X-Shooting ULLYSES: Massive stars at low metallicity: VI. Atmosphere and mass-loss properties of O-type giants in the Small Magellanic Cloud F. Backs, S. A. Brands, A. de Koter, L. Kaper, J. S. Vink, J. Puls, J. Sundqvist, F. Tramper, H. Sana, M. Bernini-Peron, J. M. Bestenlehner, P. A. Crowther, C. Hawcroft, R. Ignace, R. Kuiper, J. Th. van Loon, L. Mahy, W. Marcolino, F. Najarro, L. M. Oskinova, D. Pauli, V. Ramachandran, A. A. C. Sander, O. Verhamme Astronomy and Astrophysics, 2024 Context. Mass loss through a stellar wind is an important physical process that steers the evolution of massive stars and controls the properties of their end-of-life products, such as the supernova type and the mass of compact remnants. To probe its role in stellar evolution over cosmic time, mass loss needs to be studied as function of metallicity. For mass loss to be accurately quantified, the wind structure needs to be established jointly with the characteristics of small-scale inhomogeneities in the outflow, which are known as wind clumping. Aims. We aim to improve empirical estimates of mass loss and wind clumping for hot main-sequence massive stars, study the dependence of both properties on the metal content, and compare the theoretical predictions of mass loss as a function of metallicity to our findings. Methods. Using the model atmosphere code FASTWIND and the genetic algorithm fitting method KIWI-GA, we analyzed the optical and ultraviolet spectra of 13 O-type giant to supergiant stars in the Small Magellanic Cloud galaxy, which has a metallicity of approximately one-fifth of that of the Sun. We quantified the stellar global outflow properties, such as the mass-loss rate and terminal wind velocity, and the wind clumping properties. To probe the role of metallicity, our findings were compared to studies of Galactic and Large Magellanic Cloud samples that were analyzed with similar methods, including the description of clumping. Results. We find significant variations in the wind clumping properties of the target stars, with clumping starting at flow velocities 0.01–0.23 of the terminal wind velocity and reaching clumping factors fcl = 2–30. In the luminosity (log L/L⊙ = 5.0–6.0) and metallicity (Z/Z⊙ = 0.2–1) range we considered, we find that the scaling of the mass loss M˙ with metallicity Z varies with luminosity. At log L/L⊙ = 5.75, we find M˙ ∝ Zm with m = 1.02 ± 0.30, in agreement with pioneering work in the field within the uncertainties. For lower luminosities, however, we obtain a significantly steeper scaling of m > 2. Conclusions. The monotonically decreasing m(L) behavior adds a complexity to the functional description of the mass-loss rate of hot massive stars. Although the trend is present in the predictions, it is much weaker than we found here. However, the luminosity range for which m is significantly larger than previously assumed (at log L/L⊙ ≲ 5.4) is still poorly explored, and more studies are needed to thoroughly map the empirical behavior, in particular, at Galactic metallicity.
