The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not as Cool as We Thought

By Emily M. Levesque, Philip Massey, Kirsty Olsen, B. Plez, E. Josselin, Andre Maeder, G. Meynet. 2005

388 citations recorded by the source corpus.

We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine the effective temperatures of 74 Galactic red supergiants (RSGs). The stars are mostly members of OB associations or clusters with known distances, allowing a critical comparison with modern stellar evolutionary tracks. We find we can achieve excellent matches between the observations and the reddened model fluxes and molecular transitions, although the atomic lines Ca I λ4226 and Ca II H and K are found to be unrealistically strong in the models. Our new effective temperature scale is significantly warmer than those in the literature, with the differences amounting to 400 K for the latest type M supergiants (i.e., M5 I). We show that the newly derived temperatures and bolometric corrections give much better agreement with stellar evolutionary tracks. This agreement provides a completely independent verification of our new temperature scale. The combination of effective temperature and bolometric luminosities allows us to calculate stellar radii; the coolest and most luminous stars (KW Sgr, Case 75, KY Cyg, HD 206936=μ Cep) have radii of roughly 1500 R☉ (7 AU), in excellent accordance with the largest stellar radii predicted from current evolutionary theory, although smaller than that found by others for the binary VV Cep and for the peculiar star VY CMa. We find that similar results are obtained for the effective temperatures and bolometric luminosities using only the dereddened V - K colors, providing a powerful demonstration of the self-consistency of the MARCS models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fc1a82cbbda6c86c046e21b96c28da6c7d506124

How researchers see this paper

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In Astronomy and Astrophysics

1. S. Smartt
2. Stan Woosley
3. N. Smith
4. G. Meynet
5. N. Langer
6. S. Valenti
7. C. Conroy
8. A. Piro

In Instrumentation

1. S. Smartt
2. C. Conroy
3. N. Smith
4. Stan Woosley
5. G. Meynet
6. Benjamin D. Johnson
7. R. Hirschi
8. J. Eldridge

Citations in the corpus

• Measuring the Progenitor Masses and Dense Circumstellar Material of Type II Supernovae (2017, methodology): “This is significantly lower than the expected limit of ∼25Me, obtained from the comparison of the observed properties of RSGs with their possible evolutionary tracks (Levesque et al. 2005, 2006).”
• THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽ M/M☉ ⩽ 8.0 (2013, methodology): “(6) Compare this with last equations in Levesque et al. (2005).”
• A High-resolution Study of Presupernova Core Structure (2017, result): “These numbers are in good accord with measurements of the hottest RSGs (Davies et al. 2013; Levesque et al. 2005).”
• Progenitors of Core-Collapse Supernovae (2009, methodology): “The effective temperatures and bolometric luminosities of Galactic and Magellanic Cloud RSGs have been revised with new model atmospheres(Levesque et al. 2005, 2006).”
• Unifying Type II Supernova Light Curves with Dense Circumstellar Material (2016, result): “For example, SN 2009kr was a IIL inferred to have a reasonably normal progenitor radius of ∼ 400 − 800R , which is consistent with the radii of standard RSGs (Levesque et al. 2005, 2006).”
• Luminosities and mass-loss rates of SMC and LMC AGB stars and red supergiants (2009, background): “Most of the RSGs are consistent with the 10–20 M⊙ tracks (cf. the discussion on the revised spectral type eff ctive temperature calibration in Levesque et al. 2005, 2006).”
• A REVISED AGE FOR UPPER SCORPIUS AND THE STAR FORMATION HISTORY AMONG THE F-TYPE MEMBERS OF THE SCORPIUS–CENTAURUS OB ASSOCIATION (2011, methodology): “To estimate the H-R diagram of Antares we use the updated temperature scale of Levesque et al. (2005) for red supergiants, together with the revised Hipparcos parallax (van Leeuwen 2007) of π=5.89±1.00 mas and the angular diameter measurement of 41.3±1.0 mas (Richichi & Lisi 1990).”
• Variability in red supergiant stars: pulsations, long secondary periods and convection noise (2006, methodology): “To construct the period–K-band absolute magnitude diagram, we took the following steps:(i) Mbol values from Levesque et al. (2005) were converted toMK using the Josselin et al. (2000) relation; (ii) for α Her,α Ori and CE Tau we used Hipparcos parallaxes and K-band data to calculateMK directly;…”
• Production of dust by massive stars at high redshift (2011, background): “However, RSGs up to 25 M⊙ have been detected in the Local Group (e.g., Levesque et al, 2005, 2006).”
• Physical Properties of Wolf-Rayet Stars (2006, methodology): “This corresponds closely to the Humphreys & Davidson (1979) limit for red supergiants (RSG), according to a comparison between the current temperature calibration of RSG and stellar models that allow for mass-loss and rotation (e.g. Levesque et al. 2005).”
• Binary Population and Spectral Synthesis Version 2.1: Construction, Observational Verification, and New Results (2017, methodology): “In Figure 11, we compare population density contour plots and 1 000-d period stellar tracks to observed RSGs in the SMC, LMC, M31, and M33 taken from Levesque et al. (2005), Massey et al. (2009), Neugent et al. (2012), Drout et al. (2012), and Massey & Evans (2016).”
• A Massive Cluster of Red Supergiants at the Base of the Scutum-Crux Arm (2007, methodology): “We then interpolate the bolometric correction BCK for each star’s temperature, according to the recently rederived values of Levesque et al. (2005) to estimate their bolometric luminosities.”
• The mass-loss rates of red supergiants and the de Jager prescription (2010, background): “Several important works have recently revisited the basic properties of these stars in the Galaxy and in other systems like the Magellanic Clouds and M31 (Massey 1998; Levesque et al. 2005, hereafter LM05; Massey et al. 2008; Levesque 2009 and references therein).”
• Grids of stellar models with rotation - II. WR populations and supernovae/GRB progenitors at Z = 0.014 (2012, background): “The last value agrees better with the upper limit of RSGs, which was found by Levesque et al. (2005) to be between 5.2 and 5.4.”
• SN 2008S: An electron-capture SN from a super-AGB progenitor? (2009, methodology): “The positions of Galactic RSGs are shown (from Levesque et al. 2005) along with the region in which RSG progenitors of recent nearby type II-P SNe lie (log L/L⊙ = 4.3+0.5−0.3 Smartt et al. 2009).”
• Scaled solar tracks and isochrones in a large region of the Z-Y plane. II. From 2.5 to 20 solar masses (2009, methodology): “Afterwards Levesque et al. (2005, 2006) used moderateresolution optical spectrophotometry and the new MARCS stellar atmosphere models (Plez 2003, Gustafsson et al. 2003) to determine the physical properties of RSGs in both the Milky Way and the MCs for the comparison with the evolutionary models.”