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Extending lightcurves backwards

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BBI
BBI's picture
Extending lightcurves backwards

It's interesting to have long light curves because long-term changes can become visible. It's one of the strengths of us visual observers: We have time on our side (in contrast to professionals).

It's not only possible to extend the light curves by observing now. There is lots of historic data available. You only have to find them (http://adsabs.harvard.edu/abstract_service.html) and digitize them (retyping or using OCR). I found some old observations by Tebbutt, digitized them, and Sara Beck from the AAVSO was so kind to add them to the database. The result is a light curve extended backwards with more than 10 years.

Digitizing old data: it's fun, kind of addictive and useful, so just give it a try :-) !

WGR
WGR's picture
Mine Making

Hello

We have all heard about data mining.   But what your are doing is making the mine.  Pretty cool.  I know others have helped put data into the database, but I don't remember anyone showing the extension--a blast from the past.

Gary

SFS
Digitizing old data

Have you considered also working on the Eggen card project?

ThomasK
ThomasK's picture
Very nice. I have updated the

Very nice. I have updated the O-C diagram for R Car with your new old data at http://var.astronet.se/mirainfooc2.php. Your data cover the 7 red dots between maximum -110 to -99.

Red dots are maxima computed by me from the original observations, light blue dots are maxima published by AAVSO and dark blue dots are maxima published in other sources.

Previous has Kevin Paxson done an enormous work on digitize old observation and have contributed with many red dots in the O-C diagrams.

Thomas Karlsson

BBI
BBI's picture
@SFS: No, there is so much to

@SFS: No, there is so much to do (dgitizing, VSX, zapping, observing, ...) and as always, too little time...

@ThomasK: Nice!! Some O-C diagrams look very different compared to the others (e.g. W Dra, R Aql). Is there an (evolutionary) explanation?

ThomasK
ThomasK's picture
W Dra and R Aql together with

W Dra and R Aql together with R Hya, T UMi, R Cen, LX Cyg, BH Cru and Z Tau are the 8 mira stars that were identified by Templeton, Mattei an Willson (http://iopscience.iop.org/article/10.1086/431740/pdf) as the mira stars with the largest secular changes in their periods. A thermal pulse from a helium shell flash have been suggested as a possible course of the change of some of these stars.

I wrote an article for JAAVSO (https://www.aavso.org/media/jaavso/3039.pdf) were I did an analysis of the mira stars, except the 8 above, in my database of maxima to see if any other long term effects cold be seen. It turned out that about 60% of the stars now have an increasing period over their observed history, and that fraction seems to increase over the years. The mean period over the last 75 years have also increased by 0.15 days for the 362 miras that were included in my investigation.

Thomas Karlsson

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