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Alexander Heger - One of the best experts on this subject based on the ideXlab platform.
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Very Massive Stars in the local Universe
Proceedings of the International Astronomical Union, 2012Co-Authors: Jorick S. Vink, Paul A. Crowther, A.-n. Chené, Joachim Puls, Mark R. Krumholz, N. Castro, Alexander Heger, Sambaran Banerjee, Ke-jung Chen, A. DaminelliAbstract:Recent studies have claimed the existence of very Massive Stars (VMS) up to 300 M⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most Massive Stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.
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presupernova evolution of rotating Massive Stars ii evolution of the surface properties
The Astrophysical Journal, 2000Co-Authors: Alexander Heger, N LangerAbstract:We investigate the evolution of the surface properties of models for rotating Massive Stars, i.e., their luminosities, effective temperatures, surface rotational velocities, and surface abundances of all isotopes, from the zero-age main sequence to the supernova stage. Our results are based on the grid of stellar models by Heger, Langer, & Woosley, which covers solar metallicity Stars in the initial-mass range 8-25 M?. Results are parameterized by initial mass, initial rotational velocity and major uncertainties in the treatment of the rotational mixing inside Massive Stars. Rotationally induced mixing processes widen the main sequence and increase the core hydrogen-burning lifetime, similar to the effects of convective overshooting. It can also significantly increase the luminosity during and after core hydrogen burning, and strongly affects the evolution of the effective temperature. Our models predict surface rotational velocities for various evolutionary stages, in particular for blue supergiants, red supergiants, and for the immediate presupernova stage. We discuss the changes of the surface abundances due to rotationally induced mixing for main sequence and post-main-sequence Stars. We single out two characteristics by which the effect of rotational mixing can be distinguished from that of Massive close binary mass transfer, the only alternative process leading to nonstandard chemical surface abundances in Massive Stars. A comparison with observed abundance anomalies in various types of Massive Stars supports the concept of rotational mixing in Massive Stars and indicates that it is responsible for most of the observed abundance anomalies.
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presupernova evolution of rotating Massive Stars ii evolution of the surface properties
arXiv: Astrophysics, 2000Co-Authors: Alexander Heger, N LangerAbstract:We investigate the evolution of the surface properties of models for rotating Massive Stars, i.e., their luminosities, effective temperatures, surface rotational velocities, and surface abundances of all isotopes, from the zero age main sequence to the supernova stage. Our results are based on the grid of stellar models by Heger, Langer, & Woosley, which covers solar metallicity Stars in the initial mass range 8 - 25 solar masses. Results are parameterized by initial mass, initial rotational velocity and major uncertainties in the treatment of the rotational mixing inside Massive Stars. Rotationally induced mixing processes widen the main sequence and increase the core hydrogen burning lifetime, similar to the effects of convective overshooting. It can also significantly increase the luminosity during and after core hydrogen burning, and strongly affects the evolution of the effective temperature. Our models predict surface rotational velocities for various evolutionary stages, in particular for blue supergiants, red supergiants, and for the immediate presupernova stage. We discuss the changes of the surface abundances due to rotationally induced mixing for main sequence and post main sequence Stars. We single out two characteristics by which the effect of rotational mixing can be distinguished from that of Massive close binary mass transfer, the only alternative process leading to non-standard chemical surface abundances in Massive Stars. A comparison with observed abundance anomalies in various types of Massive Stars supports the concept of rotational mixing in Massive Stars and indicates that it is responsible for most of the observed abundance anomalies.
N Langer - One of the best experts on this subject based on the ideXlab platform.
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presupernova evolution of rotating Massive Stars ii evolution of the surface properties
The Astrophysical Journal, 2000Co-Authors: Alexander Heger, N LangerAbstract:We investigate the evolution of the surface properties of models for rotating Massive Stars, i.e., their luminosities, effective temperatures, surface rotational velocities, and surface abundances of all isotopes, from the zero-age main sequence to the supernova stage. Our results are based on the grid of stellar models by Heger, Langer, & Woosley, which covers solar metallicity Stars in the initial-mass range 8-25 M?. Results are parameterized by initial mass, initial rotational velocity and major uncertainties in the treatment of the rotational mixing inside Massive Stars. Rotationally induced mixing processes widen the main sequence and increase the core hydrogen-burning lifetime, similar to the effects of convective overshooting. It can also significantly increase the luminosity during and after core hydrogen burning, and strongly affects the evolution of the effective temperature. Our models predict surface rotational velocities for various evolutionary stages, in particular for blue supergiants, red supergiants, and for the immediate presupernova stage. We discuss the changes of the surface abundances due to rotationally induced mixing for main sequence and post-main-sequence Stars. We single out two characteristics by which the effect of rotational mixing can be distinguished from that of Massive close binary mass transfer, the only alternative process leading to nonstandard chemical surface abundances in Massive Stars. A comparison with observed abundance anomalies in various types of Massive Stars supports the concept of rotational mixing in Massive Stars and indicates that it is responsible for most of the observed abundance anomalies.
