Science with the VO:
Spectroscopic studies of premain sequence
stars
Deborah Baines
European Space Astronomy Centre
Science Archives and VO Team
5th July 2011
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 1
OUTLINE
 Introduction:
• VO Tools: VOSpec and VOScript
• VOScript Science Case: Herbig Ae/Be stars
 Building SEDs with VOSpec
 Initial Results: SEDs and spectroscopic line analysis
 Conclusions
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 2
ESA VO TOOLS: VOSPEC
 Multi-wavelength spectral
analysis tool developed at ESAC
by ESA-VO



Create
SED
from spectra
Analysis
Tools:
Synthetic
Tool
registeredSpectra
in the VO:
IUE
•
•
•
Line fitting (Gaussian, Lorentzian,
Uses the Spanish VO Filter Profile
XMM,
Voigt) FUSE, IUE, HST, ESO (high
Service
resolution UVES), ISO….
• EW, Integrated flux & line flux
• More than 300 filters
• local
data (FITS, VOT)
calculations
• Compare synthetic photometry with
• Redshift
correction
 Access
to theoretical
observed
photometry models
• Spectralin
arithmetic
registered
the VO and
convolution between spectra.
 Access to atomic and molecular
• De-reddening
line databases
• Continuum fitting (BB,
polynomial)
HST FOS
HST
HUT
EUVE
Line fitting
Polynomial fitting
• λ-to-ν conversion
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 3
INES
ISO PHT
ISO LWS
VOSPEC EXAMPLE: HD 100546
ISO & HERSCHEL
PHOTOMETRY
FUSE
HST
IUE
MODEL
FITTING
(VOSED)
(Kurucz)
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 4
ESA VO TOOLS: VOSCRIPT
 The scripting counterpart of VOSpec: provides access from scripting
interfaces to most VOSpec functionalities.
 Being developed as a direct response from feedback from the astronomy
community.
 Jar Library  can be integrated with user pre-existent spectral analysis code in
any language with Java Virtual Machine equivalent (C, Python, Jython, Tcl,
Pascal, etc) or other jar libraries (STILTS).
 Library includes a shell parsing module  can be called from the command line
(c-shell, bash, etc), and integrated with pre-existing scripts in these languages.
 Capabilities:
• Search the VO for spectra from multiple targets.
• Perform batch oriented analysis on a large number of spectra: VOSpec
functionalities: EW, Line flux, Gaussian, etc.
• SAMP interoperability.
• Spectral Data Model 1.03 compliant, spectra format conversions.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 5
VOSCRIPT SCIENCE CASE:
HERBIG AE/BE STARS
Project Aim
Using VOScript, VOSpec and other VO Tools
(mainly TOPCAT/STILTS and VOSED):
 Produce a database of line properties (EWs,
FWHMs, velocities, profiles) for the pre-main
sequence Herbig Ae/Be stars, from spectra
within the VO.
 Classify the SED types using spectra and
photometry within the VO.
 Analyse the results: What trends can be
found? E.g. between Line Strengths, effective
Temperatures, Accretion Rates, Line Profiles,
SED types, etc.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 6
VOSCRIPT SCIENCE CASE:
HERBIG AE/BE STARS
Introduction to Herbig Ae/Be stars:
 Intermediate-mass pre-main sequence
stars (2 - 8 solar masses).
• ‘e’ = emission.
• B, A and F spectral types.
• Similar characteristics to T Tauri stars (solar
masses):
• Irregular photometric & spectroscopic
variability
• Strong Hydrogen Balmer & other
emission lines
• Have a near- &/or far-IR excess
• Located near the Zero Age main
sequence in HR diagram.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 7
VOSCRIPT SCIENCE CASE: Why are Herbig
Ae/Be stars interesting to study?
 Star Formation:
• HAEBEs bridge the gap between low-mass
T Tauri stars and the optically invisible,
near-IR faint Massive Young Stellar
Objects (MYSOs).
• It is here that the star formation
mechanism switches from magnetically
controlled accretion from disks with inner
holes (T Tauris) to accretion disks
reaching directly onto the star (MYSOs).
 Planet Formation:
• HAEBEs are surrounded by circumstellar disks, believed to be the site of
ongoing planet formation. Do planets form around all Herbig Ae/Be
stars?
