Epsilon Aurigae

Although we won't be able to confirm until later, that mid-eclipse occurred as predicted during the end of July - beginning of August, all the evidence strongly suggests it's so. 

• Despite solar conjunction at the start of summer, photometric monitoring continued, but little evidence for Mid-Eclipse Brightening has been produced thus far.  In fact, a first minimum during totality was reached near RJD 55250 (V ~ 3.8), then slowly rising toward mid-eclipse values close to V ~ 3.6Read more

How the time flies.  Seems like yesterday (actually 2005) when the first observing proposals* for monitoring epsilon Aurigae were being submitted - and suddenly we have arrived at predicted mid-eclipse.  According to Jeff Hopkins, who has made a study of the light curves, he expected mid-eclipse to occur August 4th, 2010 = JD 2,455,413.

The light curve shows no strong evidence for "mid-eclipse brightening" thus far.  Now that epsilon Aurigae is getting well separated from the sun, airmass corrections are less a problem, so more accurate photometry is possible.  From Mt.Evans this week, we had an exceptional morning for J& H band work, very good signal to noise, but found the brightness was close to that reported during spring 2010 - well into totality.Read more

...or not. 
We are entering into a very special 2 month interval centered on predicted mid-eclipse, 4 August 2010 (JD 2,455,413 +/- 2 weeks).  Some expect a "mid-eclipse brightening" - as much as several tenths of a magnitude - which would demonstrate a substantial central clearing in the dark disk. 

Based on what we know from the initial round of interferometric imaging, the disk is so close to edge on, that seeing the "hole in the doughnut" is improbable.  However, there are some clues that surprises may await the persistent observer:

- the B star at the center of the disk is a significant source of ultraviolet photons, capable of vaporizing dust, possibly enlarging the central opening;Read more

Despite a spring blizzard, we made it to our 28 inch f/21 RC telescope at Mt.Evans Observatory in Colorado (14,148 ft elev) and visually inspected epsilon, zeta and eta at low airmass mid-day Tues 6/15/2010.  Brian K and I agreed that eps and zeta were of comparable brightness, after several iterations.  I think eps is slightly fainter than zeta when color differences are taken into account, but that gets subjective under bright sky conditions.  Thus, we report no indication that epsilon Aur is brighter than zeta Aur at this time.  Hence, no evidence for mid-eclipse brightening at this time, but further reports to follow.

With mid-eclipse forecast for early August 2010 and mid-eclipse brightening supposedly lasting +/- 30 to 45 days around that point, we should either begin to see evidence for it soon, or redefine the mid-eclipse light curve.

Greetings from the University of Denver's Meyer-Womble observatory perched atop Mt. Evans, CO.  As Dr. Bob mentioned in his previous blog post, we're preparing the observatory for yet another summer season, this time focusing on daytime observing of epsilon Aurigae.
 
If you are not familure with our observatory, it is located at the 14,128 ft (4,306 meters) level, just past the end of the highest paved highway in the United States, the Mt. Evans highway. This road winds around peaks, skirts along 1,000 - 2,000 ft. drop offs, and is often impassable during the winter months. The observatory is so remote that the closest power pole is nearly 10 miles away as the crow flies, therefore we have a solar power system that generates 1.5 kW of electricity under ideal conditions. Read more

This weekend marks both the 66th anniversary of D-Day, and the annual closest approach of the Sun to epsilon Aurigae - a scant 28 degree separation.  If you've been attempting observations from anywhere in the northern hemisphere, you've seen how low the star is after sunset and how bright the lingering twilight has remained.

A fine screenshot shared by Thierry Garrel is appended, showing the cumulative effect over the past days, of the increasing twilight (scattering solar spectrum photons) on attempts to acquire spectrum of epsilon Aurigae (in this case, near the H-alpha line).  Despite this, he and Robin Leadbeater appears to be able to extract consistent data (see image two).  My thanks to these stalwart observers for sharing their findings.Read more

Given that few ancient Greek or Roman astronomers are around today to help us with correct pronunciation, I'm happy to report a little gem has surface, published in 1942 by Adler Planetarium, that might help settle matters.  The pamphlet is called Report of a committee of the American Astronomical Society on Preferred Spellings and Pronunciations - see attached.  Therein, the Latin genitive (possessive) for constellation Auriga = Aurigae and is marked "o - ri - jee" - as in the concatenation of ORIon and GEE, O-RI-GEE.  However, unless you meet an ancient Greek or Roman, we'll probably know to what you refer, no matter your preferred pronunciation.

During the past week, careful observers have been struggling with the low horizon angle presented by epsilon Aurigae and its friends, due to approaching solar conjunction in early June.  Despite this, credible reports are being received that epsilon Aurigae may be as much as 0.1 mag brighter than it was during early May.  If you have a clear NW horizon and patience, try finding The Kids below Capella after sunset, and see if you can provide a brightness estimate during these challenging weeks of late spring.Read more

If you've tried to observe epsilon Aurigae lately, it is quickly sinking into the northwest at dusk, along with Orion and other winter constellations.  The star is at solar conjunction during early June, making observations more challenging over the coming several months.  To stretch the game analogy, it's essentially half-time - in terms off the eclipse schedule.  Naturally, this is just when the fabled mid-eclipse brightening is forecast to happen, suggestive of a central clearing in the midst of the dark disk.  Given the developments of the past months and the coming half-time show, it seems timely to review what's been learned, and outline some of the outstanding questions that further observations can help address. 

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Eyjafjallajokull may sound like a word lifted from Finnegans Wake (a novel by James Joyce), but the Icelandic volcano has grabbed worldwide attention by producing a dense ash cloud that threatens jet aviation over much of northern Europe again this week.  In this third blog exploration of the implication of direct detection of the disk in epsilon Aurigae, via interferometric imaging, I want to explore with you how terrestrial volcanic ash provides some analogies with the dusty material that scientists believe make up "debris disks" seen around a surprising percentage of normal stars. Read more