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1. A new resonance-like feature in the outer disc of the Milky Way

Author

Drimmel, Ronald, Khanna, Shourya, D'Onghia, Elena, Tepper-García, Thorsten, Bland-Hawthorn, Joss, Chemin, Laurent, Ripepi, Vincenzo, Romero-Gómez, Mercé, Ramos, Pau, Poggio, Eloisa, Andrae, Rene, Blomme, Ronny, Cantat-Gaudin, Tristan, Castro-Ginard, Alfred, Clementini, Gisella, Fiqueras, Francesca, Frémat, Yves, Fouesneau, Morgan, Lobel, Alex, Marshall, Douglas, and Muraveva, Tatiana

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

Modern astrometric and spectroscopic surveys have revealed a wealth of structure in the phase space of stars in the Milky Way, with evidence of resonance features and non-equilibrium processes. Using Gaia's third data release, we present evidence of a new resonance-like feature in the outer disc of the Milky Way. The feature is most evident in the angular momentum distribution of the young Classical Cepheids, a population for which we can derive accurate distances over much of the Galactic disc. We then search for similar features in the outer disc using a much larger sample of red giant stars, as well as a compiled list of over 31 million stars with spectroscopic line-of-sight velocity measurements. While much less evident in these two older samples, the distribution of stars in action-configuration space suggests that resonance features are present here as well. The position of the feature in action-configuration space suggests that the new feature may be related to the Galactic bar, but other possibilities are discussed., Comment: 13 pages, 11 figures, in press for A&A

Published
2022
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2. New self-consistent wind parameters fitting optical spectra of O-type stars observed with HERMES spectrograph

Author

Gormaz-Matamala, Alex C., Curé, Michel, Lobel, Alex, Panei, Jorge A., Cuadra, Jorge, Araya, Ignacio, Arcos, Catalina, and Figueroa-Tapia, Felipe

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We perform spectral fitting for a set of O-type stars based on self-consistent wind solutions, which provide mass-loss rate and velocity profiles directly derived from the initial stellar parameters. The great advantage of this self-consistent spectral fitting is therefore the reduction of the number of free parameters to be tuned. Self-consistent values for the line-force parameters (k,alpha,delta) and subsequently for the mass-loss rate and terminal velocity are provided by the m-CAK prescription introduced in Paper I, updated in this work with improvements such as a temperature structure for the wind, self-consistently evaluated from the line-acceleration. Synthetic spectra are calculated using the radiative transfer code FASTWIND, replacing the classical beta-law for our new calculated velocity profiles. We found that self-consistent m-CAK solutions provide values for theoretical mass-loss rates on the order of the most recent predictions of other studies. From here, we generate synthetic spectra with self-consistent hydrodynamics to fit and obtain a new set of stellar and wind parameters for our sample of O-type stars whose spectra was taken with the high resolution echelle spectrograph HERMES (R=85000). We find a satisfactory global fit for our observations, with good accuracy for photospheric He I and He II lines and a quite acceptable fit for H lines. Although this self-consistent spectral analysis is currently constrained in the optical wavelength range only, this is an important step towards the determination of stellar and wind parameters without using a beta-law. Given these results, we expect that the values introduced here should be helpful for future studies about the stars constituting this sample, together with the prospective that the m-CAK self-consistent prescription be extended to numerous studies about massive stars in future., Comment: Accepted for publication in Astronomy & Astrophysics, in 17 February 2022 In this updated version, we corrected information about funding data in Acknowledgements section

Published
2022
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3. A new outburst of the yellow hypergiant star Rho Cas

Author

Kraus, Michaela, Kolka, Indrek, Aret, Anna, Nickeler, Dieter H., Maravelias, Grigoris, Eenmäe, Tõnis, Lobel, Alex, and Klochkova, Valentina G.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Yellow hypergiants are evolved massive stars that were suggested to be in post-red supergiant stage. Post-red supergiants that evolve back to the blue, hot side of the Hertzsprung-Russell diagram can intersect a temperature domain in which their atmospheres become unstable against pulsations (the Yellow Void or Yellow Wall), and the stars can experience outbursts with short, but violent mass eruptions. The yellow hypergiant Rho Cas is famous for its historical and recent outbursts, during which the star develops a cool, optically thick wind with a very brief but high mass-loss rate, causing a sudden drop in the light curve. Here we report on a new outburst of Rho Cas which occurred in 2013, accompanied by a temperature decrease of ~3000 K and a brightness drop of 0.6 mag. During the outburst TiO bands appear, together with many low excitation metallic atmospheric lines characteristic for a later spectral type. With this new outburst, it appears that the time interval between individual events decreases, which might indicate that Rho Cas is preparing for a major eruption that could help the star to pass through the Yellow Void. We also analysed the emission features that appear during phases of maximum brightness and find that they vary synchronous with the emission in the prominent [CaII] lines. We conclude that the occasionally detected emission in the spectra of Rho Cas, as well as certain asymmetries seen in the absorption lines of low to medium-excitation potential, are circumstellar in nature, and we discuss the possible origin of this material., Comment: 19 pages, 13 figures, accepted for publication in MNRAS

Published
2018
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4. The Belgian repository of fundamental atomic data and stellar spectra (BRASS). I. Cross-matching atomic databases of astrophysical interest

Author

Laverick, Mike, Lobel, Alex, Merle, Thibault, Royer, Pierre, Martayan, Christophe, David, Marc, Hensberge, Herman, and Thienpont, Emmanuel

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Atomic Physics
Abstract

Fundamental atomic parameters, such as oscillator strengths, play a key role in modelling and understanding the chemical composition of stars in the universe. Despite the significant work underway to produce these parameters for many astrophysically important ions, uncertainties in these parameters remain large and can propagate throughout the entire field of astronomy. The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide the largest systematic and homogeneous quality assessment of atomic data to date in terms of wavelength, atomic and stellar parameter coverage. To prepare for it, we first compiled multiple literature occurrences of many individual atomic transitions, from several atomic databases of astrophysical interest, and assessed their agreement. Several atomic repositories were searched and their data retrieved and formatted in a consistent manner. Data entries from all repositories were cross-matched against our initial BRASS atomic line list to find multiple occurrences of the same transition. Where possible we used a non-parametric cross-match depending only on electronic configurations and total angular momentum values. We also checked for duplicate entries of the same physical transition, within each retrieved repository, using the non-parametric cross-match. We report the cross-matched transitions for each repository and compare their fundamental atomic parameters. We find differences in log(gf) values of up to 2 dex or more. We also find and report that ~2% of our line list and Vienna Atomic Line Database retrievals are composed of duplicate transitions. Finally we provide a number of examples of atomic spectral lines with different log(gf) values, and discuss the impact of these uncertain log(gf) values on quantitative spectroscopy. All cross-matched atomic data and duplicate transitions are available to download at brass.sdf.org., Comment: 18 pages, 12 figures, 9 tables. Accepted for publication in A&A

Published
2017
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5. Luminous blue variables: An imaging perspective on their binarity and near environment

Author

Martayan, Christophe, Lobel, Alex, Baade, Dietrich, Mehner, Andrea, Rivinius, Thomas, Boffin, H. M. J., Girard, Julien, Mawet, Dimitri, Montagnier, Guillaume, Blomme, Ronny, Kervella, Pierre, Sana, Hugues, Štefl, Stanislav, Zorec, Juan, Lacour, Sylvestre, Bouquin, Jean-Baptiste Le, Martins, Fabrice, Mérand, Antoine, Patru, Fabien, Selman, Fernando, and Frémat, Yves

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Context. Luminous blue variables (LBVs) are rare massive stars with very high luminosity. They are characterized by strong photo-metric and spectroscopic variability related to transient eruptions. The mechanisms at the origin of these eruptions is not well known. In addition, their formation is still problematic and the presence of a companion could help to explain how they form. Aims. This article presents a study of seven LBVs (about 20% of the known Galactic population), some Wolf-Rayet stars, and massive binaries. We probe the environments that surround these massive stars with near-, mid-, and far-infrared images, investigating potential nebula/shells and the companion stars. Methods. To investigate large spatial scales, we used seeing-limited and near diffraction-limited adaptive optics images to obtain a differential diagnostic on the presence of circumstellar matter and to determine their extent. From those images, we also looked for the presence of binary companions on a wide orbit. Once a companion was detected, its gravitational binding to the central star was tested. Tests include the chance projection probability, the proper motion estimates with multi-epoch observations, flux ratio, and star separations. Results. We find that two out of seven of LBVs may have a wide orbit companion. Most of the LBVs display a large circumstellar envelope or several shells. In particular, HD168625, known for its rings, possesses several shells with possibly a large cold shell at the edge of which the rings are formed. For the first time, we have directly imaged the companion of LBV stars., Comment: Astronomy and Astrophysics, EDP Sciences, 2016

Published
2016
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6. MELCHIORS. The Mercator Library of High Resolution Stellar Spectroscopy

