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The Stellar Observations Network Group (SONG) -- A Legacy Archive of Stellar Time-Domain Spectroscopy
M. N. Lund, F. Grundahl, M. S. Fredslund +41
The Stellar Observations Network Group (SONG) network has operated for more than a decade, providing long-baseline, high-cadence spectroscopic observations of bright stars and the…
Attempting an accurate age estimate of the open cluster NGC 6633 using CoRoT and Gaia
K. Brogaard, A. Miglio, T. Arentoft +5
Asteroseismology of solar-like oscillations in giant stars allow the derivation of their masses and radii. For members of open clusters, this provides an age of the cluster that sh…
Advancing accuracy in age determinations of old-disk stars using an oscillating red giant in an eclipsing binary
J. S. Thomsen, A. Miglio, K. Brogaard +26
The study of resonant oscillation modes in low-mass red giant branch stars enables their ages to be inferred with exceptional (10%) precision, unlocking the possibility to re…
Low-amplitude solar-like oscillations in the K5 V star Indi A
Mia S. Lundkvist, Hans Kjeldsen, Timothy R. Bedding +17
We have detected solar-like oscillations in the mid K-dwarf Indi A, making it the coolest dwarf to have measured oscillations. The star is noteworthy for harboring a…
An asteroseismic age estimate of the open cluster NGC 6866 using Kepler and Gaia
K. Brogaard, T. Arentoft, A. Miglio +10
Asteroseismology of solar-like oscillations in giant stars allow the derivation of their masses and radii. For members of open clusters this allows an age estimate of the cluster w…
Establishing the accuracy of asteroseismic mass and radius estimates of giant stars. II. Revised stellar masses and radii for KIC 8430105
Jeppe Sinkbæk Thomsen, Karsten Brogaard, Torben Arentoft +6
Asteroseismic scaling relations can provide high-precision measurements of mass and radius for red giant (RG) stars displaying solar-like oscillations. Their accuracy can be valida…
Establishing the accuracy of asteroseismic mass and radius estimates of giant stars III. KIC4054905, an eclipsing binary with two 10 Gyr thick disk RGB stars
K. Brogaard, T. Arentoft, D. Slumstrup +16
Eclipsing binary stars with an oscillating giant component allow accurate stellar parameters to be derived and asteroseismic methods to be tested and calibrated. To this aim, suita…
Asteroseismology of overmassive, undermassive, and potential past members of the open cluster NGC6791
K. Brogaard, T. Arentoft, J. Jessen-Hansen +1
We perform an asteroseismic investigation of giant stars in the field of NGC 6791 with previous indications of atypical evolution. The analysis makes use of observations from Keple…
Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. III. Constraints from a subgiant
K. Brogaard, F. Grundahl, E. L. Sandquist +18
Models of stellar structure and evolution can be constrained using accurate measurements of the parameters of eclipsing binary members of open clusters. Multiple binary stars provi…
Precise radial velocities of giant stars XV. Mysterious nearly periodic radial velocity variations in the eccentric binary Cygni
Paul Heeren, Sabine Reffert, Trifon Trifonov +10
Using the Hamilton Echelle Spectrograph at Lick Observatory, we have obtained precise radial velocities (RVs) of a sample of 373 G- and K-giant stars over more than 12 years, leadi…
Properties of the Hyades, the eclipsing binary HD27130, and the oscillating red giant Tau
K. Brogaard, E. Pakštienė, F. Grundahl +21
Eclipsing binary stars allow derivation of accurate and precise masses and radii. When they reside in star clusters, properties of even higher precision, along with additional info…
Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries
E. Knudstrup, F. Grundahl, K. Brogaard +10
Accurate stellar parameters of stars in open clusters can help constrain models of stellar structure and evolution. Here we wish to determine the age and metallicity content of the…
Variability in the Massive Open Cluster NGC 1817 from K2: A Rich Population of Asteroseismic Red Clump, Eclipsing Binary, and Main Sequence Pulsating Stars
Eric L. Sandquist, Dennis Stello, Torben Arentoft +13
We present a survey of variable stars detected in K2 Campaign 13 within the massive intermediate age ( Gyr) open cluster NGC 1817. We identify a complete sample of 44 red cl…
Oscillations in the Sun with SONG: Setting the scale for asteroseismic investigations
M. Fredslund Andersen, P. Pallé, J. Jessen-Hansen +12
Context. We present the first high-cadence multi-wavelength radial-velocity observations of the Sun-as-a-star, carried out during 57 consecutive days using the stellar échelle spec…
Asteroseismology of the Hyades red giant and planet host epsilon Tauri
Torben Arentoft, Frank Grundahl, Timothy R. White +23
Asteroseismic analysis of solar-like stars allows us to determine physical parameters such as stellar mass, with a higher precision compared to most other methods. Even in a well-s…
The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young
K. Brogaard, S. M. Christiansen, F. Grundahl +18
We determine the properties of the binary star V106 in the old open cluster NGC6791. We identify the system to be a blue straggler cluster member by using a combination of ground-b…
The mass and age of the first SONG target: the red giant 46 LMi
S. Frandsen, M. Fredslund Andersen, K. Brogaard +12
The Stellar Observation Network Group (SONG) is an initiative to build a worldwide network of 1m telescopes with highprecision radial-velocity spectrographs. Here we analyse the fi…
Convective-core overshoot and suppression of oscillations: Constraints from red giants in NGC6811
T. Arentoft, K. Brogaard, J. Jessen-Hansen +4
Using data from the NASA spacecraft Kepler, we study solar-like oscillations in red-giant stars in the open cluster NGC6811. We determine oscillation frequencies, frequency separat…
Detection of solar-like oscillations in relics of the Milky Way: asteroseismology of K giants in M4 using data from the NASA K2 mission
A. Miglio, W. J. Chaplin, K. Brogaard +18
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens of thousands of field stars. Tests against independent estimates of these properties…
Testing the asymptotic relation for period spacings from mixed modes of red giants observed with the Kepler mission
B. Buysschaert, P. G. Beck, E. Corsaro +7
Dipole mixed pulsation modes of consecutive radial order have been detected for thousands of low-mass red-giant stars with the NASA space telescope Kepler. Such modes have the pote…
Testing Asteroseismic Scaling Relations using Eclipsing Binaries in Star Clusters and the Field
K. Brogaard, J. Jessen-Hansen, R. Handberg +10
The accuracy of stellar masses and radii determined from asteroseismology is not known! We examine this issue for giant stars by comparing classical measurements of detached eclips…
The role of turbulent pressure as a coherent pulsational driving mechanism: the case of the delta Scuti star HD 187547
V. Antoci, M. Cunha, G. Houdek +6
HD 187547 was the first candidate that led to the suggestion that solar-like oscillations are present in delta Scuti stars. Longer observations, however, show that the modes interp…
Spectroscopic Study of the Open Cluster NGC 6811
Joanna Molenda-Zakowicz, Karsten Brogaard, Ewa Niemczura +4
The NASA space telescope Kepler has provided unprecedented time-series observations which have revolutionised the field of asteroseismology, i.e. the use of stellar oscillations to…
Limits on surface gravities of Kepler planet-candidate host stars from non-detection of solar-like oscillations
T. L. Campante, W. J. Chaplin, M. N. Lund +20
We present a novel method for estimating lower-limit surface gravities log g of Kepler targets whose data do not allow the detection of solar-like oscillations. The method is teste…