VOSA. Help and Documentation

Version 6.0, Apr 2018

1. Introduction
2. Input files
2.1. Upload files
2.2. VOSA file format
2.2.1. Required format
2.2.2. Examples
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. HR diagram
5.6. Upper Limits
5.7. 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
13. Helpdesk
14. About

VOSA file format

VOSA is mainly designed to work with several objects at the same time so that the same or equivalent operations are performed on all the objects. In order to do this, we have defined a format so that the user can upload the info about these objects together with user photometric data.

Thus, the main way to use vosa is to upload a VOSA input file with this format (or selecting a previously uploaded one).

Nevertheless, we have added the Single Object Search so that you can directly search for a single object using its coordinates. See more information below.

Required input file format

The uploaded file must be an ascii document with a line for each photometric point.

Each line should contain 10 columns:

 ----------------------------------------------------------------------------
| object  | RA  | DEC | dis | Av | filter | flux | error | pntopts | objopts |
| ---     | --- | --- | --- | ---| ---    | ---  | ---   | ---     | ---     |
| ---     | --- | --- | --- | ---| ---    | ---  | ---   | ---     | ---     |
  • 1: a one word text label, without spaces or special characters, that corresponds to the object name. See (1).
  • 2: the RA, in deg, corresponding to the object in J2000 equinox. See (2).
  • 3: the DEC, in deg, corresponding to the object in J2000 equinox. See (2).
  • 4: the distance to the object in parsec. See (4).
  • 5: the AV parameter defining the extinction. See (5).
  • 6: a label corresponding to the name of the filter. It must be in the list of available filters . See (6).
  • 7: the flux in erg/cm2/s/A, Jy or magnitude. See (7).
  • 8: the observed error in the flux (in erg/cm2/s/A) or magnitude. See (8).
  • 9: options specific for this photometric point. See (9).
  • 10: options specific for this object (they must be repeated in each line corresponding to the same object). See (10).

Take into account that:

  • (1) The only mandatory value is the object name (you can use the real one or some label of your like). The other columns can be writen as '---' (please, don't let them blank nor write '...' instead of '---') if you don't know the right value or don't want to specify it.
     
  • (1) If you include a "_" character in the object name, it will be treated as an space for object name resolution.
    This can be useful if you are using real object names that contain spaces (for instance, the variable star "R Aql") and you need to use the actual name so that it can be resolved by VOSA using VO services. In a case like that, write "R_Aql" as the object name in the file.
     
  • (2) Coordinates (as accurate as possible) are necessary to obtain photometry from VO catalogues.
    If unknown, you can write RA and DEC as '---'. In that case, if you have given the right object name in the first column, you can use the Objects:Coordinates section to find the coordinates for the object using Sesame.
     
  • (4) The distance to the object is necessary to compute the Bolometric Luminosity.
    If you don't know the distance, write it as '---' and an assumed distance of 10pc will be used in the calculations.
    You can also provide a value for the error in the distance. In order to do that write D+-ΔD (for instance: 100+-20), without spaces (Remember to write both symbols, + and -, together, not a ± symbol or something else; otherwise vosa will not understand the value)
     
  • (5) The value of visual extinction and the the extinction law by Fitzpatrick (1999), improved by Indebetouw et al (2005) in the infrared, are used to deredden the user and VO photometry in a standard way. No reddening correction is applied if Av is set to '---' or zero. Take a look to the corresponding Credits Page for more information.
     
  • (6) We use the SVO Filter Profile Service as the source for filter names and properties. Check it to see if the filter corresponding to your observed data is in the list (if not, contact us and we will try to include it).
     
  • (7) If your input file containes magnitudes or fluxes in Jy, please, be careful to mark the corresponding checkbox when uploading the file. If not, we will understand the values as fluxes in erg/cm2/s/A).
  • (7) If your data are given in Jy, we will transform them to erg/cm2/s/A using the λ value given by the SVO Filter Profile Service. If you prefer other λ value, please, transform the fluxes to erg/cm2/s/A before uploading your file.
  • (7) If your data are given as magnitudes, we will transform them to erg/cm2/s/A using the properties (photometric system, zero point, etc) given by the SVO Filter Profile Service. If you prefer a different transformation, do it yourself and upload the file with fluxes in erg/cm2/s/A.
     
  • (8) Errors must be specified in the same units as the fluxes (or magnitudes).
     
  • (9) You can specify certain options for each photometric point including a special keyword in this column. By now these options are available:
    • "---" : nothing special for this point.
    • "nofit" : this point will be included in the SED and in all the plots. But it will NOT be used for the fit.
    In the future, other options could be implemented.
     
