STUDYING NEBULAE EJECTED FROM STUDYING NEBULAE EJECTED FROM MASSIVE STARS WITH HERSCHELMASSIVE STARS WITH HERSCHEL

Chloi Vamvatira-Nakou

ARC meeting - 11 February 2010

Centre Spatiale de Liège (CSL)

(PhD student GAPHE, AGO ULg)

OutlineOutline

MESS – Herschel Guaranteed Time Key Programme MESS – Herschel Guaranteed Time Key Programme

Hershel Space ObservatoryHershel Space Observatory

Circumstellar Environment of Massive Stars:Circumstellar Environment of Massive Stars:

- Luminous Blue Variables- Luminous Blue Variables - Wolf - Rayet Stars- Wolf - Rayet Stars

Aims of this studyAims of this study

MESS – Mass-loss of Evolved StarsMESS – Mass-loss of Evolved Stars

http://www.univie.ac.at/space/MESS/

Main aims:Main aims:

To study the time dependence of the mass loss process, in order to quantify the To study the time dependence of the mass loss process, in order to quantify the total amount of mass lost at the various evolutionary stages of low to high-mass starstotal amount of mass lost at the various evolutionary stages of low to high-mass stars

To study the dust and gas chemistry as function of progenitor massTo study the dust and gas chemistry as function of progenitor mass

To study the properties and the asymmetries of a representative sample of low To study the properties and the asymmetries of a representative sample of low and intermediate mass stars (AGB, post-AGB, PN), high mass stars (RSG, WR, and intermediate mass stars (AGB, post-AGB, PN), high mass stars (RSG, WR, LBV) and Supernovae (SNe) LBV) and Supernovae (SNe)

“The circumstellar environment in post-main-sequence objects”

WavebandWaveband: the full far-IR and sub-mm (55-672 μm)the full far-IR and sub-mm (55-672 μm)

LaunchLaunch: 14 May 2009 L2 orbit14 May 2009 L2 orbit

Mission lifetimeMission lifetime: ~ 4 years~ 4 years

TelescopeTelescope: Cassegrain - mirror diameter 3.5 mCassegrain - mirror diameter 3.5 m (the largest ever flown in space)

InstrumentsInstruments: - HIFI (Heterodyne Instrument for the Far Infrared): 480 –1250 GHz (625-240 μm)- HIFI (Heterodyne Instrument for the Far Infrared): 480 –1250 GHz (625-240 μm) 1410 –1910 GHz (212-157 μm)1410 –1910 GHz (212-157 μm)

- PACS (Photodetector Array Camera and Spectrometer): 55-210 μm- PACS (Photodetector Array Camera and Spectrometer): 55-210 μm

- SPIRE (Spectral and Photometric Imaging Receiver): 194-672 μm- SPIRE (Spectral and Photometric Imaging Receiver): 194-672 μm

“cool universecool universe”

Herschel Space ObservatoryHerschel Space Observatory

Herschel Space ObservatoryHerschel Space Observatory

PACS SPIRE

Imaging Imaging PhotometryPhotometry

- 2 bands simultaneously: 60-85 or 85-125 μm and 125-210 μm

- field of view: 1.75 × 3.5 arcmin

Integral Field Line SpectroscopyIntegral Field Line Spectroscopy

- range: 55-210 - range: 55-210 μμmm

- field of view: - field of view: 47 × 47 arcsec arcsec

- resolution: between 1000-5000- resolution: between 1000-5000

Imaging PhotometryImaging Photometry

- 3 bands simultaneously: 250, 350 and 500 μm

- field of view: 4 × 8 arcmin

Imaging Fourier Transform Imaging Fourier Transform SpectroscopySpectroscopy

- range: 194-672 - range: 194-672 μμmm

- field of view: 2.6- field of view: 2.6 arcmin (diameter)

- resolution: 1000 at 250 μm

Herschel Space ObservatoryHerschel Space Observatory

Circumstellar Environment of EvolvedCircumstellar Environment of EvolvedMassive StarsMassive Stars

Standard evolutionary model for a single massive star: The outer envelopes are removed through the stellar wind revealing chemically enriched material and the star becomes a Wolf-Rayet (WR)

early type O star WR star

Episodes of extreme mass loss during a Red Supergiant or a Luminous Blue Variable (LBV) phase

- The outer layers are removed and the bare core becomes a WR star

- Extended regions of stellar ejecta are produced → circumstellar nebulae (sources of IR emission)

must lose a big fraction of its initial mass

Circumstellar Environment of EvolvedCircumstellar Environment of EvolvedMassive StarsMassive Stars

Luminous Blue Variables (S Doradus variables)Luminous Blue Variables (S Doradus variables)

Evolved, massive, very luminous, unstable hot supergiants in the upper left of the Evolved, massive, very luminous, unstable hot supergiants in the upper left of the HR diagram, suffer irregular eruptions, precursors of Wolf-Rayet starsHR diagram, suffer irregular eruptions, precursors of Wolf-Rayet stars

LuminosityLuminosity: ~10: ~1066 L Lʘʘ (close to the ‘Eddington limit’) (close to the ‘Eddington limit’)

