Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Moździerski, Dawid; Pigulski, A.; Kołaczkowski, Z.; Michalska, G.; Kopacki, G.; Carrier, F.; Walczak, P.; Narwid, A.; Stȩślicki, M.; Fu, Jian-Ning; Jiang, Xiaojun; Zhang, Ch.; Jackiewicz, Jason; Telting, J. H.; Morel, Thierry; Saesen, S.; Zahajkiewicz, E.; Bruś, P.; Śródka, P.; Vučković, M.; Verhoelst, Tijl; Helshoecht, V. Van; Lefever, K.; Gielen, C.; Decin, L.; Vanautgaerden, J.; Aerts, C.

doi:10.1051/0004-6361/201936418

“…The present-day ratio Z/X can then be calculated by assuming the abundances of minor elements follow the solar mixture. Different studies have revealed that abundances of B stars in the solar neighbourhood differ and are metal poorer than the solar abundances (Przybilla et al 2008;Morel 2009;Niemczura et al 2009;Nieva & Simón-Díaz 2011). The difference was particularly marked with past solar abundance determinations such as the Grevesse & Noels (1993), hereafter GN93, one.…”

Section: Typical Observational Errors On the Fundamental Parametersmentioning

confidence: 98%

Asteroseismology of $β$ Cephei stars: The stellar inferences tested in hare and hound exercises

Salmon,

Eggenberger,

Montalbán

et al. 2021

Preprint

0

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Context. The β Cephei pulsators are massive, ∼ 8 − 25M ⊙ essentially on the main-sequence, stars. The number of detected modes in β Cephei stars often remains limited to less than a dozen of low radial-order modes. Such oscillation modes are in principle able to constrain the internal processes acting in the star. They probe the chemical gradient at the edge of the convective core, in particular its location and extension. They hence give constraints on macroscopic processes, such as hydrodynamic or magnetic instabilities, that have an impact on the mixing there. Yet, it is not clear to what extent the seismic inferences depend on the physics employed for the stellar modelling or on the observational dataset used. Consequently, it is not easy to estimate the accuracy and precision on the parameters and the nature of the physical processes inferred. Aims. We investigate the observational constraints, in particular the properties of the minimum set of pulsations detected, which are necessary to provide accurate constraints on the mixing processes in β Cephei stars. We explore the importance of the identification of the angular degree of the modes. In addition, depending on the quality of the seismic dataset and the classical non-seismic constraints, we aim to estimate, in a systematic way, the precision achievable with asteroseismology on the determination of their stellar parameters. Methods. We propose a method extending the forward approach classically used to model β Cephei stars. With the help of Monte-Carlo simulation, the probability distributions of the asteroseismic-derived stellar parameters were obtained. With these distributions, we provide a systemic way to estimate the errors derived from the modelling. A particular effort was made to include, not only the observational errors, but also the theoretical uncertainties of the models. We then estimated the accuracy and precision of asteroseismology for β Cephei stars in a series of hare and hound exercises.Results. The results of the hare and hounds show that a set of four to five oscillation frequencies with an identified angular degree already leads to accurate inferences on the stellar parameters. Without the identification of the modes, the addition of other observational constraints, such as the effective temperature and surface gravity, still ensures the success of the seismic modelling. When the internal microscopic physics of the star and stellar models used for the modelling differ, the constraints derived on the internal structure remain valid if expressed in terms of acoustic variables, such as the radius. However, they are then hardly informative on structural variables expressed in mass. The characterisation of the mixing processes at the boundary of the convective core are model-dependent and it requires the use of models implemented with processes of a similar nature.

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“…To date, there are only a handful of hybrid SPB / β Cep stars known in binary systems (see e.g., Degroote et al 2012;González et al 2019) and a handful of either SPB or β Cep pulsators in systems that are eclipsing, (see e.g., Freyhammer et al 2005;Tkachenko et al 2014;Jerzykiewicz et al 2015). While there are several known β Cep or SPB pulsating stars in clusters (Balona & Shobbrook 1983;Handler et al 2007;Saesen et al 2013;Moździerski et al 2019), no hybrid pulsating SPB/β Cep stars in EBs have been identified in clusters to date. Although, this is likely a consequence of data quality and duty cycle, rather than a physical deficiency.…”

Section: Coherent and Stochastic Oscillations In Hd 149834 Amentioning

confidence: 99%

Discovery and Characterization of a Rare Magnetic Hybrid β Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193