X-Shooting ULLYSES: Massive stars at low metallicity: VII. Stellar and wind properties of B supergiants in the Small Magellanic Cloud M. Bernini-Peron, A. A. C. Sander, V. Ramachandran, L. M. Oskinova, J. S. Vink, O. Verhamme, F. Najarro, J. Josiek, S. A. Brands, P. A. Crowther, V. M. A. Gómez-González, A. C. Gormaz-Matamala, C. Hawcroft, R. Kuiper, L. Mahy, W. L. F. Marcolino, L. P. Martins, A. Mehner, T. N. Parsons, D. Pauli, T. Shenar, A. Schootemeijer, H. Todt, J. Th. van Loon, and Astronomy and Astrophysics, 2024 Context. With the aim of understanding massive stars and their feedback in the early epochs of our Universe, the ULLYSES and XShootU collaborations collected the biggest homogeneous dataset of high-quality hot star spectra at low metallicity. Within the rich “zoo” of massive star stellar types, B supergiants (BSGs) represent an important connection between the main sequence and more extreme evolutionary stages. Additionally, lying toward the cool end of the hot star regime, determining their wind properties is crucial to gauging our expectations on the evolution and feedback of massive stars as, for instance, they are implicated in the bi-stability jump phenomenon. Aims. Here, we undertake a detailed analysis of a representative sample of 18 Small Magellanic Cloud (SMC) BSGs within the ULLYSES dataset. Our UV and optical analysis samples early- and late-type BSGs (from B0 to B8), covering the bi-stability jump region. Our aim is to evaluate their evolutionary status and verify what their wind properties say about the bi-stability jump at a low-metallicity environment. Methods. We used the stellar atmosphere code CMFGEN to model the UV and optical spectra of the sample BSGs as well as photometry in different bands. The optical range encodes photospheric properties, while the wind information resides mostly in the UV. Further, we compare our results with different evolutionary models, with previous determinations in the literature of OB stars, and with diverging mass-loss prescriptions at the bi-stability jump. Additionally, for the first time we provide BSG models in the SMC including X-rays. Results. Our analysis yielded the following main results: (i) From a single-stellar evolution perspective, the evolutionary status of early BSGs appear less clear than late BSGs, which are agree reasonably well with H-shell burning models. (ii) Ultraviolet analysis shows evidence that the BSGs contain X-rays in their atmospheres, for which we provide constraints. In general, higher X-ray luminosity (close to the standard log(LX/L) ~ −7) is favored for early BSGs, despite associated degeneracies. For later-type BSGs, lower values are preferred, log(LX/L) ~ −8.5. (iii) The obtained mass-loss rates suggest neither a jump nor an unperturbed monotonic decrease with temperature. Instead, a rather constant trend appears to happen, which is at odds with the increase found for Galactic BSGs. (iv) The wind velocity behavior with temperature shows a sharp drop at ~19 kK, very similar to the bi-stability jump observed for Galactic stars.
CMFGEN grids of atmosphere models for massive stars: OB-Type stars at the Magellanic Clouds W. Marcolino, J.-C. Bouret, F. Martins, D. J. Hillier Astronomy and Astrophysics, 2024 Context. Large spectroscopic surveys of individual massive stars, such as ULLYSES and XShootU, provide observational data for hundreds of massive stars. Their analysis requires large numbers of synthetic spectra so that stellar parameters can be determined. In addition, libraries of massive stars’ spectra are needed to produce population synthesis models able to reproduce the observed spectra of unresolved young stellar populations, such as those revealed by the James Webb Space Telescope (JWST) in the early Universe. Aims. Our main goal is to provide an extensive library of synthetic spectra and spectral energy distributions of OB stars at metallicities of the Magellanic Clouds. This library will offer a wealth of spectrophotometric information, making it readily applicable to a variety of astrophysical problems. Methods. We used the CMFGEN code to calculate 606 NLTE, line-blanketed, expanding atmosphere models using a comprehensive set of atomic data. An overall metallicity of 1/2 Z⊙ and 1/5 Z⊙ was adopted for the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), respectively. We produced high-resolution spectra from 30 Å to 3 µm for stars on the Main Sequence and slightly beyond. Results. We provide spectral energy distributions, normalized synthetic spectra, ionizing fluxes, and photometry in various bands: Johnson UBV, Cousins RI, Bessel JHK, selected wide JWST filters, Gaia, and LSST ugrizy filters. For each of these filters, we compute bolometric corrections for all synthetic spectra and calibrations as a function of effective temperature. Conclusions. All of our synthetic spectra are publicly available through the POLLUX database, aiming to expedite multiwavelength analyses of massive stars in low metallicity environments.
