What does it mean? Part 2
Dr. Bob and I are taking turns explaining the implications of the recent Nature paper. In the first post, Dr. Bob discussed two very important questions: "How big?" and How massive?" In this post, I'm going to cover another big-picture topic: the orientation of the disk.
I'll start with what we thought happened. Most of the literature drew the disk as something that more-or-less bisected the F-star, following Kemp's 1986 drawing (note, a similar drawing was also published in the 1985 epsilon Aurigae conference proceedings):
We now know that this picture was very, very close to being correct. Considering that the parameters in the paper (see pg. L13 of Kemp's work above) all scale to the radius of the F-star, Kemp et. al. did a good job of estimating the parameters for the disk just from polarimetric data and modelling! The only large change is the point of first contact which was assumed to be in the northern hemisphere. Instead, it is clearly in the southern hemisphere.
A big question, and a good team project, might be to investigate whether or not Kemp's polarization data is consistent with the current findings. If it isn't, this could mean the disk or orbit has precessed significantly in the 27 year since the last eclipse! (if you are interested in doing this, please contact me).
For those of you who do not have access to Nature, I have extracted a few parameters in the table below (these are rounded, the parameters in the paper are more precise):
|Disk Radius*||3.8 AU|
|Disk Thickness**||0.76 AU|
|Central Opening (?)||0.5 AU?|
|Disk Inclination**||85 +/- 5 or 95 +/- 5 degrees|
|Disk Tilt**||< 20 degrees|
|Orbital Inclination (?)||88 +/- 2|
* From "Infrared images of the transiting disk in the ε Aurigae system" by Kloppenborg et. al. 2010 April, Nature
** From "Taming the Invisible Monster: System Parameter Constraints for Epsilon Aurigae from the Far-Ultraviolet to the Mid-Infrared" by Hoard et. al. 2010 ApJ.
(?) Unknown parameter, this is a best-guess.
Try out these values in the new light curve generator and see how close you can get the light curve to match with previously observed values! Do the parameters work? If not, what do you think is wrong? Do we have the entire picture or is there more to discover?