Publications (62)
The temperature and chronology of heavy-element synthesis in low-mass stars
Pieter Neyskens, Sophie Van Eck, Alain Jorissen +3
Roughly half of the heavy elements (atomic mass greater than that of iron) are believed to be synthesized in the late evolutionary stages of stars with masses between 0.8 and 8 sol…
Molecular bands in extremely metal-poor stars. Granulation effects
Piercarlo Bonifacio, Elisabetta Caffau, Hans-Günter Ludwig +4
The bands of diatomic molecules are important abundance indicators, especially in metal-poor stars, where they are still measurable in metallicity regimes where the atomic lines of…
Non-LTE iron abundances in cool stars: The role of hydrogen collisions
Rana Ezzeddine, Thibault Merle, Bertrand Plez
In the aim of determining accurate iron abundances in stars, this work is meant to empirically calibrate H-collision cross-sections with iron, where no quantum mechanical calculati…
Red Supergiants as Cosmic Abundance Probes: massive star clusters in M83, and the mass-metallicity relation of nearby galaxies
Ben Davies, Rolf-Peter Kudritzki, Carmela Lardo +6
We present an abundance analysis of seven super-star clusters in the disk of M83. The near-infrared spectra of these clusters are dominated by Red Supergiants, and the spectral sim…
The effect of winds in red supergiants: modeling for interferometry
Gemma González-TorÃ, Markus Wittkowski, Ben Davies +1
Red supergiants (RSGs) are evolved massive stars in a stage preceding core-collapse supernova. Understanding evolved-phases of these cool stars is key to understanding the cosmic m…
The Reddening of Red Supergiants: When Smoke Gets In Your Eyes
Philip Massey, Bertrand Plez, Emily M. Levesque +3
Deriving the physical properties of red supergiants (RSGs) depends upon accurate corrections for reddening by dust. We use our recent modeling of the optical spectra of RSGs to add…
The Physical Properties of the Red Supergiant WOH G64: The Largest Star Known?
Emily M. Levesque, Philip Massey, Bertrand Plez +1
WOH G64 is an unusual red supergiant (RSG) in the Large Magellanic Cloud (LMC), with a number of properties that set it apart from the rest of the LMC RSG population, including a t…
Red Supergiant Stars as Cosmic Abundance Probes: NLTE Effects in J-band Iron and Titanium Lines
Maria Bergemann, Rolf-Peter Kudritzki, Bertrand Plez +3
Detailed non-LTE calculations for red supergiant stars are presented to investigate the influence of NLTE on the formation of atomic iron and titanium lines in the J-band. With the…
Physical Properties of Red Supergiants
Philip Massey, Bertrand Plez, Emily M. Levesque +3
Red supergiants (RSGs) are an evolved stage in the life of intermediate massive stars (<25Mo). For many years their location in the H-R diagram was at variance with the evolutionar…
First release of PLATO consortium stellar limb-darkening coefficients
Giuseppe Morello, Jeffrey Gerber, Bertrand Plez +4
We release the first grid of stellar limb-darkening coefficients (LDCs) and intensity profiles (IPs) computed by the consortium of the PLAnetary Transits and Oscillations of stars…
A grid of MARCS model atmospheres for S stars
Sophie Van Eck, Pieter Neyskens, Bertrand Plez +6
S-type stars are late-type giants whose atmosphere is enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynth…
The impact of winds on the spectral appearance of Red Supergiants
Ben Davies, Bertrand Plez
The rate at which mass is lost during the Red Supergiant evolutionary stage may strongly influence how the star appears. Though there have been many studies discussing how RSGs app…
M-dwarf metallicities - A high-resolution spectroscopic study in the near infrared
Anna Ãnehag, Ulrike Heiter, Bengt Gustafsson +3
The relativley large spread in the derived metallicities ([Fe/H]) of M dwarfs shows that various approaches have not yet converged to consistency. The presence of strong molecular…
Evidence of Deep Mixing in IRS 7, a Cool Massive Supergiant Member of the Galactic Nuclear Star Cluster
Rafael Guerço, Verne V. Smith, Katia Cunha +9
The center of the Milky Way contains stellar populations spanning a range in age and metallicity, with a recent star formation burst producing young and massive stars. Chemical abu…
The outer atmosphere of the M-type supergiant alpha Orionis: KI 7699A emission
Bertrand Plez, David L. Lambert
Spatially-resolved high-resolution long-slit spectra of Betelgeuse's circumstellar shell are described for a spectral window centered on the 7699Ã resonance line of neutral potassi…
Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars
Young Sun Lee, Timothy C. Beers, Thomas Masseron +8
We describe a method for the determination of stellar [C/Fe] abundance ratios using low-resolution (R = 2000) stellar spectra from the SDSS and SEGUE. By means of a star-by-star co…
