The atmospheric structure and fundamental parameters of the red supergiants AH Scorpii, UY Scuti, and KW Sagittarii

Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Hauschildt, P. H.

doi:10.1051/0004-6361/201220920

Cited by 47 publications

(76 citation statements)

References 60 publications

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“…We also observe a monotonic decrease beyond 2.3 μm, which may be caused by pseudocontinuum contributions from CO or by contributions from water vapor. We observed the same phenomenon previously for the RSGs VY CMa (Wittkowski et al 2012), AH Sco, UY Sct, and KW Sgr (Arroyo-Torres et al (2013), as well as for the smallamplitude pulsating red giants RS Cap (Marti-Vidal et al 2011), BK Vir (Ohnaka et al 2012), α Tau (Ohnaka 2013), and β Peg (Arroyo-Torres et al 2014).…”

Section: Resultssupporting

confidence: 88%

“…These models are based on a hydrostatic atmosphere, local thermodynamic equilibrium and spherical geometry. The best-fit PHOENIX model is obtained from an iterative process using the continuum band around 2.25 μm, as explained by Arroyo-Torres et al (2013). The final values for the used PHOENIX model atmosphere are: for V602 Car, T eff = 3400 K, log(g) = −0.5; for HD 95687, T eff = 3400 K, log(g) = 0.0; and for HD 183589, T eff = 3700 K, log(g) = 1.0.…”

Section: Resultsmentioning

confidence: 99%

“…Lançon et al 2007;Arroyo-Torres et al 2013). The flux variations at wavelengths below about 2.0 μm are due to a higher noise level, possibly caused by the lower atmospheric transmission.…”

Section: Resultsmentioning

confidence: 99%

“…Although this approach may be limited by the limited spectral resolution of our observations of R ∼ 1500 and by the low number of observations per source, it is appropriate for a first comparison of the extensions of RSG stars and other evolved stars. Figure 10 shows the resulting ratios (V 2 cont /V 2 CO ) for our sources vs. log(L/L ) and ΔV, considering the RSGs by Wittkowski et al (2012), Arroyo-Torres et al (2013) Arroyo- Torres et al (2014). Results for Mira stars obtained by Wittkowski et al (2011) are also shown for comparison.…”

Section: Characterization Of the Extension Of The Molecular Atmospherementioning

confidence: 99%

“…This paper is conceived as part of a series of three previous papers (Wittkowski et al 2012;Arroyo-Torres et al 2013. In these previous works, we presented the atmosphere structure and the fundamental parameters of a sample of four RSG stars and five cool giant stars.…”

Section: Introductionmentioning

confidence: 99%

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What causes the large extensions of red supergiant atmospheres?

Arroyo-Torres

Wittkowski²,

Chiavassa

et al. 2015

A&A

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108

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Aims. This research has two main goals. First, we present the atmospheric structure and the fundamental parameters of three red supergiants (RSGs), increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. Methods. We carried out spectro-interferometric observations of the RSGs V602 Car, HD 95687, and HD 183589 in the near-infrared K-band (1.92−2.47 μm) with the VLTI/AMBER instrument at medium spectral resolution (R ∼ 1500). To categorize and comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3D convection, and new 1D self-excited pulsation models of RSGs. Results. Our near-infrared flux spectra of V602 Car, HD 95687, and HD 183589 are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models, allowing us to determine the angular diameter and the fundamental parameters of our sources. Nonetheless, in the case of V602 Car and HD 95686, the PHOENIX model visibilities do not predict the large observed extensions of molecular layers, most remarkably in the CO bands. Likewise, the 3D convection models and the 1D pulsation models with typical parameters of RSGs lead to compact atmospheric structures as well, which are similar to the structure of the hydrostatic PHOENIX models. They can also not explain the observed decreases in the visibilities and thus the large atmospheric molecular extensions. The full sample of our RSGs indicates increasing observed atmospheric extensions with increasing luminosity and decreasing surface gravity, and no correlation with effective temperature or variability amplitude. Conclusions. The location of our RSG sources in the Hertzsprung-Russell diagram is confirmed to be consistent with the red limits of recent evolutionary tracks. The observed extensions of the atmospheric layers of our sample of RSGs are comparable to those of Mira stars. This phenomenon is not predicted by any of the considered model atmospheres including available 3D convection and new 1D pulsation models of RSGs. This confirms that neither convection nor pulsation alone can levitate the molecular atmospheres of RSGs. Our observed correlation of atmospheric extension with luminosity supports a scenario of radiative acceleration on Doppler-shifted molecular lines.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Characterization Of the Extension Of The Molecular Atmospherementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

What causes the large extensions of red supergiant atmospheres?

Arroyo-Torres

Wittkowski²,

Chiavassa

et al. 2015

A&A

Self Cite

108

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A parametric model to study the mass–radius relationship of stars

2019

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In static and spherically symmetric spacetime, we solve the Einstein Maxwell equations. The effective gravitational potential and the electric field for charged anisotropic fluid are defined in terms of two free parameters. For such configuration, the mass of the star as a function of stellar radius is found in terms of two aforementioned parameters, subjected to certain stability criteria. For various values of these two parameters one finds that such mass radius relationship can model stellar objects located at various regions of Hertzsprung-Russel diagram.

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Spectroscopic evidence for a large spot on the dimming Betelgeuse

et al. 2021

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During October 2019 and March 2020, the luminous red supergiant Betelgeuse demonstrated an unusually deep minimum of its brightness. It became fainter by more than one magnitude and this is the most significant dimming observed in the recent decades. While the reason for the dimming is debated, pre-phase of supernova explosion, obscuring dust, or changes in the photosphere of the star were suggested scenarios. Here, we present spectroscopic studies of Betelgeuse using high-resolution and high signal-to-noise ratio near-infrared spectra obtained at Weihai Observatory on four epochs in 2020 covering the phases of during and after dimming. We show that the dimming episode is caused by the dropping of its effective temperature by at least 170 K on 2020 January 31, that can be attributed to the emergence of a large dark spot on the surface of the star.

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The atmospheric structure and fundamental parameters of the red supergiants AH Scorpii, UY Scuti, and KW Sagittarii

Cited by 47 publications

References 60 publications

What causes the large extensions of red supergiant atmospheres?

What causes the large extensions of red supergiant atmospheres?

A parametric model to study the mass–radius relationship of stars

Spectroscopic evidence for a large spot on the dimming Betelgeuse

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