The Physical Properties of Red Supergiants Emily Levesque IfA, University of Hawaii/SAO, Harvard Hot Massive Stars: A Lifetime of Influence Lowell Observatory

Collaborators: Philip Massey (Lowell Observatory) Knut Olsen (NOAO) Bertrand Plez (Université de Montpellier) Eric Josselin (Université de Montpellier) Andre Maeder (Geneva Observatory) Georges Meynet (Geneva Observatory) Geoff Clayton (Louisiana State University) Dave Silva (NOAO/TMT) Brian Skiff (Lowell Observatory)

Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next? What is a red supergiant? Red supergiants are a He- burning evolutionary stage of moderately high-mass ( M  ) stars. physically largest stars in the universe physically largest stars in the universe high visual luminosities (M V = -6 to -9) allow study beyond our galaxy high visual luminosities (M V = -6 to -9) allow study beyond our galaxy populate upper right region of HRD populate upper right region of HRD

Red Supergiants and the H-R Diagram Why are we interested in them? Massive star evolutionary tracks didn’t agree with the position of red supergiants on the H-R diagram. Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Levesque et al Hayashi limit  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Levesque et al forbidden region forbidden region Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Red Supergiants and the H-R Diagram Why are we interested in them? Massive star evolutionary tracks don’t agree with the position of red supergiants on the H-R diagram. Why? - Difficulties with the evolutionary tracks: uncertain opacities highly extended atmosphere high-velocity convective layers - …or problems with the observationally- determined location of these stars Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Fitting Red Supergiant Spectra How do I get the parameters from spectral fitting? Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Fitting Red Supergiant Spectra How do I get the parameters from spectral fitting? TiO band strengths Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Fitting Red Supergiant Spectra How do I get the parameters from spectral fitting? Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Levesque et al We can fit spectrophotometry of RSGs with the MARCS stellar atmosphere models: K2 I  4000 KK5 I  3750 K M3 I  3500 KM1 I  3625 K Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Determining Physical Properties What we observe:,, What we want: Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next? MW

Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Excess NUV flux, correlated with high “excess” reddening  excess circumstellar dust adapted from Levesque et al Dust and Red Supergiants Dust and Red Supergiants Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

For Milky Way RSGs, dust production rate is about 8.5 x M  yr -1 kpc 2 In starburst galaxies at large lookback times, we would expect RSGs to be major contributors to the ISM What are the mechanisms that drive this dust production? How does this mass-loss relation change with metallicity? What reddening law does the dust follow? How does this affect our determinations of RSG luminosities? Dust and Red Supergiants Dust and Red Supergiants Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

VY Canis Majoris VY Canis Majoris: a particularly unusual RSG -extraordinarily luminous -large dust reflection nebula, high mass loss rate -previous work assigned a very cold temperature (2800 K) Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

adapted from Massey et al ! VY CMa  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

VY Canis Majoris VY Canis Majoris: a particularly unusual RSG -extraordinarily luminous -large dust reflection nebula, high mass loss rate -previous work assigned a very cold temperature (2800 K) 3650 K 3450 K Massey et al VY CMa We measured a much warmer temperature of ~3650 K, which in turn suggests a much smaller radius and a lower luminosity. (note additional fit in the blue, showing a disparity between red and blue lines) Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

adapted from Massey et al but… Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

- - luminosity of dust emission is ~5 times higher than our reported VY CMa luminosity! - - suggests our measure of the luminosity is too low Smith et al …our luminosity estimate is contradicted by VY CMa’s measured thermal dust emission One explanation: If the circumstellar dust envelope is large-grain and “grey”, this would lead to our underestimate of VY CMa’s luminosity. Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Red Supergiants in the Magellanic Clouds LMC Levesque et al Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Red Supergiants in the Magellanic Clouds LMC Levesque et al Z  LMC Levesque et al Z  SMC 0.27Z  Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC  SMC  Milky Way  Levesque et al Red Supergiants in the Magellanic Clouds Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC 0.47Z  New effective temperature scales give much better agreement with the LMC: LMC Levesque et al Z  LMC Levesque et al Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC 0.47Z  New effective temperature scales give much better agreement with the LMC: LMC Levesque et al Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC Levesque et al Z  But when it comes to the SMC… SMC 0.27Z  Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

There’s still a few problems… SMC 0.27Z  Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

There’s still a few problems… SMC 0.27Z  Levesque et al weaker MS stellar winds at low metallicity increased rotational mixing as a result enhanced He abundance from mixing Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC 0.47Z  The cool new LMC RSG: WOH G64 LMC Levesque et al Z  van Loon et al. (2005) placed it similarly to VY CMa… Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC 0.47Z  The cool new LMC RSG: WOH G64 LMC Levesque et al Z  Ohnaka et al. (2008) recently updated its luminosity … Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

LMC 0.47Z  The cool new LMC RSG: WOH G64 LMC Levesque et al Z  We suspect that T eff still needs to be re- examined … ? Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

The average RSG subtype in the Clouds shifts to earlier types with decreasing metallicity: adapted from Massey & Olsen 2003 K0-1 K2-5 K5-7 M0 M1 M2 M3 M4 M5 Milky Way Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

The average RSG subtype in the Clouds shifts to earlier types with decreasing metallicity: adapted from Massey & Olsen 2003 LMC 0.47Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next? K0-1 K2-5 K5-7 M0 M1 M2 M3 M4 M5

The average RSG subtype in the Clouds shifts to earlier types with decreasing metallicity: adapted from Massey & Olsen 2003 SMC 0.27Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next? K0-1 K2-5 K5-7 M0 M1 M2 M3 M4 M5

