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  • 1
    Online Resource
    Online Resource
    The odd bunch: chrono-chemo-dynamics of sixteen unusual stars from Kepler
    Oxford University Press (OUP) ; 2023
    In:  Monthly Notices of the Royal Astronomical Society Vol. 523, No. 1 ( 2023-05-23), p. 1089-1103
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 523, No. 1 ( 2023-05-23), p. 1089-1103
    Abstract: In this study we combine asteroseismic, spectroscopic, and kinematic information to perform a detailed analysis of a sample of 16 stars from the Kepler field. Our selection focuses on stars that appear to contradict Galactic chemical evolution models: young and α-rich, old and metal-rich, as well as other targets with unclear classification in past surveys. Kinematics are derived from Gaia DR3 parallaxes and proper motions, and high-resolution spectra from HIRES/Keck are used to calculate chemical abundances for over 20 elements. This information is used to perform careful checks on asteroseismic masses and ages derived via grid-based modelling. Among the seven stars previously classified as young and α-rich, only one seems to be an unambiguously older object masking its true age. We confirm the existence of two very old (≥11 Gyr), super metal-rich (≥0.1 dex) giants. These two stars have regular thin disc chemistry and in-plane solar circle orbits that fit well in the picture of radial migration via the churning mechanism. The alternative explanation that these stars have younger ages would require mass-loss rates that strongly increase with increasing metallicity. Finally, we suggest further investigations to explore the suitability of Zn as a chemical clock in red giants.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stad1365
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 207232-4
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    SSG: 16,12
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  • 2
    Online Resource
    Online Resource
    The K2 Galactic Archaeology Program Data Release 3: Age-abundance Patterns in C1–C8 and C10–C18
    American Astronomical Society ; 2022
    In:  The Astrophysical Journal Vol. 926, No. 2 ( 2022-02-01), p. 191-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 926, No. 2 ( 2022-02-01), p. 191-
    Abstract: We present the third and final data release of the K2 Galactic Archaeology Program (K2 GAP) for Campaigns C1–C8 and C10–C18. We provide asteroseismic radius and mass coefficients, κ R and κ M , for ∼19,000 red giant stars, which translate directly to radius and mass given a temperature. As such, K2 GAP DR3 represents the largest asteroseismic sample in the literature to date. K2 GAP DR3 stellar parameters are calibrated to be on an absolute parallactic scale based on Gaia DR2, with red giant branch and red clump evolutionary state classifications provided via a machine-learning approach. Combining these stellar parameters with GALAH DR3 spectroscopy, we determine asteroseismic ages with precisions of ∼20%–30% and compare age-abundance relations to Galactic chemical evolution models among both low- and high- α populations for α , light, iron-peak, and neutron-capture elements. We confirm recent indications in the literature of both increased Ba production at late Galactic times as well as significant contributions to r -process enrichment from prompt sources associated with, e.g., core-collapse supernovae. With an eye toward other Galactic archeology applications, we characterize K2 GAP DR3 uncertainties and completeness using injection tests, suggesting that K2 GAP DR3 is largely unbiased in mass/age, with uncertainties of 2.9% (stat.) ± 0.1% (syst.) and 6.7% (stat.) ± 0.3% (syst.) in κ R and κ M for red giant branch stars and 4.7% (stat.) ± 0.3% (syst.) and 11% (stat.) ± 0.9% (syst.) for red clump stars. We also identify percent-level asteroseismic systematics, which are likely related to the time baseline of the underlying data, and which therefore should be considered in TESS asteroseismic analysis.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/ac2c83
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
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    SSG: 16,12
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  • 3
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    Online Resource
    Erratum “Milky Way Tomography with the SkyMapper Southern Survey. II. Photometric Recalibration of SMSS DR2” (2021, ApJ, 907, 68)
    American Astronomical Society ; 2022
    In:  The Astrophysical Journal Vol. 924, No. 2 ( 2022-01-01), p. 141-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 924, No. 2 ( 2022-01-01), p. 141-
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/ac425d
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 2960-9
    detail.hit.zdb_id: 1473835-1