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 8
SED CLASSIFICATIONS USING VO TOOLS
Photometric
Spectra
points
(VOSpec):
(VOSED):
Tycho,FUSE,
Stromgrem,
IUE, HST
2MASS
& ISO& IRAS
The SEDs of Herbig Ae/Be stars can be classified roughly into two groups
(Meeus et. al. (2001) A&A 365, 476)
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 9
SED CLASSIFICATIONS USING VO TOOLS
 Group I
Large flaring angle
of outer disk
 Group II
Puffed up inner
disk protects outer
disk from direct
stellar radiation
Dullemond & Dominik (2004, A&A, 417, 159) disk models link shape of the SED
to the disk geometry.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 10
SED CLASSIFICATIONS USING VO TOOLS
Group I:
Group II:
Agree with Meeus et. al. (2001) A&A 365, 476 & Acke et. al. (2004) A&A,
426, 151.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 11
VOSCRIPT SCIENCE CASE: SPECTROSCOPIC LINE
ANALYSIS USING VO TOOLS
 VOScript:
• Searched the VO for spectra for a list of ~320 Herbig Ae/Be stars.
• Calculated the Equivalent Widths of some strong spectroscopic
lines in the IR, optical and UV.
• Output are tables which can be loaded into TOPCAT.
 TOPCAT (& STILTS):
• Joined all VOScript output tables.
• Cross matched with catalogues in the VO (including all of VizieR)
for photometry, stellar parameters, line fluxes, etc.
• Added the SED classifications determined using VOSpec and
VOSED, and any classifications in catalogues.
• Produced plots to compare spectroscopic lines, looking for trends
and variability.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 12
EXAMPLE RESULTS: COMPARISON OF LINES
 Comparing line strengths (EWs). See a trend for [CII] 158µm vs [OI] 63µm.
 Comparing against the literature: Herschel observations and models of
Pinte et. al. 2010, A&A, 518, L126
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 13
EXAMPLE RESULTS: COMPARISON OF LINES
& CATALOGUE DATA
 Comparing line strengths at different wavelength regions (IR and UV), and against
catalogue data (Valenti et al, 2003, ApJS, 147, 305).
 Near-IR PAH are excited by UV-photons and proportional to the strength of the UV-field of
the central star (Acke and van den Ancker, 2004, A&A, 426, 151).
 PAH 6.2µm Equivalent Width vs log continuum flux at 2257 & 3060Å:
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 14
EXAMPLE RESULTS: COMPARISON OF LINES
& CATALOGUE DATA
 PAH 6.2µm EW vs FeII 2362Å and FeII 2600Å line fluxes also show correlation
(FeII lines from catalogue of Valenti et al, 2003):
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 15
EXAMPLE RESULTS: COMPARISON OF LINES
& SED TYPES
 Comparing line strengths and SED types (from VOSpec SED classifications and
SED classifications in catalogues).
 Only observe Group I sources with [OI] 63µm
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 16
EXAMPLE RESULTS: COMPARISON OF LINES
& SED TYPES
 Surprise result: [CII]158µm appear stronger in Group II sources than in Group I
– Pinte et. al. (2010) disk models show that the line originates from larger radii
and lower density regions than the [OI] IR lines.
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 17
CONCLUSIONS
 At ESAC, we are developing a scripting counterpart of VOSpec
(VOScript) as a direct response from feedback from the astronomy
community -> Multi target VO spectral searches, SED building and batch
processing.
 Using VOScript on various science cases: Project on Herbig Ae/Be stars at
an early stage and linked with the development of VOScript:
• Will allow the fast analysis of large numbers of spectra and targets, across a
large wavelength range.
• Using VOScript in combination with other VO Tools (mainly VOSpec,
TOPCAT/STILTS and VOSED).
 Initial Results:
• Automatic searching of VO for spectra and fitting of lines.
• SEDs and initial spectroscopic line analysis show good agreement with the
literature.
Interested? Contact [email protected]
Science with the VO | Deborah Baines | JENAM 2011, St Petersburg | 5 July 2011 | Pag. 18
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Astronomical Spectroscopy in the VO era: VOSpec