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presupernova evolution of rotating Massive Stars ii evolution of the surface properties
arXiv: Astrophysics, 2000Co-Authors: Alexander Heger, N LangerAbstract:We investigate the evolution of the surface properties of models for rotating Massive Stars, i.e., their luminosities, effective temperatures, surface rotational velocities, and surface abundances of all isotopes, from the zero age main sequence to the supernova stage. Our results are based on the grid of stellar models by Heger, Langer, & Woosley, which covers solar metallicity Stars in the initial mass range 8 - 25 solar masses. Results are parameterized by initial mass, initial rotational velocity and major uncertainties in the treatment of the rotational mixing inside Massive Stars. Rotationally induced mixing processes widen the main sequence and increase the core hydrogen burning lifetime, similar to the effects of convective overshooting. It can also significantly increase the luminosity during and after core hydrogen burning, and strongly affects the evolution of the effective temperature. Our models predict surface rotational velocities for various evolutionary stages, in particular for blue supergiants, red supergiants, and for the immediate presupernova stage. We discuss the changes of the surface abundances due to rotationally induced mixing for main sequence and post main sequence Stars. We single out two characteristics by which the effect of rotational mixing can be distinguished from that of Massive close binary mass transfer, the only alternative process leading to non-standard chemical surface abundances in Massive Stars. A comparison with observed abundance anomalies in various types of Massive Stars supports the concept of rotational mixing in Massive Stars and indicates that it is responsible for most of the observed abundance anomalies.
A.-n. Chené - One of the best experts on this subject based on the ideXlab platform.
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Massive Stars in the young cluster VVV CL074.
Astronomy & Astrophysics, 2019Co-Authors: Fabrice Martins, J.-c. Bouret, A.-n. Chené, S. Ramírez Alegría, J. Borissova, Jose H. Groh, Dante MinnitiAbstract:Context. The evolution of Massive Stars is not fully constrained. Studies of young Massive clusters hosting various populations of Massive Stars can help refine our understanding of the life and fate of Massive Stars. Aims. In this context, our goal is to study the Massive stellar content of the young Massive cluster VVV CL074. Methods. We obtained K-band spectroscopy of the brightest cluster members in order to identify the Massive star population. We also determined the stellar properties of the cluster’s Massive Stars to better quantify the evolutionary sequences linking different types of Massive Stars. We collected integral field spectroscopy of selected fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the Massive Stars from analysis with atmosphere models computed with the code CMFGEN. Results. We uncover a population of 25 early-type (OB and Wolf–Rayet) Stars, 19 being newly discovered by our observations out of which 15 are likely cluster members. The cluster’s spectrophotometric distance is 10.2 ± 1.6 kpc, placing it close to the intersection of the galactic bar and the Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young Massive clusters identified so far. Among the Massive Stars population, three objects are Wolf–Rayet Stars, the remaining are O and B Stars. From the Hertzsprung–Russell diagram we find that most Stars have an age between 3 and 6 Myr according to the Geneva evolutionary tracks. WN8 and WC8-9 Stars are the descendants of Stars with initial masses between 40 and 60 M⊙. The Massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older. From the comparison of the Massive Stars populations in these four clusters, one concludes that galactic Stars with an initial mass in the range 40–60 M⊙ likely go through a WN8-9 phase.
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Massive Stars in young VVV clusters
Proceedings of the International Astronomical Union, 2016Co-Authors: S. Ramírez Alegría, J. Borissova, A.-n. ChenéAbstract:The role of Massive Stars in the Galactic evolution is crucial. During their lifetime these Stars change the kinematics around them through stellar winds, affect the formation of new Stars, ionise and chemically enrich the media with the final supernova explosion. But the census of both Massive Stars and their host clusters is still poor. We expect that still ~100 of galactic Massive stellar clusters remains unknown (Hanson & Popescu, 2008).