The temperatures of Red Supergiants
Ben Davies, Rolf-Peter Kudritzki, Bertrand Plez +6
We present a re-appraisal of the temperatures of Red Supergiants (RSGs) using their optical and near-infrared spectral energy distributions (SEDs). We have obtained data of a sampl…
The temperatures of red supergiants in low metallicity environments
Gemma González-TorÃ, Ben Davies, Rolf-Peter Kudritzki +1
The temperatures of red supergiants (RSGs) are expected to depend on metallicity (Z) in such a way that lower-Z RSGs are warmer. In this work, we investigate the Z-dependence of th…
MARCS model atmospheres
Bertrand Plez
In this review presented at the Symposium A stellar journey in Uppsala, June 2008, I give my account of the historical development of the MARCS code from the first version publishe…
The Physical Properties of Red Supergiants: Comparing Theory and Observations
Philip Massey, Emily M. Levesque, Bertrand Plez +1
Red supergiants (RSGs) are an evolved stage in the life of intermediate massive stars (than than 25 solar masses). For many years, their location in the H-R diagram was at variance…
Analysis of the carbon-rich very metal-poor dwarf G77-61
Bertrand Plez, Judith G. Cohen
We present an analysis of the carbon dwarf G77-61, a known binary, based on high resolution Keck spectra. G77-61 has a very-low metallicity, although not as extreme as what was pre…
A non-LTE study of Li I lines in AGB stars
Dan Kiselman, Bertrand Plez
We study the formation of Li lines in a case study of an S-type AGB star in the SMC. AGB stars may be important providers of Li to the interstellar medium. Abundance analysis o…
The chemical composition of carbon stars: The R-type stars
Olga Zamora, Carlos Abia, Bertrand Plez +2
The aim of this work is to shed some light on the problem of the formation of carbon stars of R-type from a detailed study of their chemical composition. We use high-resolution and…
Non-LTE Radiative Transfer with Turbospectrum
Jeffrey M. Gerber, Ekaterina Magg, Bertrand Plez +4
Physically realistic models of stellar spectra are needed in a variety of astronomical studies, from the analysis of fundamental stellar parameters, to studies of exoplanets and st…
Explosion Imminent: the appearance of Red Supergiants at the point of core-collapse
Ben Davies, Bertrand Plez, Mike Petrault
From the early radiation of type II-P supernovae (SNe), it has been claimed that the majority of their red supergiant (RSG) progenitors are enshrouded by large amounts of circumste…
The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought
Emily M. Levesque, Philip Massey, K. A. G. Olsen +4
We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine the effective temperatures of 74 Galactic red supergiants. From these…
Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
Maria Bergemann, Rolf-Peter Kudritzki, Zach Gazak +2
Non-LTE calculations for Mg I in red supergiant stellar atmospheres are presented to investigate the importance of non-LTE for the formation of Mg I lines in the NIR J-band. Recent…
Red Supergiants as Cosmic Abundance Probes: The Magellanic Clouds
Ben Davies, Rolf-Peter Kudritzki, Zach Gazak +4
Red Supergiants (RSGs) are cool (~4000K), highly luminous stars (L - 10^5 Lsun), and are among the brightest near-infrared (NIR) sources in star-forming galaxies. This makes them p…
Measurement of telescope transmission using a Collimated Beam Projector
Thierry Souverin, Jérémy Neveu, Marc Betoule +17
The number of type Ia supernova observations will see a significant growth within the next decade, especially thanks to the Legacy Survey of Space and Time undertaken by the Vera R…
Abundance Patterns in S-type AGB stars : Setting Constraints on Nucleosynthesis and Stellar Evolution Models
Pieter Neyskens, Sophie Van Eck, Bertrand Plez +3
During the evolution on the AGB, S-type stars are the first objects to experience s-process nucleosynthesis and third dredge-ups, and therefore to exhibit sprocess signatures in th…
<3D> NLTE line formation in the atmospheres of red supergiants
Maria Bergemann, Rolf P. Kudritzki, Ben Davies +3
Red supergiants with their enormous brightness at J-band are ideal probes of cosmic chemical composition. It is therefore crucial to have realistic models of radiative transfer in…
S stars and s-process in the Gaia era I. Stellar parameters and chemical abundances in a sub-sample of S stars with new MARCS model atmospheres
Shreeya Shetye, Sophie Van Eck, Alain Jorissen +6
S stars are transition objects between M-type giants and carbon stars on the asymptotic giant branch (AGB). They are characterized by overabundances of s-process elements. Roughly…
Late-Type Red Supergiants: Too Cool for the Magellanic Clouds?
