Period search service

Please enter the lightcurve file name and period search parameters:
Lightcurve file:
Maximal trial period: days
Minimal trial period: days
Maximal phase shift:

If uploading a raw ASAS-SN .csv lightcurve

and both V and g-band data are present in the file
 shift g-band data to match V zero-point
 use V-band data only
 use g-band data only.

Note that ASAS-SN .csv lightcurves are already heliocentric-corrected.

Information needed for the Heliocentric correction:

Apply the Heliocentric correction and convert all dates to Terrestrial Time (TT)? Yes /No
TT = TAI + 32.184 = UTC + (number of leap seconds) + 32.184
Input time system (see also)? JD(UTC) /JD(TT)
Sky position (R.A. Dec., J2000):
(The correct sky position is needed only if you want to apply the Heliocentric correction.)

Auxiliary settings

Phase range for plots:  -0.5 to 1.0    0.0 to 2.0    0.0 to 1.0

The lightcurve should be a simple ASCII file in the "JD mag", "JD mag mag_err", or VaST format. The Catalina Surveys and the ASAS-SN .csv files are also supported. The lightcurve may contain comment lines. Note, that (unless the Catalina Surveys .csv file is supplied) the program expects time to be expressed as a full JD, not MJD. If MJD (or any other form of truncated JD) is used in the lightcurve file, the labeling of plots will be incorrect. Also, the Heliocentric correction cannot be applied to such lightcurves. Example lightcurves may be found here, here, and here (links to data files are at the bottom of these pages). Two period search methods are currently implemented. One is based on Lafler & Kinman (1965, ApJS, 11, 216) paper. You may find a simplier explanation of this method in Russian here. The other is Deeming (1975, Ap&SS, 36, 137) Discrete Fourier Transform (DFT) method (see also the discussion in this paper).

If you are using the Safari browser, ensure that you access this page via HTTPS (rather than unencrypted HTTP). Otherwise, Safari will repeatedly display annoying warnings about data being sent through an unencrypted channel every time the results page needs to be reloaded.

For long computations you may need to change the timeout settings of your web browser. In Firefox it can be done by typing "about:config" in the address bar and then filtering on "timeout". The paerameters you need to change are probably called network.http.connection-timeout and network.http.response.timeout

Note that the results page link is not permanent - the results will be deletead after a few hours. The reason is that the periodogram files may get quite large if the frequency steps are small. Please promptly download to your local computer all the results you may want to re-use.

This period search service is also available at the mirror sites: Mirror 1, Mirror 2, Mirror 3, Mirror 4.
You may find the source code of this service at GitHub (the old versions are available here) and install the period search service at your own web server. This program is free software provided under the terms of the GNU General Public License.

If you have questions, bug reports or suggestions how to improve this service, please fell free to contact the author (Kirill Sokolovsky) via e-mail: kirx[at]

A similar web-based period search service supporting a different set of algorithms is provided by the NASA Exoplanet Archive (legacy interface).

Notbale offline tools for period search: WinEF (Windows) by V. Goranskij, Period04 (Java) by P. Lenz and M. Breger.