The temperatures of red supergiants in low-metallicity environments

González-Torà, Gemma; Davies, Ben; Kudritzki, Rolf‐Peter; Plez, B.

doi:10.1093/mnras/stab1611

Cited by 6 publications

(13 citation statements)

References 36 publications

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“…This is expanded upon by González-Torà et al ( 2021) who re-determined the effective temperatures for the sample of (Davies et al 2013(Davies et al , 2015, and found excellent agreement with the results of Davies et al (2013) and Davies et al (2015). González-Torà et al (2021) found a systematic offset of ∼ 150 K between their results and those of TDN18, with the TDN18 temperatures being the cooler. González-Torà et al ( 2021) explain these differences as the result of a combination of not accounting for non-LTE effects (see Bergemann et al 2013) and continuum placement issues in the wavelength range studied by TDN18.…”

Section: Data Availabilitysupporting

confidence: 57%

“…Spectroscopic 𝐴 V determination is likely the most robust method to determine the extinction values of RSGs, as such estimates take into account circumstellar extinction around RSGs. That being said, spectroscopically determined 𝐴 V values have large uncertainties and the agreement between the 𝐴 V measurements between the stars in common between the spectroscopic studies of Levesque et al (2006) and Davies et al (2013), is poor, and has not been resolved with the updated calculations of González-Torà et al (2021). In particular, the stars with 𝐴 V > 0.5 mag in Levesque et al (2006), all have 𝐴 V lower values in González-Torà et al ( 2021) and those with 𝐴 V < 0.5 mag all have larger values in González-Torà et al (2021).…”

Section: Extinction and Reddeningmentioning

confidence: 99%

“…That being said, spectroscopically determined 𝐴 V values have large uncertainties and the agreement between the 𝐴 V measurements between the stars in common between the spectroscopic studies of Levesque et al (2006) and Davies et al (2013), is poor, and has not been resolved with the updated calculations of González-Torà et al (2021). In particular, the stars with 𝐴 V > 0.5 mag in Levesque et al (2006), all have 𝐴 V lower values in González-Torà et al ( 2021) and those with 𝐴 V < 0.5 mag all have larger values in González-Torà et al (2021). The studies of Levesque et al (2006) and González-Torà et al ( 2021) targeted more luminous RSGs than are present in the UVIT cross-matched sample, which are known to have additional circumstellar material and larger 𝐴 V values (Neugent et al 2020).…”

Section: Extinction and Reddeningmentioning

confidence: 99%

“…We choose to implement neither the +150 K offset suggested by González-Torà et al (2021) nor the −200 K suggested by Massey et al (2021).…”

Section: Data Availabilitymentioning

confidence: 99%

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Red supergiant stars in binary systems. I. Identification and characterisation in the Small Magellanic Cloud from the UVIT ultraviolet imaging survey

Patrick,

Thilker,

Lennon

et al. 2022

Preprint

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We aim to identify and characterise binary systems containing red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) using a newly available ultraviolet (UV) point source catalogue obtained using the Ultraviolet Imaging Telescope (UVIT) on board AstroSat. We select a sample of 560 SMC RSGs based on photometric and spectroscopic observations at optical wavelengths and cross-match this with the far-UV point source catalogue using the UVIT F172M filter, finding 88 matches down to 𝑚 𝐹 172𝑀 = 20.3 ABmag, which we interpret as hot companions to the RSGs. Stellar parameters (luminosities, effective temperatures and masses) for both components in all 88 binary systems are determined and we find mass distributions in the ranges 6.1 < 𝑀/𝑀 < 22.3 for RSGs and 3.7 < 𝑀/𝑀 < 15.6 for their companions. The most massive RSG binary system in the SMC has a combined mass of 32 ± 4 M , with a mass ratio (𝑞) of 0.92. By simulating observing biases, we find an intrinsic multipliciy fraction of 18.8 ± 1.5 % for mass ratios in the range 0.3 < 𝑞 < 1.0 and orbital periods approximately in the range 3 < log 𝑃[days] < 8. By comparing our results with those of a similar mass on the main-sequence, we determine the fraction of single stars to be ∼20 % and argue that the orbital period distribution declines rapidly beyond log 𝑃 ∼ 3.5. We study the mass-ratio distribution of RSG binary systems and find that a uniform distribution best describes the data below 14 M . Above 15 M , we find a lack of high mass-ratio systems.

