The nature of the Cygnus extreme B supergiant 2MASS J20395358+4222505

Herrero, A.; Berlanas, S. R.; Paz, A. Gil de; Comerón, F.; Puls, J.; Alegría, S. Ramírez; García, M.; Lennon, D. J.; Najarro, F.; Urbaneja, M. A.; Gallego, J.; Carrasco, E.; Iglesias, Jorge Mario Ortega; Cedazo, R.; Vargas, M.; Castillo-Morales, Á.; Pascual, S.; Cardiel, N.; Pérez-Calpena, A.; Gómez-Álvarez, P.; Martínez-Delgado, I.

doi:10.1093/mnras/stab3660

Cited by 3 publications

(2 citation statements)

References 54 publications

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“…These early and mid-O dwarfs and giants on the main sequence (MS) evolve into early B-type hypergiants (e.g. Clark et al 2012;Herrero et al 2022) and supergiants of luminosity class Ia, which constitute one of the more frequently populated regions of post-MS evolution in the HRD (e.g. Castro et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Quantitative spectroscopy of B-type supergiants

Weßmayer

Przybilla

Butler

2022

A&A

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Context. B-type supergiants are versatile tools to address a number of highly-relevant astrophysical topics, ranging from stellar atmospheres over stellar and galactic evolution to the characterisation of interstellar sightlines and to the cosmic distance scale. Aims. A hybrid non-LTE (local thermodynamic equilibrium) approach -involving line-blanketed model atmospheres computed under the assumption of LTE in combination with line formation calculations that account for deviations from LTE -is tested for quantitative analyses of B-type supergiants of mass up to about 30 M , characterising a sample of 14 Galactic objects in a comprehensive way. Methods. Hydrostatic plane-parallel atmospheric structures and synthetic spectra computed with Kurucz's Atlas12 code together with the non-LTE line-formation codes Detail/Surface are compared to results from full non-LTE calculations with Tlusty, and the effects of turbulent pressure on the models are investigated. High-resolution spectra at signal-to-noise ratio > 130 are analysed for atmospheric parameters, using Stark-broadened hydrogen lines and multiple metal ionisation equilibria, and for elemental abundances. Fundamental stellar parameters are derived by considering stellar evolution tracks and Gaia early data release 3 (EDR3) parallaxes. Interstellar reddening and the reddening law along the sight lines towards the target stars are determined by matching model spectral energy distributions to observed ones. Results. Our hybrid non-LTE approach turns out to be equivalent to hydrostatic full non-LTE modelling for the deeper photospheric layers of the B-type supergiants under consideration, where most lines of the optical spectrum are formed. Turbulent pressure can become relevant for microturbulent velocities larger than 10 km s −1 . The changes in the atmospheric density structure affect many diagnostic lines, implying systematic changes in atmospheric parameters, for instance an increase in surface gravities by up to 0.05 dex. A high precision and accuracy is achieved for all derived parameters by bringing multiple indicators to agreement simultaneously. Effective temperatures are determined to 2-3% uncertainty, surface gravities to better than 0.07 dex, masses to about 5%, radii to about 10%, luminosities to better than 25%, and spectroscopic distances to 10% uncertainty typically. Abundances for chemical species that are accessible from the optical spectra (He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe) are derived with uncertainties of 0.05 to 0.10 dex (1σ standard deviations). The observed spectra are reproduced well by the model spectra. The derived N/C versus N/O ratios tightly follow the predictions from Geneva stellar evolution models that account for rotation, and spectroscopic and Gaia EDR3 distances are closely matched. Finally, the methodology is tested for analyses of intermediate-resolution spectra of extragalactic B-type supergiants.

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Section: Introductionmentioning

confidence: 99%

Quantitative spectroscopy of B-type supergiants

Weßmayer

Przybilla

Butler

2022

A&A

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“…The code has been extensively 117 used for the analysis of B-type supergiants in the Milky Way 118 (e.g. Herrero et al 2022) as well as in other galaxies (e.g. Ur-119 baneja et al 2005;Kudritzki et al 2016).…”

Section: Notesmentioning

confidence: 99%

Runaway BN supergiant star HD 93840: Progenitor of an imminent core-collapse supernova above the Galactic plane

Weßmayer,

Urbaneja,

Butler

et al. 2024

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We present a quantitative spectral analysis of the extreme nitrogen-enhanced supergiant HD 93840 (BN1 Ib) at an intermediate galactic latitude. Based on an optical high-resolution spectrum and complementary ultraviolet and infrared (spectro-)photometry, in addition to Gaia data, we carried out a full characterisation of the star’s properties. We used both hydrostatic and unified (photosphere+wind) model atmospheres that account for deviations from local thermodynamic equilibrium. A highly unusual surface CNO-mixing signature and a marked stellar overluminosity compared to the mass imply a binary channel for the star’s past evolution. The kinematics shows that it has reached its current position above the Galactic plane as a runaway star, likely ejected by the supernova explosion of its former companion star. Its current bulk composition, with a notably increased mean molecular weight due to core He- and progressed shell H-burning, suggests an advanced evolutionary stage. It is poised to yield a rare core-collapse supernova of a blue supergiant about ten OB star population scale heights above the Galactic disk relatively soon, contributing to the metal enrichment of the circumgalactic medium.

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