Author

Royer, P., Merle, Thibault, Dsilva, Karan Singh, Sekaran, Sanjay, Van Winckel, Hans, Frémat, Yves, Van Der Swaelmen, Mathieu, Gebruers, S., Tkachenko, Andrew, Laverick, Mike, Dirickx, M., Raskin, Gert, Hensberge, Herman, Abdul-Masih, Michael, Acke, Bram, Alonso, M. L., Bandhu Mahato, S., Beck, P.~G., Behara, Natalie Thérèse, Bloemen, Steven, Buysschaert, B., Cox, N., Debosscher, J., De Cat, Peter, Degroote, P., De Nutte, R., De Smedt, K., de Vries, B., Dumortier, L., Escorza Santos, Ana, Exter, Katrina, Goriely, Stéphane, Gorlova, Nadya, Hillen, M., Homan, Ward, Jorissen, Alain, Kamath, Devika, Karjalainen, M., Karjalainen, R., Lampens, Patricia, Lobel, Alex, Lombaert, R., Marcos-Arenal, P., Menu, J., Merges, F., Moravveji, Ehsan, Nemeth, P., Neyskens, Pieter, Ostensen, R., Pápics, P.~I., Perez, J., Prins, Saskia, Royer, S., Samadi-Ghadim, A., Sana, Hugues, Sans Fuentes, A., Scaringi, Simone, Schmid, V., Siess, Lionel, Siopis, Christos, Smolders, Kristof, Sódor, Á., Thoul, Anne, Triana, Santiago Andrés S., Vandenbussche, Bart, Van de Sande, M., Van De Steene, Griet, Van Eck, Sophie, van Hoof, P.A.M., Van Marle, A. J., Van Reeth, Timothy, Vermeylen, L., Volpi, Delia, Vos, J., Waelkens, Christoffel, Royer, P., Merle, Thibault, Dsilva, Karan Singh, Sekaran, Sanjay, Van Winckel, Hans, Frémat, Yves, Van Der Swaelmen, Mathieu, Gebruers, S., Tkachenko, Andrew, Laverick, Mike, Dirickx, M., Raskin, Gert, Hensberge, Herman, Abdul-Masih, Michael, Acke, Bram, Alonso, M. L., Bandhu Mahato, S., Beck, P.~G., Behara, Natalie Thérèse, Bloemen, Steven, Buysschaert, B., Cox, N., Debosscher, J., De Cat, Peter, Degroote, P., De Nutte, R., De Smedt, K., de Vries, B., Dumortier, L., Escorza Santos, Ana, Exter, Katrina, Goriely, Stéphane, Gorlova, Nadya, Hillen, M., Homan, Ward, Jorissen, Alain, Kamath, Devika, Karjalainen, M., Karjalainen, R., Lampens, Patricia, Lobel, Alex, Lombaert, R., Marcos-Arenal, P., Menu, J., Merges, F., Moravveji, Ehsan, Nemeth, P., Neyskens, Pieter, Ostensen, R., Pápics, P.~I., Perez, J., Prins, Saskia, Royer, S., Samadi-Ghadim, A., Sana, Hugues, Sans Fuentes, A., Scaringi, Simone, Schmid, V., Siess, Lionel, Siopis, Christos, Smolders, Kristof, Sódor, Á., Thoul, Anne, Triana, Santiago Andrés S., Vandenbussche, Bart, Van de Sande, M., Van De Steene, Griet, Van Eck, Sophie, van Hoof, P.A.M., Van Marle, A. J., Van Reeth, Timothy, Vermeylen, L., Volpi, Delia, Vos, J., and Waelkens, Christoffel

Abstract

Aims .Over the past decades, libraries of stellar spectra have been used in a large variety of science cases, including as sources of reference spectra for a given object or a given spectral type. Despite the existence of large libraries and the increasing number of projects of large-scale spectral surveys, there is to date only one very high-resolution spectral library offering spectra from a few hundred objects from the southern hemisphere (UVES-POP). We aim to extend the sample, offering a finer coverage of effective temperatures and surface gravity with a uniform collection of spectra obtained in the northern hemisphere. Methods .Between 2010 and 2020, we acquired several thousand echelle spectra of bright stars with the Mercator-HERMES spectrograph located in the Roque de Los Muchachos Observatory in La Palma, whose pipeline offers high-quality data reduction products. We have also developed methods to correct for the instrumental response in order to approach the true shape of the spectral continuum. Additionally, we have devised a normalisation process to provide a homogeneous normalisation of the full spectral range for most of the objects. Results .We present a new spectral library consisting of 3256 spectra covering 2043 stars. It combines high signal-to-noise and high spectral resolution over the entire range of effective temperatures and luminosity classes. The spectra are presented in four versions: raw, corrected from the instrumental response, with and without correction from the atmospheric molecular absorption, and normalised (including the telluric correction)., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2024

7. X-shooter, NACO, and AMBER observations of the LBV Pistol Star \footnote{Based on ESO runs 85.D-0182A, 085.D-0625AC}

Author

Martayan, Christophe, Blomme, Ronny, Bouquin, Jean-Baptiste Le, Merand, Antoine, Montagnier, Guillaume, Selman, Fernando, Girard, Julien, Fox, Andrew, Baade, Dietrich, Fremat, Yves, Lobel, Alex, Martins, Fabrice, Patru, Fabien, Rivinius, Thomas, Sana, Hugues, Stefl, Stan, Zorec, Jean, and Semaan, Thierry

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We present multi-instruments and multi-wavelengths observations of the famous LBV star Pistol Star. These observations are part of a larger program about early O stars at different metallicities. The Pistol star has been claimed as the most massive star known, with 250 solar masses. We present the preliminary results based on X-Shooter spectra, as well as the observations performed with the VLTI-AMBER and the VLT-NACO adaptive optics. The X-shooter spectrograph allows to obtain simultaneously a spectrum from the UV to the K-band with a resolving power of $\sim$15000. The preliminary results obtained indicate that Pistol Star has similar properties of Eta Car, including shells of matter, but also the binarity. Other objects of the program, here briefly presented, were selected for their particular nature: early O stars with mass discrepancies between stellar evolution models and observations, discrepancies with the wind momentum luminosity relation., Comment: Poster at the 39th LIAC, submitted version of the proceedings

Published
2010

8. High-angular resolution observations of the Pistol Star

Author

Martayan, Christophe, Blomme, Ronny, Bouquin, Jean-Baptiste Le, Merand, Antoine, Montagnier, Guillaume, Selman, Fernando, Girard, Julien, Fox, Andrew, Baade, Dietrich, Fremat, Yves, Lobel, Alex, Martins, Fabrice, Patru, Fabien, Rivinius, Thomas, Sana, Hugues, Stefl, Stan, Zorec, Jean, and Semaan, Thierry

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

First results of near-IR adaptive optics (AO)-assisted imaging, interferometry, and spectroscopy of this Luminous Blue Variable (LBV) are presented. They suggest that the Pistol Star is at least double. If the association is physical, it would reinforce questions concerning the importance of multiplicity for the formation and evolution of extremely massive stars., Comment: poster at IAUS272

Published
2010
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9. Chromospheric Dynamics of Betelgeuse from STIS Spectra

Author

Lobel, Alex

Subjects
Astrophysics
Abstract

We present a high-resolution spectral analysis of Betelgeuse (M2 Iab). Between 1998 January and 1999 March four spatially resolved raster scans (http://cfa-www.harvard.edu/cfa/ep/pressrel/alobel0100.html) have been obtained with the STIS on the Hubble Space Telescope. The near-UV echelle spectra reveal double-peaked permitted emission lines of neutral and singly ionized metals, with self-absorbed line cores. We observe reversals in the intensity of both emission line components when scanning across the UV disk, for four unsaturated lines of Si I, Fe I, Al II], and Fe II. We model the Si I lam2516 resonance line with detailed non-LTE radiative transport calculations in spherical geometry, and constrain the mean velocity structure in the projected aperture area, for each scan position on the chromospheric disk. We infer the spatial velocity structure of Betelgeuse's extended chromosphere, which reveals localized upflows in the western front hemisphere in 1998 September, that expand further toward the eastern hemisphere in 1999 March. The spatial scans exhibit simultaneous up- and downflows across the lower chromosphere with mean velocities of ~2 km/s. We infer non-radial (or non-coherent) mass movements during certain phases of the stellar variability cycle from these subsonic flows. We present a discussion of constructing semi-empiric models for the chromosphere of this cool supergiant, and of its temporal variability., Comment: 15 pages, 12 color figures, Proceedings of a meeting held at Boulder, Colorado, USA. The 12th Cool Stars, Stellar Systems and the Sun, July 30th - August 3rd, 2001. Presentation: Oral Contribution. Program at http://origins.Colorado.EDU/cs12/

