The massive eclipsing system ALS 1135 and variable stars in the field of the distant OB association Bochum 7

Michalska, G.; Niemczura, E.; Pigulski, A.; Stȩślicki, M.; Williams, A.

doi:10.1093/mnras/sts419

Cited by 6 publications

(9 citation statements)

References 41 publications

(63 reference statements)

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“…For the method to work, both mass and radius have to be derived precisely, which means that it is applicable only to massive components of eclipsing binaries. An example of using this method was presented by Michalska et al (2013) for ALS 1135 in the Bochum 7 association. Not many stellar systems contain massive eclipsing binaries like this, however.…”

Section: Summary and Discussionmentioning

confidence: 99%

Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Moździerski

Pigulski

Kołaczkowski

et al. 2019

A&A

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Asteroseismology offers the possibility of probing stellar interiors and testing evolutionary and seismic models. Precise photometry and spectroscopy obtained during multi-site campaigns on young open clusters allows discovering rich samples of pulsating stars and using them in a simultaneous seismic modelling called ensemble asteroseismology. The aim of this study is to obtain the age of the open cluster NGC 6910 by means of ensemble asteroseismology of the early-type pulsating members, to derive their stellar parameters, and to classify the excited modes. We used time-series analysis, performed photometric and spectroscopic mode identification, and calculated grids of evolutionary and seismic models to apply the procedure of ensemble asteroseismology for nine pulsating members of NGC 6910. With two iterations of the procedure of ensemble asteroseismology applied to nine pulsating stars we derived an age of 10.6 +0.9 −0.8 Myr for NGC 6910. We also identified the degree l for 8 of 37 modes detected in these stars and classified all modes in terms of p, g, and mixed-mode pulsations. Of the nine pulsating stars examined in the paper, eight are β Cep stars, including three that are hybrid β Cep and slowly pulsating B-type (SPB) pulsators, and one is an SPB star. Interestingly, the least massive β Cep star, NGC 6910-38, has a mass of about 5.6 M . The present theory does not predict unstable p modes in B-type stars with such a low mass. The g modes with relatively high frequencies (> 3.5 d −1 ), observed in three members of the cluster, are also stable according to seismic modelling. Both findings pose a challenge for theoretical calculations and prompt a revision of the opacities. The procedure of ensemble asteroseismology was found to be successful for NGC 6910 and χ Per on the basis of pulsating B-type stars and can therefore be applied to other young open clusters that are rich in such stars.

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Section: Summary and Discussionmentioning

confidence: 99%

Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Moździerski

Pigulski

Kołaczkowski

et al. 2019

A&A

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“…Classification of the Quintuplet OB supergiants is particularly difficult; via comparison to the Arches we reclassify LH099 as WN7-9ha but of the 84 stars Liermann et al (2009) list as O stars we are unable to determine accurate spectral types and/or luminosity classes.Following the literature convention we restrict YHGs to spectral types A, F and G. Finally, we assign a tentative classification of LBV to V439 Cyg; a star with an uncertain history which Polcaro & Norci (1998) quote as being identified as respectively 'Mira-like', B3e, a carbon star, B0ep, B1.5 Ve and a candidate LBV over the last ∼ 70yrs. References used in the construction of this table are 1 Massey et al (2001), 2 Harayama et al (2008), 3 Melena et al (2008), 4 Schnurr et al (2008), 5 Massey et al (1995), 6 Shi & Hu (1999), 7,8 Rauw et al (2007, 9 Hillenbrand et al (1993), 10 Martayan et al (2008), 11 Martins et al (2008), 12 Hanson et l. ( 2010), 13,14 Borissova et al (200813,14 Borissova et al ( ,2012, 15 Bibby et al (2008), 16 Kurtev et al (2007), 17 Chené et al (2013), 18 Messineo et al (2009), 19 Figer et al (1999), 20,21 Liermann et al (2009, 22 Davies et al (2012b), 23 de La Fuente et al (2012), 24 Messineo et al (2011), 25 Crowther et al (2006b), 26 Michalska et al (2013), 27 Wang & Hu (2000), 28 Clark et al (2005), 29 Negueruela et al (2010a), 30 Barbon et al (2000),…”

Section: Appendix A: Summary Of the Evolved Stellar Content Of Galact...mentioning

confidence: 99%

The circumstellar environment and evolutionary state of the supergiant B[e] star Wd1-9

Clark

Ritchie

Negueruela

2013

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Context. Historically, supergiant (sg)B[e] stars have been difficult to include in theoretical schemes for the evolution of massive OB stars. Aims. The location of Wd1-9 within the coeval starburst cluster Westerlund 1 means that it may be placed into a proper evolutionary context and we therefore aim to utilise a comprehensive multiwavelength dataset to determine its physical properties and consequently its relation to other sgB[e] stars and the global population of massive evolved stars within Wd1. Methods. Multi-epoch R-and I-band VLT/UVES and VLT/FORS2 spectra are used to constrain the properties of the circumstellar gas, while an ISO-SWS spectrum covering 2.45-45 μm is used to investigate the distribution, geometry and composition of the dust via a semi-analytic irradiated disk model. Radio emission enables a long term mass-loss history to be determined, while X-ray observations reveal the physical nature of high energy processes within the system. Results. Wd1-9 exhibits the rich optical emission line spectrum that is characteristic of sgB[e] stars. Likewise its mid-IR spectrum resembles those of the LMC sgB[e] stars R66 and 126, revealing the presence of equatorially concentrated silicate dust, with a mass of ∼10 −4 M . Extreme historical and ongoing mass loss ( 10 −4 M yr −1 ) is inferred from the radio observations. The X-ray properties of Wd1-9 imply the presence of high temperature plasma within the system and are directly comparable to a number of confirmed short-period colliding wind binaries within Wd1. Conclusions. The most complete explanation for the observational properties of Wd1-9 is that it is a massive interacting binary currently undergoing, or recently exited from, rapid Roche-lobe overflow, supporting the hypothesis that binarity mediates the formation of (a subset of) sgB[e] stars. The mass loss rate of Wd1-9 is consistent with such an assertion, while viable progenitor and descendent systems are present within Wd1 and comparable sgB[e] binaries have been identified in the Galaxy. Moreover, the rarity of sgB[e] stars -only two examples are identified from a census of ∼68 young massive Galactic clusters and associations containing ∼600 post-Main Sequence stars -is explicable given the rapidity (∼10 4 yr) expected for this phase of massive binary evolution.

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“…The frequency was tentatively attributed to pulsations of one of the components. Unfortunately, follow-up observations showed (Michalska et al 2013) that it is a nearby eclipsing binary, unresolved in the ASAS frames, that is responsible for this variability.…”

Section: Characteristics Of the Asas Datamentioning

confidence: 99%