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  • 4
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    The K2 Asteroseismic KEYSTONE sample of Dwarf and Subgiant Solar-Like Oscillators : I. Data and Asteroseismic parameters
    EDP Sciences ; 2024
    In:  Astronomy & Astrophysics Vol. 688 ( 2024-8), p. A13-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 688 ( 2024-8), p. A13-
    Abstract: Aims . The KEYSTONE project aims to enhance our understanding of solar-like oscillators by delivering a catalogue of global asteroseismic parameters (Δ v and v max ) for 173 stars, comprising mainly dwarfs and subgiants, observed by the K2 mission in its short-cadence mode during campaigns 6–19. Methods . We derive atmospheric parameters and luminosities using spectroscopic data from TRES, astrometric data from Gaia , and the infrared flux method (IRFM) for a comprehensive stellar characterisation. Asteroseismic parameters are robustly extracted using three independent methods, complemented by an iterative refinement of the spectroscopic analyses using seismic log g values to enhance parameter accuracy. Results . Our analysis identifies new detections of solar-like oscillations in 159 stars, providing an important complement to already published results from previous campaigns. The catalogue provides homogeneously derived atmospheric parameters and luminosities for the majority of the sample. Comparison between spectroscopic T eff and those obtained from the IRFM demonstrates excellent agreement. The iterative approach to spectroscopic analysis significantly enhances the accuracy of the stellar properties derived.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202450055
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2024
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    detail.hit.zdb_id: 1458466-9
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  • 5
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    Online Resource
    The GALAH survey: tracing the Milky Way’s formation and evolution through RR Lyrae stars
    Oxford University Press (OUP) ; 2024
    In:  Monthly Notices of the Royal Astronomical Society Vol. 531, No. 1 ( 2024-05-13), p. 137-162
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 531, No. 1 ( 2024-05-13), p. 137-162
    Abstract: Stellar mergers and accretion events have been crucial in shaping the evolution of the Milky Way (MW). These events have been dynamically identified and chemically characterized using red giants and main-sequence stars. RR Lyrae (RRL) variables can play a crucial role in tracing the early formation of the MW since they are ubiquitous, old (t ≥ 10 Gyr) low-mass stars and accurate distance indicators. We exploited Data Release 3 of the GALAH survey to identify 78 field RRLs suitable for chemical analysis. Using synthetic spectra calculations, we determined atmospheric parameters and abundances of Fe, Mg, Ca, Y, and Ba. Most of our stars exhibit halo-like chemical compositions, with an iron peak around [Fe/H] ≈ −1.40, and enhanced Ca and Mg content. Notably, we discovered a metal-rich tail, with [Fe/H] values ranging from −1 to approximately solar metallicity. This sub-group includes almost 1/4 of the sample, it is characterized by thin disc kinematics and displays sub-solar α-element abundances, marginally consistent with the majority of the MW stars. Surprisingly, they differ distinctly from typical MW disc stars in terms of the s-process elements Y and Ba. We took advantage of similar data available in the literature and built a total sample of 535 field RRLs for which we estimated kinematical and dynamical properties. We found that metal-rich RRLs (1/3 of the sample) likely represent an old component of the MW thin disc. We also detected RRLs with retrograde orbits and provided preliminary associations with the Gaia–Sausage–Enceladus, Helmi, Sequoia, Sagittarius, and Thamnos stellar streams.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stae1149
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2024
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  • 6
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    Combined APOGEE-GALAH stellar catalogues using the Cannon
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 513, No. 1 ( 2022-04-21), p. 232-255
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 513, No. 1 ( 2022-04-21), p. 232-255