Published
2002

10. Two Decades of Hypergiant Research

Author

Lobel, Alex

Subjects
Astrophysics
Abstract

This article is a brief review of the research by Dr. C. de Jager and co-workers over the past twenty years into the physics of hypergiant atmospheres. Various important results on the microturbulence, mass-loss, circumstellar environment, atmospheric velocity fields, and the Yellow Evolutionary Void of these enigmatic stars are summarized. Aspects of recent developments and future work are also communicated., Comment: 11 pages, 1 picture. Review on cool hypergiants, in honour of the 80th birthday of Prof. C. de Jager

Published
2001

11. The Gaia-ESO Survey: Homogenisation of stellar parameters and elemental abundances

Author

Universidad de Alicante. Departamento de Física Aplicada, Hourihane, A., François, P., Worley, C.C., Magrini, L., Gonneau, A., Casey, A.R., Gilmore, Gerard, Randich, Sofia, Sacco, G.G., Recio-Blanco, A., Korn, A., Allende Prieto, C., Smiljanic, R., Blomme, Ronny, Bragaglia, A., Walton, N., Van Eck, S., Bensby, T., Lanzafame, A.C., Frasca, A., Franciosini, E., Damiani, F., Lind, K., Bergemann, M., Bonifacio, P., Hill, V., Lobel, Alex, Montes, David, Feuillet, D.K., Tautvaišienė, G., Guiglion, G., Tabernero, Hugo M., González Hernández, J.I., Gebran, M., Van der Swaelmen, M., Mikolaitis, Š., Daflon, Simone, Merle, T., Morel, Thierry, Lewis, J., González Solares, E.A., Murphy, D.N.A., Jeffries, R., Jackson, R.J., Feltzing, S., Prusti, T., Carraro, G., Biazzo, K., Prisinzano, L., Jofre, P., Zaggia, S., Drazdauskas, A., Stonkuté, E., Marfil, E., Jiménez Esteban, Francisco M., Mahy, Laurent, Gutiérrez Albarrán, M.L., Berlanas, Sara R., Santos, W., Morbidelli, L., Spina, L., Minkevičiūtė, R., Universidad de Alicante. Departamento de Física Aplicada, Hourihane, A., François, P., Worley, C.C., Magrini, L., Gonneau, A., Casey, A.R., Gilmore, Gerard, Randich, Sofia, Sacco, G.G., Recio-Blanco, A., Korn, A., Allende Prieto, C., Smiljanic, R., Blomme, Ronny, Bragaglia, A., Walton, N., Van Eck, S., Bensby, T., Lanzafame, A.C., Frasca, A., Franciosini, E., Damiani, F., Lind, K., Bergemann, M., Bonifacio, P., Hill, V., Lobel, Alex, Montes, David, Feuillet, D.K., Tautvaišienė, G., Guiglion, G., Tabernero, Hugo M., González Hernández, J.I., Gebran, M., Van der Swaelmen, M., Mikolaitis, Š., Daflon, Simone, Merle, T., Morel, Thierry, Lewis, J., González Solares, E.A., Murphy, D.N.A., Jeffries, R., Jackson, R.J., Feltzing, S., Prusti, T., Carraro, G., Biazzo, K., Prisinzano, L., Jofre, P., Zaggia, S., Drazdauskas, A., Stonkuté, E., Marfil, E., Jiménez Esteban, Francisco M., Mahy, Laurent, Gutiérrez Albarrán, M.L., Berlanas, Sara R., Santos, W., Morbidelli, L., Spina, L., and Minkevičiūtė, R.

Abstract

The Gaia-ESO Survey is a public spectroscopic survey that targeted ≳105 stars covering all major components of the Milky Way from the end of 2011 to 2018, delivering its final public release in May 2022. Unlike other spectroscopic surveys, Gaia-ESO is the only survey that observed stars across all spectral types with dedicated, specialised analyses: from O (Teff ~ 30 000–52 000 K) all the way to K-M (≳3500 K). The physics throughout these stellar regimes varies significantly, which has previously prohibited any detailed comparisons between stars of significantly different types. In the final data release (internal data release 6) of the Gaia-ESO Survey, we provide the final database containing a large number of products, such as radial velocities, stellar parameters and elemental abundances, rotational velocity, and also, for example, activity and accretion indicators in young stars and membership probability in star clusters for more than 114 000 stars. The spectral analysis is coordinated by a number of working groups (WGs) within the survey, each specialised in one or more of the various stellar samples. Common targets are analysed across WGs to allow for comparisons (and calibrations) amongst instrumental setups and spectral types. Here we describe the procedures employed to ensure all survey results are placed on a common scale in order to arrive at a single set of recommended results for use by all survey collaborators. We also present some general quality and consistency checks performed on the entirety of the survey results.

Published
2023

13. The Gaia-ESO Survey: The analysis of the hot-star spectra

Author

Universidad de Alicante. Departamento de Física Aplicada, Blomme, Ronny, Daflon, Simone, Gebran, M., Herrero, Artemio, Lobel, Alex, Mahy, Laurent, Martins, Fabrice, Morel, Thierry, Berlanas, Sara R., Blazère, A., Frémat, Y., Gosset, E., Maíz Apellániz, Jesús, Santos, W., Semaan, T., Simón Díaz, Sergio, Volpi, D., Holgado, Gonzalo, Jiménez Esteban, Francisco M., Nieva, M.F., Przybilla, Norbert, Gilmore, Gerard, Randich, Sofia, Negueruela, Ignacio, Prusti, T., Vallenari, A., Alfaro, Emilio J., Bensby, T., Bragaglia, A., Flaccomio, E., Francois, P., Korn, A., Lanzafame, A.C., Pancino, E., Smiljanic, R., Bergemann, M., Carraro, G., Franciosini, E., Gonneau, A., Heiter, U., Hourihane, A., Jofre, P., Magrini, L., Morbidelli, L., Sacco, G.G., Worley, C.C., Zaggia, S., Universidad de Alicante. Departamento de Física Aplicada, Blomme, Ronny, Daflon, Simone, Gebran, M., Herrero, Artemio, Lobel, Alex, Mahy, Laurent, Martins, Fabrice, Morel, Thierry, Berlanas, Sara R., Blazère, A., Frémat, Y., Gosset, E., Maíz Apellániz, Jesús, Santos, W., Semaan, T., Simón Díaz, Sergio, Volpi, D., Holgado, Gonzalo, Jiménez Esteban, Francisco M., Nieva, M.F., Przybilla, Norbert, Gilmore, Gerard, Randich, Sofia, Negueruela, Ignacio, Prusti, T., Vallenari, A., Alfaro, Emilio J., Bensby, T., Bragaglia, A., Flaccomio, E., Francois, P., Korn, A., Lanzafame, A.C., Pancino, E., Smiljanic, R., Bergemann, M., Carraro, G., Franciosini, E., Gonneau, A., Heiter, U., Hourihane, A., Jofre, P., Magrini, L., Morbidelli, L., Sacco, G.G., Worley, C.C., and Zaggia, S.

Abstract

Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey that has collected, over a period of six years, spectra of ~105 stars. This survey provides not only the reduced spectra, but also the stellar parameters and abundances resulting from the analysis of the spectra. Aims. The GES dataflow is organised in 19 working groups. Working group 13 (WG13) is responsible for the spectral analysis of the hottest stars (O, B, and A type, with a formal cutoff of Teff > 7000 K) that were observed as part of GES. We present the procedures and techniques that have been applied to the reduced spectra in order to determine the stellar parameters and abundances of these stars. Methods. The procedure used was similar to that of other working groups in GES. A number of groups (called Nodes) each independently analyse the spectra via state-of-the-art techniques and codes. Specific for the analysis in WG13 was the large temperature range covered (Teff ≈ 7000–50 000 K), requiring the use of different analysis codes. Most Nodes could therefore only handle part of the data. Quality checks were applied to the results of these Nodes by comparing them to benchmark stars, and by comparing them to one another. For each star the Node values were then homogenised into a single result: the recommended parameters and abundances. Results. Eight Nodes each analysed part of the data. In total 17 693 spectra of 6462 stars were analysed, most of them in 37 open star clusters. The homogenisation led to stellar parameters for 5584 stars. Abundances were determined for a more limited number of stars. The elements studied are He, C, N, O, Ne, Mg, Al, Si, and Sc. Abundances for at least one of these elements were determined for 292 stars. Conclusions. The hot-star data analysed here, as well as the GES data in general, will be of considerable use in future studies of stellar evolution and open clusters.

Published
2022

14. The Gaia-ESO Survey: The analysis of the hot-star spectra

Author

Blomme, Ronny, Daflon, S, Gebran, M., Herrero, A, Lobel, Alex, Mahy, L, Martins, F, Morel, Thierry, Berlanas, S.R., Blazere, A, Frémat, Yves, Gosset, E., Maiz Appellaniz, J, Santos, W, Seeman, T, Simon, Diaz, Volpi, Delia, Holgado, G, Jimenez-Esteban, F., Nieva, M.F., Blomme, Ronny, Daflon, S, Gebran, M., Herrero, A, Lobel, Alex, Mahy, L, Martins, F, Morel, Thierry, Berlanas, S.R., Blazere, A, Frémat, Yves, Gosset, E., Maiz Appellaniz, J, Santos, W, Seeman, T, Simon, Diaz, Volpi, Delia, Holgado, G, Jimenez-Esteban, F., and Nieva, M.F.

