EE Cep observations requested for upcoming eclipse

PTS

AAVSO Alert Notice 502

July 9, 2014

EE Cep observations requested for upcoming eclipse

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

EE Cep is being observed by a number of amateur andprofessional 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 inPoland; several individual AAVSO observers are already participating in thiseffort. The AAVSO is not currently a partner in that campaign, but all datasubmitted to the AAVSO will be publicly available. The AAVSO stronglyencourages observers to begin following this star now, and to continueobservations into October 2014 at least.

EE Cephei is a Be star - a B-type star with emissionlines - 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 anddepth of the eclipses are highly variable.

Amplitudes vary from about 0.5 to 2.0 magnitudes, andeclipse shapes can be highly asymmetrical. This variation in eclipse shape islikely due to precession in the obscuring disk. Photometry of this object canbe used to model the size, shape, and orbital properties of the disk. The EECep system is physically similar to epsilon Aurigae, but with much largervariation in eclipse profile from one event to the next.

EE Cep is V=10.8 out of eclipse, and may fade below 12.5if the eclipse is deep. The total duration of the eclipse can be more than

60 days from first contact to last. Daily monitoring issuggested to track the eclipse light curve as finely as possible. We alsoencourage instrumental observers to transform their filtered observations to astandard system, and to observe in multiple filters if they are available.

Coordinates:  RA 2209 22.75 , Dec +55 45 24.2 (J2000)

Finder charts for EE Cep with sequence may be createdusing the AAVSO Variable Star Plotter (VSP, http://www.aavso.org/vsp).The AAVSO photometry table for EE Cep includes the four comparison starssuggested 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 ofthese stars for performing photometry, and we encourage observers to use theAAVSO comparison star magnitudes found in VSP for these stars; the AAVSO usesCousins R and I magnitudes rather than the Johnson  R and I given by Galan et al., so using thelatter will result in an offset with AAVSO data. In either case, please clearlynote your source for comparison star magnitudes in your report: specify eitherthe AAVSO ChartID, or that you are using the magnitudes from the Galancampaign. Note that the 112 and 113 stars are both NSV stars, though evidencefor variability in either star is weak (Piotr Wychudzki, EE Cep 2014 campaign,private communication). If you wish to limit your comparisons to the foursuggested by the Galan et al. campaign, we suggest using the 104 and 119instead of the 112 and 113 until the latter are definitively found to benon-variable.

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

This AAVSO Alert Notice was prepared by M. Templeton.