PDM Light Curve Explorer

Load Object CDS Light Curve Filters Search Period Analysis Settings How-To

PDM Tutorial

FAQ

Overview

Photometric Surveys Support

Looking up an Object

Photometry Upload

CDS Data Aggregation

Light Curve Components Explorer

Merging Observation Data

Trying a fixed-value Period

Searching a Period (PDM)

Applying Filters to the Data

Light Curve Evolution Research *

Light Curve Fitting *

Light Curve Auto Positioning *

Saving Results

* - experimental

Light Curve Auto Positioning *

For more details on how to match extremums analytically, please read the Fitting Extremums section.

For a given period value - considering the fitting curve is found - it is possible to automatically determine moments of the minimum and the maximum. As the calculated curve's initial position not necessarily perfectly aligned, we may use these knowledge to perform an automatic phased curve alignment to whatever phase value. Being able to make such an useful operation just by a single click, an user can reduce the amount of searching the epoch's value time significantly. Sure, for variable stars the interest here is primarily an ability to put the extremum to the beginning of a cycle.

This approach has been tested a lot to confirm its preciseness by calculating Epoch's value and comparing with the epoch for a known variable star. And it does. For example, for a "good quality curve", it is very easy to verify the following: take known Epoch and the calculated one using the service, get an absolute difference between those moments and divide by the period value. Ideally, you should get a whole number (literally is the number of whole cycles passed between those moments). For the tested data, the was a quality better than 0.01 fraction of a cycle for over 5000 cycles between the two given moments of the primary extremum for a variable star. Obviously, the result highly depends on the fitted curve's quality, but the approach works by its nature. For most cases, this is fairly applicable.