Abstract

info:eu-repo/semantics/published

Published
2022

15. The Gaia-ESO Public Spectroscopic Survey: Implementation, data products, open cluster survey, science, and legacy

Author

Universidad de Alicante. Departamento de Física Aplicada, Randich, Sofia, Gilmore, Gerard, Magrini, L., Sacco, G.G., Jackson, R.J., Jeffries, R., Worley, C.C., Hourihane, A., Gonneau, A., Viscasillas Vázquez, C., Franciosini, E., Sbordone, L., Sousa, S.G., Zaggia, S., Adibekyan, V.Zh., Bonito, R., Caffau, E., Daflon, Simone, Feuillet, D.K., Drazdauskas, A., Gebran, M., Lagarde, N., González Hernández, J.I., Guiglion, G., Herrero, Artemio, Lobel, Alex, Maíz Apellániz, Jesús, Merle, T., Mikolaitis, Š., Montes, David, Morel, Thierry, Evans, N.W., Mahy, Laurent, Soubiran, C., Spina, L., Tabernero, Hugo M., Tautvaišienė, G., Traven, G., Valentini, M., Van der Swaelmen, M., Villanova, S., Wright, N.J., Abbas, U., Mapelli, M., Famaey, B., Aguirre Børsen-Koch, V., Alves, J., Balaguer-Nunez, L., Barklem, P.S., Barrado, D., Berlanas, Sara R., Binks, A.S., Bressan, A., Capuzzo-Dolcetta, R., Marfil, E., Casagrande, L., Franchini, M., Casamiquela, L., Collins, R.S., D'Orazi, V., Dantas, M.L.L., Debattista, V.P., Frémat, Y., Friel, E., Fu, X., Martell, S.L., Geisler, Douglas, Lewis, J., Gerhard, Ortwin, González Solares, E.A., Grebel, E.K., Gutiérrez Albarran, M.L., Hatzidimitriou, D., Held, E.V., Jiménez Esteban, Francisco M., Jönsson, H., Messina, S., Jordi, C., Khachaturyants, T., Alfaro, Emilio J., Kordopatis, G., Kos, J., Miglio, A., Minchev, I., Allende Prieto, C., Moitinho, A., Negueruela, Ignacio, Montalban, J., Monteiro, M.J.P.F.G., Morossi, C., Mowlavi, N., Mucciarelli, A., Murphy, D.N.A., Nardetto, N., Ortolani, S., Paletou, F., Bensby, T., Prusti, T., Palouš, J., Paunzen, E., Pickering, J.C., Quirrenbach, A., Re Fiorentin, P., Read, J.I., Romano, D., Ryde, N., Sanna, N., Santos, W., Rix, H.-W., Blomme, Ronny, Seabroke, G.M., Spagna, A., Steinmetz, M., Stonkuté, E., Sutorius, E., Thévenin, F., Tosi, M., Tsantaki, M., Vink, Jorick S., Vallenari, A., Wright, N., Bragaglia, A., Wyse, R.F.G., Zoccali, M., Zorec, J., Zucker, D.B., Walton, N., Flaccomio, E., François, P., Irwin, M., Bayo, A., Koposov, S., Korn, A., Lanzafame, A.C., Pancino, E., Recio-Blanco, A., Smiljanic, R., Van Eck, S., Zwitter, T., Asplund, M., Bonifacio, P., Bergemann, M., Feltzing, S., Binney, J., Drew, J., Ferguson, A., Micela, G., Biazzo, K., Carraro, G., Casey, A.R., Damiani, F., Delgado-Mena, E., Frasca, A., Heiter, U., Hill, V., Jofre, P., Laverny, P. de, Lind, K., Marconi, G., Martayan, C., Masseron, T., Monaco, L., Di Marcantonio, P., Morbidelli, L., Prisinzano, L., Universidad de Alicante. Departamento de Física Aplicada, Randich, Sofia, Gilmore, Gerard, Magrini, L., Sacco, G.G., Jackson, R.J., Jeffries, R., Worley, C.C., Hourihane, A., Gonneau, A., Viscasillas Vázquez, C., Franciosini, E., Sbordone, L., Sousa, S.G., Zaggia, S., Adibekyan, V.Zh., Bonito, R., Caffau, E., Daflon, Simone, Feuillet, D.K., Drazdauskas, A., Gebran, M., Lagarde, N., González Hernández, J.I., Guiglion, G., Herrero, Artemio, Lobel, Alex, Maíz Apellániz, Jesús, Merle, T., Mikolaitis, Š., Montes, David, Morel, Thierry, Evans, N.W., Mahy, Laurent, Soubiran, C., Spina, L., Tabernero, Hugo M., Tautvaišienė, G., Traven, G., Valentini, M., Van der Swaelmen, M., Villanova, S., Wright, N.J., Abbas, U., Mapelli, M., Famaey, B., Aguirre Børsen-Koch, V., Alves, J., Balaguer-Nunez, L., Barklem, P.S., Barrado, D., Berlanas, Sara R., Binks, A.S., Bressan, A., Capuzzo-Dolcetta, R., Marfil, E., Casagrande, L., Franchini, M., Casamiquela, L., Collins, R.S., D'Orazi, V., Dantas, M.L.L., Debattista, V.P., Frémat, Y., Friel, E., Fu, X., Martell, S.L., Geisler, Douglas, Lewis, J., Gerhard, Ortwin, González Solares, E.A., Grebel, E.K., Gutiérrez Albarran, M.L., Hatzidimitriou, D., Held, E.V., Jiménez Esteban, Francisco M., Jönsson, H., Messina, S., Jordi, C., Khachaturyants, T., Alfaro, Emilio J., Kordopatis, G., Kos, J., Miglio, A., Minchev, I., Allende Prieto, C., Moitinho, A., Negueruela, Ignacio, Montalban, J., Monteiro, M.J.P.F.G., Morossi, C., Mowlavi, N., Mucciarelli, A., Murphy, D.N.A., Nardetto, N., Ortolani, S., Paletou, F., Bensby, T., Prusti, T., Palouš, J., Paunzen, E., Pickering, J.C., Quirrenbach, A., Re Fiorentin, P., Read, J.I., Romano, D., Ryde, N., Sanna, N., Santos, W., Rix, H.-W., Blomme, Ronny, Seabroke, G.M., Spagna, A., Steinmetz, M., Stonkuté, E., Sutorius, E., Thévenin, F., Tosi, M., Tsantaki, M., Vink, Jorick S., Vallenari, A., Wright, N., Bragaglia, A., Wyse, R.F.G., Zoccali, M., Zorec, J., Zucker, D.B., Walton, N., Flaccomio, E., François, P., Irwin, M., Bayo, A., Koposov, S., Korn, A., Lanzafame, A.C., Pancino, E., Recio-Blanco, A., Smiljanic, R., Van Eck, S., Zwitter, T., Asplund, M., Bonifacio, P., Bergemann, M., Feltzing, S., Binney, J., Drew, J., Ferguson, A., Micela, G., Biazzo, K., Carraro, G., Casey, A.R., Damiani, F., Delgado-Mena, E., Frasca, A., Heiter, U., Hill, V., Jofre, P., Laverny, P. de, Lind, K., Marconi, G., Martayan, C., Masseron, T., Monaco, L., Di Marcantonio, P., Morbidelli, L., and Prisinzano, L.

Abstract

Context. 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 for large samples of Galactic stars, complementing Gaia astrometry. Among those surveys, the Gaia-ESO Public Spectroscopic Survey, the only one performed on a 8m class telescope, was designed to target 100 000 stars using FLAMES on the ESO VLT (both Giraffe and UVES spectrographs), covering all the Milky Way populations, with a special focus on open star clusters. Aims. This article provides an overview of the survey implementation (observations, data quality, analysis and its success, data products, and releases), of the open cluster survey, of the science results and potential, and of the survey legacy. A companion article reviews the overall survey motivation, strategy, Giraffe pipeline data reduction, organisation, and workflow. Methods. We made use of the information recorded and archived in the observing blocks; during the observing runs; in a number of relevant documents; in the spectra and master catalogue of spectra; in the parameters delivered by the analysis nodes and the working groups; in the final catalogue; and in the science papers. Based on these sources, we critically analyse and discuss the output and products of the Survey, including science highlights. We also determined the average metallicities of the open clusters observed as science targets and of a sample of clusters whose spectra were retrieved from the ESO archive. Results. The Gaia-ESO Survey has determined homogeneous good-quality radial velocities and stellar parameters for a large fraction of its more than 110 000 unique target stars. Elemental abundances were derived for up to 31 elements for targets observed with UVES. Lithium abundances are delivered for about 1/3 of the sample. The analysis and homogenisation strategies have proven to be successful; several science topics have been addressed by t

