Precise Radial Velocities of 2046 Nearby FGKM Stars and 131 Standards

Chubak, C.; Marcy, G.; Fischer, D. A.; Howard, A. W.; Isaacson, H.; Johnson, J. A.; Wright, J. T.

doi:10.48550/arxiv.1207.6212

Cited by 58 publications

(97 citation statements)

References 24 publications

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“…We derived radial velocities by cross-correlating our spectra with a template spectrum of the metal-poor giant HD122563 that was obtained on the second night of data collection. The rest velocity of HD122563 was assumed to be −26.51 km s −1 (Chubak et al 2012), and the cross-correlation was performed over the Mg b absorption region (4900 Å to 5400 Å). We further performed a cross-correlation over the Telluric A-band absorption region (7590 Å to 7710 Å) between our spectra and a template spectrum of the hot, rapidly rotating giant HR4781 to correct for any slit mis-centering.…”

Section: Radial Velocity Measurementsmentioning

confidence: 99%

Discovery of 18 Stars with −3.10 < [Fe/H] < −1.45 in the Sagittarius Dwarf Galaxy*

Chiti

Hansen

Frebel

2020

ApJ

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Studies of the early chemical evolution of some larger dwarf galaxies (> 10 7 M ) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for eighteen stars with metallicities between −3.08 ≤ [Fe/H] ≤ −1.47 in the Sagittarius dwarf spheroidal galaxy, using medium-resolution spectra from the MagE spectrograph on the Magellan-Baade Telescope. This sample more than doubles the number of known very metal-poor stars ([Fe/H] ≤ −2.0) in the Sagittarius dwarf galaxy, and identifies one of the first known extremely metal-poor stars ([Fe/H] ≤ −3.0) in the system. These stars were identified as likely metal-poor members of Sagittarius using public, metallicity-sensitive photometry from SkyMapper DR1.1 and proper motion data from Gaia DR2, demonstrating that this dearth of metal-poor stars in some dwarf galaxies can be addressed with targeted searches using public data. We find that none of the stars in our sample are enhanced in carbon, in contrast to the relative prevalence of such stars in the Milky Way halo. Subsequent high-resolution spectroscopy of these stars would be key in detailing the early chemical evolution of the system.

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Section: Radial Velocity Measurementsmentioning

confidence: 99%

Discovery of 18 Stars with −3.10 < [Fe/H] < −1.45 in the Sagittarius Dwarf Galaxy*

Chiti

Hansen

Frebel

2020

ApJ

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“…Signal to noise ratios (SNR) per pixel of the final reduced spectra at 4100 Å and 5500 Å are listed in Table 1. Heliocentric radial velocities of the stars were determined by cross-correlation (Tonry & Davis 1979) of the target spectra with a spectrum of the radial-velocity stan-dard star HD122563 (V hel = −26.51 km s −1 ; Chubak et al (2012)) obtained with the same instrument setup as the target stars. Depending on the SNR of the target spectra, 30 to 50 individual orders were used for the cross-correlation.…”

Section: Observationsmentioning

confidence: 99%

Chemical Analysis of the Ultra-Faint Dwarf Galaxy Grus~II. Signature of high-mass stellar nucleosynthesis

Hansen,

Marshall,

Simon

et al. 2020

Preprint

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We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultra faint dwarf galaxy Grus II. All stars exhibit a higher than expected [Mg/Ca] ratio compared to metal-poor stars in other ultra faint dwarf galaxies and in the Milky Way halo. Nucleosynthesis in high mass ( 20M ) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (3) stars suggests the chemical enrichment of Grus II could have occurred through substantial high-mass stellar evolution, and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it can not be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture (r-process) elements. The abundance pattern of the r-process elements in this star matches the scaled r-process pattern of the solar system and r-process enhanced stars in other dwarf galaxies and in the Milky Way halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of r-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of Grus II would increase the likelihood of any of these events occurring. The time delay between the α and r-process element enrichment of the galaxy favours a neutron star merger as the origin of the r-process elements in Grus II.

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“…These measurements and their corresponding uncertainties are given the symbols v t and σ vt , respectively. These RVs were calculated following the methodology of Chubak et al (2012). They 4.07 ± 0.10 V sin i (km s −1 ) 3.29 ± 1.0…”

Section: Application Of the Matched-template Technique To Kic 5951458mentioning

confidence: 99%

“…These individual measurements are yet unpublished, but the Gaia Data Release 2 included their median value (−23.0 ± 1.3 km s −1 ) and the corresponding epoch (2015.5 or BJD = 2457204.5). This Gaia RV can be compared to the telluric-calibrated, absolute RVs produced from the HIRES spectra by the methodology of Chubak et al (2012), which we list in Table 4. Using standard stars, Soubiran et al (2018) found excellent agreement between the Gaia RVs and the catalog of Chubak et al (2012), quantified by a dispersion of only 0.072 km s −1 , which is much lower than the error on the Gaia RV measurement of KIC 5951458.…”

Section: The Long-term Rv Trendmentioning

confidence: 99%

“…This Gaia RV can be compared to the telluric-calibrated, absolute RVs produced from the HIRES spectra by the methodology of Chubak et al (2012), which we list in Table 4. Using standard stars, Soubiran et al (2018) found excellent agreement between the Gaia RVs and the catalog of Chubak et al (2012), quantified by a dispersion of only 0.072 km s −1 , which is much lower than the error on the Gaia RV measurement of KIC 5951458. In Figure 12, we show the Gaia RV and the Keck-HIRES telluric RVs of KIC 5951458.…”

Section: The Long-term Rv Trendmentioning

confidence: 99%

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Multiple Explanations for the Single Transit of KIC 5951458 based on Radial Velocity Measurements Extracted with a Novel Matched-template Technique

Dalba,

Fulton,

Isaacson

et al. 2020

Preprint

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Planetary systems that show single-transit events are a critical pathway to increasing the yield of long-period exoplanets from transit surveys. From the primary Kepler mission, KIC 5951458 b (Kepler-456b) was thought to be a single-transit giant planet with an orbital period of 1310 days. However, radial velocity (RV) observations of KIC 5951458 from the HIRES instrument on the Keck telescope suggest that the system is far more complicated. To extract precise RVs for this V ≈ 13 star, we develop a novel matched-template technique that takes advantage of a broad library of template spectra acquired with HIRES. We validate this technique and measure its noise floor to be 4-8 m s −1 (in addition to internal RV error) for most stars that would be targeted for precision RVs. For KIC 5951458, we detect a long-term RV trend that suggests the existence of a stellar companion with an orbital period greater than a few thousand days. We also detect an additional signal in the RVs that is possibly caused by a planetary or brown dwarf companion with mass in the range of 0.6-82 M Jup and orbital period below a few thousand days. Curiously, from just the data on hand, it is not possible to determine which object caused the single "transit" event. We demonstrate how a modest set of RVs allows us to update the properties of this unusual system and predict the optimal timing for future observations.

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Precise Radial Velocities of 2046 Nearby FGKM Stars and 131 Standards

Cited by 58 publications

References 24 publications

Discovery of 18 Stars with −3.10 < [Fe/H] < −1.45 in the Sagittarius Dwarf Galaxy*

Discovery of 18 Stars with −3.10 < [Fe/H] < −1.45 in the Sagittarius Dwarf Galaxy*

Chemical Analysis of the Ultra-Faint Dwarf Galaxy Grus~II. Signature of high-mass stellar nucleosynthesis

Multiple Explanations for the Single Transit of KIC 5951458 based on Radial Velocity Measurements Extracted with a Novel Matched-template Technique

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