A near-UV reconnaissance of metal-poor massive stars Chris Evans, Wagner Marcolino, Jean-Claude Bouret, Miriam Garcia Experimental Astronomy, 2023 We use synthetic model spectra to investigate the potential of near-ultraviolet (3000-4050 Å) observations of massive O-type stars. We highlight the He I $$\\lambda $$ λ 3188 and He II $$\\lambda $$ λ 3203 pair as a potential temperature diagnostic in this range, supported by estimates of gravity using the high Balmer series lines. The near-ultraviolet also contains important metallic lines for determinations of chemical abundances (oxygen in particular) and estimates of projected rotational velocities for O-type spectra. Using the model spectra we present performance estimates for observations of extragalactic massive stars with the Cassegrain U-Band Efficient Spectrograph (CUBES) now in construction for the Very Large Telescope. The high efficiency of CUBES will open-up exciting new possibilities in the study of massive stars in external galaxies. For instance, CUBES will provide new insights into the physical properties of O-type stars, including oxygen abundances, in metal-poor irregular galaxies at $$\\sim $$ ∼ 1 Mpc from integrations of just 2-3 hrs. Moreover, CUBES will bring quantitative spectroscopy of more distant targets within reach for the first time, such as the O-type star (V $$\\sim $$ ∼ 21.5 mag) in Leo P (at 1.6 Mpc) in only half a night of observations.
Clumping and X-rays in cooler B supergiant stars M. Bernini-Peron, W. L. F. Marcolino, A. A. C. Sander, J.-C. Bouret, V. Ramachandran, J. Saling, F. R. N. Schneider, L. M. Oskinova, F. Najarro Astronomy and Astrophysics, 2023 Context. B supergiants (BSGs) are evolved stars with effective temperatures between ~10 to ~30 kK. Knowing the properties of these objects is important to understand massive star evolution. Located on the cool end of the line-driven wind regime, the study of their atmospheres can help us to understand the physics of their winds and phenomena such as the bi-stability jump. Aims. Despite being well-studied stars, key UV features of their spectra have so far not been reproduced by atmosphere models for spectral types later than B1. In this study, we aim to remedy this situation by performing quantitative spectral analyzes that account for the effects of X-rays and clumping in the wind. In addition, we also briefly investigate the evolutionary status of our sample stars based on the stellar parameters we obtained. Methods. We determined photospheric and wind parameters via quantitative spectroscopy using atmosphere models computed with CMFGEN and PoWR. These models were compared to high-resolution UV and optical spectra of four BSGs: HD206165, HD198478, HD53138, and HD164353. We further employed GENEC and MESA tracks to study the evolutionary status of our sample. Results. When including both clumping and X-rays, we obtained a good agreement between synthetic and observed spectra for our sample stars. For the first time, we reproduced key wind lines in the UV, where previous studies were unsuccessful. To model the UV spectra, we require a moderately clumped wind (fV∞ ≳ 0.5). We also infer a relative X-ray luminosity of about 10−7.5 to 10−8, which is lower than the typical ratio of 10−7. Moreover, we find a possible mismatch between evolutionary mass predictions and the derived spectroscopic masses, which deserves deeper investigation as this might relate to the mass-discrepancy problem present in other types of OB stars. Conclusions. Our results provide direct spectroscopic evidence that both X-rays and clumping need to be taken into account to describe the winds of cool BSGs. However, their winds seem to be much less structured than in earlier OB-type stars. Our findings are in line with observational X-rays and clumping constraints as well as recent hydrodynamical simulations. The evolutionary status of BSGs seems to be diverse with some objects potentially being post-red supergiants or merger products. The obtained wind parameters provide evidence for a moderate increase of the mass-loss rate around the bi-stability jump.