Published
2022

16. The Gaia-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products

Author

Universidad de Alicante. Departamento de Física Aplicada, Gilmore, Gerard, Randich, Sofia, Worley, C.C., Hourihane, A., Gonneau, A., Sacco, G.G., Lewis, J., Magrini, L., François, P., Jeffries, R., Koposov, S., Binks, A.S., Bressan, A., Capuzzo-Dolcetta, R., Casagrande, L., Casamiquela, L., Collins, R.S., D'Orazi, V., Dantas, M.L.L., Debattista, V.P., Delgado-Mena, E., Bragaglia, A., Di Marcantonio, P., Drazdauskas, A., Evans, N.W., Famaey, B., Franchini, M., Frémat, Y., Fu, X., Geisler, Douglas, Gerhard, Ortwin, González Solares, E.A., Alfaro, Emilio J., Grebel, E.K., Gutiérrez Albarrán, M.L., Jiménez Esteban, Francisco M., Jönsson, H., Khachaturyants, T., Kordopatis, G., Kos, J., Lagarde, N., Ludwig, H.-G., Mahy, Laurent, Allende Prieto, C., Mapelli, M., Marfil, E., Martell, S.L., Messina, S., Miglio, A., Minchev, I., Moitinho, A., Montalban, J., Monteiro, M.J.P.F.G., Morossi, C., Blomme, Ronny, Mowlavi, N., Mucciarelli, A., Murphy, D.N.A., Nardetto, N., Ortolani, S., Paletou, F., Palouš, J., Pickering, J.C., Quirrenbach, A., Re Fiorentin, P., Korn, A., Read, J.I., Romano, D., Ryde, N., Sanna, N., Santos, W., Seabroke, G.M., Spina, L., Steinmetz, M., Stonkuté, E., Sutorius, E., Lanzafame, A.C., Thévenin, F., Tosi, M., Tsantaki, M., Wright, N., Wyse, R.F.G., Zoccali, M., Zorec, J., Zucker, D.B., Pancino, E., Recio-Blanco, A., Smiljanic, R., Van Eck, S., Zwitter, T., Bensby, T., Flaccomio, E., Irwin, M., Franciosini, E., Morbidelli, L., Damiani, F., Bonito, R., Friel, E., Vink, Jorick S., Prisinzano, L., Abbas, U., Hatzidimitriou, D., Held, E.V., Jordi, C., Paunzen, E., Spagna, A., Jackson, R.J., Maíz Apellániz, Jesús, Asplund, M., Bonifacio, P., Feltzing, S., Binney, J., Drew, J., Ferguson, A., Micela, G., Negueruela, Ignacio, Prusti, T., Rix, H.-W., Vallenari, A., Bergemann, M., Casey, A.R., Laverny, P. de, Frasca, A., Hill, V., Lind, K., Sbordone, L., Sousa, S.G., Adibekyan, V.Zh., Caffau, E., Daflon, Simone, Feuillet, D.K., Gebran, M., González Hernández, J.I., Guiglion, G., Herrero, Artemio, Lobel, Alex, Merle, T., Mikolaitis, Š., Montes, David, Morel, Thierry, Ruchti, G., Soubiran, C., Tabernero, Hugo M., Tautvaišienė, G., Traven, G., Valentini, M., Van der Swaelmen, M., Villanova, S., Viscasillas Vázquez, C., Bayo, A., Biazzo, K., Carraro, G., Edvardsson, B., Heiter, U., Jofre, P., Marconi, G., Martayan, C., Masseron, T., Monaco, L., Walton, N., Zaggia, S., Aguirre Børsen-Koch, V., Alves, J., Balaguer-Nunez, L., Barklem, P.S., Barrado, D., Bellazzini, M., Berlanas, Sara R., Universidad de Alicante. Departamento de Física Aplicada, Gilmore, Gerard, Randich, Sofia, Worley, C.C., Hourihane, A., Gonneau, A., Sacco, G.G., Lewis, J., Magrini, L., François, P., Jeffries, R., Koposov, S., Binks, A.S., Bressan, A., Capuzzo-Dolcetta, R., Casagrande, L., Casamiquela, L., Collins, R.S., D'Orazi, V., Dantas, M.L.L., Debattista, V.P., Delgado-Mena, E., Bragaglia, A., Di Marcantonio, P., Drazdauskas, A., Evans, N.W., Famaey, B., Franchini, M., Frémat, Y., Fu, X., Geisler, Douglas, Gerhard, Ortwin, González Solares, E.A., Alfaro, Emilio J., Grebel, E.K., Gutiérrez Albarrán, M.L., Jiménez Esteban, Francisco M., Jönsson, H., Khachaturyants, T., Kordopatis, G., Kos, J., Lagarde, N., Ludwig, H.-G., Mahy, Laurent, Allende Prieto, C., Mapelli, M., Marfil, E., Martell, S.L., Messina, S., Miglio, A., Minchev, I., Moitinho, A., Montalban, J., Monteiro, M.J.P.F.G., Morossi, C., Blomme, Ronny, Mowlavi, N., Mucciarelli, A., Murphy, D.N.A., Nardetto, N., Ortolani, S., Paletou, F., Palouš, J., Pickering, J.C., Quirrenbach, A., Re Fiorentin, P., Korn, A., Read, J.I., Romano, D., Ryde, N., Sanna, N., Santos, W., Seabroke, G.M., Spina, L., Steinmetz, M., Stonkuté, E., Sutorius, E., Lanzafame, A.C., Thévenin, F., Tosi, M., Tsantaki, M., Wright, N., Wyse, R.F.G., Zoccali, M., Zorec, J., Zucker, D.B., Pancino, E., Recio-Blanco, A., Smiljanic, R., Van Eck, S., Zwitter, T., Bensby, T., Flaccomio, E., Irwin, M., Franciosini, E., Morbidelli, L., Damiani, F., Bonito, R., Friel, E., Vink, Jorick S., Prisinzano, L., Abbas, U., Hatzidimitriou, D., Held, E.V., Jordi, C., Paunzen, E., Spagna, A., Jackson, R.J., Maíz Apellániz, Jesús, Asplund, M., Bonifacio, P., Feltzing, S., Binney, J., Drew, J., Ferguson, A., Micela, G., Negueruela, Ignacio, Prusti, T., Rix, H.-W., Vallenari, A., Bergemann, M., Casey, A.R., Laverny, P. de, Frasca, A., Hill, V., Lind, K., Sbordone, L., Sousa, S.G., Adibekyan, V.Zh., Caffau, E., Daflon, Simone, Feuillet, D.K., Gebran, M., González Hernández, J.I., Guiglion, G., Herrero, Artemio, Lobel, Alex, Merle, T., Mikolaitis, Š., Montes, David, Morel, Thierry, Ruchti, G., Soubiran, C., Tabernero, Hugo M., Tautvaišienė, G., Traven, G., Valentini, M., Van der Swaelmen, M., Villanova, S., Viscasillas Vázquez, C., Bayo, A., Biazzo, K., Carraro, G., Edvardsson, B., Heiter, U., Jofre, P., Marconi, G., Martayan, C., Masseron, T., Monaco, L., Walton, N., Zaggia, S., Aguirre Børsen-Koch, V., Alves, J., Balaguer-Nunez, L., Barklem, P.S., Barrado, D., Bellazzini, M., and Berlanas, Sara R.

Abstract

Context. The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to obtain astrophysical parameters and elemental abundances for 100 000 stars, including large representative samples of the stellar populations in the Galaxy, and a well-defined sample of 60 (plus 20 archive) open clusters. We provide internally consistent results calibrated on benchmark stars and star clusters, extending across a very wide range of abundances and ages. This provides a legacy data set of intrinsic value, and equally a large wide-ranging dataset that is of value for the homogenisation of other and future stellar surveys and Gaia's astrophysical parameters. Aims. This article provides an overview of the survey methodology, the scientific aims, and the implementation, including a description of the data processing for the GIRAFFE spectra. A companion paper introduces the survey results. Methods. Gaia-ESO aspires to quantify both random and systematic contributions to measurement uncertainties. Thus, all available spectroscopic analysis techniques are utilised, each spectrum being analysed by up to several different analysis pipelines, with considerable effort being made to homogenise and calibrate the resulting parameters. We describe here the sequence of activities up to delivery of processed data products to the ESO Science Archive Facility for open use. Results. The Gaia-ESO Survey obtained 202 000 spectra of 115 000 stars using 340 allocated VLT nights between December 2011 and January 2018 from GIRAFFE and UVES. Conclusions. The full consistently reduced final data set of spectra was released through the ESO Science Archive Facility in late 2020, with the full astrophysical parameters sets following in 2022. A companion article reviews the survey implementation, scientific highlights, the open cluster survey, and data products.

