Publications (81)
Chemical evolution of the Galactic Center
V. Grieco, F. Matteucci, N. Ryde +2
In recent years, the Galactic Center (GC) region (200 pc in radius) has been studied in detail with spectroscopic stellar data as well as an estimate of the ongoing star formation…
Detailed abundance analysis of a metal-poor giant in the Galactic Center
N. Ryde, T. K. Fritz, R. M. Rich +4
We report the first results from our program to examine the metallicity distribution of the Milky Way nuclear star cluster connected to SgrA*, with the goal of inferring the star f…
Systematic investigation of chemical abundances derived using IR spectra obtained with GIANO
E. Caffau, P. Bonifacio, E. Oliva +10
Detailed chemical abundances of Galactic stars are needed in order to improve our knowledge of the formation and evolution of our galaxy, the Milky Way. We took advantage of the GI…
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…
Supergiant GCIRS 22 in the Milky Way Nuclear Star Cluster: Revised alpha abundances
B. Thorsbro, S. Khalidy, R. M. Rich +7
Context: The chemical abundances of alpha-elements in Galactic Centre (GC) supergiants provide key insights into the chemical enrichment and star formation history of the Milky Way…
The Gaia-ESO Public Spectroscopic Survey: Implementation, data products, open cluster survey, science, and legacy
S. Randich, G. Gilmore, L. Magrini +161
In the last 15 years different ground-based spectroscopic surveys have been started (and completed) with the general aim of delivering stellar parameters and elemental abundances f…
ALMA and VLA reveal the lukewarm chromospheres of the nearby red supergiants Antares and Betelgeuse
E. O'Gorman, G. M. Harper, K. Ohnaka +8
We first present spatially resolved ALMA and VLA continuum observations of the early-M red supergiant Antares to search for the presence of a chromosphere at radio wavelengths. We…
Detailed abundances in the Galactic center: Evidence of a metal-rich alpha-enhanced stellar population
B. Thorsbro, N. Ryde, R. M. Rich +8
We present a detailed study of the composition of 20 M giants in the Galactic center with 15 of them confirmed to be in the Nuclear Star Cluster. As a control sample we have also o…
Non-thermal Mg I emission at 12 um from Procyon
N. Ryde, M. J. Richter
We report on stellar Mg I emission at 12 um from alpha CMi (Procyon), a star slightly hotter than the Sun. Solar Mg I emission is well-known and its formation was successfully expl…
The nature of the circumstellar CO_2 emission from M giants
N. Ryde, K. Eriksson, B. Gustafsson
The 13-16 um region observed by the Infrared Space Observatory (ISO) of several ABG stars are discussed. We present and analyse spectra of seven M giants which show carbon dioxide…
Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars
R. Smiljanic, A. J. Korn, M. Bergemann +99
The Gaia-ESO Survey is obtaining high-quality spectroscopic data for about 10^5 stars using FLAMES at the VLT. UVES high-resolution spectra are being collected for about 5000 FGK-t…
Fluorine in the Solar Neighborhood: Chemical Evolution Models
E. Spitoni, F. Matteucci, H. Jönsson +2
In the light of the new observational data related to fluorine abundances in the solar neighborhood stars, we present here chemical evolution models testing different fluorine nucl…
The Chemical Evolution of Fluorine in the Bulge - High-resolution K-band spectra of giants in three fields
H. Jönsson, N. Ryde, G. M. Harper +6
Possible main formation sites of F in the Universe include AGB stars, the ν-process in Type II SNe, and/or W-R stars. The importance of the W-R stars has theoretically been questi…
Modelling CO emission from Mira's wind
N. Ryde, F. L. Schoeier
We have modelled the circumstellar envelope of {\it o} Ceti (Mira) using new observational constraints. These are obtained from photospheric light scattered in near-IR vibrational-…
Detailed abundance trends in the inner Galactic bulge
N. Nieuwmunster, G. Nandakumar, E. Spitoni +7
In this paper, we aim to derive high-precision alpha-element abundances using CRIRES high-resolution IR spectra of 72 cool M giants of the inner Galactic bulge. Silicon, magnesium,…
