tde-i18n/tde-i18n-en_GB/docs/tdeedu/kstars/lightcurves.docbook

<sect1 id="tool-aavso">

<sect1info>
<author
><firstname
>Aaron</firstname
> <surname
>Price</surname
> <affiliation
><address
> <email
>aavso@aavso.org</email>
</address
></affiliation>
</author>
</sect1info>

<title
>AAVSO Light Curves</title>
<indexterm
><primary
>Tools</primary>
<secondary
>AAVSO Lightcurve Generator</secondary>
</indexterm>

<screenshot>
<screeninfo
>The AAVSO Lightcurves Tool </screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="aavso.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase
>AAVSO Lightcurves</phrase>
  </textobject>
</mediaobject>
</screenshot>

<sect2 id="aavso-intro">
<title
>Introduction</title>
<para
>&kstars; can display light curves for variable stars from the observing program of the <ulink url="http://www.aavso.org"
>American Association of Variable Star Observers</ulink
> (<abbrev
>AAVSO</abbrev
>). This program monitors over 6,000 variable stars and consists of 10 million observations going back almost a century. &kstars; downloads the very latest data directly from the <abbrev
>AAVSO</abbrev
> database via the Internet, so a network connection is required to use this tool. </para>
<para
>To use the tool, select a variable star either by <firstterm
>designation</firstterm
> or name in the left panel, and set the start and end dates to be plotted. In the right panel, select the type of data that should be plotted (see below). When you have made you selections, press the <guibutton
>Retrieve Curve</guibutton
> button. &kstars; will automatically connect to the AAVSO server, which will generate the lightcurve plot and send it to your computer for display. A sample lightcurve plot is shown below: </para>

<screenshot>
<screeninfo
>A Sample Lightcurve </screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="lightcurve.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase
>Sample Lightcurve</phrase>
  </textobject>
</mediaobject>
</screenshot>

<para
>Please not these light curves should <emphasis
>NEVER</emphasis
> be used in research, papers, presentations, publications, &etc;. They are only meant to be used as a source of info for &kstars;. They have not been validated and passed the <abbrev
>AAVSO</abbrev
>'s strict quality control measures. We will be glad to give you good raw data simply by requesting it at <ulink url="http://www.aavso.org/adata/onlinedata/"
>http://www.aavso.org/adata/onlinedata/</ulink
>. </para>
<para
>Specific questions about the data in the light curves can be sent to <email
>aavso@aavso.org</email
>. </para>
</sect2>

<sect2 id="aavso-about">
<title
>About Variable Stars</title>
<para
><firstterm
>Variable stars</firstterm
> are stars that change in brightness. A <firstterm
>light curve</firstterm
> is a plot of a variable star's brightness over time. By looking at a light curve you can see how the star has behaved in the past and try to predict how it will behave in the future. Astronomers also use this data to model astrophysical processes in the star. This important to help us understand how stars work. </para>
</sect2>

<sect2 id="aavso-data">
<title
>The Data</title>

<para
>Here is a summary of the various types of data available in the light curves: <itemizedlist
>  
<listitem
><para
><firstterm
>Visual Observation</firstterm
>: This is an observation of a variable star by an observer with a regular telescope. It means that an observer saw the star at Y brightness on X date and time.</para
></listitem>

<listitem
><para
><firstterm
>Fainter than</firstterm
>: Sometimes the star is too faint to be seen by the observer. When that happens, the observer reports the faintest star seen in the field. These are called <quote
>fainter thans</quote
> because the variable star was fainter than the brightness reported.</para
></listitem>

<listitem
><para
><firstterm
>Average</firstterm
>: This is a computed running average of all the data reported. The <firstterm
>bin</firstterm
> number tells the computer how many days to use in each average calculation. This will need to be adjusted based on the frequency of observations. The error bars represent the 1 sigma standard deviation of error.</para
></listitem>

<listitem
><para
><firstterm
>CCDV</firstterm
>: These are observations reported using a <abbrev
>CCD</abbrev
> with a Johnson <abbrev
>V</abbrev
> filter. <abbrev
>CCDV</abbrev
> observations tend to be more accurate than visual (but not always).</para
></listitem>

<listitem
><para
><firstterm
>CCDB</firstterm
>: <abbrev
>CCD</abbrev
> observations with a Johnson <abbrev
>B</abbrev
> filter.</para
></listitem>

<listitem
><para
><firstterm
>CCDI</firstterm
>: <abbrev
>CCD</abbrev
> observations with a Cousins <abbrev
>Ic</abbrev
> filter.</para
></listitem>

<listitem
><para
><firstterm
>CCDR</firstterm
>: <abbrev
>CCD</abbrev
> observations with a Cousins <abbrev
>R</abbrev
> filter.</para
></listitem>

<listitem
><para
><firstterm
>Discrepant Data</firstterm
>: This is data that has been flagged by an <abbrev
>AAVSO</abbrev
> staff member as being discrepant following <abbrev
>HQ</abbrev
> rules for data validation. Contact <email
>aavso@aavso.org</email
> for more information.</para
></listitem>

<listitem
><para
><firstterm
>Dates</firstterm
>: The observational database the light curves are based on is updated every 10 minutes so you can get data in near real-time. Right now light curve data is only available back to 1961, but this will likely be expanded further back in time in the future.</para
></listitem>

</itemizedlist>
</para>
</sect2>

<sect2 id="aavso-update">
<title
>Updating your local copy of Variable Stars</title>
<para
>The <abbrev
>AAVSO</abbrev
> publishes the <ulink url="http://www.aavso.org/valnam.txt"
>full list of variable stars</ulink
> in their monitoring program. This file is updated monthly with newly discovered variable stars. To sync the list that &kstars; uses with the <abbrev
>AAVSO</abbrev
> master list, click on the <guibutton
>Update List</guibutton
> button in the <abbrev
>AAVSO</abbrev
> dialogue. &kstars; will then attempt to connect to the <abbrev
>AAVSO</abbrev
> database and download the latest list. </para>
<note>
<para
>The customised data stream provided by the AAVSO was implemented for &kstars; by Aaron Price. Thank you, Aaron! </para>
</note>
</sect2>
</sect1>