VOSA. Help and Documentation

Version 7.0, July 2021

1. Introduction
2. Input files
2.1. Upload files
2.2. VOSA file format
2.3. Single object
2.4. Manage files
2.5. Archiving
2.6. Filters
3. Objects
3.1. Coordinates
3.2. Distances
3.3. Extinction
4. Build SEDs
4.1. VO photometry
4.2. SED
4.3. Excess
5. Analysis
5.1. Model Fit
5.2. Bayes analysis
5.3. Template Fit
5.4. Templates Bayes
5.5. Binary Fit
5.6. HR diagram
5.7. Upper Limits
5.8. Statistics
6. Save results
6.1. Download
6.2. SAMP
6.3. References
6.4. Log file
6.5. Plots
7. VOSA Architecture
8. Phys. Constants
9. FAQ
10. Use Case
11. Quality
11.1. Stellar libraries
11.2. VO photometry
12. Credits
12.1. VOSA
12.2. Th. Spectra
12.3. Templates
12.4. Isochrones
12.5. VO Photometry
12.6. Coordinates
12.7. Distances
12.8. Dereddening
12.9. Extinction
13. Helpdesk
14. About
. Excess calculation
. Total flux calculation
. VOphot quality info


Version 7.0

July 2021


  • Possibility of using both magnitudes and flux densities in the VOSA input file. More information.

Build SEDs / VO photometry

  • New photometric bands: MSX B1, B2
  • New treatment of negative magnitudes. Magnitudes <= -9 (both user and VO photometry) or fluxes < 0 return a warning message. This photometric points are not considered in the subsequent steps.
  • Photometric points flagged as "ignored", "bad", "nofit" are not taken into account in the computation of the average photometry. Average photometry is computed when there is more than one photometric value for a given filter. This occurs with catalogues sharing the same filters (e.g. SDSS and APASS), catalogues with multi-epoch information or when VO photometry and user photometry are put together.
  • Possibility of including user photometry from a list of spectra using Specphot. More information.
  • Possibiity of choosing a common search radius for all the VO catalogues.
  • New catalogues:
    • Galex GR6/7, GALEX GR5/MIS.
    • CMC 15.
    • SDSS DR12.
    • J-PLUS DR1.
    • PanStarrs DR2.

Build SEDs / SED edit/visualize

  • New interactive plots.

Analyse SED

  • Detection of outliers among the VO photometric data before the SED fitting. More information.
  • Improve calculation of the total flux in the chi-square fitting. More information.
  • Obsolete collections of theoretical models are now under the section "Previous models".
  • Two-bodies model fit. More information
  • New models
    • TMAP.
    • ATMO 2020 (CEQ, NEQ Strong, NEQ weak).

HR diagram

  • More flexible and interactive query form. See an example.
  • New isochrones / evolutionary tracks.
    • ATMO 2020 (CEQ, NEQ Strong, NEQ weak).
    • Geneva 2011.
    • Geneva, Haemmerle 2019.
    • Parsec 1.2.
    • SPOTS.


  • Single-page HTML document.
  • A new section ("VO quality info") has been included in the Appendix. It describes the quality information used by VOSA to classify a photometric point as good / bad / upper limit.
  • A new entry has been included in the FAQ section to explain why, for very faint objects, SDSS photometry may result in negative fluxes.
  • Some developement has been made so that, in the "Credits" section, more information can be included about due acknowledgements or links to web pages.

Previous versions