The stellar spectra service is a compilation of several libraries distributed by large observatories, which are intended to serve as reference to calibrate telescopic observations – including Solar System objects. The current data service provides simple and easy access to this data and powerful search functions from the VESPA portal, including cross-matches with other services of similar content.
Virtual Observatory service
The spectro_stars service currently provides access to two libraries of reference stars distributed by ESO and NASA IRTF. The spectro_stars service has been set up to provide easier access to these spectra in the Virtual Observatory, and to allow simple use in calibration workflows or pipelines.
The collection is presented in a table with descriptive parameters for each spectrum:
– Each row links to a single spectrum, corresponding to a stellar type
– Bibliographic references are included as bibcode (used by ADS)
– Thumbnails, also provided by the observatories, are used to provide a quick visual diagnostic in a search interface
Data is accessible via a link to the original file provided by the Observatories:
– these are always self-described fits files
– however, their internal organization may be non-standard and is not always supported by VO tools
The service table is formatted according to the EPN-TAP standard, which implies that column names and units are standardized. The data service can be queried using the TAP protocol, in particular from the VESPA portal of Solar System data: https://vespa.obspm.fr/
See the complete data service in the VESPA portal (the schema name is spectro_stars).
A tutorial for spectral studies in the Planetary Science VO context is available here:
http://voparis-europlanet.obspm.fr/utilities/Tuto_Spectro_VESPA.pdf
In particular with the CASSIS tool:
http://voparis-europlanet.obspm.fr/utilities/Tuto_CASSIS_VESPA.pdf
In short: you first identify data of interest from a search interface, then send selected results in a visualization and analysis tool. Although the plotting tools of choice for spectra are CASSIS, SPLAT-VO, and TOPCAT, they may not be able to directly read the fits files provided in these libraries. Python or IDL access may be more adapted.
Looking for spectra
Searches based on descriptive parameters can be performed from the VESPA portal or any TAP interface (TAPhandle, TOPCAT, etc).
Query results are tables, with a row describing each match. The column access_url provides a link to the spectrum file.
Important search parameters include:
target_name – name provided in the library, either the name of the star or a generic stellar type in case of composite observations or simulations
alt_target_name – aternative name when available, typically IAU proper name or designation (greek letters are transposed to latin alphabet)
external_link – links to the Simbad page for actual stars (IRTF database)
spectral_type – allows selection by spectral type & luminosity class
metal_abundance – qualitatively indicates metal abundance for ESO spectra
spectral_range_min / spectral_range_max – limits of the spectral range (given in Hz in the table, convertible to µm in the VESPA portal)
spectral_resolution_min / spectral_resolution_max – as resolving power [(delta lambda) / lambda]
measurement_type – provided as a UCD (always a flux)
access_format – all files are provided as fits, however with various internal organization
obs_id – grouping according to origin of data / original collection (also in original_publisher)
granule_gid – grouping according to post-processing actions
granule_uid – a unique identifier derived from the original collection
Data included
This service currently provides easy access to two libraries of stellar spectra distributed by ESO and NASA IRTF on their web sites, covering both the optical and NIR ranges. Files are linked in the original archives.
Please note that these libraries derive from refereed publications which must be cited when using the spectra.
The ESO Library of Stellar Spectra is a selection of composite spectra distributed here: https://www.eso.org/sci/observing/tools/standards/IR_spectral_library.html
The NASA IRTF Spectral Library is a selection of individual stars observed with SpeX at IRTF, distributed here: http://irtfweb.ifa.hawaii.edu/~spex/IRTF_Spectral_Library/References_files/All.html
Also useful for calibration purpose, various solar spectra and an indicative Earth atmospheric transmission spectrum are available in the EPN-TAP service spectro_planets
Other stellar spectra libraries
Additional stellar spectra (encompassing all spectral types) include:
• VizieR catalogues from publications, e. g.:
https://cdsarc.cds.unistra.fr/viz-bin/Cat?III/124
https://cdsarc.cds.unistra.fr/viz-bin/Cat?III/153
https://cdsarc.cds.unistra.fr/viz-bin/Cat?III/196
https://cdsarc.cds.unistra.fr/viz-bin/Cat?III/232
https://cdsarc.cds.unistra.fr/viz-bin/Cat?III/92
http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/629/A100 (= MUSE library below)
In the VizieR page click on the VizieR button, select a table (if several ones are available), then click Submit in the next page. Plotting / download functionalities will be available there (you may have to first adjust the number of table rows displayed to retrieve complete spectra).
• Stellar spectral atlases at STScI:
A large collection is available here: https://www.stsci.edu/hst/instrumentation/reference-data-for-calibration-and-tools/astronomical-catalogs
• The MUSE library of stellar spectra at ESO:
is a selection of high S/N ratio measurements with reliable continuum shapes:
Description: https://www.eso.org/sci/publications/announcements/sciann17288.html
Interactive access: https://archive.eso.org/scienceportal/home?data_collection=MUSE-STD&publ_date=2020-02-26
• The python AstroLib module
Includes routines to load modelled stellar spectra: https://pyastronomy.readthedocs.io/en/latest/pyaslDoc/resBasedDoc/specLib.html#
Extensions and updates
The current data service may be improved by adding more published spectra – contact the helpdesk for comments: support.vespa@obspm.fr
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This data service is provided in the framework of the VESPA activity in Europlanet-2024-RI by Paris Astronomical Data Centre (PADC)
The Europlanet 2024 Research Infrastructure project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871149. Additional funding was provided by the Action Spécifique Observatoire Virtuel and Programme National de Planétologie / INSU.