# Documentation

Find information, examples, FAQs and extensive descriptions of the data, curated by the survey teams.

#### Reference

A complete guide to using Data Central
May 20, 2020 by L. O'Shea
May 20, 2020, 5:30 a.m. J. Tocknell

## Finding Potential Binary Systems

A binary system is two stars that share the same point of gravity. To identify a binary system an object must be observed at least twice and if the radial velocity of the object is significantly different then it implies that the object could be a binary system. To determine if the difference of the radial velocities is significant the value must be greater than the allowed difference determined by the error.

Note: There could be a difference of only 0.01 but it is up to the user’s discretion for how much of a difference is needed.

Below is an example completed using data from RAVE, this produces data where the difference in radial velocities is greater than the allowed difference of the errors with no additional analysis.

The lines ‘WHERE t1.Obsdate < t2.Obsdate AND t1.Obsdate != t2.Obsdate’ are to ensure that the dates aren’t the same nor repeated.

SELECT
t1.Obsdate as t1_Obsdate,
t2.Obsdate as t2_Obsdate,
t1.RAVEID as t1_RAVEID,
t2.RAVEID as t2_RAVEID,
t1.HRV as t1_HRV,
t2.HRV as t2_HRV,
t1.eHRV as t1_eHRV,
t2.eHRV as t2_eHRV,
ABS(ABS(t1.HRV) - ABS(t2.HRV)) AS Difference_HRV,
(t1.eHRV + t2.eHRV) AS Difference_eHRV
FROM rave_dr5.RAVE as t1
INNER JOIN rave_dr5.RAVE as t2 on t2.RAVEID = t1.RAVEID
WHERE t1.Obsdate < t2.Obsdate
AND t1.Obsdate != t2.Obsdate
AND ABS(ABS(t1.HRV) - ABS(t2.HRV)) > (t1.eHRV + t2.eHRV)
May 20, 2020 by L. O'Shea
May 20, 2020, 5:30 a.m. J. Tocknell