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Properties of Massive Stars in four clusters of the VVV survey
New Astronomy, 2016Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorissovaAbstract:The evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting Massive Stars. We present an analysis of Massive Stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of Massive Stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve Stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung-Russell diagram, the Wolf-Rayet Stars are more luminous or hotter than the O Stars. From the log(C/N) - log(C/He) diagram, we show quantitatively that WN Stars are more chemically evolved than O Stars, WC Stars being more evolved than WN Stars. Mass loss rates among Wolf-Rayet Stars are a factor of 10 larger than for O Stars, in agreement with previous findings.
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Properties of Massive Stars in four clusters of the VVV survey
New Astronomy, 2016Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorissovaAbstract:International audienceThe evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey “VISTA Variables in the Via Lactea (VVV)” discovered several new clusters hosting Massive Stars. We present an analysis of Massive Stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of Massive Stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve Stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung Russell diagram, the Wolf-Rayet Stars are more luminous or hotter than the O Stars. From the log(C/N) log(C/He) diagram, we show quantitatively that WN Stars are more chemically evolved than O Stars, WC Stars being more evolved than WN Stars. Mass loss rates among Wolf-Rayet Stars are a factor of 10 larger than for O Stars, in agreement with previous findings. (C) 2015 Elsevier B.V. All rights reserved
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Properties of Massive Stars in VVV Clusters
EAS Publications Series, 2015Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorrissovaAbstract:The evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting Massive Stars (Borrissova et al . [1]). We derive the stellar parameters of all targets as well as surface abundances for a subset of them. For the cluster with the largest number of objects, we establish firmly that the WN and WC Stars were initially more Massive than the O Stars still present in the cluster.
J. Borissova - One of the best experts on this subject based on the ideXlab platform.
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Massive Stars in the young cluster VVV CL074.
Astronomy & Astrophysics, 2019Co-Authors: Fabrice Martins, J.-c. Bouret, A.-n. Chené, S. Ramírez Alegría, J. Borissova, Jose H. Groh, Dante MinnitiAbstract:Context. The evolution of Massive Stars is not fully constrained. Studies of young Massive clusters hosting various populations of Massive Stars can help refine our understanding of the life and fate of Massive Stars. Aims. In this context, our goal is to study the Massive stellar content of the young Massive cluster VVV CL074. Methods. We obtained K-band spectroscopy of the brightest cluster members in order to identify the Massive star population. We also determined the stellar properties of the cluster’s Massive Stars to better quantify the evolutionary sequences linking different types of Massive Stars. We collected integral field spectroscopy of selected fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the Massive Stars from analysis with atmosphere models computed with the code CMFGEN. Results. We uncover a population of 25 early-type (OB and Wolf–Rayet) Stars, 19 being newly discovered by our observations out of which 15 are likely cluster members. The cluster’s spectrophotometric distance is 10.2 ± 1.6 kpc, placing it close to the intersection of the galactic bar and the Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young Massive clusters identified so far. Among the Massive Stars population, three objects are Wolf–Rayet Stars, the remaining are O and B Stars. From the Hertzsprung–Russell diagram we find that most Stars have an age between 3 and 6 Myr according to the Geneva evolutionary tracks. WN8 and WC8-9 Stars are the descendants of Stars with initial masses between 40 and 60 M⊙. The Massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older. From the comparison of the Massive Stars populations in these four clusters, one concludes that galactic Stars with an initial mass in the range 40–60 M⊙ likely go through a WN8-9 phase.
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Massive Stars in young VVV clusters
Proceedings of the International Astronomical Union, 2016Co-Authors: S. Ramírez Alegría, J. Borissova, A.-n. ChenéAbstract:The role of Massive Stars in the Galactic evolution is crucial. During their lifetime these Stars change the kinematics around them through stellar winds, affect the formation of new Stars, ionise and chemically enrich the media with the final supernova explosion. But the census of both Massive Stars and their host clusters is still poor. We expect that still ~100 of galactic Massive stellar clusters remains unknown (Hanson & Popescu, 2008).
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Properties of Massive Stars in four clusters of the VVV survey
New Astronomy, 2016Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorissovaAbstract:The evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting Massive Stars. We present an analysis of Massive Stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of Massive Stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve Stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung-Russell diagram, the Wolf-Rayet Stars are more luminous or hotter than the O Stars. From the log(C/N) - log(C/He) diagram, we show quantitatively that WN Stars are more chemically evolved than O Stars, WC Stars being more evolved than WN Stars. Mass loss rates among Wolf-Rayet Stars are a factor of 10 larger than for O Stars, in agreement with previous findings.