Published
2022

17. Oscillator strength measurements of atomic absorption lines from stellar spectra

Author

Lobel, Alex

Subjects
Spectra (Spectroscopy) -- Research, Astrophysics -- Research, Oscillation -- Research, Physics
Abstract

Herein we develop a new method to determine oscillator strength values of atomic absorption lines with state-of-the-art detailed spectral synthesis calculations of the optical spectrum of the Sun and of standard spectral reference stars. We update the log(gf) values of 911 neutral lines observed in the KPNO-FTS flux spectrum of the Sun and high-resolution echelle spectra (R = 80 000) of Procyon (F5 IV-V) and ζ Eri (K2 V) observed with large signal-to-noise (S/N) ratios of ~2000 using the new Mercator-Hermes spectrograph at La Palma Observatory (Spain). We find for 483 Fe I,85 Ni I, and 51 Si I absorption lines in the sample a systematic overestimation of the literature log(gf) values with central line depths below 15%. We employ a curve-of-growth analysis technique to test the accuracy of the new oscillator strength values and compare calculated equivalent line widths to the Moore, Minnaert, and Houtgast atlas of the Sun. The online SpectroWeb database at spectra.freeshell.org interactively displays the observed and synthetic spectra and provides the new log(gf) values together with important atomic line data. The graphical database is under development for stellar reference spectra of every spectral sub-class observed with large spectral resolution and S/N ratios. PACS No: 95.30.Ky Ci-dessous nous developpons une nouvelle methode pour determiner les forces d'oscillateur de raies atomiques d'absorption avec des calculs synthetiques a la fine pointe spectrale du spectre optique du Soleil et d'etoiles de reference spectrale standard. Nos mettons a jour les valeurs de log(gf) des 911 raies neutres observees dans le spectre du Soleil observe au spectrometre a transformee de Fourier du Kitt Peak National Observatory (KPNO-FTS) et les spectres de haute resolution (R = 80 000) de Alpha Canis Minoris (F5 IV-V) et ζ-Eri (K2 V) observes avec un grand rapport signal sur bruit de ~2000 en utilisant le nouveau spectrographe Mercator-Hermes a l'Observatoire La Palma (Espagne). Pour les 483 lignes d'absorption du Fe I, les 85 de Ni I et les 51 de Si I de l'echantillon, nous trouvons une surestimation des valeurs de log(gf) de la litterature avec elargissement de raie centrale sous 15 %. Nous utilisons une technique d'analyse de courbe de croissance pour verifier la precision des nouvelles valeurs de force d'oscillateur et comparer les largeurs de raie calculees equivalentes avec celles de l' atlas du Soleil de Moore, Minnaert et Houtgast. La base de donnees en ligne SpectroWeb a spectra. freeshell.org presente de facon interactive les spectres synthetiques et observes et fournit les nouvelles valeurs de log(gf), avec spectres de reference pour chaque sous-classe spectrale observee, avec haute resolution et fort rapport signal sur bruit. [Traduit par la Redaction], 1. Introduction Accurate oscillator strength values are of central importance for the analysis and interpretation of astrophysical spectra. Detailed radiative transfer modeling of the profiles of absorption and emission lines [...]

Published
2011
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19. Instability Regions in the Upper HR Diagram

Author

deJager, Cornelis, Lobel, Alex, Nieuwenhuijzen, Hans, Stothers, Richard, and Hansen, James E

Subjects
Astrophysics
Abstract

The following instability regions for blueward evolving supergiants are outlined and compared: (1) Areas in the Hertzsprung-Russell(HR) diagram where stars are dynamically unstable. (2) Areas where the effective acceleration in the upper part of the photospheres is negative, hence directed outward. (3) Areas where the sonic points of the stellar wind (Where wind velocity = sound velocity) are situated inside the photospheres, at a level deeper than tau(sub Ross) = 0.01. We compare the results with the positions of actual stars in the HR diagram and we find evidence that the recent strong contraction of the yellow hypergiant HR8752 was initiated in a period during which (g(sub eff)) is less than 0, whereupon the star became dynamically unstable. The instability and extreme shells around IRC+10420 are suggested to be related to three factors: (g(sub eff)) is less than 0; the sonic point is situated inside the photosphere; and the star is dynamically unstable.

Published
2001

21. The Belgian repository of fundamental atomic data and stellar spectra (BRASS): II. Quality assessment of atomic data for unblended lines in FGK stars

Author

Laverick, Mike, Lobel, Alex, Royer, Pierre, Merle, Thibault, Martayan, Christophe, Van Hoof, Peter P.A.M., Van Der Swaelmen, Mathieu, David, Marc, Hensberge, Herman, Thienpont, E., Laverick, Mike, Lobel, Alex, Royer, Pierre, Merle, Thibault, Martayan, Christophe, Van Hoof, Peter P.A.M., Van Der Swaelmen, Mathieu, David, Marc, Hensberge, Herman, and Thienpont, E.

Abstract

Context. Fundamental atomic transition parameters, such as oscillator strengths and rest wavelengths, play a key role in modelling and understanding the chemical composition of stars in the universe. Despite the significant work under way to produce these parameters for many astrophysically important ions, uncertainties in these parameters remain large and can limit the accuracy of chemical abundance determinations. Aims. The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide a large systematic and homogeneous quality assessment of the atomic data available for quantitative spectroscopy. BRASS shall compare synthetic spectra against extremely high-quality observed spectra, at a resolution of ∼85 000 and signal-noise ratios of ∼1000, for approximately 20 bright BAFGK spectral-type stars, in order to critically evaluate the atomic data available for over a thousand potentially useful spectral lines. Methods. A large-scale homogeneous selection of atomic lines is performed by synthesising theoretical spectra of literature atomic lines for FGK-type stars including the Sun, resulting in a selection of 1091 theoretically deep and unblended lines in the wavelength range 4200-6800 Å, which may be suitable for quality assessment. Astrophysical log(g f) values are determined for the 1091 transitions using two commonly employed methods. The agreement of these log(g f) values are used to select well-behaved lines for quality assessment. Results. We found 845 atomic lines to be suitable for quality assessment, of which 408 were found to be robust against systematic differences between analysis methods. Around 53% of the quality-assessed lines were found to have at least one literature log(g f) value in agreement with our derived values, though the remaining values can disagree by as much as 0.5 dex. Only ∼38% of Fe※ I lines were found to have sufficiently accurate log(g f) values, increasing to ∼70-75% for the remaining Fe-group lines., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2019

22. The BINA collaboration: science at the Royal Observatory of Belgium

Author

Blomme, Ronny, Groenewegen, Martin, De Cat, Peter, Lampens, Patricia, Cuypers, Jan, Frémat, Yves, Lobel, Alex, Pauwels, Thierry, Van de Steene, Griet, and van Hoof, Peter

Subjects
instrumentation, spectroscopy, Engineering, Multidisciplinary, astrophysics, photometry, observatoires, business.industry, observatories, Astronomy, spectroscopie, astronomy, Photometry (optics), photométrie, Observatory, astronomie, business, astrophysique
Abstract

The Belgo-Indian Network for Astronomy and Astrophysics (BINA) is a collaboration between Indian and Belgian astronomical institutes with the main aim to optimize the scientific output of the Indo-Belgian telescopes, being the 4.0-m International Liquid Mirror Telescope and the 3.6-m Devasthal Optical Telescope. These new facilities are both located at the Devasthal Observatory near Nainital, India. In this contribution, we introduce projects that are of scientific interest for colleagues of the department “Astronomy and Astrophysics” of the Royal Observatory of Belgium (ROB). It serves as an invitation for Indian astronomers to participate. We highlight how these projects could benefit from observations with the Indo-Belgian telescopes by using instruments from the first-generation (currently offered) and/or the next-generation (development or design phase). We show that, from an ROB point-of-view, the BINA would be the most successful if the 3.6-m DOT would be equipped with an efficient optical high-resolution spectrograph.

Published
2018
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26. The Belgian repository of fundamental atomic data and stellar spectra (BRASS): I. Cross-matching atomic databases of astrophysical interest

Author

Laverick, Mike, Lobel, Alex, Merle, Thibault, Royer, Pierre, Martayan, Christophe, David, M., Hensberge, Herman, Thienpont, E., Laverick, Mike, Lobel, Alex, Merle, Thibault, Royer, Pierre, Martayan, Christophe, David, M., Hensberge, Herman, and Thienpont, E.

