Mini-Observing Campaign on the Secondary Eclipse of Zeta Aurigae
Oh boy are we lucky! Not only is one star in Aurigae undergoing an eclipse this year, but two! The other star, Zeta Aurigae is a bright (V ~ 3.75 out of eclipse), northern eclipsing variable with a known period of 2.66 years. The system contains a hot, luminous B7V star and a more luminous K5II star. During primary eclipse (which occurred in March 2009), the blue B7V star is obscured by the larger orange K5II star. The secondary eclipse is more difficult to detect, because the B7V star obscures a small portion of the K5II star's light. The approximate date of the eclipse is November 17, 2009, with an anticipated duration of about 40 days. The K5II star is known to exhibit variations of 0.05 magnitude, therefore high precision photometry is necessary for this short campaign.
The anticipated eclipse depth is very shallow, perhaps 0.1 mag, and is not well characterized. Given this information, obtaining visual estimates of the system may prove to be difficult, and obtaining good photometry of the eclipse may be a challenge. Therefore I request that Experienced observers, both photometric and visual contribute observations of the eclipse during the remainder of the month of November and the first few weeks of December. Inexperienced observers are encouraged to add Zeta Aurigae to the list of 10-star tutorial target objects and submit their data as detailed in the 10-star tutorial in order to hone their observing skills.
Visual observers may find this particular star difficult to observe due to the anticipated slight change in magnitude. Please observe the star two or three times per week, using the charts available via. VSP or from the AAVSO website.
Instrumental observers of all kinds are also requested to take part. Photoelectric observers belonging to the AAVSO PEP-V program may submit data as usual via. the WebObs feature of the Blue&Gold section of the AAVSO website.
Wide-field CCD and DSLR systems are also encouraged to participate. Zet Aur is a reasonably bright target object and care must be taken to ensure to not saturate. We recommend taking a large number (10-100) of very short exposures (< 2 seconds) and stacking the resulting images so that the variable may be observed without saturation, and the faint in-field comparison stars may be easily observed.
It is requested that a few observers also submit their raw, uncalibrated data to the Citizen Sky project for use as training data for a photometric reduction workshop at the upcoming Citizen Sky conference in September. Please contact Brian Kloppenborg (U. of Denver, bkloppenborg on Citizen Sky) or Aaron Price (AAVSO) if you are interested in contributing your data to this project.
It is suggested that observers use lambda Aurigae as the comparison star and eta Aurigae as the check star during these observations.
The following is a summary of the most recent observation of zeta Aurigae submitted to the AAVSO database:
ZET AUR 2455144.2813 NOV 08.7813 3.4 Vis. SDAV 3.1 SPA N
ZETA AUR 2455113.4167 OCT 08.9167 3.1 Vis. BL SDAV 3.1 SPA N
The J2000 equatorial coordinates of zeta, lambda, and eta Aurigae and their corresponding magnitudes (uncertainties shown in square brackets) are as follows:
05 02 28.6869 +41 04 33.015
B 4.927 [~], V 3.769 [~] , J 1.154 [0.218] , H 0.358 [0.166]
05 19 08.4745 +40 05 56.586
B 5.34 [~], V 4.70 [~], R 4.3 [~], I 4.0 [~], J 3.397 [0.260], H 3.154 [0.204]
05 06 30.8928 +41 14 04.108
U 2.33 [~], B 3.012 [~], V 3.158 [~], J 3.611 [0.262], H 3.761 [0.238]
I will continue to add campaign updates will be posted to this forum as the eclipse progresses. It'll be short, but well worth observing.