3/23/2010-- As reported by Hoard, Howell and Stencel...
(2010 to appear in the Astrophysical Journal), data have become available that span a wide spectral range, from the far-ultraviolet, through the visible range and out into the far-infrared. Because of calibration efforts, it has proven possible to combine these well calibrated data into a complete and self-consistent picture of the sources of light in epsilon Aurigae. Key to understanding this result is that interlocking requirements of distance and other constraints on F star diameter drive us to these self-consistent conclusions.
The full paper is available, free, at website:
How the data is reduced.
In short, we use a program developed specifically for reducing spectra from SPEX called SPEXTOOL. It is written in a commonly used programming language for Astronomers called IDL. I'm going to skip over a lot of the details, but in SPEXTOOL there are basically two steps:
- Construct Calibration Frames (for wavelength calibration, flat-field subtraction).
- Extract the spectral orders.
Bounce during totality: have you noticed that epsilon is a bit brighter this month compared to last? Totality is with us, but the Out of Eclipse variations continue. We anticipate a significant brightening starting next month as the central opening in the disk begins crossing in front of the F star...
It's been a pleasure to attend the 5 year science review meeting of the CHARA collaboration (http://www.chara.gsu.edu/CHARA/ ) an amazing group that runs the interferometer atop Mt. Wilson, CA. This 300 meter baseline telescope is capable of delivering milli-arcsecond imaging that has made the details of the epsilon Aur eclipse much more obvious, as has been reported in recent popular articles in Sky & Telescope, Astronomy and Astronomy Now. Read more
(Update: The updated CDROM is now ready.) Donna Young, the Science Olympiad astronomy event coordinator, has completed a Teacher's Guide for the Citizen Sky project which will be on the next version of the Science Olympiad coach's CDROM. Next year's CD will be available in late summer or fall, but we have place the teacher's guide online right now. You can download it here.Read more
As I have mentioned before, the instrument we used at IRTF is called SPEX. It is a medium resolution spectrograph. Specifically, it's a cross-dispersing spectrograph. What does this mean? Well, instead of dispersing light like a prism where the colors are all in one line, SPEX breaks the spectrally dispersed light into several orders that are displayed along side each other. I've included a copy of a figure I made for a previous presentation that includes SPEX data in LXD1.9 mode to give you an idea about the dispersion:
Picking up where I left off, in this blog post I will cover two topics: how we prepare for an observing session and how we conduct the observations.
How we prepare for an observing session.
The answer is short: meetings. Lots and lots of meetings. As part of our proposal we already specified our primary target (eps Aur) and verified that the instrument is capable of observing the star. We also specified at least one A0V star to use as a calibration star for telluric (atmospheric) line removal. In our final meetings, we double-check exposure times, calibration stars, and coordinates. During this time we finalize our observing plan by deciding the order in which we will observe the stars on our list and insert flats, darks, and arcs (all required for calibration) so that we can maximize our observing time.Read more
We have a guest blog article from a coauthor of a recent paper published about epsilon Aurigae. The author describes the system overall for new participants, then describes what they discovered with their radial velocity data. 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
Before I entered graduate school, I had no idea about the complexity of research proposals, especially those in astronomy/astrophysics.
All telescope time for which I have applied has been peer reviewed. This means that my proposal is read by fellow astronomers/astrophysicists and evaluated against some scoring method. It is my responsibility, as the proposer, to convince the committee that not only is my research interesting, but also doable from a technical perspective.
The basic outline of the proposal process is thus:Read more