the uniqueness of antarctica for the study of agb stars undergoing thermal pulses

16/6/200616/6/2006 Optical and Infrared Wide-Field AstronoOptical and Infrared Wide-Field Astronomy in Antarcticamy in Antarctica

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The uniqueness of Antarctica for the The uniqueness of Antarctica for the study of AGB stars undergoing study of AGB stars undergoing

thermal pulses.thermal pulses.

Optical and Infrared Wide-Field Optical and Infrared Wide-Field Astronomy in AntarcticaAstronomy in Antarctica

Paris - 16/06/2006Paris - 16/06/2006

Roald Guandalini – University of Perugia


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ABSTRACTABSTRACTABSTRACTABSTRACT

Main Topics:Main Topics:

•Introduction on ground-based observations from Antarctica of AGB stars p. 3-7

•Importance of mid-IR observations and variability for AGB stars p. 8-19

•Mid-IR observations from Antarctica: p. 20-21•Some preliminary results and possible

improvements through ground-based observations p. 22-31

Main Topics:Main Topics:

•Introduction on ground-based observations from Antarctica of AGB stars p. 3-7

•Importance of mid-IR observations and variability for AGB stars p. 8-19

•Mid-IR observations from Antarctica: p. 20-21•Some preliminary results and possible

improvements through ground-based observations p. 22-31


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IntroductionIntroduction:: Why AGB stars…..Why AGB stars…..

IntroductionIntroduction:: Why AGB stars…..Why AGB stars…..

There are still many unclear points in the study of the AGB evolution…There are still many unclear points in the study of the AGB evolution…

Uncertain Parameters…

Stellar LUMINOSITY (whose uncertainty influences estimates of other parameters…);

Stellar MASS;

MASS LOSS rates as a function of the evolutionary stage and of total mass;

Production of CHEMICAL ELEMENTS.


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IntroductionIntroduction:: Mid-Infrared BandsMid-Infrared Bands

IntroductionIntroduction:: Mid-Infrared BandsMid-Infrared Bands

Mid-IR Bands……

Very important in the study of AGB stars (see later):

3-5 um. >10 um up to 30 um.


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AGB stars have been observed by several space-borne telescopes in the mid-IR:IRAS, ISO, MSX, IRTS.

BUTBUTIR space-borne observations present some disadvantages:

The duration of the operational period is expected to be quite limited.Observations with long time of integration are difficult.

Single-epoch observations in most cases.

IntroductionIntroduction:: Why Ground-Based Observations…..Why Ground-Based Observations…..

IntroductionIntroduction:: Why Ground-Based Observations…..Why Ground-Based Observations…..

ISO MSX


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Dome C: Dome C:

Best place on the Earth to perform astronomical observations in the mid-IR.

See previous talks:

1) Site testing Dome C

2) Comparison of Dome C with other ground-based locations (i.e. Mauna Kea)

IntroductionIntroduction:: Why Dome C…..Why Dome C…..

IntroductionIntroduction:: Why Dome C…..Why Dome C…..


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Important analysis needed for AGB stars:A. Light curves and therefore variability.B. Accurate study of the variations of luminosity (variability) over the

wide region of the electromagnetic spectrum including optical and IR.

Which kind of observations can be done from the ground ? Surveys through wide field (future) or small area (IRAIT) imaging of

interesting stellar systems. Multiple observations of chosen AGB sources at different epochs &

wavelengths.

N.B. Extended wavelength coverage is fundamental. Indeed…..

IntroductionIntroduction:: Why Surveys from Dome C…..Why Surveys from Dome C…..

IntroductionIntroduction:: Why Surveys from Dome C…..Why Surveys from Dome C…..


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Mid-IR and VariabilityMid-IR and Variability:: Mid-IR Observations with ISO(SWS)Mid-IR Observations with ISO(SWS)

Mid-IR and VariabilityMid-IR and Variability:: Mid-IR Observations with ISO(SWS)Mid-IR Observations with ISO(SWS)

Lb Sr

PostAGBMira

Mira

PostAGB


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Mid-IR and VariabilityMid-IR and Variability:: Period-LuminosityPeriod-Luminosity

Mid-IR and VariabilityMid-IR and Variability:: Period-LuminosityPeriod-Luminosity

The contribute from mid-IR is fundamental to estimate luminosity of AGB stars.Period-luminosity relations are important to estimate important parameters of AGB stars.

Kwok et al. 1999Wood et al. 1999


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Mid-IR and VariabilityMid-IR and Variability:: Variability and EvolutionVariability and Evolution

Mid-IR and VariabilityMid-IR and Variability:: Variability and EvolutionVariability and Evolution

Luminosity varies with time during the evolution of the star on the AGB phase.

Commonly believed so far:Semiregulars in the the post-flash dips, Miras at the top of interpulse luminosity.Hence, one expects more Miras than SRs.

Instead, the 2 populations are more or less equal (Guandalini et al 2006).

The variability is also dependent on the The variability is also dependent on the evolutionary status.evolutionary status.


