Photometry

I spent the entire day Friday reading papers. I can already imagine your groans of disapproval for such an exciting blog post idea, but in reality reading papers is a critical portion of research. Sometimes the papers you read really help you with your research, and other times they smash your hopes of making a new contribution. It's this horrible aspect that happened today and I thought I would spend a few minutes discussing where one can go from here.

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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

...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

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

Observers are beginning to report a sea change.  Totality is upon us and the center of the dark turbulent disk is just about to make its presence felt atop the beacon of light that is the F star in epsilon Aurigae.

Photometrically, bumps and wiggles have persisted, a mix of out of eclipse variations and the stately progression of the eclipse itself.

Spectroscopically, the enhanced absorption of shell lines has been waxing and waning as though disk substructure is coming increasingly into view.  What we've been seeing is the "morning side" of the disk - the portion that has been facing cold space and is just starting to rotate toward the hot glare of the F star (7750K). As soon as we reduce this week's IRTF spectra, we'll share any info about changes detected in the near-infrared.Read more

I decided to postpone my discussion of IRTF for one more day to announce something even cooler!  The DSLR Documentation and Reduction team has released their first set of tutorials for general use. These tutorials walk you through how you can use your DSLR camera (or any other camera that can take RAW files) to do high-precision photometry, acheiving results of 0.01 or 0.001 mag precision!Read more

It's December 8th evening, Julian Date (J.D.) 2,455,175 and we are only a few days from predicted time of Second Contact when total eclipse starts.

The words "1st, 2nd, 3rd, 4th contact" refer to moments when objects in eclipsing systems overlap partially and totally.  Consider a small circle crossing in front of a bigger circle: first, just the outsides touch (1st contact); then the small circle just gets fully inside the larger (2nd contact); later, the smaller circle begins to exit from inside the larger circle (3rd contact), and at the end, the circles stop touching at their edges, before separating (4th contact).Read more

Brian is leading a mini-campaign on zeta Aurigae. It is undergoing a short eclipse (compared to epsilon Aurigae) with a dip of only 0.1 mag sometime this month. Thus it will be quite a feat for even advanced observers. Up to the challenge?

Observers are reporting visual magnitude approaching 3.4, which is half-way between the out of eclipse average, close to 3.0, and the anticipated magnitude during totality, 3.8.  Hopkins and Santangelo have begun to converge on JD 2,455,065 (+/- a few days) as the likely time of first contact (start of eclipse).  Today being JD 2,455,127 (23 Oct), that was 62 days ago.   At this rate, we'll bottom out in totality by JD 2,455,189 or slightly sooner - close to winter solstice.  Jeff Hopkins predicts 2,455,183 for visual, and earlier in photometrically bluer wavelengths.Read more

Like the autumn leaves, light from epsilon Aurigae is dropping fast.  I've been using a simple digital camera and recorded a fade to V ~ 3.35 this weekend (10/3/09).  If you have been watching the show week to week, epsilon is clearly fainter than eta now, and on its way to being no brighter than zeta in a matter of week, if all keeps to schedule.

As Aurigae is rising by 10pm local time, you no longer need to catch it during pre-dawn hours to see the eclipse happening before your eyes.  Catch those clear, cool nights of autumn and enjoy the spectacle!Read more