Stassun

¹

,

Torres

²

,

Johnston

³

et al. 2021

ApJ

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As many as 10% of OB-type stars have global magnetic fields, which is surprising given their internal structure is radiative near the surface. A direct probe of internal structure is pulsations, and some OBtype stars exhibit pressure modes (β Cep pulsators) or gravity modes (slowly pulsating B-type stars; SPBs); a few rare cases of hybrid β Cep/SPBs occupy a narrow instability strip in the H-R diagram. The most precise fundamental properties of stars are obtained from eclipsing binaries (EBs), and those in clusters with known ages and metallicities provide the most stringent constraints on theory. Here we report the discovery that HD 149834 in the ∼5 Myr cluster NGC 6193 is an EB comprising a hybrid β Cep/SPB pulsator and a highly irradiated low-mass companion. We determine the masses, radii, and temperatures of both stars; the ∼9.7 M primary resides in the instability strip where hybrid pulsations are theoretically predicted. The presence of both SPB and β Cep pulsations indicates that the system has a near-solar metallicity, and is in the second half of the main-sequence lifetime. The radius of the ∼1.2 M companion is consistent with theoretical pre-main-sequence isochrones at 5 Myr, but its temperature is much higher than expected, perhaps due to irradiation by the primary. The radius of the primary is larger than expected, unless its metallicity is super-solar. Finally, the light curve shows residual modulation consistent with the rotation of the primary, and Chandra observations reveal a flare, both of which suggest the presence of starspots and thus magnetism on the primary.

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“…To date, there are only a handful of hybrid SPB / β Cep stars known in binary systems (see e.g., Degroote et al 2012;González et al 2019) and a handful of either SPB or β Cep pulsators in systems that are eclipsing, (see e.g., Freyhammer et al 2005;Tkachenko et al 2014;Jerzykiewicz et al 2015). While there are several known β Cep or SPB pulsating stars in clusters (Balona & Shobbrook 1983;Handler et al 2007;Saesen et al 2013;Moździerski et al 2019), no hybrid pulsating SPB/β Cep stars in EBs have been identified in clusters to date. Although, this is likely a consequence of data quality and duty cycle, rather than a physical deficiency.…”

Section: Coherent and Stochastic Oscillations In Hd 149834 Amentioning

confidence: 99%

Discovery and Characterization of a Rare Magnetic Hybrid $β$ Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193

Stassun,

Torres,

Johnston

et al. 2021

Preprint

0

View full text Add to dashboard Cite

As many as 10% of OB-type stars have global magnetic fields, which is surprising given their internal structure is radiative near the surface. A direct probe of internal structure is pulsations, and some OBtype stars exhibit pressure modes (β Cep pulsators) or gravity modes (slowly pulsating B-type stars; SPBs); a few rare cases of hybrid β Cep/SPBs occupy a narrow instability strip in the H-R diagram. The most precise fundamental properties of stars are obtained from eclipsing binaries (EBs), and those in clusters with known ages and metallicities provide the most stringent constraints on theory. Here we report the discovery that HD 149834 in the ∼5 Myr cluster NGC 6193 is an EB comprising a hybrid β Cep/SPB pulsator and a highly irradiated low-mass companion. We determine the masses, radii, and temperatures of both stars; the ∼9.7 M primary resides in the instability strip where hybrid pulsations are theoretically predicted. The presence of both SPB and β Cep pulsations indicates that the system has a near-solar metallicity, and is in the second half of the main-sequence lifetime. The radius of the ∼1.2 M companion is consistent with theoretical pre-main-sequence isochrones at 5 Myr, but its temperature is much higher than expected, perhaps due to irradiation by the primary. The radius of the primary is larger than expected, unless its metallicity is super-solar. Finally, the light curve shows residual modulation consistent with the rotation of the primary, and Chandra observations reveal a flare, both of which suggest the presence of starspots and thus magnetism on the primary.

show abstract

Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Cited by 23 publications

References 73 publications

Asteroseismology of $β$ Cephei stars: The stellar inferences tested in hare and hound exercises

Asteroseismology of $β$ Cephei stars: The stellar inferences tested in hare and hound exercises

Discovery and Characterization of a Rare Magnetic Hybrid β Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193

Discovery and Characterization of a Rare Magnetic Hybrid $β$ Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193

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