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Properties of Massive Stars in four clusters of the VVV survey
New Astronomy, 2016Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorissovaAbstract:International audienceThe evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey “VISTA Variables in the Via Lactea (VVV)” discovered several new clusters hosting Massive Stars. We present an analysis of Massive Stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of Massive Stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve Stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung Russell diagram, the Wolf-Rayet Stars are more luminous or hotter than the O Stars. From the log(C/N) log(C/He) diagram, we show quantitatively that WN Stars are more chemically evolved than O Stars, WC Stars being more evolved than WN Stars. Mass loss rates among Wolf-Rayet Stars are a factor of 10 larger than for O Stars, in agreement with previous findings. (C) 2015 Elsevier B.V. All rights reserved
Fabrice Martins - One of the best experts on this subject based on the ideXlab platform.
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Massive Stars in the young cluster VVV CL074.
Astronomy & Astrophysics, 2019Co-Authors: Fabrice Martins, J.-c. Bouret, A.-n. Chené, S. Ramírez Alegría, J. Borissova, Jose H. Groh, Dante MinnitiAbstract:Context. The evolution of Massive Stars is not fully constrained. Studies of young Massive clusters hosting various populations of Massive Stars can help refine our understanding of the life and fate of Massive Stars. Aims. In this context, our goal is to study the Massive stellar content of the young Massive cluster VVV CL074. Methods. We obtained K-band spectroscopy of the brightest cluster members in order to identify the Massive star population. We also determined the stellar properties of the cluster’s Massive Stars to better quantify the evolutionary sequences linking different types of Massive Stars. We collected integral field spectroscopy of selected fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the Massive Stars from analysis with atmosphere models computed with the code CMFGEN. Results. We uncover a population of 25 early-type (OB and Wolf–Rayet) Stars, 19 being newly discovered by our observations out of which 15 are likely cluster members. The cluster’s spectrophotometric distance is 10.2 ± 1.6 kpc, placing it close to the intersection of the galactic bar and the Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young Massive clusters identified so far. Among the Massive Stars population, three objects are Wolf–Rayet Stars, the remaining are O and B Stars. From the Hertzsprung–Russell diagram we find that most Stars have an age between 3 and 6 Myr according to the Geneva evolutionary tracks. WN8 and WC8-9 Stars are the descendants of Stars with initial masses between 40 and 60 M⊙. The Massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older. From the comparison of the Massive Stars populations in these four clusters, one concludes that galactic Stars with an initial mass in the range 40–60 M⊙ likely go through a WN8-9 phase.
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Properties of Massive Stars in four clusters of the VVV survey
New Astronomy, 2016Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorissovaAbstract:The evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting Massive Stars. We present an analysis of Massive Stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of Massive Stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve Stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung-Russell diagram, the Wolf-Rayet Stars are more luminous or hotter than the O Stars. From the log(C/N) - log(C/He) diagram, we show quantitatively that WN Stars are more chemically evolved than O Stars, WC Stars being more evolved than WN Stars. Mass loss rates among Wolf-Rayet Stars are a factor of 10 larger than for O Stars, in agreement with previous findings.
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Properties of Massive Stars in four clusters of the VVV survey
New Astronomy, 2016Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorissovaAbstract:International audienceThe evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey “VISTA Variables in the Via Lactea (VVV)” discovered several new clusters hosting Massive Stars. We present an analysis of Massive Stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of Massive Stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve Stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung Russell diagram, the Wolf-Rayet Stars are more luminous or hotter than the O Stars. From the log(C/N) log(C/He) diagram, we show quantitatively that WN Stars are more chemically evolved than O Stars, WC Stars being more evolved than WN Stars. Mass loss rates among Wolf-Rayet Stars are a factor of 10 larger than for O Stars, in agreement with previous findings. (C) 2015 Elsevier B.V. All rights reserved
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Properties of Massive Stars in VVV Clusters
EAS Publications Series, 2015Co-Authors: A. Hervé, J.-c. Bouret, Fabrice Martins, A.-n. Chené, J. BorrissovaAbstract:The evolution of Massive Stars is only partly understood. Observational constraints can be obtained from the study of Massive Stars located in young Massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting Massive Stars (Borrissova et al . [1]). We derive the stellar parameters of all targets as well as surface abundances for a subset of them. For the cluster with the largest number of objects, we establish firmly that the WN and WC Stars were initially more Massive than the O Stars still present in the cluster.
