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Alert Notice 502: EE Cep observations requested for upcoming eclipse

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July 9, 2014: The AAVSO requests observations for the upcoming eclipse of EE Cephei, a long-period eclipsing variable. EE Cep has a period of 2,050 days, and shows strong variations in the eclipse light curve from one event to the next. Observations are needed to study the morphology of the upcoming eclipse, which will be used to better understand the shape of the eclipsing disk and how it precesses. Mid-eclipse is predicted to be August 23, 2014, but the early stages of the eclipse may begin as much as a month earlier.

EE Cep is being observed by a number of amateur and professional astronomers using multiple telescopes at multiple wavelengths. Among these is a collaboration (see https://sites.google.com/site/eecep2014campaign/) headed by Cezary Galan at the Nicolaus Copernicus Astronomical Center in Poland; several individual AAVSO observers are already participating in this effort. The AAVSO is not currently a partner in that campaign, but all data submitted to the AAVSO will be publicly available. The AAVSO strongly encourages observers to begin following this star now, and to continue observations into October 2014 at least.

EE Cephei is a Be star - a B-type star with emission lines - eclipsed by an orbiting dusty disk that belongs to an unseen companion. The system has a long period of 5.6 years (2,050 days) and both the shape and depth of the eclipses are highly variable. Amplitudes vary from about 0.5 to 2.0 magnitudes, and eclipse shapes can be highly asymmetrical. This variation in eclipse shape is likely due to precession in the obscuring disk. Photometry of this object can be used to model the size, shape, and orbital properties of the disk. The EE Cep system is physically similar to epsilon Aurigae, but with much larger variation in eclipse profile from one event to the next.

EE Cep is V=10.8 out of eclipse, and may fade below 12.5 if the eclipse is deep. The total duration of the eclipse can be more than 60 days from first contact to last. Daily monitoring is suggested to track the eclipse light curve as finely as possible. We also encourage instrumental observers to transform their filtered observations to a standard system, and to observe in multiple filters if they are available.

Coordinates:  RA 22 09 22.75 , Dec +55 45 24.2 (J2000)

Finder charts for EE Cep with sequence may be created using the AAVSO Variable Star Plotter (VSP, http://www.aavso.org/vsp). The AAVSO photometry table for EE Cep includes the four comparison stars suggested by Galan et al. for their campaign: 104 (000-BCQ-031), 112 (000-BCQ-029), 113 (000-BCQ-036), and 119 (000-BCQ-040). We recommend using one or more of these stars for performing photometry, and we encourage observers to use the AAVSO comparison star magnitudes found in VSP for these stars; the AAVSO uses Cousins R and I magnitudes rather than the Johnson R and I given by Galan et al., so using the latter will result in an offset with AAVSO data. In either case, please clearly note your source for comparison star magnitudes in your report: specify either the AAVSO ChartID, or that you are using the magnitudes from the Galan campaign. Note that the 112 and 113 stars are both NSV stars, though evidence for variability in either star is weak (Piotr Wychudzki, EE Cep 2014 campaign, private communication). If you wish to limit your comparisons to the four suggested by the Galan et al. campaign, we suggest using the 104 and 119 instead of the 112 and 113 until the latter are definitively found to be non-variable.

Please promptly submit all observations to the AAVSO International Database via the WebObs feature of our website using the name "EE CEP".

This AAVSO Alert Notice was prepared by M. Templeton.

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