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Mid-IR and VariabilityMid-IR and Variability:: Bolometric Variability (ISO)Bolometric Variability (ISO)



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1313




1414




1515




1616




1717




1818




1919



Bolometric variabilityBolometric variability………

How is this generatedHow is this generated ?1. Shock waves caused by dynamic events in the photosphere? 2. Magneto-hydrodynamical modes (and magnetic storms)?

In which way we can examine itIn which way we can examine it?We need to observe AGB stars at different epochs ALSO in mid-IR!!

Simultaneous observations in near & mid IR could be fundamental to understand these phenomena.

Moreover, correlation with optical variability could be necessary.


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As mentioned before by Dolci (see talk)As mentioned before by Dolci (see talk)IRAIT : IRAIT : valid observations for fluxes > 0.5 Jy

Mid-IR Observations from Antarctica:Mid-IR Observations from Antarctica:

Magellanic CloudsMagellanic CloudsMid-IR Observations from Antarctica:Mid-IR Observations from Antarctica:

Magellanic CloudsMagellanic Clouds

IRAIT will observe stars of the Magellanic CloudsMagellanic Clouds down to the base AGB in mid-IR.

A 4m IR telescope placed in Antarctica could study stars of the Magellanic CloudsMagellanic Clouds down to the RGB. This telescope could also observe the AGB stars beyond the M31 M31 groupgroup (see previous talk).


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Mid-IR Observations from Antarctica:Mid-IR Observations from Antarctica:

dSph Satellites of the Milky WaydSph Satellites of the Milky WayMid-IR Observations from Antarctica:Mid-IR Observations from Antarctica:

dSph Satellites of the Milky WaydSph Satellites of the Milky Way

An IR 4m telescope placed in Antarctica will allow us also to study stars in the final phases of their evolution from all the Dwarf all the Dwarf Spheroidal Satellites of the Milky Spheroidal Satellites of the Milky WayWay, at very different metallicities.

(For the dSphs we could observe at least the giants at the tip of the RGB phase).


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Results with space-borne mid-IR observationsResults with space-borne mid-IR observations :: Observations Used…..Observations Used…..

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations :: Observations Used…..Observations Used…..

Surveys from the ground in near-IR: 2MASS/DENIS.

Observations in mid-IR (mainly through space-borne telescopes):ISO (SWS) : 3-45 umMSX : 8-21 um

BUTBUT

A low number of sources is observed and usually only with a single observation.


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Different variability types are well Different variability types are well distinguished by IR colors.distinguished by IR colors.

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: PostPost--AGB StarsAGB Stars

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: PostPost--AGB StarsAGB Stars

Guandalini et al. 2006Kwok et al. 1999


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Results with ground-based mid-IR observationsResults with ground-based mid-IR observations:: Post-AGB Stars and TIRCAM2Post-AGB Stars and TIRCAM2

Results with ground-based mid-IR observationsResults with ground-based mid-IR observations:: Post-AGB Stars and TIRCAM2Post-AGB Stars and TIRCAM2

Busso et al. 2006


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Magellanic Clouds Milky Way

Costa & Frogel 1996;Van Loon et al. 1999

Guandalini et al. 2006

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: Luminosity Of AGB Stars: C StarsLuminosity Of AGB Stars: C StarsResults with space-borne mid-IR observationsResults with space-borne mid-IR observations:: Luminosity Of AGB Stars: C StarsLuminosity Of AGB Stars: C Stars


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Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: Luminosity Of AGB Stars: S StarsLuminosity Of AGB Stars: S Stars

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: Luminosity Of AGB Stars: S StarsLuminosity Of AGB Stars: S Stars


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Guandalini et al. 2006Marigo et al.Molec. Opac. ?

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: HR Diagrams for C starsHR Diagrams for C stars

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: HR Diagrams for C starsHR Diagrams for C stars


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Results with ground-based mid-IR observationsResults with ground-based mid-IR observations:: HR Diagram for C starsHR Diagram for C stars

Results with ground-based mid-IR observationsResults with ground-based mid-IR observations:: HR Diagram for C starsHR Diagram for C stars

Busso et al. 2006


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Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: HR Diagram for S starsHR Diagram for S stars

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: HR Diagram for S starsHR Diagram for S stars

SC branch

S branch


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Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: Mass Loss – IR ColorsMass Loss – IR Colors

Results with space-borne mid-IR observationsResults with space-borne mid-IR observations:: Mass Loss – IR ColorsMass Loss – IR Colors


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Results with ground-based mid-IR observationsResults with ground-based mid-IR observations:: Mass Loss – IR ColorsMass Loss – IR Colors

Results with ground-based mid-IR observationsResults with ground-based mid-IR observations:: Mass Loss – IR ColorsMass Loss – IR Colors


Busso et al. 2006


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ConclusionsConclusionsConclusionsConclusions

There is the need of understanding the final evolutionary phases of AGB sources (luminosity, mass loss…..):

the amount of the matter returned to the InterStellar Medium chemical evolution mass of the White Dwarfs

Update of the photometrical analysis of these stars up to 40 um(beyond 20 um this might require new detectors).

The future class of IR telescopes at Dome C can do studies like those shown here for the Local Group.

Dome C might become THE place where stellar evolution gets clarified.

the uniqueness of antarctica for the study of agb stars undergoing thermal pulses

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