X-Shooting ULLYSES: Massive stars at low metallicity: I. Project description Jorick S. Vink, A. Mehner, P. A. Crowther, A. Fullerton, M. Garcia, F. Martins, N. Morrell, L. M. Oskinova, N. St-Louis, A. ud-Doula, A. A. C. Sander, H. Sana, J.-C. Bouret, B. Kubátová, P. Marchant, L. P. Martins, A. Wofford, J. Th. van Loon, O. Grace Telford, Y. Götberg, D. M. Bowman, C. Erba, V. M. Kalari, M. Abdul-Masih, T. Alkousa, F. Backs, C. L. Barbosa, S. R. Berlanas, M. Bernini-Peron, J. M. Bestenlehner, R. Blomme, J. Bodensteiner, S. A. Brands, C. J. Evans, A. David-Uraz, F. A. Driessen, K. Dsilva, S. Geen, V. M. A. Gómez-González, L. Grassitelli, W.-R. Hamann, C. Hawcroft, A. Herrero, E. R. Higgins, D. John Hillier, R. Ignace, A. G. Istrate, L. Kaper, N. D. Kee, C. Kehrig, Z. Keszthelyi, J. Klencki, A. de Koter, R. Kuiper, E. Laplace, C. J. K. Larkin, R. R. Lefever, C. Leitherer, D. J. Lennon, L. Mahy, J. Maíz Apellániz, G. Maravelias, W. Marcolino, A. F. McLeod, S. E. de Mink, F. Najarro, M. S. Oey, T. N. Parsons, D. Pauli, M. G. Pedersen, R. K. Prinja, V. Ramachandran, M. C. Ramírez-Tannus, G. N. Sabhahit, A. Schootemeijer, S. Reyero Serantes, T. Shenar, G. S. Stringfellow, N. Sudnik, F. Tramper, L. Wang Astronomy and Astrophysics, 2023 Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observing ∼250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES programme. The complementary X-Shooting ULLYSES (XShootU) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO’s Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the XShootU project is expected to be a game changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope spectra of the first stellar generations, the individual spectra of low-Z stars need to be understood, which is exactly where XShootU can deliver.
The CUBES science case Chris Evans, Stefano Cristiani, Cyrielle Opitom, Gabriele Cescutti, Valentina D’Odorico, Juan Manuel Alcalá, Silvia H. P. Alencar, Sergei Balashev, Beatriz Barbuy, Nate Bastian, Umberto Battino, Pamela Cambianica, Roberta Carini, Brad Carter, Santi Cassisi, Bruno Vaz Castilho, Norbert Christlieb, Ryan Cooke, Stefano Covino, Gabriele Cremonese, Katia Cunha, André R. da Silva, Valerio D’Elia, Annalisa De Cia, Gayandhi De Silva, Marcos Diaz, Paolo Di Marcantonio, Heitor Ernandes, Alan Fitzsimmons, Mariagrazia Franchini, Boris T. Gänsicke, Matteo Genoni, Riano E. Giribaldi, Andrea Grazian, Camilla Juul Hansen, Fiorangela La Forgia, Monica Lazzarin, Wagner Marcolino, Marcella Marconi, Alessandra Migliorini, Pasquier Noterdaeme, Claudio Pereira, Bogumil Pilecki, Andreas Quirrenbach, Sofia Randich, Silvia Rossi, Rodolfo Smiljanic, Colin Snodgrass, Julian Stürmer, Andrea Trost, Eros Vanzella, Paolo Ventura, Duncan Wright, Tayyaba Zafar Experimental Astronomy, 2023 We introduce the scientific motivations for the development of the Cassegrain U-Band Efficient Spectrograph (CUBES) that is now in construction for the Very Large Telescope. The assembled cases span a broad range of contemporary topics across Solar System, Galactic and extragalactic astronomy, where observations are limited by the performance of current ground-based spectrographs shortwards of 400 nm. A brief background to each case is presented and specific technical requirements on the instrument design that flow-down from each case are identified. These were used as inputs to the CUBES design, that will provide a factor of ten gain in efficiency for astronomical spectroscopy over 300-405 nm, at resolving powers of $$R~\\sim$$ R ∼ 24,000 and $$\\sim$$ ∼ 7,000. We include performance estimates that demonstrate the ability of CUBES to observe sources that are up to three magnitudes fainter than currently possible at ground-ultraviolet wavelengths, and we place its predicted performance in the context of existing facillities.
Clumping and X-rays in cool B Supergiants Matheus Bernini-Peron, W. L. F. Marcolino, A. A. C. Sander Proceedings of the International Astronomical Union, 2023 B supergiants (BSGs) are evolved objects on the cool end of the line-driven wind regime. Studying their atmospheres provides important insights on the stellar wind physics of these objects and their evolutionary status. So far important features of their spectra, especially in the UV region, could not be reproduced consistently with atmosphere models. This translates directly into problems of our understanding of their wind properties. Here, we present new insights about the BSGs on the cooler side of the Bi-Stability Jump, corresponding to spectral types later than B1. Using UV and optical data, we analysed a sample of Galactic cool BSGs. Including for the first time X-rays and clumping the wind models, we show that the spectra of cool BSGs cannot be explained without X-rays, despite any clear detection of the target stars.
