The K2-HERMES Survey. I. Planet-candidate Properties from K2 Campaigns 1–3

Wittenmyer, Robert A.; Sharma, Sanjib; Stello, Dennis; Buder, Sven; Kos, Janez; Asplund, Martin; Duong, Ly; Lin, Jane; Lind, Karin; Ness, Melissa; Zwitter, T.; Horner, Jonathan; Clark, Jake T.; Kane, Stephen R.; Huber, Daniel; Bland-Hawthorn, Joss; Casey, Andrew R.; Silva, Gayandhi M. De; D’Orazi, V.; Freeman, K. C.; Martell, Sarah L.; Simpson, Jeffrey D.; Zucker, D. B.; Anguiano, Borja; Casagrande, Luca; Esdaile, James; Hon, Marc; Ireland, Michael; Kafle, Prajwal R.; Khanna, Shourya; Marshall, Jonathan P.; Saddon, Mohd Hafiz Mohd; Traven, G.; Wright, D. E.

doi:10.3847/1538-3881/aaa3e4

Cited by 52 publications

(57 citation statements)

References 74 publications

(73 reference statements)

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“…If available and not flagged, stellar parameters from a prior version of The Cannon (version 1.3) are chosen. This version was also used for previous data releases of GALAH (Martell et al 2017), TESS-HERMES (Sharma et al 2018), and K2-HERMES (Wittenmyer et al 2018). If these parameters are flagged or not available, the synthesis commences with the stellar parameter estimates from the reduction process.…”

Section: Analysis Step 1: the Training Set Analysis With Spectroscopymentioning

confidence: 99%

The GALAH Survey: second data release

Buder

Asplund

Duong

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way and designed to deliver chemical information complementary to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342,682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multi-step approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (T eff , log g, [Fe/H], [X/Fe], v mic , v sin i, A K S ) for a representative training set of stars. This information is then propagated to the whole survey with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.

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Section: Analysis Step 1: the Training Set Analysis With Spectroscopymentioning

confidence: 99%

The GALAH Survey: second data release

Buder

Asplund

Duong

et al. 2018

Monthly Notices of the Royal Astronomical Society

Self Cite

361

447

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“…The spectroscopic data used here is taken from an internal release of GALAH DR2, which includes, public data (Buder et al 2018, DR2 ), and fields observed as part of the K2-HERMES (Wittenmyer et al 2018) and TESS-HERMES Table 2. Parameters for the isolated Galaxy (Model P).…”

Section: Galah Dr2 Sample With Elemental Abundancesmentioning

confidence: 99%

The GALAH survey and Gaia DR2: Linking ridges, arches, and vertical waves in the kinematics of the Milky Way

Khanna

Sharma

Tepper-García

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Gaia DR2 has revealed new small-scale and large-scale patterns in the phase-space distribution of stars in the Milky Way. In cylindrical Galactic coordinates (R, φ, z), ridge-like structures can be seen in the (R, V φ ) plane and asymmetric arch-like structures in the (V R , V φ ) plane. We show that the ridges are also clearly present when the third dimension of the (R, V φ ) plane is represented by z , V z , V R , [Fe/H] and [α/Fe] . The maps suggest that stars along the ridges lie preferentially close to the Galactic midplane (|z| < 0.2 kpc), and have metallicity and α elemental abundance similar to that of the Sun. We show that phase mixing of disrupting spiral arms can generate both the ridges and the arches. It also generates discrete groupings in orbital energy − the ridges and arches are simply surfaces of constant energy. We identify 8 distinct ridges in the Gaia DR2 data: six of them have constant energy while two have constant angular momentum. Given that the signature is strongest for stars close to the plane, the presence of ridges in z and V z suggests a coupling between planar and vertical directions. We demonstrate, using N-body simulations that such coupling can be generated both in isolated discs and in discs perturbed by an orbiting satellite like the Sagittarius dwarf galaxy.

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“…We now have a large sample of stars with very precise metallicity measurements from spectroscopic surveys like the Galactic Archaeology for HERMES (GALAH De Silva et al 2015) , K2-HERMES (a GALAH-like survey dedicated to K2 follow-up, Wittenmyer et al 2018) and Apache Point Observatory Galactic Evolution Experiment (APOGEE Ma-jewski et al 2017) surveys. In this paper, we use data from the GALAH survey to determine the metallicity distribution of the stellar populations in the Besançon-based Galactic model that we later use for asteroseismic analysis.…”

Section: Introductionmentioning

confidence: 99%

The K2-HERMES Survey: age and metallicity of the thick disc

Sharma

Stello

Bland-Hawthorn

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Asteroseismology is a promising tool to study Galactic structure and evolution because it can probe the ages of stars. Earlier attempts comparing seismic data from the Kepler satellite with predictions from Galaxy models found that the models predicted more low-mass stars compared to the observed distribution of masses. It was unclear if the mismatch was due to inaccuracies in the Galactic models, or the unknown aspects of the selection function of the stars. Using new data from the K2 mission, which has a well-defined selection function, we find that an old metal-poor thick disc, as used in previous Galactic models, is incompatible with the asteroseismic information. We show that spectroscopic measurements of [Fe/H] and [α/Fe] elemental abundances from the GALAH survey indicate a mean metallicity of log(Z/Z ) = −0.16 for the thick disc. Here Z is the effective solar-scaled metallicity, which is a function of [Fe/H] and [α/Fe]. With the revised disc metallicities, for the first time, the theoretically predicted distribution of seismic masses show excellent agreement with the observed distribution of masses. This provides an indirect verification of the asteroseismic mass scaling relation is good to within five percent. Using an importance-sampling framework that takes the selection function into account, we fit a population synthesis model of the Galaxy to the observed seismic and spectroscopic data. Assuming the asteroseismic scaling relations are correct, we estimate the mean age of the thick disc to be about 10 Gyr, in agreement with the traditional idea of an old α-enhanced thick disc.

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The K2-HERMES Survey. I. Planet-candidate Properties from K2 Campaigns 1–3

Cited by 52 publications

References 74 publications

The GALAH Survey: second data release

The GALAH Survey: second data release

The GALAH survey and Gaia DR2: Linking ridges, arches, and vertical waves in the kinematics of the Milky Way

The K2-HERMES Survey: age and metallicity of the thick disc

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