Photometric variabilityPhotometric variability: : - giant eruptions of - giant eruptions of ≥2 mag, uncertain time scale 10≥2 mag, uncertain time scale 102 2 -10-1033 yr (Eta Car, P Cyg) yr (Eta Car, P Cyg)- eruptions of 1-2 mag, time scale of 10-40 yr (AG Car, S Dor & R 127 in LMC)- eruptions of 1-2 mag, time scale of 10-40 yr (AG Car, S Dor & R 127 in LMC)- oscillations of ~0.5 mag, time scale of months-years (on top of normal eruptions)- oscillations of ~0.5 mag, time scale of months-years (on top of normal eruptions)- microvariations of - microvariations of ≤0.1 mag (R 71, AG Car, HR Car) ≤0.1 mag (R 71, AG Car, HR Car)

SpectraSpectra: variable (visual min: hot supergiant, visual max: cooler supergiant A or F) : variable (visual min: hot supergiant, visual max: cooler supergiant A or F)

TemperaturesTemperatures: 12,000-30,000 K at visual min, ~7000-8000 K at visual max : 12,000-30,000 K at visual min, ~7000-8000 K at visual max

Mass loss ratesMass loss rates: 10: 10-5-5 – 10 – 10-4-4 M Mʘʘyr yr -1 -1 at the active-shell ejection phaseat the active-shell ejection phase

Circumstellar Environment of EvolvedCircumstellar Environment of EvolvedMassive StarsMassive Stars

Luminous Blue VariablesLuminous Blue Variables

Ejected nebulae:

- Diameter of 0.5 - 2 pc

- Expansion velocity between 25 and 140 km s-1

- Dynamical age of 5×103 to 5×104 yr

- Morphology: axisymmetric-mildly to extremely bipolar or elliptical, except P Cygni (Barlow et al. 1994, Nota & Clampin 1997)

- Spectra: typical nebular emission lines (Ηα, [Ν ΙΙ], λλ6548, 6583,5755, [Ο ΙΙ] λλ3726, 3729, [S II])

- Contain significant amounts of CO and dust (e.g. McGregor et al. 1988, Hutsemékers 1997), mainly in the form of amorphous silicates, minor contribution from crystalline silicates (Voors et al. 2000), P Cygni does not contain dust

Eta Car

Circumstellar Environment of EvolvedCircumstellar Environment of EvolvedMassive StarsMassive Stars

Wolf-Rayet StarsWolf-Rayet Stars

Hot, luminous objects (‘bare cores’) with strong broad emission lines in the optical region due to stellar winds.

MassMass: 5 – 50 M: 5 – 50 Mʘʘ

LuminosityLuminosity: 10: 104.54.5 - 10 - 106 6 LLʘʘ

TemperatureTemperature: 30,000-90,000 K: 30,000-90,000 K

Mass loss rateMass loss rate: : 1010-5-5 – 10 – 10-4-4 M Mʘʘyr yr -1-1 (average 4×10 (average 4×10-5 -5 MMʘʘyr yr -1-1))

SpectraSpectra: strong broad emission lines : strong broad emission lines - strong lines of He and N (WN subtype show the products of CNO, H-- strong lines of He and N (WN subtype show the products of CNO, H- burning, cycle)burning, cycle) - strong lines of He, C and O (WC and WO subtypes show the products of- strong lines of He, C and O (WC and WO subtypes show the products of triple-triple-α, Ηα, Ηe-burning) e-burning)

Circumstellar Environment of EvolvedCircumstellar Environment of EvolvedMassive StarsMassive Stars

Circumstellar bubbles: Circumstellar bubbles:

Nebulae around one third of the Galactic WR stars Nebulae around one third of the Galactic WR stars in the optical (Marston 1997) in the optical (Marston 1997)

WR Ring nebulae believed represent material ejected WR Ring nebulae believed represent material ejected during the RSG or LBV phase that is photoionized by the WR star.during the RSG or LBV phase that is photoionized by the WR star.

Chu 1981, based on nebular dynamics: Chu 1981, based on nebular dynamics: - R-type nebulae: not dynamically shaped by the WR star- R-type nebulae: not dynamically shaped by the WR star- W-type nebulae: bubbles blown by the WR stars- W-type nebulae: bubbles blown by the WR stars- E-type nebulae: ejected nebulae- E-type nebulae: ejected nebulae

A WR star is surrounded by an inner circumstellar bubble and an outer interstellar A WR star is surrounded by an inner circumstellar bubble and an outer interstellar bubble (Garcia-Segura et al. 1996)bubble (Garcia-Segura et al. 1996)

Wolf-Rayet Stars

NGC 6888 around WR 136

Aims of this StudyAims of this Study

Study of the dust and the gas in the circumstellar environment of evolved massive stars, ejected nebulae around LBVs and circumstellar bubbles around WR stars

Photometry:

- nature, structure, mass and size of the dust shells

- dust grain size

Spectroscopy:

- chemical composition of the gas (accurate abundances)

- dust mineralogy

He 3-519

Spitzer MIPS 24 μm

Spitzer IRAC 3.6 μm

HD 168625

Spitzer IRAC 4.5 μm

Spitzer IRAC 5.8 μm Spitzer IRAC 8.0 μm Smith 2007

SPIRAL GALAXY M74