Epsilon Aurigae

About a month ago I wrote a post discussing what I'm doing with some astrometric data from the Sproul Observatory. This week I'm happy to report I have the paper almost entirely written and am working out the last few kinks in the analysis. It's been a serious uphill battle in both learning about astrometry and reducing the data, but I think it's been worth it.

In this post I'm going to talk a little more about the data and how it is reduced. In the prior post I mentioned that the data was taken on photographic plates starting in 1938 and ending in the early 1980s. I only have a small subset of the entire set from Sproul (about 40% actually) which is enough to show the effect I was looking for, but not much more.Read more

Photometric observer Richard Miles reported a V band magnitude of 3.02 for epsilon Aurigae this past week, which essentially matches the pre-eclipse average and signals the end of optical eclipse (4th contact).  The long march through eclipse is over.  However, we still need your observations for at least the balance of this year in order to more precisely define 4th contact after-the-fact, and to characterize the magnitude of out of eclipse variations (~0.1 mag in V).   Information on the latter will be helpful in comparison with planned post-eclipse observations with both the CHARA Array MIRC imager (with exciting new 6 telescope mode) and the IRTF SpeX infrared instrument.

What do we learn from the fine light curves now collected?
Step one: timing of events in the light curves.
Step two: analysis of "fine structure" present in the light curves.

Step one: Read more

Dr. Elizabeth Griffin, an esteemed astronomer at the Herzberg Institute of Astrophysics, recently contributed a forum post about her analysis of hundreds of spectra from the 1956 and 1983 eclipses.

The following bio for Dr. Griffin is from this abstract to a talk about data security she gave in Maerch, 2011:Read more

It's not that often that I put up two blog posts in the same day, but I couldn't wait for this one.  In the past I've had trouble answering the question of "what has astronomy done for me" or "how can pure research benefit the economy."  

Well, today I have a clear example of how something from astronomy is helping a different field which, in turn, helps people:

Adaptive optics technology reveals eye's cellular structure with unprecedented detail

In the article they describe how AO, used to stabilize astronomical images from being blurred by Earth's atmosphere, has now been used to image a living retina.  This could, in turn, lead to earlier diagnosis of eye diseases earlier and save people's eyesight!Read more

Back in January 2011 Eric Jensen of Swarthmore College, home of the Sproul Observatory, provided me with three stacks of papers from the late Dr. Peter Van de Kamp. These pages contained raw and processed astrometric data on epsilon Aur which. As you might recall, my initial post on this topic explained that there is a strong disagreement between the orbits implied by the Van de Kamp orbital solution and the more recent interferometric data from CHARA.

 Read more

The next few days mark the closest approach of the Sun to epsilon Aurigae, as part of the annual solar motion.  This also makes observations rather difficult, given the lingering twilight and the high airmasses involved.  At last report, epsilon appeared to be between 3.2 and 3.3 mag, visual.  This is behind schedule, relative to predictions based on prior eclipse light curves - epsilon Aurigae was predicted to have reached full brightness, mag 3.0, by mid-May 2011.  The evidence suggests that this portion of the disk may be less transparent than the corresponding ingress portion of the disk.Read more

More than one thousand professional astronomers will be meeting in Boston to compare notes on a wide variety of astronomy and astrophysics at the spring meeting of the American Astronomical Society, jointly held with AAVSO.  On the varied agenda will be 4 posters and at least 2 talks about the status of epsilon Aurigae eclipse studies and Citizen Sky support of these activities.  I plan to summarize what the campaign effort has meant for professionals and amateurs, as well as report on the discovery of high temperature helium absorption in infrared spectra during mid-eclipse.  Naomi Pequette has applied powerful disk modelling software to epsilon Aur data and concludes that a fair amount of accretion must be occuring.  Brian Kloppenborg will report on progress toward improving the orbital solution for epsilon Aurigae, by combining astrometric, spectroscopic and interferometric data.  Brian will also be reporting on how Citizen Sky teamwork has fared, and ARead more

Back in February I posted an image showing the outline of the disk:

but after talking with Aaron about his recent visit to Tufts, I realized that I didn't actually explain what was in the image.  So I thought I would take a moment and put up a different graphic:

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This semester the Tufts University introduction to astronomy class observed epsilon Aurigae as their course lab. The class has around 250 students and they do not have access to equipment for a formal lab. So epsilon Aurigae was perfect since it is bright enough to be seen from campus with the unaided eye and happens to be emerging from the eclipse. They were tasked to observe once every two weeks and report their data to Citizen Sky.

(about light curves)

The above light curve includes all Citizen Sky data since February 1, 2011. The blue line is the 7 day mean curve based on data only from Tufts students. The red line is the 7d mean for visual observation from non-Tufts Citizen Sky participants and the green line is for photometric observations from Citizen Sky participants.Read more