Kinematics and chemistry of recently discovered Reticulum 2 and Horologium 1 dwarf galaxies
Sergey E. Koposov, Andrew R. Casey, Vasily Belokurov +17
Photometry alone is not sufficient to unambiguously distinguish between ultra-faint star clusters and dwarf galaxies because of their overlap in morphological properties. Here we r…
CO line observations of OH/IR stars in the inner Galactic Bulge: Characteristics of stars at the tip of the AGB
H. Olofsson, T. Khouri, B. A. Sargent +10
12CO and 13CO lines, as well as a mm-wave continuum, have been observed for a sample of 22 OH/IR stars in directions within 2 degrees of the Galactic Centre. Photometry data have b…
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…
M Giants with IGRINS II. Chemical Evolution of Fluorine at High Metallicities
G. Nandakumar, N. Ryde, G. Mace
The origin and evolution of fluorine in the Milky Way galaxy is still in debate. In particular, the increase of the [F/Fe] in metal-rich stars found from near-IR HF-lines is challe…
Temperatures and metallicities of M giants in the galactic Bulge from low-resolution K-band spectra
M. Schultheis, N. Ryde, G. Nandakumar
With the existing and upcoming large multi-fibre low-resolution spectrographs, the question arises how precise stellar parameters such as Teff and [Fe/H] can be obtained from low-r…
The Nephele ecosystem: stars, globular clusters, and stellar streams associated with the progenitor galaxy of Centauri
G. Pagnini, P. Di Matteo, M. Haywood +7
Globular clusters (GCs) and their associated stellar streams are key tracers of the hierarchical assembly history of the Milky Way. Centauri, the most massive and chemically c…
Modelling the chemical evolution of Zr, La, Ce and Eu in the Galactic discs and bulge
V. Grisoni, G. Cescutti, F. Matteucci +3
We study the chemical evolution of Zr, La, Ce and Eu in the Milky Way discs and bulge by means of chemical evolution models compared with recent spectroscopic data. We consider det…
MOONS: a Multi-Object Optical and Near-infrared Spectrograph for the VLT
M. Cirasuolo, J. Afonso, R. Bender +77
MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope (VLT), selected by ESO for a Phase A study. The baseline des…
Metallicity-dependent kinematics and orbits in the Milky Way's nuclear stellar disc
F. Nogueras-Lara, N. Nieuwmunster, M. Schultheis +7
The nuclear stellar disc (NSD) is a flat and dense stellar structure at the centre of the Milky Way. Previous work has identified the presence of metal-rich and metal-poor stars in…
Chemical abundances for 11 bulge stars from high-resolution, near-IR spectra
N. Ryde, B. Gustafsson, B. Edvardsson +10
It is debated whether the Milky Way bulge has the characteristics of a classical bulge sooner than those of a pseudobulge. Detailed abundance studies of bulge stars is a key to inv…
A Community Science Case for E-ELT HIRES
R. Maiolino, M. Haehnelt, M. T. Murphy +57
Building on the experience of the high-resolution community with the suite of VLT high-resolution spectrographs, which has been tremendously successful, we outline here the (scienc…
Reassessing the low- massive sequence stars in Gaia RVS
G. Nandakumar, G. Kordopatis, M. Schultheis +4
Recently, a chemically depleted young massive stellar population was identified using the spectroscopic catalogue of Gaia DR3. To explain its characteristics, a recent enhanced sta…
Stellar Population Astrophysics (SPA) with the TNG: Identification of a Sulphur line at lambda(air) = 1063.600nm in GIANO-B stellar spectra
N. Ryde, H. Hartman, E. Oliva +6
Context. In the advent of new infrared, high-resolution spectrometers, accurate and precise atomic data in the infrared is urgently needed. Identifications, wavelengths, strengths,…
OH/IR stars in the inner Galactic bulge: I. Colour, CO line, and stellar light curve characteristics
H. Olofsson, T. Khouri, S. Muller +11
Stars on the asymptotic giant branch (AGB) play important roles in a number of astronomical contexts. To quantify these roles, it is necessary to establish the mass-loss characteri…
TEXES Observations of M Supergiants: Dynamics and Thermodynamics of Wind Acceleration