Clumping and X-rays in cool B-Supergiants Matheus Bernini-Peron, W. L. F. Marcolino, A. A. C. Sander Proceedings of the International Astronomical Union, 2022 B supergiants (BSGs) lie on the cool end of line-driven wind regime, such that the study of their atmospheres can help us to understand the physics of line-driven winds. So far key features of their spectra, especially in the UV region, could not be reproduced consistently with atmosphere models. This represents a significant gap in our knowledge of their physical properties and behavior, which is particularly striking for BSGs on the cool side of the Bi-Stability Jump (cooler than B1). To address this problem, we analysed a sample of Galactic cool BSGs, with sufficient UV and optical coverage. None of our targets are detected in X-rays with only upper limits existing for some of them.
Wind properties of Milky Way and SMC massive stars: Empirical Z dependence from cmfgen models W L F Marcolino, J -C Bouret, H J Rocha-Pinto, M Bernini-Peron, J S Vink Monthly Notices of the Royal Astronomical Society, 2022 Detailed knowledge about stellar winds and evolution at different metallicities is crucial for understanding stellar populations and feedback in the Local Group of galaxies and beyond. Despite efforts in the literature, we still lack a comprehensive, empirical view of the dependence of wind properties on metallicity (Z). Here, we investigate the winds of O and B stars in the Milky Way (MW) and Small Magellanic Cloud (SMC). We gathered a sample of 96 stars analysed by means of the nlte code cmfgen. We explored their wind strengths and terminal velocities to address the Z dependence, over a large luminosity range. The empirical wind–luminosity relation (WLR) obtained updates and extends previous results in the literature. It reveals a luminosity and Z dependence, in agreement with the radiatively driven wind theory. For bright objects (log L/L⊙ ≳ 5.4), we infer that $\\dot{M} \\sim Z^{0.5-0.8}$. However, this dependence seems to get weaker or vanish at lower luminosities. The analysis of the terminal velocities suggests a shallow Zn dependence, with n ∼ 0.1−0.2, but it should be confirmed with a larger sample and more accurate V∞ determinations. Recent results on SMC stars based on the PoWR code support our inferred WLR. On the other hand, recent bow-shocks measurements stand mostly above our derived WLR. Theoretical calculations of the WLR are not precise, specially at low L, where the results scatter. Deviations between our results and recent predictions are identified to be due to the weak wind problem and the extreme terminal velocities predicted by the models. The Z dependence suggested by our analysis deserves further investigations, given its astrophysical implications.
