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Alert Notice 336: CCD campaign to observe 1059+23 AH Leo

April 4, 2006

Subject: CCD CAMPAIGN TO OBSERVE 1059+23 AH LEO

Coordinates: 11:05:05.30 +23:21:08.0 (2000.0)

AAVSO Council member Dr. Pamela Gay, Harvard University, has requested our assistance in observing the RR Lyrae variable star AH Leo closely this spring and early summer. She is studying the Blazhko cycle and other periodicities in this star, and precise, well time-sampled observations are essential.

Here is an excerpt from Dr. Gay's /vsots_archive//vsots_archive presentation on AH Leo:

"AH Leo rises from and falls back to a minimum magnitude of about V = 14.35 every 0.466 day and the period is slowly evolving. Roughly every 25 days AH Leo's Blazhko cycle repeats itself, causing the star's amplitude to vary from deltaV = 0.5 to 1.2 magnitudes. To understand the star's every rise and fall, we need to observe each of these two cycles in detail. Perhaps most importantly, by covering the Blazhko cycle for multiple consecutive cycles we can say with certainty what repeats (or fails to repeat) when, and identify any additional, previously unknown, longer periodicities.

"While observations of RR Lyrae stars often focus on the ascending branch and maximum light, we ask that observers please obtain images of the star during all phases so that Fourier analysis can be used to fit the star's light curve. This method works best when the entire curve is well sampled. We are also very interested in any bumps that may appear during the descending branch of the light curve, and changes in the shape of the light curve during minimum light."

V-band CCD observations are preferred, but filtered observations in all optical bands are welcome. Please observe AH Leo as much as you can until the end of its observing season in June, and submit your observations to the AAVSO using the appropriate CCD upload tool.

An AAVSO chart for AH Leo will be posted to the following URL: http://www.aavso.org/cgi-bin/searchcharts3.pl?name=ah%20leo   [obsolete link; create charts using AAVSO Variable Star Plotter at http://www.aavso.org/vsp  ]

Report observations to the AAVSO as: 1059+23 AH LEO

This campaign is being coordinated by E. Waagen (eowaagen@aavso.org).

Many thanks for your valuable astronomical contributions and your efforts.

Good observing!

Elizabeth O. Waagen
Senior Technical Assistant

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