G. M. Harper, M. J. Richter, N. Ryde +4
We have detected [Fe II] 17.94 um and 24.52 um emission from a sample of M supergiants using TEXES on the IRTF. These low opacity emission lines are resolved at R = 50, 000 and pro…
Evolved stars with complex atmospheres - the high spectral resolution, mid-IR view
N. Ryde, J. Lambert, M. J. Richter +12
The physical structures of the outer atmospheres of red giants are not known. They are certainly complex and a range of recent observations are showing that we need to embrace to n…
Water Vapor on Betelgeuse as Revealed by TEXES High-Resolution 12 Micron Spectra
N. Ryde, G. M. Harper, M. J. Richter +2
The outer atmosphere of the M supergiant Betelgeuse is puzzling. Published observations of different kinds have shed light on different aspects of the atmosphere, but no unified pi…
Understanding AGB evolution in Galactic bulge stars from high-resolution infrared spectroscopy
S. Uttenthaler, J. A. D. L. Blommaert, P. R. Wood +4
An analysis of high-resolution near-infrared spectra of a sample of 45 asymptotic giant branch (AGB) stars towards the Galactic bulge is presented. The sample consists of two subsa…
The Gaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk
M. Bergemann, G. Ruchti, A. Serenelli +42
We study the relationship between age, metallicity, and alpha-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra…
Fluorine in the Solar neighborhood: No evidence for the neutrino process
H. Jönsson, N. Ryde, E. Spitoni +5
Asymptotic Giant Branch stars are known to produce `cosmic' fluorine but it is uncertain whether these stars are the main producers of fluorine in the Solar neighborhood or if any…
A First Study of Giant Stars in the Galactic Bulge based on Crires spectra
N. Ryde, B. Edvardsson, B. Gustafsson +1
We present our on-going work on the determination of elemental abundances of giants in the Galactic Bulge by means of infrared spectroscopy. We show a preliminarily reduced spectru…
Detailed near-IR stellar abundances of red giants in the Inner Bulge and Galactic Center
N. Ryde, R. M. Rich, B. Thorsbro +3
Owing to their extreme crowding and high and variable extinction, stars in the Galactic Bulge, within +-2 degrees of the Galactic plane, and especially those in the Nuclear Star Cl…
Detailed Abundances for the Old Population near the Galactic Center: I. Metallicity distribution of the Nuclear Star Cluster
R. M. Rich, N. Ryde, B. Thorsbro +4
We report the first high spectral resolution study of 17 M giants kinematically confirmed to lie within a few parsecs of the Galactic Center, using R=24,000 spectroscopy from Keck/…
The inner two degrees of the Milky Way. Evidence of a chemical difference between the Galactic Center and the surrounding inner bulge stellar populations
M. Schultheis, R. M. Rich, L. Origlia +4
Although there have been numerous studies of chemical abundances in the Galactic bulge, the central two degrees have been relatively unexplored due to the heavy and variable inters…
Abundances of disk and bulge giants from hi-res optical spectra: II. O, Mg, Ca, and Ti in the bulge sample
H. Jönsson, N. Ryde, M. Schultheis +1
Determining elemental abundances of bulge stars can, via chemical evolution modeling, help to understand the formation and evolution of the bulge. Recently there have been claims b…
Abundances of disk and bulge giants from hi-res optical spectra: I. O, Mg, Ca, and Ti in the Solar neighborhood and Kepler field samples
H. Jönsson, N. Ryde, T. Nordlander +4
The galactic bulge is a significant part of our galaxy, but it is hard to observe, being both distant and covered by dust in the disk. Therefore there do not exist many hi-res opti…
Detection of Water Vapor in the Photosphere of Arcturus
N. Ryde, D. L. Lambert, M. J. Richter +1
We report detections of pure rotation lines of OH and H2O in the K1.5 III red-giant star Arcturus (alpha Bootis) using high-resolution, infrared spectra covering the regions 806-82…
M giants with IGRINS IV. Identification and characterization of a near-IR line of the s-element Barium
G. Nandakumar, N. Ryde, H. Hartman +1