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Section: Data Availabilitysupporting

confidence: 57%

Section: Extinction and Reddeningmentioning

confidence: 99%

Section: Extinction and Reddeningmentioning

confidence: 99%

“…We choose to implement neither the +150 K offset suggested by González-Torà et al (2021) nor the −200 K suggested by Massey et al (2021).…”

Section: Data Availabilitymentioning

confidence: 99%

See 2 more Smart Citations

Red supergiant stars in binary systems. I. Identification and characterisation in the Small Magellanic Cloud from the UVIT ultraviolet imaging survey

Patrick,

Thilker,

Lennon

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…However, some studies provide evidence that a fixed mixing length is not suitable for all types of stars (e.g., Guenther & Demarque 2000;Bonaca et al 2012;Tayar et al 2017) and that the mixing length depends on metallicity for both low-and high-mass stars (Joyce & Chaboyer 2018;Chun et al 2018). More recently, González-Torà et al (2021) also found that the standard solar mixing length is not applicable to RSGs in their comparison of effective temperature of the Wolf-Lundmark-Mellote (WLM) galaxy with the Geneva evolutionary models. Chun et al (2018) calibrated the mixing length values in RSGs for various metallicities by comparing a grid of massive star evolutionary models with RSGs observed in the nearby universe, and found that the mixing length decreases for decreasing metallicity.…”

Section: Introductionmentioning

confidence: 99%

Red Supergiant Stars in IC 1613 and Metallicity-dependent Mixing Length in the Evolutionary Model

Chun

Yoon

et al. 2022

ApJ

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We report a spectroscopic study on red supergiant stars (RSGs) in the irregular dwarf galaxy IC 1613 in the Local Group. We derive the effective temperatures (T eff) and metallicities of 14 RSGs by synthetic spectral fitting to the spectra observed with the MMIRS instrument on the MMT telescope for a wavelength range from 1.16 to 1.23 μm. A weak bimodal distribution of the RSG metallicity centered on [Fe/H] = −0.65 is found, which is slightly lower than or comparable to that of the Small Magellanic Cloud (SMC). There is no evidence for spatial segregation between the metal-rich ([Fe/H] > −0.65) and -poor ([Fe/H] < −0.65) RSGs throughout the galaxy. The mean effective temperature of our RSG sample in IC 1613 is higher by about 250 K than that of the SMC. However, no correlation between T eff and metallicity within our RSG sample is found. We calibrate the convective mixing length (α MLT) by comparing stellar evolutionary tracks with the RSG positions on the H-R diagram, finding that models with α MLT = 2.2–2.4H P can best reproduce the effective temperatures of the RSGs in IC 1613 for both Schwarzschild and Ledoux convection criteria. This result supports our previous finding that a metallicity-dependent mixing length is needed to explain the RSG temperatures observed in the Local Group, but we find that this dependence becomes relatively weak for RSGs having a metallicity equal to or less than the SMC metallicity.

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Properties of luminous red supergiant stars in the Magellanic Clouds

Wit

Bonanos

Tramper

et al. 2023

A&A

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Context. There is evidence that some red supergiants (RSGs) experience short-lived phases of extreme mass loss, producing copious amounts of dust. These episodic outburst phases help strip the hydrogen envelope from evolved massive stars, drastically affecting their evolution. However, to date, the observational data of episodic mass loss is limited. Aims. This paper aims to derive surface properties of a spectroscopic sample of 14 dusty sources in the Magellanic Clouds using the Baade telescope. These properties can be used for future spectral energy distribution fitting studies to measure the mass-loss rates from present circumstellar dust expelled from the star through outbursts. Methods. We applied marcs models to obtain the effective temperature (T eff ) and extinction (A V ) from the optical TiO bands. We used a χ 2 routine to determine the model that best fits the obtained spectra. We computed the T eff using empirical photometric relations and compared this to our modelled T eff . Results. We have identified a new yellow supergiant and spectroscopically confirmed eight new RSGs and one bright giant in the Magellanic Clouds. Additionally, we observed a supergiant B[e] star and find that the spectral type has changed compared to previous classifications, confirming that the spectral type is variable over decades. For the RSGs, we obtained the surface and global properties, as well as the extinction (A V ). Conclusions. Our method has picked up eight new, luminous RSGs. Despite selecting dusty RSGs, we find values for A V that are not as high as expected given the circumstellar extinction of these evolved stars. The most remarkable object from the sample, LMC3, is an extremely massive and luminous evolved massive star and may be grouped amongst the largest and most luminous RSGs known in the Large Magellanic Cloud (log(L * /L ⊙ ) ∼5.5 and R = 1400 R ⊙ ).

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The temperatures of red supergiants in low-metallicity environments

Cited by 6 publications

References 36 publications

Red supergiant stars in binary systems. I. Identification and characterisation in the Small Magellanic Cloud from the UVIT ultraviolet imaging survey

Red supergiant stars in binary systems. I. Identification and characterisation in the Small Magellanic Cloud from the UVIT ultraviolet imaging survey

Red Supergiant Stars in IC 1613 and Metallicity-dependent Mixing Length in the Evolutionary Model

Properties of luminous red supergiant stars in the Magellanic Clouds

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