Shift in Spectral Subtype 1) Line depth effects from changing metallicity Levesque et al K2 IK5 I M1 IM3 I Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

3650 K  M2 I (MW), M1-1.5 I (LMC), K5-M0 I (SMC) LMC  SMC  Milky Way  Shift in Spectral Subtype 1) Line depth effects from changing metallicity Levesque et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Shift in Spectral Subtype 2) Metallicity-dependent shift of Hayashi limit Limits of hydrostatic equilibrium get warmer at lower metallicities, imposing limits on how cool (and hence, how late-type), massive stars can get… Levesque et al Milky Way Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Shift in Spectral Subtype 2) Metallicity-dependent shift of Hayashi limit Limits of hydrostatic equilibrium get warmer at lower metallicities, imposing limits on how cool (and hence, how late-type), massive stars can get… Levesque et al LMC Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

Shift in Spectral Subtype 2) Metallicity-dependent shift of Hayashi limit Limits of hydrostatic equilibrium get warmer at lower metallicities, imposing limits on how cool (and hence, how late-type), massive stars can get… Levesque et al SMC Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

The Late-Type Red Supergiant Sample Despite evolutionary limitations, some Cloud RSGs are later than would be expected Investigated the properties of 7 late- type LMC stars and 5 late-type SMC stars, reobserved in 2005 M 4.5 M 3-4 SMC LMC Levesque et al SMC average is K5-M0 LMC average is M 1 Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004 Spectral Type: K0 I  Temperature: 4300  Reddening (A V ): 1.35  V magnitude:  Bolometric magnitude: -9.1  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004  2005 Spectral Type: K0 I  M4 I Temperature: 4300  3500 Reddening (A V ): 1.35  0.10 V magnitude:  Bolometric magnitude: -9.1  -8.5 Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004  2005 Spectral Type: K0 I  M4 I Temperature: 4300  3500 Reddening (A V ): 1.35  0.10 V magnitude:  Bolometric magnitude: -9.1  -8.5 Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004  2005 Spectral Type: K0 I  M4 I Temperature: 4300  3500 Reddening (A V ): 1.35  0.10 V magnitude:  Bolometric magnitude: -9.1  -8.5 Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004  2005 Spectral Type: K0 I  M4 I Temperature: 4300  3500 Reddening (A V ): 1.35  0.10 V magnitude:  Bolometric magnitude: -9.1  -8.5 Massey et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004  2005 Spectral Type: K0 I  M4 I Temperature: 4300  3500 Reddening (A V ): 1.35  0.10 V magnitude:  Bolometric magnitude: -9.1  -8.5 Be sure to say what it’s doing explicity HERE; don’t wait until the next slide: warmer = brighter, dustier, more luminous Massey et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next?

HV HV an unusual find in the SMC Massey et al Date of Observation 2004  2005 Spectral Type: K0 I  M4 I Temperature: 4300  3500 Reddening (A V ): 1.35  0.10 V magnitude:  Bolometric magnitude: -9.1  -8.5 Be sure to say what it’s doing explicity HERE; don’t wait until the next slide: warmer = brighter, dustier, more luminous Massey et al Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV Where to next? When HV gets warmer it is also brighter, dustier, and more luminous.

Three more “unusual finds”… M4.5 I M1.5 I M4.5 I M2 I M4.5 I M3-4 I Mo I M2 I K2-3 I Levesque et al Two more SMC stars and one LMC star exhibit the same unusual behaviors: when these stars are warmer they are also brighter, dustier, and more luminous. While V variability in RSGs is common, such spectral variability is unheard of! Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Levesque et al Two more SMC stars and one LMC star exhibit the same unusual behaviors: when these stars are warmer they are also brighter, dustier, and more luminous. Three more “unusual finds”… Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Levesque et al Two more SMC stars and one LMC star exhibit the same unusual behaviors: when these stars are warmer they are also brighter, dustier, and more luminous. Three more “unusual finds”… Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Levesque et al We suspect that these stars are in a unique unstable evolutionary state not previously observed in red supergiants. Two more SMC stars and one LMC star exhibit the same unusual behaviors: when these stars are warmer they are also brighter, dustier, and more luminous. Three more “unusual finds”… Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Where To Next? Continuing to expand our metallicity range In published work: factor of 4 In Local Group: factor of 15! Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Where To Next? Continuing to expand our metallicity range In published work: factor of 4 In Local Group: factor of 15! M31: 2Z  2Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Where To Next? Continuing to expand our metallicity range In published work: factor of 4 In Local Group: factor of 15! M31: 2Z  …Z  ? Z  Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Where To Next? Continuing to expand our metallicity range In published work: factor of 4 In Local Group: factor of 15! M31: 2Z  …Z  ? WLM: 0.12Z  Local Group Galaxy Survey Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Where To Next? Continuing to expand our metallicity range In published work: factor of 4 In Local Group: factor of 15! M31: 2Z  …Z  ? WLM: 0.12Z  Improved studies of RSGs and dust Study these variables in more detail! - What effect does this behavior have on stellar yields and mass-loss-dependent properties? - What new properties and environmental effects should evolutionary models strive to accommodate? - What will these variable stars evolve into? Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?

Questions? Mountains from the Cerro Tololo 4-meter Galactic RSGs - T eff scale - H-R Diagram - Dust & VY CMa Cloud RSGs - H-R Diagram - WOH-G64 - Spectral types HV & Co.! Where to next?