RSGs and AGBs in the Optical and Infrared -- Mass Loss, Circumstellar Ejecta and Episodic Events

Roberta M Humphreys University of Minnesota

VY CMa

IRC +10420

ESO Workshop – Stellar End Products June 2015

Cep

NML Cyg

A Little Bit of History – infrared, CS dust, RSGs, AGBs, masers and the OH/IR stars

10 silicate feature in RSGs

(Woolf and Ney 1969)

LPVs – oxygen and carbon-rich

OH maser emission (Wilson & Barrett 1968) from LPVs, and very red supergiants, followed by H2O, SiO maser emission. Identified with strong infrared sources (Wilson, Barrett &Moran 1970, Hyland 1972) -- the OH/IR stars – RSGs, LPVs (AGBs)

Mass loss mechanism ? -- radiation pressure on grains? pulsation (LPVs) convection (RSGs) But ---

The Upper HR Diagram

The evidence for episodic high mass loss events

VY CMa -- the extreme red supergiant, powerful OH/IR source

Due to multiple, asymmetric ejection episodes possibly from large-scale convective regions on the star.

1” = 1500 AU

10”

Smith, Humphreys, Davidson, Gehrz, & Schuster, 2001

Distance ~ 1.3 kpc

Luminosity ~ 3 x 105 L sun

Initial Mass ~ 30 M sun

Mass Loss rate 2 -- 4 x 10-4 M sun / year

Size ~ 8 -- 10 A.U., or ~ 1500 -- 2000 Rsun

It is visible as a small red nebula ~ 10 arcsec across

NW Arc

Arc 2

Arc 1

S Knots SW Knots/clump

Complex structure in ejecta

Prominent arcs, numerous filaments and clumps of knots, overall mass loss rate 5 x 10-4

Humphreys, Davidson, Ruch & Wallerstein 2005

High Resolution, Long-Slit Spectroscopy --Keck HIRES Spectrograph

From surface brightness of NW arc mass ~ 3 x 10-3 Msun . With a

dynamical timescale of ~ 3yrs, suggest a mass loss rate of 10-3

2D spectra of strong K I emission lines across the arcs

NW Arc

Arcs 1 and 2

Feature Vel. Orientation Direction Age (yrs) km/s relative to sky of motion

NW arc 46 22 degrees ~ west 500

Arc 1 68 -33 SW 800

Arc 2 64 -17 ~ south 460

SW knots 36 -25 ~ west 250

S knots 42 -27 SSE 157

SE loop 65 -21 SE 320

Humphreys, Helton & Jones, 2007, Jones, Humphreys, & Helton 2007

Second epoch HST images

Measure transverse velocities combined with radial velocities long slit spectra (Keck) of K I em line (resonant scattering)

Total velocity, orientation, direction and age 3D morphology

Results from LMIRCam (2 – 5m) on the LBT with AO

The SW clump – in the visible resolved into individual knots but very red and dusty. In the near-IR an unresolved knot .

Shenoy, et al. 2013

Clump is optically thick. Mass loss > 5 x 10-3 Msun

SOFIA imaging 20 – 37 m

37m contours on HST visual image

Note asymmetric shape. Outer ejecta at most about 1500 yrs old

Shenoy et al. 2015 submitted

Ziurys et al 2007 noted molecules in red/blue outflows. 8.5 arcsec

Asymmetric Mass Loss Events and the Origin of the Discrete Ejecta

Arcs and Knots are spatially and kinematically distinct; ejected in different directions at different times; not aligned with any axis of symmetry.

They represent localized, relatively massive (few x 10-3 Msun) ejections

Large-scale surface activity -- starspots

Surface asymmetries supergiants, AGBs – Ori, Sco, Her, VX Sgr, NML Cyg, VX Sgr, IK Tau etc. (Tuthill et al. 1999, Monnier et al. 2004)

Convective activity Magnetic Fields 200 – 400G (Vlemmings et al. 2005)

VY CMa light curve (Robinson 1971)

XMM observations (Montez, Kastner, Humphreys et al. 2015) set an upper limit on the X-ray flux and the surface magnetic field, f B <= 2 x 10-3G.

9 -12 m imaging MMT/MIRAC/AO

Recent results on the iconic RSG – Cep

Shenoy et al. 2015 submmited

Mass loss for inner region – 3– 8 10-7 Msun/yr

SOFIA 11- 37 m

Herschel 70m (Cox et al 2012)

Shenoy et al. 2015 submitted

Mass loss outer ejecta 6 x 10-7 Msun/yr

Post-RSGs ( and post-AGBs) and a dynamical instability

The Warm Hypergiants and post RSG evolution

IRAS 17163-3907 – 12m (the fried egg) Lagedec et al 2011

HD179821 – 11.7 um (Jura & Werner 1999)Post RSG or AGB?

Jones et al 1993 Oudmaijer et al 1994, 1996Humphreys et al.1997, 2002

Other examples of post RSGs ( Cas, HR5171a, HR8752 etc.)

IRC+10420

Variable A in M33 – a warm hypergiant ~ 45 years in eruption!

Var A – Spectrum and Circumstellar IR excess

Humphreys et al. 1987, 2006

45 years in “eruption”Cool dense windLooked like an M supergiant

Other supergiants

NML Cyg (M6 I, OH/IR) -- extended CS ejecta (HST)S Per (M4 Ia, OH/IR) -- extended CS ejecta (HST/MIRAC/SOFIA) VX Sgr (M4 Ia –M8 , OH/IR) -- extended CS ejecta (HST) W Per (M3 Iab) -- null RW Cep (K0: Ia +) -- extended CS ejecta (MIRAC) RW Cyg (M3-4 Ia) -- extended CS ejecta (MIRAC) BD +24 3902 (M1 Ia+ ) -- extended CS ejecta (MIRAC) T Per (M2 Iab) -- extended CS ejecta (MIRAC)

A correlation among:

Surface asymmetries (spots) -> convective cells? -> mass loss -> circumstellar dust/ejecta

Enhanced surface activity -> high mass loss events -> complex CS ejecta

Mass loss mechanism for RSGs? Pulsation Convection + ?

Some thoughts on the evolutionary state of the RSGs

Why not more VY CMa’s ?

Do RSGs evolve through the red supergiant stage getting apparently cooler, more extended envelopes and high mass loss episodes?

Like lower mass stars, could there be more than one RSG stage? warm hypergiant RSG again – extreme RSG (VY CMa) ?

Evidence for increased mass loss, CS ejecta with higher luminosity and cooler temperatures (?)

Clusters – RSG clusters (Figer, Davies, Clark) Stepenson2, N7419 (Negueruela)and even Per OB1

Collaborators Kris Davidson

Andrew HeltonGeorge HerbigTerry J. JonesGerald Ruch Dinesh ShenoyNathan Smith George Wallerstein

Kris Davidson Terry J. JonesDinesh ShenoyNathan SmithChelsea Tiffany

Terry J. Jones

Massimo Marengo

Dinesh Shenoy

Michael Schuster

Michael SchusterMassimo Marengo