Abstract

Context. Fundamental atomic parameters, such as oscillator strengths, play a key role in modelling and understanding the chemical composition of stars in the Universe. Despite the significant work underway to produce these parameters for many astrophysically important ions, uncertainties in these parameters remain large and can propagate throughout the entire field of astronomy. Aims. The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide the largest systematic and homogeneous quality assessment of atomic data to date in terms of wavelength, atomic and stellar parameter coverage. To prepare for it, we first compiled multiple literature occurrences of many individual atomic transitions, from several atomic databases of astrophysical interest, and assessed their agreement. In a second step synthetic spectra will be compared against extremely high-quality observed spectra, for a large number of BAFGK spectral type stars, in order to critically evaluate the atomic data of a large number of important stellar lines. Methods. Several atomic repositories were searched and their data retrieved and formatted in a consistent manner. Data entries from all repositories were cross-matched against our initial BRASS atomic line list to find multiple occurrences of the same transition. Where possible we used a new non-parametric cross-match depending only on electronic configurations and total angular momentum values. We also checked for duplicate entries of the same physical transition, within each retrieved repository, using the non-parametric cross-match. Results. We report on the number of cross-matched transitions for each repository and compare their fundamental atomic parameters. We find differences in log(gf) values of up to 2 dex or more. We also find and report that ~2% of our line list and Vienna atomic line database retrievals are composed of duplicate transitions. Finally we provide a number of examples of atomic spectral lines wit, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2018

28. BRASS: Cross-match of atomic repositories and spectral line blending investigations1

Author

Laverick, M., Lobel, Alex, Royer, Pierre, Martayan, Christophe, Merle, Thibault, Laverick, M., Lobel, Alex, Royer, Pierre, Martayan, Christophe, and Merle, Thibault

Abstract

The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to critically evaluate atomic data, from publicly available repositories, by comparing state-of-the-art synthetic spectra against high-quality benchmark stellar spectra. In preparation for our assessment we have cross-matched atomic line transitions from several different databases. Our investigation revealed significant updates in log(gf) values, sometimes as large as 2-4 dex, that fully justify the need for systematic quality assessments of the atomic data. We have also investigated the spectral line blending of an initial subset of 2647 atomic lines using spectral synthesis calculations, for the spectral types BAFGK., SCOPUS: cp.j, info:eu-repo/semantics/published

Published
2017

29. The Belgian repository of fundamental atomic data and stellar spectra1

Author

Lobel, Alex, Royer, Pierre, Martayan, Christophe, Laverick, M., Merle, Thibault, David, M., Hensberge, Herman, Thienpont, E., Lobel, Alex, Royer, Pierre, Martayan, Christophe, Laverick, M., Merle, Thibault, David, M., Hensberge, Herman, and Thienpont, E.

Abstract

BRASS is an international networking project of the Federal Government of Belgium for the development of a new public database providing accurate fundamental atomic data of vital importance for stellar spectroscopic research. The BRASS database will offer atomic line data that is thoroughly tested by comparing theoretical and observed stellar spectra. We are in the course of performing extensive quality assessments of selected atomic input data with advanced radiative transfer spectrum synthesis calculations that we compare in detail to high-resolution Mercator-HERMES and ESO-VLT-UVES spectra of very high signal-to-noise ratios for about 30 hot and cool bright stars of B, A, F, G, and K spectral types. The new database will provide the tested and validated values of absorption lines we retrieve from various existing atomic repositories, such as NIST and VAMDC. The validated atomic datasets, combined with the observed and theoretical spectra, will be interactively offered online at brass.sdf.org. The combination of these datasets is a novel approach for its development, which will provide a universal reference for advanced stellar spectroscopic research. We present the atmospheric parameter results of a subset of five benchmark stars observed with signal-to-noise ratios of 800-1200. The observed and theoretical spectra of the Sun and 51 Peg between 4000 and 6800 A are offered online in the BRASS Data Interface. It also incorporates a new list of ∼900 metal lines for which we compute blending below 5% of the equivalent width useful for detailed line profile modeling and synthetic spectrum fit quality assessments of atomic line data., SCOPUS: cp.j, info:eu-repo/semantics/published

Published
2017

30. Luminous blue variables: An imaging perspective on their binarity and near environment

Author

Martayan, Christophe, primary, Lobel, Alex, additional, Baade, Dietrich, additional, Mehner, Andrea, additional, Rivinius, Thomas, additional, Boffin, Henri M. J., additional, Girard, Julien, additional, Mawet, Dimitri, additional, Montagnier, Guillaume, additional, Blomme, Ronny, additional, Kervella, Pierre, additional, Sana, Hugues, additional, Štefl, Stanislav, additional, Zorec, Juan, additional, Lacour, Sylvestre, additional, Le Bouquin, Jean-Baptiste, additional, Martins, Fabrice, additional, Mérand, Antoine, additional, Patru, Fabien, additional, Selman, Fernando, additional, and Frémat, Yves, additional

Published
2016
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31. Modeling the Asymmetric Wind of Massive LBV Binary MWC 314

Author

Lobel, Alex, Groh, J., Torres Dozinel, K., Gorlova, Nadya, Martayan, C., Raskin, Gert, Winckel, Hans, Saskia Prins, Pessemier, W., Waelkens, Ch, Frémat, Yves, Hensberge, Herman, Dummortier, L., Jorissen, Alain, Eck, Sophie, and Lehmann, Holger

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract

Spectroscopic monitoring with Mercator-HERMES over the past two years reveals that MWC 314 is a massive binary system composed of an early B-type primary LBV star and a less-luminous supergiant companion. We determine an orbital period Porb of 60.85 d from optical S II and Ne I absorption lines observed in this single-lined spectroscopic binary. We find an orbital eccentricity of e=0.26, and a large amplitude of the radial velocity curve of 80.6 km/s. The ASAS V light-curve during our spectroscopic monitoring reveals two brightness minima (\Delta V~0.1 mag.) over the orbital period due to partial eclipses at an orbital inclination angle of ~70 degrees. We find a clear correlation between the orbital phases and the detailed shapes of optical and near-IR P Cygni-type line profiles of He I, Si II, and double- or triple-peaked stationary cores of prominent Fe II emission lines. A preliminary 3-D radiative transfer model computed with Wind3D shows that the periodic P Cygni line profile variability results from an asymmetric common-envelope wind with enhanced density (or line opacity) in the vicinity of the LBV primary. The variable orientation of the inner LBV wind region due to the orbital motion produces variable P Cygni line profiles (with wind velocities of ~200 km/s) between orbital phases \phi = 0.65 to 0.85, while weak inverse P Cygni profiles are observed half an orbital period later around \phi = 0.15 to 0.35. We do not observe optical or near-IR He II, C III, and Si III lines, signaling that the LBV's spectral type is later than B0. Detailed modeling of the asymmetrical wind properties of massive binary MWC 314 provides important new physical information about the most luminous hot (binary) stars such as Eta Carinae., Comment: To appear in ASP Conference Series 2012, Four Decades of Massive Star Research - A Scientific Meeting in Honor of A. F. J. Moffat, Eds. L. Drissen, C. Robert, and N. St-Louis, 11-15 July 2011, Auberge du Lac Taureau, Qu\'ebec, Canada

Published
2011

32. Extensive study of HD 25558, a long-period double-lined binary with two SPB components

Author

Sódor, Á., De Cat, Peter, Wright, David, Neiner, Coralie, Briquet, Maryline, Lampens, Patricia, Dukes, Robert, Henry, Gregory W., Williamson, Michael, Brunsden, E., Pollard, Karen, Cottrell, Peter, Maisonneuve, F., Kilmartin, Pam, Matthews, Jaymie, Kallinger, Thomas, Beck, Paul, Kambe, Eiji, Engelbrecht, Chris, Czanik, R.J., Yang, Stephenson, Hashimoto, Osamu, Honda, Satoshi, Fu, J.N., Castanheira, Bárbara Garcia, Lehmann, Holger, Bognár, Zs, Behara, Natalie Thérèse, Scaringi, Simone, Van Winckel, Hans, Menu, Jonathan, Lobel, Alex, Mathias, Ph, Saesen, Sophie, Vučković, Maja, Sódor, Á., De Cat, Peter, Wright, David, Neiner, Coralie, Briquet, Maryline, Lampens, Patricia, Dukes, Robert, Henry, Gregory W., Williamson, Michael, Brunsden, E., Pollard, Karen, Cottrell, Peter, Maisonneuve, F., Kilmartin, Pam, Matthews, Jaymie, Kallinger, Thomas, Beck, Paul, Kambe, Eiji, Engelbrecht, Chris, Czanik, R.J., Yang, Stephenson, Hashimoto, Osamu, Honda, Satoshi, Fu, J.N., Castanheira, Bárbara Garcia, Lehmann, Holger, Bognár, Zs, Behara, Natalie Thérèse, Scaringi, Simone, Van Winckel, Hans, Menu, Jonathan, Lobel, Alex, Mathias, Ph, Saesen, Sophie, and Vučković, Maja

Abstract

We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ≈2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about nine years. The observations do not allow the inference of an orbital solution. We determined the physical parameters of the components, and found that both lie within the SPB instability strip. Accordingly, both show line-profile variations due to stellar pulsations. 11 independent frequencies were identified in the data. All the frequencies were attributed to one of the two components based on pixel-by-pixel variability analysis of the line profiles. Spectroscopic and photometric mode identification was also performed for the frequencies of both stars. These results suggest that the inclination and rotation of the two components are rather different. The primary is a slow rotator with ≈6 d period, seen at ≈60° inclination, while the secondary rotates fast with ≈1.2 d period, and is seen at ≈20° inclination. Spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field can be detected in the primary. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2014

33. Pulsating red giant stars in eccentric binary systems discovered from Kepler space-based photometry. A sample study and the analysis of KIC 5006817

