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Common Methods of Stellar Spectra Analysis and their Support in VO
Petr ŠkodaAstronomical Institute Academy of Sciences
Ondřejov Czech Republic
ESA workshop „Astronomical Spectroscopy and the Virtual Observatory“,ESAC,Spain, 22 March 2007
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Outline of the Talk Motivation (biased to stellar x VO people)Motivation (biased to stellar x VO people) Basic methods using only spectra and timeBasic methods using only spectra and time
Visual RV + other moments
More advanced methods – estimated periodMore advanced methods – estimated period Period analysis – Folding
Complex methodsComplex methods Fourier space disentangling Doppler imaging, tomography
Report on VO – enabled tools (no SDSS SS!)Report on VO – enabled tools (no SDSS SS!) Conclusions – What ? When ? Why ? (legacy)Conclusions – What ? When ? Why ? (legacy)
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Visual Spectral Analysis
(Over) Ploting spectra(Over) Ploting spectra Different objectsDifferent objects Different ranges (UV over IR)Different ranges (UV over IR) Different time (RV, profile changes)Different time (RV, profile changes) All heritage packages (bplot, splot, specplot, All heritage packages (bplot, splot, specplot,
spectool, DIPSO, XALICE) can do thisspectool, DIPSO, XALICE) can do this And VO-enabled as well !And VO-enabled as well !
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Measured Pulsations
Rho Pup – del Sct type Eps Cep - del Sct type
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Simulation of NR Pulsations
Aerts 2003
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WD Models by Fitting wavelength scale
Kawka 2005
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Different Lines overploted RV scale
V838 Mon: Kipper et al. 2004
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Dynamic Spectra
CX Dra: Skoda and Koubsky 1998
Interactive features, color cuts, LUT Multiple lines at the same timeQuotient or Differential X axis : lambda or RVY axis : phase or time
For study of LPV (asteroseismology, winds)Requires
time (JD) - windsperiod (see Period analysis) - phase (LPV)change of template (average, median)removing bad data (interactive overplotting)
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Dynamic Spectra
Netolický 2004
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Rectification (Normalization)
SPEFO (SPLAT) – Hermit. polynoms (+Akima)
Echelle - tricky
Anchor the edges -edges bad (chip,optics)How flexible is it ?Visible interaction – extrapolationThe REAL continuum – (V838 – Pcyg)IRAF – select region - only existing data Chi^2 ? - Model Wavelet - C_infty = continuum ???Merged echelle – many different unblazed ?
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Merged Echelle
Arcturus: Hinkle et al.
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Echelle Spectra Problems
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Measurement of RV, z
Normalization Normalization Fits of Gauss, Fits of Gauss,
Maxwell, VoigtMaxwell, Voigt Asymetry ??Asymetry ??
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RV by Mirroring
SPEFO - Oscilloscopic SPLAT
Shift until best match of direct and flipped profile - interactiveComplicated profiles (Be)Adjustable region of interest (wing/core)Needs reference line position
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Mirorring Method
Separate match of core from match of wings – where in depth ? Different physics (shells, shears, winds)
Asymetry – how to handle ?
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Bisector Method
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Bisector Analysis
Quantitative study of LPVQuantitative study of LPV Searching exoplanetsSearching exoplanets High resolution - echelleHigh resolution - echelle Rectified (normalized) spectraRectified (normalized) spectra Various smoothingVarious smoothing Cuts in relative depth of line - half of spanCuts in relative depth of line - half of span Zoom of bisectors positionZoom of bisectors position Results in 3D cube (time, line, depth)Results in 3D cube (time, line, depth)
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RV by Cross Correlation
IRAF xrv
Template!
Normalization
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Rotational Broadening
Hot stars
needed to use synthetic spectrum
limb darkening problem
estimate of v sin i
interactivelyoverplot model
complicated in non-LTE
absorption in Ha – double peak emission (Hadrava)
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FT of Line Profile
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Changes of EW in Time
Omi Cas : Koubsky et al. 2004 HD6226 : Slechta and Skoda 2004
Moments in general (asteroseismology – mode identification)Emission lines – negative EWEstimates of expanding shellSensitive to continuum placement – shallow linesAbundances - check normalization – different lines same ion
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Period Analysis
Power spectrum FT Theta statistics
PDM, Fourier (CLEAN), many others (LombScargle)Rectified spectrumTime RangesInitial estimate of period
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Periodogram of Line Profile NRP
Lambda Sco: Uytterhoeven 2004
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Zet Oph: Koubsky et al. 2005
Period in local RVs – Different Depths
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Doppler Imaging - Bumps
Vogt & Penrod -80sZet Oph Ball VOGT
Requires high SNR (>300-500) Perfect rotation coverage Artefacts otherwise NRP or solar spots
Doppler Tomography Accretion jets in Algols Orbits in RV phase space
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Spectra Disentangling
For blended spectra of binary (multiple) starsFor blended spectra of binary (multiple) stars Very powerfulVery powerful Requires good orbital coverage, estimate of Requires good orbital coverage, estimate of
orbital parameters (SIMBAD) orbital parameters (SIMBAD) Wavelength space disentangling - computing Wavelength space disentangling - computing
power, space power, space Fourier disentangling - perfect continuum, cut Fourier disentangling - perfect continuum, cut
regions, log lambda regions, log lambda P. Hadrava KOREL S. Ilijic - FDBINARY
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Many Spectra Overploted
V436 Per Janík 2003
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Spectra Disentangling in Fourier Space - KOREL
HD208905: Koubsky et al. 2006
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VOSpec (ESAC)
Very simple Very simple
Polynomial fitsPolynomial fits
No RV measurementNo RV measurement
No complex operationsNo complex operations
In VizieR nowIn VizieR now
Can work with SLAP!Can work with SLAP!
Theoretical VO supportedTheoretical VO supported
Rapid development :-)Rapid development :-)
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SpecView (STScI)
Fitting profiles from Fitting profiles from modelsmodels
Simple polynomialsSimple polynomials Analysis strong Analysis strong
(deredening, (deredening, CLOUDY)CLOUDY)
Supported !!Supported !! Not good for IRAF Not good for IRAF
WCS (1D FITS)WCS (1D FITS) BinTables+ExtensionBinTables+Extension
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SPLAT-VO
Custom line listCustom line list Development not Development not
justified ?justified ? Most advanced for Most advanced for
stellar astronomystellar astronomy JCMT nowJCMT now PlasticPlastic Reads 1D FITS...Reads 1D FITS...
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FROG - Period04
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Conclusions
To convince stellar astronomers – give them VO tools working in similar manner
Easy publishing of FITS files – even for restricted access archive
Functionality in client easy – but is this the real VO idea ?
Server side (Igor mentioned ) - plugins for different data processing (Apache mods)
Seamless unit transformation
If pipeline processed – keep the unprocessed together (normalization of continuum)
Switch on and off in client
When will be SSAP finished ? (should it be complete , intermediate stage !)
SSA by query without RA,DEC (Jupiter spectra, Solar VO ?)
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Is VO fighting against Data Avalanche?