Aaron Price

     aavso@aavso.org

# AAVSO Light Curves

The AAVSO Lightcurves Tool AAVSO Lightcurves

## Introduction

&kstars; can display light curves for variable stars from the observing program of the American Association of Variable Star Observers (AAVSO). 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 AAVSO database via the Internet, so a network connection is required to use this tool.

To use the tool, select a variable star either by designation 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 Retrieve Curve 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:

A Sample Lightcurve Sample Lightcurve

Please not these light curves should NEVER 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 AAVSO's strict quality control measures. We will be glad to give you good raw data simply by requesting it at http://www.aavso.org/adata/onlinedata/.

Specific questions about the data in the light curves can be sent to aavso@aavso.org.

## About Variable Stars

Variable stars are stars that change in brightness. A light curve 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.

## The Data

Here is a summary of the various types of data available in the light curves:

- Visual Observation: 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.

- Fainter than: 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 fainter thans because the variable star was fainter than the brightness reported.

- Average: This is a computed running average of all the data reported. The bin 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.

- CCDV: These are observations reported using a CCD with a Johnson V filter. CCDV observations tend to be more accurate than visual (but not always).

- CCDB: CCD observations with a Johnson B filter.

- CCDI: CCD observations with a Cousins Ic filter.

- CCDR: CCD observations with a Cousins R filter.

- Discrepant Data: This is data that has been flagged by an AAVSO staff member as being discrepant following HQ rules for data validation. Contact aavso@aavso.org for more information.

- Dates: 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.

## Updating your local copy of Variable Stars

The AAVSO publishes the full list of variable stars in their monitoring program. This file is updated monthly with newly discovered variable stars. To sync the list that &kstars; uses with the AAVSO master list, click on the Update List button in the AAVSO dialogue. &kstars; will then attempt to connect to the AAVSO database and download the latest list.

The customised data stream provided by the AAVSO was implemented for &kstars; by Aaron Price. Thank you, Aaron!