Neutron-capture elements represent an important nucleosynthetic channel in the study of the Galactic Chemical Evolution of stellar populations. For stellar populations behind signi…
The Gaia-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products
G. Gilmore, S. Randich, C. C. Worley +165
The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to obtain astrophysical parameters and elemental abundances for 100,000 stars, including large representat…
Sulphur abundances in halo giants from the [S I] line at 1082 nm and the S I triplet around 1045 nm
H. Jönsson, N. Ryde, P. E. Nissen +4
It is still debated whether or not the Galactic chemical evolution of sulphur in the halo followed the constant or flat trend with [Fe/H], ascribed to the result of explosive nucle…
X-shooter spectroscopy of giant stars in the nuclear star cluster
L. Origlia, C. Fanelli, A. Mucciarelli +5
Near-IR spectra of a homogeneous sample of 15 red giants in the Galactic nuclear star cluster, within 1.5 pc of SgrA*, have been acquired with X-shooter at the Very Large Telescope…
M giants with IGRINS I. Stellar parameters and -abundance trends of the solar neighborhood population
G. Nandakumar, N. Ryde, L. Casagrande +1
Cool stars, such as M giants, can only be analysed in the near-infrared (NIR) regime due to the ubiquitous TiO features in optical spectra of stars with Teff < 4000 K. In dust obsc…
The first r-process enhanced star confirmed to be a member of the Galactic bulge
R. Forsberg, R. M. Rich, N. Nieuwmunster +4
Aims. Stars with strong enhancements of r-process elements are rare and tend to be metal-poor, with generally [Fe/H] <-2 dex and found in the halo. In this work we aim to investiga…
Probing the mass loss history of carbon stars using CO line and dust continuum emission
F. L. Schoeier, N. Ryde, H. Olofsson
An extensive modelling of CO line emission from the circumstellar envelopes around a number of carbon stars is performed. By combining radio observations and infrared observations…
The Galactic Chemical Evolution of phosphorus observed with IGRINS
G. Nandakumar, N. Ryde, M. Montelius +30
Phosphorus (P) is considered to be one of the key elements for life, making it an important element to look for in the abundance analysis of spectra of stellar systems. Yet, there…
The Determination of Stellar Parameters of Giants in the Galactic Disks and Bulge
J. Byström, N. Ryde, S. Feltzing +2
Here, we present our on-going work on the determination of stellar parameters of giants in the Galactic Disks and Bulge observed with UVES on the VLT. We present some preliminarily…
4MOST Consortium Survey 4: Milky Way Disc and Bulge High-Resolution Survey (4MIDABLE-HR)
T. Bensby, M. Bergemann, J. Rybizki +21
The signatures of the formation and evolution of a galaxy are imprinted in its stars. Their velocities, ages, and chemical compositions present major constraints on models of galax…
Evidence against anomalous compositions for giants in the Galactic Nuclear Star Cluster
B. Thorsbro, N. Ryde, M. Schultheis +5
Very strong Sc I lines have been found recently in cool M giants in the Nuclear Star Cluster in the Galactic Center. Interpreting these as anomalously high scandium abundances in t…
Chemical Abundances in the Milky Way's Nuclear Stellar Disc
N. Ryde, G. Nandakumar, R. Albarracin +3
The Nuclear Stellar Disc (NSD) is a rotating, disc-like structure in the Galactic Center, believed to have a distinct star formation. However, its formation history and evolutionar…
Chemical Abundances in the Nuclear Star Cluster of the Milky Way: alpha-Element Trends and Their Similarities with the Inner Bulge
N. Ryde, G. Nandakumar, M. Schultheis +15
A chemical characterization of the Galactic Center is essential for understanding its formation and structural evolution. Trends of alpha-elements, such as Mg, Si, and Ca, serve as…
The LEGARE Project. I. Chemical evolution model of the Nuclear Stellar Disc in a Bayesian framework
E. Spitoni, M. Schultheis, F. Matteucci +5
The Nuclear Stellar Disc (NSD) of the Milky Way is a dense, rotating stellar system in the central 200 pc. The NSD is thought to be primarily fuelled by bar-driven gas inflows from…
Fluorine in the solar neighborhood - is it all produced in AGB-stars?
