AAVSO Alert Notice 410:
Request for additional epsilon Aurigae observations
October 29, 2009

Dr. Robert Stencel (Denver U.) requests enhanced coverage of the bright, long-period eclipsing binary star epsilon Aurigae through Wednesday. Observations are requested beginning immediately (October 29, 2009; JD 2455134) and continuing through November 5, 2009 (JD 2455141). This request is in conjunction with scheduled observations with the CHARA optical interferometer at Mount Wilson in California. Optical photometry by a number of observers will provide a continuous photometric baseline of epsilon Aurigae during the course of the interferometry, enabling Stencel and collaborators to more easily interpret the interferometric images.

These interferometric observations are being made to image the system as it enters eclipse; the optical interferometric observations being made by CHARA are completely analogous to those made with radio interferometers like the Very Large Array, and allow ground based observers to obtain images with far higher resolution than a single optical telescope is capable of. The CHARA observations are scheduled for the nights of November 1, 2, and 3 (through mid-day UT on November 4, 2009). All observations, including visual estimates, DSLR and CCD photometry, and photoelectric photometry, are encouraged.

The observations are part of a larger, long-term collaborative effort to study epsilon Aurigae. For more information on epsilon Aurigae, see the Citizen Sky website:
http://www.citizensky.org/

Epsilon Aurigae is currently in the ingress phase of the eclipse, which likely began in August of 2009. The star is now near V ~ 3.4 and declining. The nature of the eclipsing object is not known, but is likely to be an opaque disk surrounding an unseen, massive secondary star or binary pair. Interferometric images of epsilon Aurigae may yield strong constraints on the shape of the eclipsing disk and size of the system.

Epsilon Aurigae is located at the following (J2000) coordinates:
RA: 05:01:58.134, Dec: +43:49:23.91

Up-to-date charts of epsilon Aurigae may be generated via VSP:
http://www.aavso.org/observing/charts/vsp/index.html?pickname=eps%20Aur

A chart specifically for photoelectric and wide-field DSLR observers is available at this URL:
http://www.aavso.org/images2/eps-aur-pep.png

For more background on the history of epsilon Aurigae see the January 2008 Variable Star of the Season article:
http://www.aavso.org/vstar/vsots/eps_aur.shtml

For more information on the Citizen Sky project please visit:
http://www.citizensky.org

This AAVSO Alert Notice was prepared by M. Templeton.

SUBMIT OBSERVATIONS TO THE AAVSO

Information on submitting observations to the AAVSO may be found at:

http://www.aavso.org/observing/submit/

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