Radii and Effective Temperatures for K and M Giants and Supergiants. II.

Dyck, H. M.; Belle, Gerald van; Thompson, R. R.

doi:10.1086/300453

Cited by 109 publications

(96 citation statements)

References 13 publications

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“…8, we plot the resulting effective temperatures vs. spectral types of our targets. For comparison, we include the calibrations of the effective temperature scale by Dyck et al (1998) We note that the red giants with luminosities below log(L/L ) ∼ 4 are located systematically to the right of the Ekström tracks, and that a better agreement for these sources can be found using the STAREVOL grid (Lagarde et al 2012), which includes thermaline mixing unlike Ekström's grid (Arroyo-Torres et al 2014).…”

Section: Fundamental Parametersmentioning

confidence: 99%

What causes the large extensions of red supergiant atmospheres?

Arroyo-Torres

Wittkowski²,

Chiavassa

et al. 2015

A&A

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: Fundamental Parametersmentioning

confidence: 99%

What causes the large extensions of red supergiant atmospheres?

Arroyo-Torres

Wittkowski²,

Chiavassa

et al. 2015

A&A

108

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“…a Dy98 = Dyck et al 1998;Fe90 = Fernandez-Villacanas, Rego, & Cornide 1990;SL90 = Smith & Lambert 1990;SL86 = Smith & Lambert 1986;Dy96 = Dyck et al 1996;Ram97 = Ramírez et al 1997;SL85 = Smith & Lambert 1985;Lu82a = Luck 1982a;LB80 = Luck & Bond 1980;CSB00 = Carr et al 2000;Ri98 = Richichi et al 1998;Ba98 = Barthes 1998;La86 = Lambert et al 1986;vB97 = van Belle et al 1997;Hip = Perryman et al 1997;La91 = Lafon & Berruyer 1991;Be98 = Bedding & Zijlstra 1998;Dumm98 = Dumm & Schild 1998;Lu82b = Luck 1982b;Hu78 = Humphreys 1978;EFH85 = Elias, Frogel, & Humphreys 1985;MJE95 = Massey, Johnson, & Degioia-Eastwood 1995;BL96 = Benson & Little-Marenin 1996;vL97 = van Leeuwen et al 1997. b IRS (CTIO 4 m): =D ¼ 560, OSIRIS (CTIO 4 m): =D ¼ 1200, MOSAIC (MDM 1.3 m): =D ¼ 750. c Analysis uses spectrum for this star is presented by Blum et al 1996bor Lançon & Rocca-Volmerange 1992 The M bol for R Hya is more luminous than the predicted maximum for AGB stars given by Paczyń ski 1970; see also the discussion by Blum et al 1996b. However, the 1 uncertainty on its distance encompasses the luminosity limit.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…In addition, we have used five digital spectra previously presented by BSD96 and Lançon & Rocca-Volmerange (1992) for several comparison stars, which we were not able to reobserve (see Table 1) but which met our criteria on M bol and T eff . We observed two stars (FL Ser and Z UMa) that we later removed from our sample because they had discrepant T eff compared with stars of similar spectral type (Dyck, van Belle, & Thompson 1998).…”

Section: Comparison Starsmentioning

confidence: 99%

Really Cool Stars and the Star Formation History at the Galactic Center

Blum

Ramírez

Sellgren

et al. 2003

ApJ

131

248

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We present =D ¼ 550-1200 near-infrared H and K spectra for a magnitude-limited sample of 79 asymptotic giant branch and cool supergiant stars in the central %5 pc (diameter) of the Galaxy. We use a set of similar spectra obtained for solar neighborhood stars with known T eff and M bol that is in the same range as the Galactic center (GC) sample to derive T eff and M bol for the GC sample. We then construct the H-R diagram for the GC sample. Using an automated maximum likelihood routine, we derive a coarse star formation history of the GC. We find that (1) roughly 75% of the stars formed in the central few parsecs are older than 5 Gyr; (2) the star formation rate (SFR) is variable over time, with a roughly 4 times higher SFR in the last 100 Myr compared to the average SFR; (3) our model can match dynamical limits on the total mass of stars formed only by limiting the initial mass function to masses above 0.7 M (this could be a signature of mass segregation or of the bias toward massive star formation from the unique star formation conditions in the GC); (4) blue supergiants account for 12% of the total sample observed, and the ratio of red to blue supergiants is roughly 1.5; and (5) models with isochrones with ½Fe=H ¼ 0:0 over all ages fit the stars in our H-R diagram better than models with lower [Fe/H]

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“…The red giant radius in both systems is known from interferometric measurements, ∼1.9 AU in R Aqr , and references therein), and ∼1.2 AU in CH Cyg (e.g. Dyck et al 1998), with uncertainty set mostly by the uncertainty in their distances, ∼15% in both cases.…”

Section: Introductionmentioning

confidence: 98%

CO observations of symbiotic stellar systems

Bujarrabal

Mikołajewska

Quintana-Lacaci

2010

A&A

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Aims. We have studied the molecular content of the circumstellar environs of symbiotic stellar systems, in particular of the well know objects R Aqr and CH Cyg. The study of molecules in these stars will help for understanding the properties of the very inner shells around the cool stellar component from which molecular emission is expected to come. Methods. We performed mm-wave observations with the IRAM 30 m telescope of the 12 CO J = 1−0 and J = 2−1, 13 CO J = 1−0 and J = 2−1, and SiO J = 5−4 transitions in the symbiotic stars R Aqr, CH Cyg, and HM Sge. The data were analyzed by means of a simple analytical description of the general properties of molecular emission from the inner shells around the cool star. Numerical calculations of the expected line profiles were also performed that took the level population and radiative transfer under such conditions into account. Results. Weak emission of 12 CO J = 1−0 and J = 2−1 was detected in R Aqr and CH Cyg and a good line profile of 12 CO J = 2−1 in R Aqr was obtained. The intensities and profile shapes of the detected lines are compatible with emission coming from a very small shell around the Mira-type star, with a radius comparable to or slightly smaller than the distance to the hot dwarf companion, 10 14 −2 × 10 14 cm. We argue that other possible explanations are improbable. This region probably shows properties similar to those characteristic of the inner shells around standard AGB stars: outwards expansion at about 5-25 km s −1 , with a significant acceleration of the gas, temperatures decreasing with radius between about 1000 and 500 K, and densities ∼10 9 −3 × 10 8 cm −3 . Our model calculations are able to explain the asymmetric line shape observed in 12 CO J = 2−1 from R Aqr, in which the relatively weaker blue part of the profile would result from selfabsorption by the outer layers (in the presence of a velocity increase and a temperature decrease with radius). The mass-loss rates are somewhat higher than in standard AGB stars, as often happens for symbiotic systems. In R Aqr, we find that the total mass of the CO emitting region is ∼2−3 × 10 −5 M , corresponding toṀ ∼ 5 × 10 −6 −10 −5 M yr −1 and compatible with results obtained from dust emission. Considering other existing data on molecular emission, we suggest that the limited extent of the molecule-rich gas in symbiotic systems is mainly due to molecule photodissociation by the radiation of the hot dwarf star.

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Radii and Effective Temperatures for K and M Giants and Supergiants. II.

Cited by 109 publications

References 13 publications

What causes the large extensions of red supergiant atmospheres?

What causes the large extensions of red supergiant atmospheres?

Really Cool Stars and the Star Formation History at the Galactic Center

CO observations of symbiotic stellar systems

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