RSGs and AGBs in the Optical and Infrared -- Mass Loss, Circumstellar Ejecta and Episodic Events Roberta M Humphreys University of Minnesota VY CMa IRC 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 H 2 O, 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 10 5 L sun Initial Mass ~ 30 M sun Mass Loss rate x M sun / year Size ~ A.U., or ~ R sun 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 Humphreys, Davidson, Ruch & Wallerstein 2005 High Resolution, Long-Slit Spectroscopy --Keck HIRES Spectrograph From surface brightness of NW arc mass ~ 3 x M sun. 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 degrees ~ west 500 Arc SW 800 Arc ~ south 460 SW knots ~ west 250 S knots SSE 157 SE loop 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 – 5  m) 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 Clump is optically thick. Mass loss > 5 x Msun

SOFIA imaging 20 – 37  m 37  m contours on HST visual image Note asymmetric shape. Outer ejecta at most about 1500 yrs old Shenoy et al 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 M sun ) 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 G.

9 -12  m imaging MMT/MIRAC/AO Recent results on the iconic RSG –  Cep Shenoy et al submmited Mass loss for inner region – 3– M sun /yr

SOFIA  m Herschel 70  m (Cox et al 2012) Shenoy et al submitted Mass loss outer ejecta 6 x M sun /yr

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

The Warm Hypergiants and post RSG evolution IRAS – 12  m (the fried egg) Lagedec et al 2011 HD – 11.7 um (Jura & Werner 1999) Post RSG or AGB? Jones et al 1993 Oudmaijer et al 1994, 1996 Humphreys 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, years in “eruption” Cool dense wind Looked 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 (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 Helton George Herbig Terry J. Jones Gerald Ruch Dinesh Shenoy Nathan Smith George Wallerstein Kris Davidson Terry J. Jones Dinesh Shenoy Nathan Smith Chelsea Tiffany Terry J. Jones Massimo Marengo Dinesh Shenoy Michael Schuster Massimo Marengo