181 citations · 1.9k across the 42 of their papers we have counts for
43 papers
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…
Asteroseismology of the G8 subgiant beta Aquilae with SONG-Tenerife, SONG-Australia and TESS
Hans Kjeldsen, Timothy R. Bedding, Yaguang Li +28
We present time-series radial velocities of the G8 subgiant star beta Aql obtained in 2022 and 2023 using SONG-Tenerife and, for the first time, SONG-Australia. We also analyse a s…
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…
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…
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…
Observing the changing surface structures of the active K giant sigma Gem with SONG
H. Korhonen, R. M. Roettenbacher, S. Gu +6
Aims: We aim to study the spot evolution and differential rotation in the magnetically active cool K-type giant star sigma Gem from broadband photometry and continuous spectroscopi…
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…
Asteroseismic masses of four evolved planet-hosting stars using SONG and TESS: resolving the retired A-star mass controversy
Sai Prathyusha Malla, Dennis Stello, Daniel Huber +12
The study of planet occurrence as a function of stellar mass is important for a better understanding of planet formation. Estimating stellar mass, especially in the red giant regim…
The subgiant HR 7322 as an asteroseismic benchmark star
Amalie Stokholm, Poul Erik Nissen, Victor Silva Aguirre +5
We present an in-depth analysis of the bright subgiant HR 7322 (KIC 10005473) using Kepler short-cadence photometry, optical interferometry from CHARA, high-resolution spectra from…
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…
Establishing the accuracy of asteroseismic mass and radius estimates of giant stars. I. Three eclipsing systems at [Fe/H]~ -0.3 and the need for a large high-precision sample
K. Brogaard, C. J. Hansen, A. Miglio +12
We aim to establish and improve the accuracy level of asteroseismic estimates of mass, radius, and age of giant stars. This can be achieved by measuring independent, accurate, and…
The [Y/Mg] clock works for evolved solar metallicity stars
D. Slumstrup, F. Grundahl, K. Brogaard +5
Previously [Y/Mg] has been proven to be an age indicator for solar twins. Here, we investigate if this relation also holds for helium-core-burning stars of solar metallicity. High…
Spectroscopic survey of Kepler stars. II. FIES/NOT observations of A- and F-type stars
E. Niemczura, M. Polińska, S. J. Murphy +7
We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed with the FIES spectrograph at the Nordic Optical Telescope. We provide spectral types,…
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…
First Results From The Hertzsprung Song Telescope: Asteroseismology Of The G5 Subgiant Star {\Mu}Her
F. Grundahl, M. Fredslund Andersen, J. Christensen-Dalsgaard +26
We report the first asteroseismic results obtained with the Hertzsprung SONG Telescope from an extensive high-precision radial-velocity observing campaign of the subgiant muHerculi…
Do A-type stars flare?
M. G. Pedersen, V. Antoci, H. Korhonen +5
For flares to be generated, stars have to have a sufficiently deep outer convection zone (F5 and later), strong large--scale magnetic fields (Ap/Bp-type stars) or strong, radiative…
MiNDSTEp differential photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756: Microlensing and a new time delay
E. Giannini, R. W. Schmidt, J. Wambsganß +52
We present V and R photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope…
The Age and Distance of the Kepler Open Cluster NGC 6811 from an Eclipsing Binary, Turnoff Star Pulsation, and Giant Asteroseismology
Eric L. Sandquist, J. Jessen-Hansen, Matthew D. Shetrone +9
We present the analysis of an eccentric, partially eclipsing long-period ( d) binary system KIC 9777062 that contains main sequence stars near the turnoff of the intermedi…
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…
The K2-ESPRINT Project V: a short-period giant planet orbiting a subgiant star
Vincent Van Eylen, Simon Albrecht, Davide Gandolfi +31
We report on the discovery and characterization of the transiting planet K2-39b (EPIC 206247743b). With an orbital period of 4.6 days, it is the shortest-period planet orbiting a s…