H. Jönsson, N. Ryde, G. M. Harper +2
The origin of 'cosmic' fluorine is uncertain, but there are three proposed production sites/mechanisms: AGB stars, nucleosynthesis in Type II supernovae, and/or the winds of W…
The 3 micron spectrum of R Doradus observed with the ISO-SWS
N. Ryde, K. Eriksson
We have modeled the 2.6 - 3.7 um spectrum of the red semiregular variable R Doradus observed with the Short-Wavelength Spectrometer on board the Infrared Space Observatory. The wav…
M Giants with IGRINS III. Abundance Trends for 21 Elements in the Solar Neighborhood from High-Resolution, Near-Infrared Spectra
G. Nandakumar, N. Ryde, R. Forsberg +4
In order to investigate the chemical history of the entire MilkyWay, it is imperative to also study the dust-obscured regions, where most of the mass lies. The Galactic Center is a…
Systematic trend of water vapour absorption in red giant atmospheres revealed by high resolution TEXES 12 micron spectra
N. Ryde, J. Lambert, M. Farzone +5
The structures of the outer atmospheres of red giants are very complex. The notion of large optically thick molecular spheres around the stars (MOLspheres) has been invoked in orde…
The very low mass multiple system LHS\,1070 -- a testbed for model atmospheres for the lower end of the main sequence
A. S. Rajpurohit, C. Reyle, M. Schultheis +8
LHS1070 is a nearby multiple system of low mass stars. It is an important source of information for probing the low mass end of the main sequence, down to the hydrogen-burning limi…
Near-infrared spectroscopic observations of massive young stellar object candidates in the Central Molecular Zone
G. Nandakumar, M. Schultheis, A. Feldmeier-Krause +6
We present a spectroscopic follow-up of photometrically-selected young stellar object (YSO) candidates in the Central Molecular Zone of the Galactic center. Our goal is to quantify…
Chemical evolution of the inner 2 degrees of the Milky Way bulge: [alpha/Fe] trends and metallicity gradients
N. Ryde, M. Schultheis, V. Grieco +3
The structure, formation, and evolution of the Milky Way bulge is a matter of debate. Important diagnostics for discriminating between bulge models include alpha-abundance trends w…
Abundances of disk and Bulge giants from high-resolution optical spectra III. Sc, V, Cr, Mn, Co, Ni
M. Lomaeva, H. Jönsson, N. Ryde +2
Context. Recent observations of the Bulge, e.g., its X-shape, cylindrical stellar motions, and a potential fraction of young stars propose that it formed through secular evolution…
Chemical Evolution of Ytterbium in the Galactic Disk
M. Montelius, R. Forsberg, N. Ryde +8
Measuring the abundances of neutron-capture elements in Galactic disk stars is an important part of understanding key stellar and galactic processes. In the optical wavelength regi…
Water vapor on supergiants. The 12 micron TEXES spectra of mu Cephei
N. Ryde, M. J. Richter, G. M. Harper +2
Several recent papers have argued for warm, semi-detached, molecular layers surrounding red giant and supergiant stars, a concept known as a MOLsphere. Spectroscopic and interferom…
Carbon stars in local group dwarf galaxies: C and O abundances
R. Wahlin, K. Eriksson, B. Gustafsson +4
We present abundances of carbon and oxygen as well as abundance ratios 12C/13C for a sample of carbon stars in the LMC, SMC, Carina, Sculptor and Fornax dwarf galaxies. The overall…
Chemical Abundances of M giants in the Galactic Center: a Single Metal-Rich Population with Low [alpha/Fe]
N. Ryde, M. Schultheis
Context. The formation and evolution of the Milky Way bulge is still largely an unanswered question. One of the most essential observables needed in its modelling are the metallici…