    Abstract: APOGEE and GALAH are two high resolution multi-object spectroscopic surveys that provide fundamental stellar parameters and multiple elemental abundance estimates for about half a million stars in the Milky Way. Both surveys observe in different wavelength regimes and use different data reduction pipelines leading to significant offsets and trends in stellar parameters and abundances for the common stars observed in both surveys. Such systematic differences/offsets in stellar parameters and abundances make it difficult to effectively utilize them to investigate Galactic abundance trends in spite of the unique advantage provided by their complementary sky coverage and different Milky Way components they observe. Hence, we use the Cannon data-driven method selecting a training set of 4418 common stars observed by both surveys. This enables the construction of two catalogues, one with the APOGEE-scaled and the other with the GALAH-scaled stellar parameters. Using repeat observations in APOGEE and GALAH, we find high precision in metallicity (∼0.02–0.4 dex) and alpha abundances (∼0.02–0.03 dex) for spectra with good signal-to-noise ratio (SNR & gt; 80 for APOGEE and SNR & gt; 40 for GALAH). We use open and globular clusters to validate our parameter estimates and find small scatter in metallicity (0.06 dex) and alpha abundances (0.03 dex) in APOGEE-scaled case. The final catalogues have been cross-matched with the Gaia EDR3 catalogue to enable their use to carry out detailed chemo-dynamic studies of the Milky Way from perspectives of APOGEE and GALAH.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac873
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 207232-4
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 7
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    Prospects for Galactic and stellar astrophysics with asteroseismology of giant stars in the TESS continuous viewing zones and beyond
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 502, No. 2 ( 2021-02-06), p. 1947-1966
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 502, No. 2 ( 2021-02-06), p. 1947-1966
    Abstract: The NASA Transiting Exoplanet Survey Satellite (NASA-TESS) mission presents a treasure trove for understanding the stars it observes and the Milky Way, in which they reside. We present a first look at the prospects for Galactic and stellar astrophysics by performing initial asteroseismic analyses of bright (G & lt; 11) red giant stars in the TESS southern continuous viewing zone (SCVZ). Using three independent pipelines, we detect νmax and Δν in 41 per cent of the 15 405 star parent sample (6388 stars), with consistency at a level of $\sim \! 2{{\ \rm per\ cent}}$ in νmax and $\sim \! 5{{\ \rm per\ cent}}$ in Δν. Based on this, we predict that seismology will be attainable for ∼3 × 105 giants across the whole sky and at least 104 giants with ≥1 yr of observations in the TESS-CVZs, subject to improvements in analysis and data reduction techniques. The best quality TESS-CVZ data, for 5574 stars where pipelines returned consistent results, provide high-quality power spectra across a number of stellar evolutionary states. This makes possible studies of, for example, the asymptotic giant branch bump. Furthermore, we demonstrate that mixed ℓ = 1 modes and rotational splitting are cleanly observed in the 1-yr data set. By combining TESS-CVZ data with TESS-HERMES, SkyMapper, APOGEE, and Gaia, we demonstrate its strong potential for Galactic archaeology studies, providing good age precision and accuracy that reproduces well the age of high [α/Fe] stars and relationships between mass and kinematics from previous studies based on e.g. Kepler. Better quality astrometry and simpler target selection than the Kepler sample makes this data ideal fo r studies of the local star formation history and evolution of the Galactic disc. These results provide a strong case for detailed spectroscopic follow-up in the CVZs to complement that which has been (or will be) collected by current surveys.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stab098
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
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    SSG: 16,12
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  • 8
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    Online Resource
    Chemo-dynamics and asteroseismic ages of seven metal-poor red giants from the Kepler field
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 510, No. 2 ( 2021-12-30), p. 1733-1747
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 510, No. 2 ( 2021-12-30), p. 1733-1747
    Abstract: In this work, we combine information from solar-like oscillations, high-resolution spectroscopy, and Gaia astrometry to derive stellar ages, chemical abundances, and kinematics for a group of seven metal-poor red giants and characterize them in a multidimensional chrono-chemo-dynamical space. Chemical abundance ratios were derived through classical spectroscopic analysis employing 1D LTE atmospheres on Keck/HIRES spectra. Stellar ages, masses, and radii were calculated with grid-based modelling, taking advantage of availability of asteroseismic information from Kepler. The dynamical properties were determined with galpy using Gaia EDR3 astrometric solutions. Our results suggest that underestimated parallax errors make the effect of Gaia parallaxes more important than different choices of model grid or – in the case of stars ascending the red giant branch – mass-loss prescription. Two of the stars in this study are identified as potentially evolved halo blue stragglers. Four objects are likely members of the accreted Milky Way halo, and their possible relationship with known accretion events is discussed.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stab3545