Author

Beck, Paul, Hambleton, Kelly, Vos, Jaap, Kallinger, Thomas, Bloemen, Steven, Tkachenko, Andrew, Garcia, R.A., Ostensen, R.~H., Aerts, Conny, Kurtz, D.W, De Ridder, Joris, Hekker, S., Pavlovski, Krešimir, Mathur, S, De Smedt, Kenneth, Derekas, K., Corsaro, E, Mosser, B., Van Winckel, Hans, Huber, D., Degroote, Pieter, Davies, G, Prsa, A., Debosscher, Jonas, Elsworth, Y., Nemeth, P., Siess, Lionel, Schmid, Volker, Pápics, Péter, de Vries, Bernard, van Marle, A.-J., Marcos-Arenal, P., Lobel, Alex, Beck, Paul, Hambleton, Kelly, Vos, Jaap, Kallinger, Thomas, Bloemen, Steven, Tkachenko, Andrew, Garcia, R.A., Ostensen, R.~H., Aerts, Conny, Kurtz, D.W, De Ridder, Joris, Hekker, S., Pavlovski, Krešimir, Mathur, S, De Smedt, Kenneth, Derekas, K., Corsaro, E, Mosser, B., Van Winckel, Hans, Huber, D., Degroote, Pieter, Davies, G, Prsa, A., Debosscher, Jonas, Elsworth, Y., Nemeth, P., Siess, Lionel, Schmid, Volker, Pápics, Péter, de Vries, Bernard, van Marle, A.-J., Marcos-Arenal, P., and Lobel, Alex

Abstract

Context. The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to improved understanding of red giant stars and binary stars. Seismology allows us to constrain the properties of red giants. In addition to eclipsing binaries, eccentric non-eclipsing binaries that exhibit ellipsoidal modulations have been detected with Kepler. Aims. We aim to study the properties of eccentric binary systems containing a red giant star and to derive the parameters of the primary giant component. Methods. We applied asteroseismic techniques to determine the masses and radii of the primary component of each system. For a selected target, light and radial velocity curve modelling techniques were applied to extract the parameters of the system and its primary component. Stellar evolution and its effects on the evolution of the binary system were studied from theoretical models. Results. The paper presents the asteroseismic analysis of 18 pulsating red giants in eccentric binary systems, for which masses and radii were constrained. The orbital periods of these systems range from 20 to 440 days. The results of our ongoing radial velocity monitoring programme with the Hermes spectrograph reveal an eccentricity range of e = 0.2 to 0.76. As a case study we present a detailed analysis of KIC 5006817, whose rich oscillation spectrum allows for detailed seismic analysis. From seismology we constrain the rotational period of the envelope to be at least 165 d, which is roughly twice the orbital period. The stellar core rotates 13 times faster than the surface. From the spectrum and radial velocities we expect that the Doppler beaming signal should have a maximum amplitude of 300 ppm in the light curve. Fixing the mass and radius to the asteroseismically determined values, we find from our binary modelling a value of the gravity darkening exponent that is significantly larger than expected. Through binary modelling, we determine the mass of the secondary component to be, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2014

34. Modelling the asymmetric wind of the luminous blue variable binary MWC 314

Author

Lobel, Alex, Groh, J., Martayan, C., Frémat, Yves, Torres Dozinel, K., Raskin, Gert, Van Winckel, Hans, Prins, S., Pessemier, W., Waelkens, Ch, Hensberge, Herman, Dumortier, L., Jorissen, Alain, Van Eck, Sophie, Lehmann, Holger, Lobel, Alex, Groh, J., Martayan, C., Frémat, Yves, Torres Dozinel, K., Raskin, Gert, Van Winckel, Hans, Prins, S., Pessemier, W., Waelkens, Ch, Hensberge, Herman, Dumortier, L., Jorissen, Alain, Van Eck, Sophie, and Lehmann, Holger

Abstract

Aims. We present a spectroscopic analysis of MWC 314, a luminous blue variable (LBV) candidate with an extended bipolar nebula. The detailed spectroscopic variability is investigated to determine if MWC 314 is a massive binary system with a supersonically accelerating wind or a low-mass B[e] star. We compare the spectrum and spectral energy distribution to other LBVs (such as P Cyg) and find very similar physical wind properties, indicating strong kinship. Methods. We combined long-term high-resolution optical spectroscopic monitoring and V-band photometric observations to determine the orbital elements and stellar parameters and to investigate the spectral variability with the orbital phases. We developed an advanced model of the large-scale wind-velocity and wind-density structure with 3-D radiative transfer calculations that fit the orbitally modulated P Cyg profile of He i λ5876, showing outflow velocities above 1000 km s-1. Results. We find that MWC 314 is a massive semi-detached binary system of ≈1.22 AU, observed at an inclination angle of i = 72.8 with an orbital period of 60.8 d and e = 0.23. The primary star is a low-vsini LBV candidate of m1 = 39.6 M and R1 = 86.8 R. The detailed radiative transfer fits show that the geometry of wind density is asymmetric around the primary star with increased wind density by a factor of 3.3, which leads the orbit of the primary. The variable orientation causes the orbital modulation that is observed in absorption portions of P Cyg wind lines. Wind accretion in the system produces a circumbinary disc. Conclusions. MWC 314 is in a crucial evolutionary phase of close binary systems, when the massive primary star has its H envelope being stripped and is losing mass to a circumbinary disc. MWC 314 is a key system for studying the evolutionary consequences of these effects. © 2013 ESO., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2013

35. Modeling the Asymmetric Wind of Massive LBV Binary MWC 314

Author

Lobel, Alex, Groh, J., Torres Dozinel, K., Gorlova, Nadya, Martayan, C., Raskin, Gert, Van Winckel, Hans, Prins, S., Pessemier, W., Waelkens, Ch, Frémat, Yves, Hensberge, Herman, Dummortier, L., Jorissen, Alain, Van Eck, Sophie, Lehmann, Holger, Lobel, Alex, Groh, J., Torres Dozinel, K., Gorlova, Nadya, Martayan, C., Raskin, Gert, Van Winckel, Hans, Prins, S., Pessemier, W., Waelkens, Ch, Frémat, Yves, Hensberge, Herman, Dummortier, L., Jorissen, Alain, Van Eck, Sophie, and Lehmann, Holger

Abstract

info:eu-repo/semantics/published

Published
2012

38. Instability regions in the upper HR diagram.

Author

de Jager, Cornelis, Lobel, Alex, Nieuwenhuijzen, Hans, and Stothers, Richard

Subjects
*SUPERGIANT stars, *HR diagrams
Abstract

The following instability regions for blueward evolving-supergiants are outlined and compared. (1) Areas in the Hertzsprung–Russell (HR) diagram where stars are dynamically unstable. (2) Areas where the effective acceleration in the upper part of the photospheres is negative, hence directed outward. (3) Areas where the sonic points of the stellar winds (where are situated inside the photospheres, at a level deeper than . We compare the results with the positions of actual stars in the HR diagram and we find evidence that the recent strong contraction of the yellow hypergiant HR 8752 was initiated in a period during which , whereupon the star became dynamically unstable. The instability and extreme shells around IRC+10420 are suggested to be related to three factors: the sonic point is situated inside the photosphere; and the star is dynamically unstable. [ABSTRACT FROM AUTHOR]

Published
2001
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39. On the CO Near-Infrared Band and the Line-splitting Phenomenon in the Yellow Hypergiant ? Cassiopeiae

Author

Gorlova, Nadya, Lobel, Alex, Burgasser, Adam J., Rieke, George H., Ilyin, Ilya, and Stauffer, John R.

Abstract

We report on multiepoch optical and near-infrared spectroscopy around the first-overtone rovibrational band of CO in the pulsating yellow hypergiant r Cas, one of the most massive stars in the Galaxy and a candidate SN II progenitor. We argue that the double cores of the CO absorption lines, which have previously been attributed to separate circumstellar shells expelled during its recurrent outbursts, result in fact from a superposition of a wide absorption line and a narrow central emission line. The CO line doubling returns over subsequent pulsation cycles, where the superposed line emission assumes its largest intensity near phases of maximum light. We find that the morphology and behavior of the CO band closely resemble the remarkable "line-splitting phenomenon" also observed in optical low-excitation atomic lines. Based on radiative transport calculations, we present a simplified model of the near-infrared CO emission emerging from cooler atmospheric layers in the immediate vicinity of the photosphere. We speculate that the kinetic temperature minimum in our model results from a periodic pulsation-driven shock wave. We further discuss a number of alternative explanations for the origin of the ubiquitous emission-line spectrum, possibly due to a quasi-chromosphere or a steady shock wave at the interface of a fast expanding wind and the interstellar medium. We present a number of interesting spectroscopic similarities between r Cas and other types of cool variable supergiants, such as the RV Tau and R CrB stars. We further propose a possibly common mechanism for the enigmatic outburst behavior of these luminous pulsating cool stars.

Published
2006

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