CNO abundances in the Galactic bulge
N. Ryde
The carbon, nitrogen, and oxygen abundances and trends in the bulge are discussed in the context of our recent analysis of these elements in an on-going project based on near-IR sp…
Chemical Characterization of the Inner Galactic bulge:North-South Symmetry
G. Nandakumar, N. Ryde, M. Schultheis +5
While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasingly rapidly, the inner Galactic bulge ( |b| < 2) remains poorly st…
The Gaia-ESO Survey: A globular cluster escapee in the Galactic halo
K. Lind, S. E. Koposov, C. Battistini +37
A small fraction of the halo field is made up of stars that share the light element (Z<=13) anomalies characteristic of second generation globular cluster (GC) stars. The ejected s…
On the Galactic chemical evolution of sulphur. Sulphur abundances from the [S i] 1082 nm line in giants
E. Matrozis, N. Ryde, A. K. Dupree
Context. The Galactic chemical evolution of sulphur is still under debate. At low metallicities some studies find no correlation between [S/Fe] and [Fe/H], others find [S/Fe] incre…
On the galactic chemical evolution of sulfur
N. Ryde, D. L. Lambert
Sulfur abundances have been determined for ten stars to resolve a debate in the literature on the Galactic chemical evolution of sulfur in the halo phase of the Milky Way. Our anal…
Mira's wind explored in scattering infrared CO lines
N. Ryde, B. Gustafsson, K. Eriksson +1
We have observed the intermediate regions of the circumstellar envelope of Mira (o Ceti) in photospheric light scattered by three vibration-rotation transitions of the fundamental…
SOFIA/EXES Observations of Water Absorption in the Protostar AFGL 2591 at High Spectral Resolution
Nick Indriolo, D. A. Neufeld, C. N. DeWitt +8
We present high spectral resolution (~3 km/s) observations of the nu_2 ro-vibrational band of H2O in the 6.086--6.135 micron range toward the massive protostar AFGL 2591 using the…
4MOST: Project overview and information for the First Call for Proposals
R. S. de Jong, O. Agertz, A. Agudo Berbel +335
We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Vis…
The carbon star IRAS 15194-5115: Circumstellar CO radio and FIR rotational lines
N. Ryde, F. L. Schoeier, H. Olofsson
We have modelled radio and far-infrared rotational lines of 12^CO and 13^CO obtained from the circumstellar envelope of the infrared-bright carbon star IRAS 15194-5115. Eleven rota…
Mg I emission lines at 12 and 18 micrometer in K giants
J. O. Sundqvist, N. Ryde, G. M. Harper +2
The solar Mg I emission lines at 12 micrometer have already been observed and analyzed well. Previous modeling attempts for other stars have, however, been made only for Procyon an…
The Abundance of Elements in Cool Stars, as Determined from High-Resolution, 1-5 Micron Spectroscopy
N. Ryde, B. Gustafsson, K. Eriksson +1
We review the field of abundance determinations of elements in cool stars, with special interest paid to determinations based on analyses of high-resolution, 1-5 micron spectra. We…
4MOST Consortium Survey 3: Milky Way Disc and Bulge Low-Resolution Survey (4MIDABLE-LR)
C. Chiappini, I. Minchev, E. Starkenburg +35
The mechanisms of the formation and evolution of the Milky Way are encoded in the orbits, chemistry and ages of its stars. With the 4MOST MIlky way Disk And BuLgE Low-Resolution Su…
The origin of carbon, investigated by spectral analysis of solar-type stars in the Galactic Disk
B. Gustafsson, T. Karlsson, E. Olsson +2
Abundance analysis of carbon has been performed in a sample of 80 late F and early G type dwarf stars in the metallicity range -1.06 < [Fe/H] < 0.26 using the forbidden [C I] line…