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 207232-4
    detail.hit.zdb_id: 2016084-7
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  • 9
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    Online Resource
    Milky Way Tomography with the SkyMapper Southern Survey. II. Photometric Recalibration of SMSS DR2
    American Astronomical Society ; 2021
    In:  The Astrophysical Journal Vol. 907, No. 2 ( 2021-02-01), p. 68-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 907, No. 2 ( 2021-02-01), p. 68-
    Abstract: We apply the spectroscopy-based stellar-color regression (SCR) method to perform an accurate photometric recalibration of the second data release from the SkyMapper Southern Survey (SMSS DR2). From comparison with a sample of over 200,000 dwarf stars with stellar atmospheric parameters taken from GALAH+ DR3 and with accurate, homogeneous photometry from Gaia DR2, zero-point offsets are detected in the original photometric catalog of SMSS DR2, in particular for the gravity- and metallicity-sensitive uv bands. For the uv bands, the zero-point offsets are close to zero at very low extinction, and then steadily increase with E ( B  −  V ), reaching as large as 0.174 and 0.134 mag respectively, at E ( B  −  V ) ∼ 0.5 mag. These offsets largely arise from the adopted dust term in the transformations used by SMSS DR2 to construct photometric calibrators from the ATLAS reference catalog. For the gr bands, the zero-point offsets exhibit negligible variations with the E ( B  −  V ) of Schlegel et al. due to their tiny coefficients on the dust term in the transformation. Our study also reveals small but significant spatial variations of the zero-point offsets in all uvgr bands. External checks using Strömgren photometry, WD loci, and the SDSS Stripe 82 standard-star catalog independently confirm the zero-points found by our revised SCR method.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/abca37
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2960-9
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 10
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    The GALAH+ survey: Third data release
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 506, No. 1 ( 2021-07-06), p. 150-201
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 506, No. 1 ( 2021-07-06), p. 150-201
    Abstract: The ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution of the Milky Way. With this third data release of the Galactic Archaeology with HERMES (GALAH) survey, we publish 678 423 spectra for 588 571 mostly nearby stars (81.2 per cent of stars are within & lt;2 kpc), observed with the HERMES spectrograph at the Anglo-Australian Telescope. This release (hereafter GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, and faint survey, 70 per cent), K2-HERMES (17 per cent), TESS-HERMES (5 per cent), and a subset of ancillary observations (8 per cent) including the bulge and & gt;75 stellar clusters. We derive stellar parameters Teff, log g, [Fe/H], vmic, vbroad, and vrad using our modified version of the spectrum synthesis code Spectroscopy Made E asy (sme) and 1D marcs model atmospheres. We break spectroscopic degeneracies in our spectrum analysis with astrometry from Gaia DR2 and photometry from 2MASS. We report abundance ratios [X/Fe] for 30 different elements (11 of which are based on non-LTE computations) covering five nucleosynthetic pathways. We describe validations for accuracy and precision, flagging of peculiar stars/measurements and recommendations for using our results. Our catalogue comprises 65 per cent dwarfs, 34 per cent giants, and 1 per cent other/unclassified stars. Based on unflagged chemical composition and age, we find 62 per cent young low-$\alpha$, 9 per cent young high-$\alpha$, 27 per cent old high-$\alpha$, and 2 per cent stars with [Fe/H] ≤ −1. Based on kinematics, 4 per cent are halo stars. Several Value-Added-Catalogues, including stellar ages and dynamics, updated after Gaia eDR3, accompany this release and allow chrono-chemodynamic analyses, as we showcase.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stab1242
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 207232-4
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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