Emily M. Levesque, Philip Massey, K. A. G. Olsen +1
We have identified seven red supergiants (RSGs) in the Large Magellanic Cloud (LMC) and four RSGs in the Small Magellanic Cloud (SMC), all of which have spectral types that are con…
Solar carbon abundance from 3D non-LTE modelling of the diagnostic lines of the CH molecule
Richard Hoppe, Maria Bergemann, Philipp Eitner +5
The spectral lines of the CH molecule are a key carbon (C) abundance diagnostic in FGKM-type stars. These lines are detectable in metal-rich and, in contrast to atomic C lines, als…
Ultra metal-poor stars: Spectroscopic determination of stellar atmospheric parameters using iron Non-LTE line abundances
Rana Ezzeddine, Anna Frebel, Bertrand Plez
We present new ultra-metal-poor (UMP) stars parameters with [Fe/H]<-4.0 based on line-by-line non-local thermodynamic equilibrium (NLTE) abundances using an up-to-date iron model a…
An empirical recipe for inelastic hydrogen-atom collisions in non-LTE calculations
Rana Ezzeddine, Thibault Merle, Bertrand Plez +3
We investigate the role of hydrogen collisions in NLTE spectral line synthesis, and introduce a new general empirical recipe to determine inelastic charge transfer (CT) and bound-b…
Bringing VY Canis Majoris Down to Size: An Improved Determination of Its Effective Tempeature
Philip Massey, Emily M. Levesque, Bertrand Plez
The star VY CMa is a late-type M supergiant with many peculiarities, mostly related to the intense circumstellar environment due to the star's high mass-loss rate. Claims have been…
StarDICE III: Characterization of the photometric instrument with a Collimated Beam Projector
Thierry Souverin, Jérémy Neveu, Marc Betoule +18
The measurement of type Ia supernovae magnitudes provides cosmological distances, which can be used to constrain dark energy parameters. Large photometric surveys require a substan…
Red Supergiants in the Andromeda Galaxy (M31)
Philip Massey, David R. Silva, Emily M. Levesque +5
Red supergiants are a short-lived stage in the evolution of moderately massive stars (10-25Mo), and as such their location in the H-R diagram provides an exacting test of stellar e…
Red Supergiant Stars as Cosmic Abundance Probes: II. NLTE Effects in J-band Silicon Lines
Maria Bergemann, Rolf-Peter Kudritzki, Matthias Wueurl +3
Medium resolution J-band spectroscopy of individual red supergiant stars is a promising tool to investigate the chemical composition of the young stellar population in star forming…
The APOGEE Data Release 16 Spectral Line List
Verne V. Smith, Dmitry Bizyaev, Katia Cunha +15
The updated H-band spectral line list (from λ15,000 - 17,000à ) adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) for the SDSS IV Data Release 16 (DR1…
Model Atmospheres for Cool Massive Stars
Bertrand Plez
In this review given at the Hot and Cool: Bridging Gaps in Massive Star Evolution conference, I present the state of the art in red supergiant star atmosphere modelling. The last g…
Stellar synthetic spectroscopy in the Virtual Observatory era
Bertrand Plez
Arguments for including in the VO large grids of synthetic spectra fully covering the HR diagram are presented. One obvious need is that of population synthesis at all redshifts. T…
Observational constraints on the origin of the elements. III. Evidence for the dominant role of sub-Chandrasekhar SN Ia in the chemical evolution of Mn and Fe in the Galaxy
Philipp Eitner, Maria Bergemann, Camilla Juul Hansen +4
The abundance ratios of manganese to iron in late-type stars across a wide metallicity range place tight constraints on the astrophysical production sites of Fe-group elements. In…
Observational constraints on the origin of the elements. I. 3D NLTE formation of Mn lines in late-type stars
Maria Bergemann, Andrew J. Gallagher, Philipp Eitner +9
Manganese (Mn) is a key Fe-group elements, commonly employed in stellar population and nucleosynthesis studies to explore the role of SN Ia. We have developed a new non-local therm…
The PLATO Mission
Heike Rauer, Conny Aerts, Juan Cabrera +842
PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large numb…
Red Supergiants as Cosmic Abundance Probes: The Sculptor Galaxy NGC 300
J. Zachary Gazak, Rolf Kudritzki, Chris Evans +9
We present a quantitative spectroscopic study of twenty-seven red supergiants in the Sculptor Galaxy NGC 300. J-band spectra were obtained using KMOS on the VLT and studied with st…
StarDICE IV: correcting visible photometry from atmospheric gray extinction using thermal infrared observations
Kélian Sommer, Bertrand Plez, Johann Cohen-Tanugi +11