  • (10) You can specify certain options for each object including a special keyword in this column. By now these options are available:
    • "---" : nothing special for this object.
    • "Av:av_min/av_max" : Range of values for Av. If you give a range here, the visual extintion will be considered as an additional parameter in model fit, bayes analysis and template fit. See the corresponding section for details.
    • "Veil:value" : value in Angstroms so that photometric points with smaller wavelength will be considered to present UV/blue excess.
    • "excfil:FilterName" : name of the filter where infrared excess starts for this object.
    Several options can be given for the same object separating them by "," (with no spaces). For instance: "Av:0.5/1.5,Veil:6000"
    In the future, other options could be implemented.
     

Please, check in advance that your file conforms to these requirements. Next, after uploading it, you can try to see the analyzed contents of the file in "Upload files → Show". If what you see does not correspond to what you expect it will probably mean that there is something wrong in your data file. Delete it from the system, try to correct the mistake and upload it again.

Examples of valid files

1.- A complete file

Obj1 19.5  23.2 80 1.2 DENIS/DENIS_I     5.374863e-16 4.950433e-19 ---    Av:0.5/5.5
Obj1 19.5  23.2 80 1.2 CAHA/Omega2000_Ks 2.121015e-16 1.953527e-19 ---    Av:0.5/5.5
Obj1 19.5  23.2 80 1.2 Spitzer/MIPS_M1   6.861148e-15 1.390352e-16 nofit  Av:0.5/5.5
Obj2 18.1 -13.2 80 1.2 WHT/INGRID_H      1.082924e-14 2.194453e-16 ---    ---
Obj2 18.1 -13.2 80 1.2 2MASS/2MASS_J     2.483698e-17 2.287603e-19 ---    ---

In this file we have two different objects, their positions (RA and DEC), the distance to the objects, the AV parameter and some values of the photometry (three for Obj1 and two for Obj2). For the first object, the MIPS_M1 will not be used for the fit, and Av will be considered as a fit parameters with values from 0.5 to 5.5

2.-Only object names

BD+292091 --- --- --- --- --- --- --- --- ---
HD000693  --- --- --- --- --- --- --- --- ---
HD001835  --- --- --- --- --- --- --- --- ---

This file is also correct, and although we have little information in it, VOSA can try to find some more data about these objects so that the analysis can be performed. Assuming that the names for the three objects are the real ones, we can try to find these objects coordinates. Then, using these coordinates, some observed photometry could be retrieved from VO catalogues, and so on.

2.-A mixed case

#objname  RA   DEC     DIS Av  Filter          Flux               Error             PntOpts ObjOpts
#=======  ===  ======= === === =============== ================== ================= ======= =======
BD+292091 ---  ---     --- --- 2MASS/2MASS_J   7.14724167946E-14  5.14601400921E-16 ---     ---
BD+292091 ---  ---     --- --- 2MASS/2MASS_H   3.69142119547E-14  2.3625095651E-16  ---     ---
Obj2      18.1 -13.2   80  1.2 DENIS/DENIS_I   1.082924e-14       2.194453e-16 	    ---     ---
Obj2      18.1 -13.2   80  1.2 2MASS/2MASS_J   2.483698e-17       2.287603e-19 	    ---     ---
HD000693  2.81 -15.467 --- --- ---             ---  		  --- 		    ---     ---
HD001835  ---  ---     --- 1.4 ---             --- 		  --- 		    ---     ---
Obj3      19.5 23.2    80  1.2 Omega2000_Ks    2.121015e-16 	  1.953527e-19 	    ---     ---
Obj3      19.5 23.2    80  1.2 Spitzer/MIPS_M1 6.861148e-15 	  1.390352e-16 	    ---     ---
HD003567  ---  ---     --- --- ---             ---           	  --- 		    ---     ---

You can combine in the same file objects with different type of information. Just keep in mind that each line must have 10 columns and, when you want to leave a data blank, you must write it as '---'.

And remember that the different columns can be separated by blanks or tabs or any combination of them. For instance, this next example would be completely equivalent to the previous one:

BD+292091 --- --- --- --- 2MASS/2MASS_J 7.14724167946E-14 5.14601400921E-16 --- ---
BD+292091 --- --- --- --- 2MASS/2MASS_H 3.69142119547E-14 2.3625095651E-16 --- ---
Obj2 18.1 -13.2 80 1.2 DENIS/DENIS_I 1.082924e-14 2.194453e-16 --- ---
Obj2 18.1 -13.2 80 1.2 2MASS/2MASS_J 2.483698e-17 2.287603e-19 --- ---
HD000693 2.81 -15.467 --- --- --- --- --- --- ---
HD001835 --- --- --- 1.4 --- --- --- --- ---
Obj3 19.5 23.2 80 1.2 Omega2000_Ks 2.121015e-16 1.953527e-19 --- ---
Obj3 19.5 23.2 80 1.2 Spitzer/MIPS_M1 6.861148e-15 1.390352e-16 --- ---
HD003567 --- --- --- --- --- --- --- --- ---