Dr.Bob's blog posts

     Now that the eclipse of 2009-2011 has ended, we can begin to reflect on the discoveries and realizations made possible by the new data.  To see where we are going, let's reflect on some more of the story leading up to the present.Read more

As 2011 dwindles down to a close, so does any spectroscopic evidence for the eclipse.  Photometrically, the star returned to its 'normal' out of eclipse variations during late summer, featuring +/- 0.05 mag quasi-periodic fluctuations.

It's been a trail of discovery during 2009-2011, and study of the results will go on for years, but during the next few months, reviewing and updating early statements and claims seems appropriate.

Epsilon Aurigae has fascinated astronomers for parts of three centuries -- so far. The NASA Astrophysical Database Service keeps track of publications related to stars like this one. For the period prior to 1930, 23 papers are on record; for 1930-1960, 54 papers appeared, for 1961-1990 there were 200 papers, reflecting the explosion of interest surrounding the 1983 eclipse (with 173 of those during 1981-1990); more recently (1991-2011) there have been many dozens of papers, thus far.Read more

Greetings.  Winter is nigh, and epsilon Aurigae is fast becoming part of the evening sky, making observing easy - except for the cold conditions.
While the photometric eclipse ended this summer, there remain spectroscopic traces of material from the disk still between us and the F star.  These remnants can be seen in the H-alpha and sodium D lines, as well as in the neutral potassium line far in the red.
Large telescope observations are continuing, and so should your visual and photometric reports.  Remote and robotic observations during November include:
CHARA+MIRC interferometric imaging (Nov.2nd);
MIRAC4 mid-IR spectroscopy (Nov.5th)
Spitzer IRAC near-IR photometry (Nov.17th)
IRTF/SpeX near-IR spectroscopy (Nov.27th)
and more in December.
In the coming weeks, I'll detail some of the recent findings, but you can read results of SpeX data newly published in the Astronomical Journal, at weblink:Read more

Robin Leadbeater, Three Hills Observatory in northern Britain, has assembled a master list of quite a few spectra obtained during the epsilon Aurigae campaign, many with direct access available.  For details see:
http://www.threehillsobservatory.co.uk/epsaur_spectra.htm
We are encouraging Robin and all the contributors to work up summaries of their results for the JAAVSO special issue on epsilon Aurigae, scheduled for early next year.
Meanwhile, do have a look at zeta Aur eclipsing during November - see Brian's blog entry and my comment thereupon.

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

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

Greetings.  Barely a month from solar conjunction again (early June) and epsilon Aurigae is sinking into the sunset.  At the same time, the star has 'taken a breather' - after rising in brightness by 0.5 mag (up nearly 60% in energy terms), the star stalled at V~3.3 during April.  A similar still-stand was seen during the 1984 eclipse egress as well, suggesting some persistent opacity around the trailing side of the disk.  No clear spectroscopic signatures reported so far, but stay tuned.
Nonetheless, the egress is predicted to end during May, and as many will put the star up on the shelf for another 27 years, some of us will continue to observe and work on data reduction.  We encourage everyone in Citizen Sky to continue in one or both modes for at least the balance of the year.
A variety of major telescope observations have been obtained recently as well, including the following:Read more

Well folks, the end is near: third contact arguably arrived 2 weeks earlier than predicted - sometime during late Feb, early March**.  We've seen a rise from V ~ 3.75 then, to V ~3.55 last night according to several observers.  At this rate, ~50 milli-mag per week (0.050 mag/week), we will climb to out of eclipse level, V ~ 3.0, during April and May.
**Caution: there is a chance, albeit small, that we are being fooled by one of those out of eclipse variations that can add/subtract up to 0.1 mag to brigthness trends, so careful watch is still needed.Read more

Observers are reporting a slight increase in brightness during these final 2 weeks until PREDICTED "third contact" (March 19, 2011) - signaling the end of total phase of this long, long eclipse. 
When two spherical stars of unequal size eclipse, there is a moment when one star is inside but in tangential contact - like the end of a total lunar eclipse, when the moon emerges from the darker part (umbra) of the earth's shadow.  We can this moment the Third Contact - see attached figure.  
However, epsilon Aurigae differs from the classical model in at least 2 respects:
1. the two "stars" aren't simple spheres - the eclipser is an elongated disk, and,
2. egress seems to happen twice as fast as ingress.Read more