INTRODUCING AVE by Rafael Barberá english version by Jordi Iparraguirre Versión en
Castellano
WHAT'S AVE?
In 1995, GEA (Grup d'Estudis Astronomics) started a program to study the NSV (New Suspected Variable)
stars catalogued. It is being a huge project but very rewarding too. Since Feb 95 to Dec. 98 (almost 3 years) the
GEA team has studied more than 500 variable stars, classifying for the first time ever lots of them and
discovering about 100 new variable stars.
All GEAs results have been published in the IBVS. As you can imagine, all that means loooots of photometric
data to process and analyze. It was clear that we needed a tool, so I started AVE to fit the GEA needs.AVE,
Analisis de Variabilidad Estelar, stands for Analysis of Estellar Variability.
The requirements to develop AVE where pretty simple:
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User friendly
To cooperate with other tools (namely LAIA).
Nice look and feel.
To solve the problems that GEA had.
WORKING WITH AVE
AVE reads plain ASCII files that contain the Julian dates and the differential magnitude. If you use LAIA, you
do not need to worry about the file and its format as LAIA does it all for you. A data file could look like this:
2450339.4750136
2450339.4800717
2450339.4842684
2450339.4877663
2450339.4913430
2450339.4945300
2450339.4982626
2450339.5014504
2450339.5058791
-0.098
-0.102
-0.101
-0.098
-0.104
-0.091
-0.103
-0.097
-0.098
If we open one of those data files with AVE, our screen will show something like:
Nice isn't it ? Now let's have a look to some interesting details. First of all, if you want to have a full resolution
graphic (800 x 600) just click twice on it.
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You can appreciate that every night (set of almots vertical dots) is shown using a different color. This
helps you to identify the good and bad nights (from a photometric stand point).
AVE has calculated and adjusted the scales automatically, so the curve is shown at full amplitude.
There are context menus. Following the latest trends in user interfaces, AVE provides this feature at
any moment. Just click the right button of your mouse and the most desirable options menu will be
displayed on your screen.
It is possible to configure several items of the light curve graphic.
As AVE recognizes points made in different nights, you can go to the tool/menu option of Nights to
obtain the light curve night by night. Scale is adjusted automatically for every night.
Beside surfing by nights, AVE allows us to mark intervals on the X axis (abcises) and the curve adjusts
it self (Y axis too if needed) to the new interval.
But AVE is much more than a light-curve-displaying-tool. To prove it, let's select the option called
Tools/Period Searching and we will see (after clicking on the desired option in the context menu) a dialog box
like the following one:
The dialog box is asking us for an interval of periodes where to look for, number of samples inside the interval
and to select an algorithm (as there are different algorithms to find a periode in a cloud of points). The AVE
sets a merit function (depends on the algorithm selected) for each sample. Then, by simply having a look to the
Periode/Merit function graphic, you can determine the possible periodes of the data.
In the example, we have selected the PDM algorithm, (also known as Theta transformation). In that case, the
Merit curve represents how clustered are the points respect the the average curve. That implies that the lowest
the value of the function, the highest probabilitys is that the periode produced on this mimimum is significative.
Whoou !! Difficult ? Do not worry, it is easy now. Right mouse button to select a minimum, and Right mouse
button again to generate a phase curve in that periode and ....
...Voila ! A nice eclipsing light curve.
What we need now is to determine several minima and the exact moment of each one of them. Is AVE able to
all that automatically for us ? Of course it is !
First set a threshold clicking with the right button of the mouse on the curve (having the minima-detection tool
activaded). Then select the Find All option and after few moments all the minima will be indicated on the curve
with a blue arrow. Now we just need to create a file with all this information (minima epoch and its error).
Minima are identified using the Van Woerden method and it can be configured to adapt to your curves (i.e. in
case of having a few dots). OTHER OPTIONS
Among the options not explained above, AVE is able to:
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Add, substract, average, shift and scale curves.
Convert flux to magnidude and vice versa.
Obtain statistical data from light curves.
Compose (collage) of different curves.
Even if there is no help file, nor a manual, the best way to appreciate the power and features of AVE is
downloading it !. If you have questions about AVE do not hesitate to get in touch with me by email.
FUTURE
There are not going to be new 16 bit versions of AVE. The tool is being moved to 32 bits to take more
advantadge of the new generation of Windows operating systems. Future features will only be implemented on
the 32 bits version. Some of those features are:
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Ephemerides.
Processing of "complete" LAIA files.
Lineal and non-lineal regression adjustments.
Fourier methods to process multi-period oscillations.
Modelling of eclipsing stars.
New releases will be announced and available for download in this page. There is also a mail list of AVE users
that will allow you to talk with the developer and to exchage experiences with other users. Send your coments
to [email protected]
References [ Personal Page ][ GEA ]
Last modification: Dec. 1996