Ground-based surveys such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time require photometric calibration that is both long-term stable and spatially uniform at…
The SAPP pipeline for the determination of stellar abundances and atmospheric parameters of stars in the core program of the PLATO mission
Matthew Raymond Gent, Maria Bergemann, Aldo Serenelli +25
We introduce the SAPP (Stellar Abundances and atmospheric Parameters Pipeline), the prototype of the code that will be used to determine parameters of stars observed within the cor…
Quantitative Spectroscopic J-band Study of Red Supergiants in Perseus OB-1
J. Zachary Gazak, Ben Davies, Rolf Kudritzki +2
We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ~3000 in the J-band. We have obtained high…
M3DIS -- A grid of 3D radiation-hydrodynamics stellar atmosphere models for stellar surveys
Philipp Eitner, Maria Bergemann, Richard Hoppe +3
Large-scale stellar surveys, such as SDSS-V, 4MOST, WEAVE, and PLATO, require accurate atmospheric models and synthetic spectra of stars for accurate analyses of fundamental stella…
The Effective Temperatures and Physical Properties of Magellanic Cloud Red Supergiants: The Effects of Metallicity
Emily M. Levesque, Philip Massey, K. A. G. Olsen +3
We use the MARCS stellar atmosphere to derive the physical properties of 36 red supergiants (RSGs) in the LMC, and 39 RSGs in the SMC using moderate-resolution optical spectrophoto…
StarDICE I: sensor calibration bench and absolute photometric calibration of a Sony IMX411 sensor
Marc Betoule, Sarah Antier, Emmanuel Bertin +18
The Hubble diagram of type-Ia supernovae (SNe-Ia) provides cosmological constraints on the nature of dark energy with an accuracy limited by the flux calibration of currently avail…
A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
Bengt Gustafsson, Bengt Edvardsson, Kjell Eriksson +3
We have constructed a grid of about 10,000 spherically symmetric and plane-parallel models with the MARCS program, and make it available for public use. Parameter ranges are: Teff=…
Photospheric constraints, current uncertainties in models of stellar atmospheres, and spectroscopic surveys
Bertrand Plez, Nicolas Grevesse
We summarize here the discussions around photospheric constraints, current uncertainties in models of stellar atmospheres, and reports on ongoing spectroscopic surveys. Rather than…
The Coolest Stars in the Clouds: Unusual Red Supergiants in the Magellanic Clouds
Emily M. Levesque, Philip Massey, K. A. G. Olsen +1
Red supergiants (RSGs) are a He-burning phase in the evolution of moderately high mass stars (10-25 solar masses). The evolution of these stars, particularly at low metallicities,…
Observational constraints on the origin of the elements. IV: The standard composition of the Sun
Ekaterina Magg, Maria Bergemann, Aldo Serenelli +11
The chemical composition of the Sun is requested in the context of various studies in astrophysics, among them in the calculation of the standard solar models (SSMs), which describ…
The photospheric solar oxygen project: I. Abundance analysis of atomic lines and influence of atmospheric models
Elisabetta Caffau, Hans-G. Ludwig, Matthias Steffen +5
The solar oxygen abundance has undergone a major downward revision in the last decade, the most noticeable one being the update including 3D hydrodynamical simulations to model the…
[O/Fe] Estimates for Carbon-Enhanced Metal-Poor Stars from Near-IR Spectroscopy
Catherine R. Kennedy, Thirupathi Sivarani, Timothy C. Beers +6
We report on oxygen abundances determined from medium-resolution near-IR spectroscopy for a sample of 57 carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/ESO surve…
A New Method for Measuring Metallicities of Young Super Star Clusters
J. Zachary Gazak, Ben Davies, Nate Bastian +7
We demonstrate how the metallicities of young super star clusters can be measured using novel spectroscopic techniques in the J-band. The near-infrared flux of super star clusters…
Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study
Timothy C. Beers, Thirupathi Sivarani, Brian Marstellar +3
We report on an abundance analysis for a pilot study of seven Carbon-Enhanced Metal-Poor (CEMP) stars, based on medium-resolution optical and near-infrared spectroscopy. The optica…
S stars and s-process in the Gaia era II. Constraining the luminosity of the third dredge-up with Tc-rich S stars
Shreeya Shetye, Sophie Van Eck, Alain Jorissen +6
S stars are late-type giants that are transition objects between M-type stars and carbon stars on the asymptotic giant branch (AGB). They are classified into two types: intrinsic o…