Working with Observation Sources
This manual is partially obsolete. You can use the ZTF plug-in
Currently (Jan 2021), VStar does not have a ZTF (https://www.ztf.caltech.edu/) plug-in. However, it is possible to load ZTF data using Flexible Text Format plug-in.
To access ZTF light curves, go to https://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?submit=Select&projshort=ZTF, select a catalog, and press [SELECT] button:
Enter object’s coordinates then click [Run Query]:
Identify the object in the table, select desired filter(s) and click [To Time Series Tool]:
Click an object id (oid):
Now, you should see a screen with a data table and a light curve.
Press “Save” button above the data table, then (in the new dialog window) select “Comma-separated values (.csv)” format and press [Save]:
By default, a name of the file is too long (like https___irsa_ipac_caltech_edu_cgi-bin_g2p_nph-g2p dataid=oid&projectshort=ztf&ws=_89_c2_7a1d905b264e0450cd88b3b1e8b0_g2p_6674&id=806104400011333.csv) so change it to more convenient, let’s say, “ZTF_zg.csv”. Open the file in a plain-text editor (under Windows, Notepad, or, for example, Notepad++) and add the following lines at the top:
#FIELDS=,,TIME,,MAG,MAGERR
#TIME=HJD
It is also recommended to put the # sign at the beginning of a line with field names to suppress warning while loading data into VStar:
The first directive (#FIELDS) describes the format of the file (time information is in the 3rd column, magnitude is in the 5th, and uncertainty in the 6th).
The second directive (#TIME=HJD) tells Flexible Text Format plug-in that time values are Heliocentric Julian Dates.
Save the file, launch VStar and open the data file with Flexible Text Format plug-in:
The light curve is for a star 2MASS J00101695+5840460. It is a variable of BY type with a period of 2.6891 d:
Now, the data are displayed as "Unspecified". You can improve the representation by adding additional directives at the top of the light curve file:
#FILTER=zg
#DEFINESERIES=zg,zg,#00AA00
The directive #FILTER=zg specifies a photometric filter of the data series (actually, a name of the series). As far as the name of the filter (zg) is unknown to VStar, the next directive (#DEFINESERIES) defines this filter and the color of data marks (see Flexible Text Format plug-in documentation for details). Here is the result:
This manual is partially obsolete. You can use Gaia DR2/DR3 plug-in
With the Gaia Data Release 3, an extensive light curves database (epoch photometry) became available. Currently, VStar does not have a plug-in to access the Gaia DR3 epoch photometry directly. Yet it is possible with several extra steps with the help of a Python script.
[Note on 2023-03-13: In fact, VStar has Gaia DR2 plug-in, it seems it CAN access the same data.]
Note: You have to have Python installed. The Python script used in this recipe can be downloaded from here: https://github.com/AAVSO/VStar/blob/master/script/GaiaDR3.py . The author tested the script against Python 3.9.13.
The steps:
-
Find the Gaia DR3 identifier (source ID) for the object of interest (i.e., via https://vizier.cds.unistra.fr/viz-bin/VizieR ). For example, for RR Lyr, it is 2125982599343482624.
-
Enter a query specifying the source ID of the target:
select * from gaiadr3.epoch_photometry
where source_id = 2125982599343482624
- After submitting the query, wait until the execution is complete (it takes a few seconds or less). Check if there is a result on the [Results Table] tab:
Then go to the [Download] tab and download the result as 'Comma separated Values':
Save it as GaiaDR3.csv in the directory where the GaiaDR3.py script is placed.
- Run the Python script
GaiaDR3.py. The data in the VStar Flexible Table Format should be in the resultingGaiaDR3.txtfile:
- Now you can open the file in VStar via the Flexible Text Format plug-in:
Here is a phase plot of the data:
