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g Herculis

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g Herculis is a bright semiregular variable of the SRb subclass that exhibits a number of interesting features in its light curve.  Although a period of 89.2 days is the one noted in VSX, there's also a much more prominent variation of a half magnitude or more with a period over 800 days.  Along with both are a number of low amplitude grumblings with timescales of 10 days.  Although the full range of variation is under 1.5 magnitudes, there's a lot going on!  g Her has long been a target of the AAVSO, with a visual light curve extending to the early 20th century.  It's also been a target for a cutting edge research program -- ground-based optical interferometry to image the surface of the star.  Observations by Sam Ragland and collaborators could find no discernable  asymmetries in their interferometric observations, in line with what was observed in other semiregular variables.  (It was the Miras that showed the most prominent asymmetries.) It is perhaps unsurprising given the smaller amplitudes seen in semiregulars; smaller amplitudes might correspond to smaller temperature or brightness variations across the surface of the star, or might indicate that what asymmetries there are are smaller than what can be resolved with the current generation of photometers.  Interestingly, Ragland and collaborators worked with the AAVSO to obtain phasing for all of their targets using visual data; your observations played a part in interpreting these exciting observations, and likely will in the future as well!

g Her is a bright variable around magnitude 5, and is well within range of nearly all observers.  We hope you can help keep this light curve growing well into the 21st century!

For more information visit: http://adsabs.harvard.edu/abs/2006ApJ...652..650R
Prepared By: Matthew Templeton
AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484