25 pc) low-mass stars and achieved typical single-measurement precisions of 8-15 m s −1 with a long-term stability of 15-50 m s −1 over longer baselines. We obtain the best NIR RV constraints to date on 27 targets in our sample, 19 of which were never followed by high-precision RV surveys. Our results indicate that very active stars can display long-term RV variations as low as ∼25-50 m s −1 at ≈2.3125 μm, thus constraining the effect of jitter at these wavelengths. We provide the first multiwavelength confirmation of GJ876bc and independently retrieve orbital parameters consistent with previous studies. We recovered RV variabilities for HD160934AB and GJ725AB that are consistent with their known binary orbits, and nine other targets are candidate RV variables with a statistical significance of 3σ-5σ. Our method, combined with the new iSHELL spectrograph, will yield long-term RV precisions of 5 m s −1 in the NIR, which will allow the detection of super-Earths near the habitable zone of mid-M dwarfs.

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“…Star catalogues have been developed for space telescopes which provide a systematic foundation for searching out potential targets in the near galactic neighbourhood (see e.g. Gray et al 2003;Turnbull and Tarter 2003;Brown 2006;Porto de Mello et al 2006;Kaltenegger et al 2009). In preparation for such searches it is important to identify the types of planetary bodies on which photosynthesis might occur beyond the familiar paradigm of solar-driven photosynthesis on a planet such as the Earth.…”

Section: Introductionmentioning

confidence: 99%

Planetary targets in the search for extrasolar oxygenic photosynthesis

Cockell

Raven

Kaltenegger

et al. 2009

Plant Ecology & Diversity

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Background:In the coming decades space telescopes will be constructed that will attempt to find the gaseous products of oxygenic photosynthesis, the most promising biosignatures of life, in the atmospheres of temperate Earth-like planets orbiting distant stars. Aims: This paper aims to provide a synthesis of the range of feasible targets -either planets or their satellites -that could harbour photosynthesis. Methods: We calculated photosynthetically active radiation (PAR) fluxes on a diversity of planetary bodies including those receiving direct light from a single star, similarly to the Earth, and investigated the potential of these fluxes to support photosynthesis. Results: All main sequence stars emit radiation that is capable of supporting photosynthesis on Earth-like planets. We discuss tidally-locked M star planets as a special case. Less conventional targets for searches include large moons orbiting gas giant planets, which receive reflected light from their host planets and from the host star, planets in stable orbits in binary star systems, and the search for two planets within the same star system with photosynthetic signatures. Conclusions: A diversity of planetary bodies are targets in the search for extrasolar photosynthesis. The demonstration that many or none of these candidate planetary bodies harbour photosynthesis would be an important conclusion in understanding the evolution and prevalence of photosynthesis.

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Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I.

Cited by 429 publications

References 30 publications

To Ba or not to Ba: Enrichment ins-process elements in binary systems with WD companions of various masses

To Ba or not to Ba: Enrichment ins-process elements in binary systems with WD companions of various masses

A High-Precision Near-Infrared Survey for Radial Velocity Variable Low-Mass Stars Using Cshell and a Methane Gas Cell

Planetary targets in the search for extrasolar oxygenic photosynthesis

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