near-ir spectroscopy of ob stars with crires · • objects: ob main sequence & giant stars...
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NearNear--IRIR SpectroscopySpectroscopy of OB of OB starsstars withwith CRIRES:CRIRES:pilotpilot studystudy forfor an ELT an ELT sciencescience casecase
M. Fernanda Nieva
Norbert Przybilla (Obs. Bamberg/ Univ. Erlangen)Andreas Seifahrt (Univ. Göttingen)
Keith Butler (LMU München)Hans-Ulrich Käufl (ESO)
Andreas Kaufer (ESO)
Max-Planck-Institute for Astrophysics (MPA)
OB-type dwarfs & giants
Young age ~ 107 yrsMassive M ~ 9-20 MsunHot Teff ~ 20-35 x104 KLuminous L ~ 104 Lsun
in contrast to late-type stars:no convective envelope
no chromosphere
in contrast to OB supergiants:no strong mass loss & winds
OB OB starsstars: : latelate O & O & earlyearly BB--typetype
Precise & absolute (physical) chemical composition @ present day
Well-understood atmospheric structureradiative envelope thin atmosphere
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Jascheck & Jascheck
Muliple science motivationsMuliple science motivations
OB dwarfs and giants:
- metallicity indicators in starstar--formation regionsformation regions
- present-day chemical abundance indicators @ short and large distances in the Milky Way and neighbour galaxies:galactochemical evolutiongalactochemical evolution
-- progenitors of BA-supergiants: stellar evolutionstellar evolution
- OB stars in the Galactic CenterGalactic Center previous talk by N. Przybilla
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
e.g. OB stars in stare.g. OB stars in star--formation regionsformation regions
1- deposit energy & momentum to the ISM
2- can ionize gas clouds through UV radiation
3- less evolved dwarfs & giants: similar composition than parent
clouds
4- luminous: can be studied at large distance
NGC 3603: original image courtesy ESO
N
e.g. OB stars in the Galactic Centere.g. OB stars in the Galactic Center
http://www.mpe.mpg.de/ir/GC/
“ON THE NATURE OF THE FAST MOVING STAR S2 IN THE GALACTIC CENTER”F. Martins et al. 2008 (Genzel Group, MPE)“A high quality SINFONI H and K band spectrum obtained from co-adding 23.5 hours of observation between 2004 and 2007 reveals that S2 is an early B dwarf (B0–2.5V)…”
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Southern Hemisphere
Some Galactic regions observable both in optical & near-IRBUT: some regions observable in near-IR onlyPresent and future generation of telescopes
Why nearWhy near--IR spectroscopy of OB stars?IR spectroscopy of OB stars?
Galactic stellar astronomy
diffraction-limited observation with ELTusing AO near-IR spectroscopy
Future generation of ELTsExtragalactic stellar astronomy
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Pilot study withPilot study with CRIRES CRIRES for future ELT applications:for future ELT applications:why 1st high resolution?
Telluric lines resolved (R~100 000)
Spectral line identification (detailed line profiles)
Comparison observation / synthetic spectrum
Model atoms calibrations (non-LTE physics)
Benchmark study
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Aim of present workAim of present work
Atmospheric parameter & chemical abundancefrom the near-IR spectrum
in agreement with precise results in the optical
+ metal line identification
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
SpectraSpectra
• objects: OB main sequence & giant starssolar neighbourhoodapparently slow rotators
well studied in the visual
• data: high-S/N CRIRES spectra broad wavelengh range: ~ .99 – 4.3 μm
• data reduction: 1st approach: pipelinenow: customized reduction
Käufl et al. (2004)
VLT / ESO
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Previous work in the opticalPrevious work in the optical
precise atmospheric parameters & metal abundancesunprecedented reduction of systematic uncertainties
stellar analyses from quantitative spectroscopy:
derivation of stellar parameters & abundances from spectrum
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Nieva & Przybilla / Przybilla et al. seriestalk by N. Przybilla
Simultaneous fits to most measurable H/He linesSimultaneous fits to most measurable H/He lines
Data: FEROS, ESO
H Balmer
He I
He II
HR 3055
Visual
H Paschen
Data: FOCES, Calar Alto, Spain
He I K-Band
Data: Subaru, Hawaii
Nieva & Przybilla 2007Nieva & Przybilla 2007Near-IR
Data: FEROS, ESO
S/N up to 800
Fits to C linesFits to C lines
All lines have very similar abundances
low 1σ−uncertainties
Similar analysis for other metals
C II
C IV
C III
τ Sco
Visual
Precise quantitative analysis
Nieva & Przybilla 2008Nieva & Przybilla 2008
ModelsModels
• Hybrid non-LTE approach: hydrostatic metal blanketed model atmospheres in plan-parallel geomety + non-LTE line formation (DETAIL+SURFACE)
good for OB dwarfs & giants Nieva & Przybilla (2007)
• State-of-the-art model atoms in visual:H: Przybilla & Butler (2004)He: Przybilla (2005)C: Nieva & Przybilla (2006, 2008)α–elements: from Munich group (Butler, Becker, Przybilla, ...), updated
extended to the near-IR
• Non-LTE effects much larger in near-IR than in visual
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Difficulties from observations: Difficulties from observations: regions with strong telluric lines
Telluric lines modeling: 1st approach
(Now: improved !)
(Example for old data reduction)
Hydrogen
Modeling CRIRES stellar spectraModeling CRIRES stellar spectra
H lines Teff & log gHe lines Teff & ε(He)HeI/II ioniz. equil. Teff & log g
preliminary analysis:
• consistency with visual• strong NLTE effects
B1.5 III
Nieva et al. 2008
Helium
H lines Teff & log gHe lines Teff & ε(He)He I/II ioniz. equil. Teff & log gCC II/IIIII/III ioniz. equil.ioniz. equil. TTeffeff & log g& log g
Quantitative agreement with visual
Also: α-elements
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
standard modelNieva et al. 2008
our models
Modeling CRIRES stellar spectraModeling CRIRES stellar spectra
Model: so far NLTE populations from visual !
Still no best fits from grid interpolations
Customized data reductionCustomized data reduction
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
telluric linesSeveral new observable spectral lines arose from
new data reduction !
New data reduction + our modelsNew data reduction + our models
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
ByBy--product: OB stars as telluric standardsproduct: OB stars as telluric standards
• sucsessful modeling and analysis of most identified lines
• OB stars have fewer lines than cooler stars
OB stars: ideal telluric standardstelluric line removal of other science spectra
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Achievements (so far)
unprecedented metal line identification in massive stars @ high resolutionreliable modeling of most identified lines (H, He & metals)hotter stars: simultaneous He I/II& C II/III ionization balance
In agreement with analysis in the optical
OB stars as science spectraOB stars as science spectra
Important for chemical abundance studies in Important for chemical abundance studies in regions observable in nearregions observable in near--IR onlyIR only
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
Some lines are still unidentified !
NearNear--IR @ ELTsIR @ ELTsdirect application of present models & analysis
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
near-IR spectroscopic studies of massive starschemical composition @ high precision (star formation regions/stellar & galactochemical evolution/GC)
in the Milky Way & other galaxies (Local Group – Sculptor)telluric standards for other science spectralower resolution R~ 10 000-20 000 (limited also by stellar vsini)
Cerro Macon (Northern Argentina)
home
☺
Max-Planck-Institute for Astrophysics JENAM 2008 – Science with the ELTVienna, 09.11.2008
M.F. Nieva
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