CUBES, the Cassegrain U-Band Efficient Spectrograph Stefano Cristiani, Juan Manuel Alcalá, Alencar Silvia, Serj Balashev, Nate Bastian, Beatriz Barbuy, Battino Umberto, Ariadna Calcines Rosario, Giorgio Calderone, Pamela Cambianica, Roberta Carini, Brad Carter, Santi Cassisi, Bruno Castilho, Gabriele Cescutti, Norbert Christlieb, Roberto Cirami, Igor Coretti, Ryan J. Cooke, Stefano Covino, Gabriele Cremonese, Katia Cunha, Guido Cupani, André da Silva, Vincenzo De Caprio, Annalisa De Cia, Hans Dekker, Valerio D'Elia, Gayandhi de Silva, Marcos P. Diaz, Paolo Di Marcantonio, Domenico D'Auria, Valentina D'Odorico, Alan Fitzsimmons, Heitor Ernandes, Chris Evans, Mariagrazia Franchini, Matteo Genoni, Boris Gänsicke, Riano Escate Giribaldi, Clemens D. Gneiding, Andrea Grazian, Camilla Juul Hansen, Fiorangela La Forgia, Marco Landoni, Monica Lazzarin, David Lunney, Walter J. Maciel, Wagner Marcolino, Marcella Marconi, Alessandra Migliorini, Chris Miller, Pasquier Noterdaeme, Cyrielle Opitom, Giorgio Pariani, Bogumil Pilecki, Silvia Piranomonte, Andreas Quirrenbach, Edoardo Maria Alberto Redaelli, Claudio Pereira, Sofia Randich, Silvia Rossi, Ruben Sanchez-Janssen, Walter Seifert, Rodolfo Smiljanic, Colin Snodgrass, Ingo Stilz, Julian Stürmer, Eros Vanzella, Paolo Ventura, Orlando Verducci, Chris Waring, Stephen Watson, Martyn Wells, Duncan Wright, Tayyaba Zafar, Alessio Zanutta Proceedings of SPIE the International Society for Optical Engineering, 2022
The MiMeS survey of magnetism in massive stars: Introduction and overview G. A. Wade, C. Neiner, E. Alecian, J. H. Grunhut, V. Petit, B. de Batz, D. A. Bohlender, D. H. Cohen, H. F. Henrichs, O. Kochukhov, J. D. Landstreet, N. Manset, F. Martins, S. Mathis, M. E. Oksala, S. P. Owocki, Th. Rivinius, M. E. Shultz, J. O. Sundqvist, R. H. D. Townsend, A. ud-Doula, J.-C. Bouret, J. Braithwaite, M. Briquet, A. C. Carciofi, A. David-Uraz, C. P. Folsom, A. W. Fullerton, B. Leroy, W. L. F. Marcolino, A. F. J. Moffat, Y. Nazé, N. St Louis, M. Aurière, S. Bagnulo, J. D. Bailey, R. H. Barbá, A. Blazère, T. Böhm, C. Catala, J.-F. Donati, L. Ferrario, D. Harrington, I. D. Howarth, R. Ignace, L. Kaper, T. Lüftinger, R. Prinja, J. S. Vink, W. W. Weiss, I. Yakunin Monthly Notices of the Royal Astronomical Society, 2016
HR5907: Discovery of the most rapidly rotating magnetic early B-type star by the MiMeS Collaboration† J. H. Grunhut, Th. Rivinius, G. A. Wade, R. H. D. Townsend, W. L. F. Marcolino, D. A. Bohlender, Th. Szeifert, V. Petit, J. M. Matthews, J. F. Rowe, A. F. J. Moffat, T. Kallinger, R. Kuschnig, D. B. Guenther, S. M. Rucinski, D. Sasselov, W. W. Weiss, the MiMeS Collaboration Monthly Notices of the Royal Astronomical Society, 2012
τ Sco: The discovery of the clones Véronique Petit, Derck L. Massa, Wagner L. F. Marcolino, Gregg A. Wade, Richard Ignace, the MiMeS Collaboration Proceedings of the International Astronomical Union, 2011
The constant magnetic field of ξ1 CMa: Geometry or slow rotation? Chloé Fourtune-Ravard, Gregg A. Wade, Wagner L. F. Marcolino, Matthew Shultz, Jason H. Grunhut, Huib F. Henrichs, the MiMeS Collaboration Proceedings of the International Astronomical Union, 2011
Of?p stars: A class of slowly rotating magnetic massive stars Gregg A. Wade, Jason H. Grunhut, Wagner L. F. Marcolino, Fabrice Martins, Ian D. Howarth, Yael Nazé, Nolan R. Walborn, the MiMeS Collaboration Proceedings of the International Astronomical Union, 2011
Confirmation of the magnetic oblique rotator model for the Of?p star HD191612 G. A. Wade, I. D. Howarth, R. H. D. Townsend, J. H. Grunhut, M. Shultz, J.-C. Bouret, A. Fullerton, W. Marcolino, F. Martins, Y. Nazé, A. ud Doula, N. R. Walborn, J.-F. Donati, the MiMeS Collaboration Monthly Notices of the Royal Astronomical Society, 2011
