eclipse; light curve; photometry; spectroscopy; interferometry
September 2010 featured a variety of observations possible with epsilon Aurigae rising earlier, nightly. The star brightened slightly during the month, somewhat at variance with post-mid-eclipse expectations of fading. Among other key observations made during the month were:
A Hubble Space Telescope far-UV spectrum obtained with the Cosmic Origins Spectrograph, on 9/1/2010. The analysis will help confirm the identification of the central star inside the dark disk, claimed by Hoard, Howell and Stencel to be a hot, B5V star.
Robin Leadbeater reported that the strength of neutral potassium once again started increasing after a several month plateau around mid-eclipse.
Next, a second CHARA interferometric imaging run of the fall season at Mt. Wilson resulted in images on the mornings of Sept.23/24. These images are being compiled in the PhD dissertation of Brian Kloppenborg at the University of Denver.Read more
November 2010 will be remembered for the final phases of totality, with hints of 3rd contact beginning to appear.
During the course of the month and since mid-eclipse in August 2010, a 63 day periodicity in the visual light curve has become more noticeable, as noticed by Thomas Karlsson. Recent minima occurred in late Aug and early Nov, and recent maxima in early Oct and presumably in early Dec 2010.
The latest CHARA+MIRC observations were obtained in late Oct (poor observing conditions) and again in early Nov (better conditions). While the data reduction remains challenging, these images show a hint of elongation of light toward the egress end of the disk. Our next chance to confirm this is with scheduled time Dec. 9+10, 2010.Read more
As the year of total eclipse draws to a close, we are beginning to see hints of the end of eclipse, now only a matter of weeks away. OK, mid-March is 2+ months away, but have you noticed how the time flies by? So-called third contact is predicted for 19 March, when the light is anticipated to begin rising quickly. Previous eclipses have seen the time between third contact (end of totality) and fourth contact (end of eclipse) abbreviated to as little as 50-60 days, which would mean mid-May in this cycle. But these are merely predictions, and your continued observational effort will help tell the tale.
Since mid-eclipse in late July, a steady 60+ day light oscillation emerged, although the most recent observations suggest this has lengthened to ~80 days. Check out the visual data record to explore this.
December 2010 has been a busy month observationally, with the following large telescope observations obtained:Read more
this updated blog deals mainly with invited talks at the Seattle meeting in Jan. 2011, at the American Astronomical Society and commenting on the remaining weeks of eclipse. First, we report on a recent cyber-conversation between Edward Guinan (Prof. Astronomy, Villanova University) and Bradley Schaefer (Prof. Astronomy, Louisiana State University). Both have studied ancient star catalogs for years as part of their research into the lives of stars. Ed Guinan, in a 1990 conference paper reported the following records for visual estimates of epsilon Aurigae over time:
Era Visual mag. SourcesRead 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
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:
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.
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
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