O-C and period diagrams for 510 Miras

Science Long Period Variables
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DASCH, the project to digitize the collection of glass plates at the Harvard Observatory, have now come to end. With data release 7 is the southern galactic hemisphere now available. I have spent the last months to update my database of Mira maxima with the new data from DASCH. About 3500 new maxima was added and the total is now 74800 maxima for 510 Mira stars.

The database is available as O-C diagrams at http://var.saaf.se/mirainfooc.php or as period diagrams at http://var.saaf.se/mirainfoper.php

Some extra interesting stars that received new data are LX Cyg and DO Her. LX Cyg is a Mira well known for its large period increase from 1970-2005. Before that, it was assumed to have had a stable period. With the new data it appears that the star also had a previous period increase and from what I can see the period has varied approximately like this:
1890-1910; Plateau at 425 days
1910-1925: Increase from 425 to 460 days.
1925-1970: Slow increase from 460 to 470 days.
1970-2005: Rapid increase from 470 to 585 days.
2005-2024: Slight decrease from 585 to 580 days.

DO Her appears more and more like another Mira with a continuously decreasing period. From 1897 to now, the period has decreased from 222 to 210 days. In its behavior, it is very similar to WX Her. Both are short-period Miras with the same rate of decrease, 0.045 days/cycle. However, for DO Her, the data series is 26 years longer.

Thomas Karlsson

LXCyg

1 Like
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Amazing piece of work!!
Do you also have the bibliographic references for the period durations (as they do not appear in the tables for for periods).
I am new to astronomy…but I can only imagine that, combined with spectral analysis, this could provide interesting insights into stellar evolution.
-leo

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Leo, do you mean the table you get when you click on a period diagram? The date given there is the date for a maximum and the local period is the mean period from five maxima before and after the current maxima. If you look at the O-C diagrams and click on a diagram there, you get references to each maximum. Most of them (red dots) have I calculated myself from observations from AAVSO and other sources. Light blue dots are maxima published by AAVSO and dark blue dots are maxima published elsewhere.
I have used this database myself for looking for miras with continuous or abrupt period changes or miras with meandering periods.

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Thank you very-very much for your titanic work, Thomas! I would be glad to find in your database nice humped mira NSVS 2572317 from very heart of UMa, but I understand your strict limitations.