VOSA. Help and Documentation

Version 7.5, July 2022

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
11.3. Binary Fit Quality
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


VOSA offers several options to analyze the observed Spectral Energy Distributions and estimate physical properties for the studied objects.

First, observed photometry is compared to synthetic photometry for different collections of theoretical models or observational templates in two different ways:

The Chi-square fit provides the best fit model and thus an estimation of the stellar parameters (temperature, gravity, metallicity, ...). It also estimates a bolometric luminosity using the distance to the object, the best fit model total flux and the observed photometry.

On the other hand, the Bayesian analysis provides the projected probability distribution functions (PDFs) for each parameter of the grid of synthetic spectra.

When these analysis tools are applied to observational templates (chi-square and bayes), we obtain an estimation of the Spectral Type too.

Once the best fit values for temperature and luminosity have been obtained, it is possible to build an HR diagram using isochrones and evolutionary tracks from VO services and making interpolations to estimate values of the age and mass for each object.