A sample radial light curve from the DDO Binary Star Program,
which has now resolved the orbits of 50 systems
(abscissa is phase, ordinate is velocity in km/s).
Volume 32, Number 3
October 2001
by Christopher Tycner
Is is hard to believe that a new school year has already started. This also means that there are a lot of changes in our department and as always, we will try to keep track of all of them. Once again, we have succeeded in introducing to all of you the new graduate students in our department. We all want them to feel welcome and we also want them to understand that they are now part of a larger community that some of us call home, or workplace, or school.
I would also like to remind everyone that The Doings are written by
us, the people at the Department of Astronomy and Astrophysics, as
well as the David Dunlap Observatory, and for us. Thus remember that
the Doings are what you make it to be! If you are reading this issue
now, the only natural conclusion is that you enjoy reading it, and
that we can expect your contribution soon.
by Slavek Rucinski
The binary star program at the DDO has passed the point of 50 radial-velocity orbits.
Since the middle of 1999, the DDO 1.88m telescope has been used to obtain radial velocity curves for close binary stars. The survey is conducted for several reasons. (1) The Hipparcos satellite discovered many new eclipsing systems even among bright stars; down to the completeness limit of about V=7.5, 40% of all short-period (<1 day) binaries are new Hipparcos discoveries. (2) So far, no systematic survey of radial-velocity orbits has been conducted even among the bright stars. (3) The literature is full of light-curve solutions which frequently have problems with determination of the astrophysically crucial parameter of the mass-ratio (it is quite common that such solutions give entirely wrong results) whereas, for spectroscopic observations, this is the most securely determined parameter. Last, but not least, (4) for systems with known parallaxes, we have a chance of fully describing the systems in absolute terms by combining light curve, radial velocity and parallax information.
Although - even quite recently - one radial velocity orbit would be worth one published paper, from the outset a decision was made to publish 10 orbits per paper. This seemed to be a reasonable compromise between the literature clutter and the number of publishable orbits per year. The survey started with bright, short-period binaries, with the orbital periods below 1 day. The current setup (0.2A/pix or about 11 km/s/pix, the Cassegrain spectrograph with the grating of 1800 lines/mm) permits observations down to about V=11 and gives accuracy in velocity amplitudes better than about 1-2 km/s. The high precision and freedom of systematic effects in radial velocity measurements is to a large extent due to a new approach of the "broadening functions (BF)". This formalism has been developed in place of the commonly used cross-correlation function (CCF). While the CCFs are easy to use and very popular, they give wrong answers when spectral lines are broad and heavily blended. In addition, with our very high rate of discovery of triple systems (about 30%), we wanted to have a tool to determine accurate velocities of all components. The attached figure shows a few examples of the BFs for triple systems. One can see the wide signatures of rapidly rotating and revolving close binaries, with the third components giving strong, narrow slowly-rotating star peaks. In such cases the CCFs have been giving entirely wrong results, frequently having problems even with distinguishing components. (The author is ready to keep on convincing you that you should abandon using CCFs for radial velocity determinations!).
So far, we have published five papers in the Astronomical Journal (see the five figures), but - already - the next 10 orbits wait to be described in the sixth paper. Most objects are contact binaries (they are very common among stars, about 1/100 ordinary dwarfs!). Among them we found real gems (and a bit of embarrassment to theoreticians): V753 Mon with the mass-ratio q=0.970 +/- 0.003, the largest currently known (the contact binaries are supposed to avoid q=1 and indeed such are very rare) and SX Crv with q=0.066 +/- 0.002, which is not only another record beater, but also a serious problem for theoreticians because, at about q=0.09, the tidal instability is expected to convert contact systems into single rapidly-rotating stars.
The program is successful because of the contribution of several committed individuals. While the undersigned have written all the papers and have done a lot of reductions (using his "baby", the BF method), the contribution of Wen Lu should be particularly emphasised, especially in the initial stages of the project. Wen unfortunately left the DDO for NASA a few months ago, but he assured me that this was not because of this project. The other committed participants of the project have been Stefan Mochnacki and Chris Capobianco and the two observers from Cracow, Poland, Waldek Ogloza and Greg Stachowski. Our excellent Telescope Operators, Jim Thomson and Heide DeBond, also contributed to the project by obtaining many service observations. Many observations have been also obtained by Mel Blake, Anita Chung and Chun Du.
The project, if limited only to the orbital periods shorter than
one day and with the current CCD, can continue through another 50-60
orbits. The new CCD will permit to go deeper by another magnitude or
so. While this would mean a 4-fold increase in objects, we would
probably concentrate only on the most interesting which are more
representative for the faintest population. At present, with the
current magnitude-limited sample, we already tend to observe the
intrinsically brightest objects in the solar neighbourhood.
The other meeting was a workshop on Observational Studies of Pulsating B and A Stars, held at Vrije Universiteit in Brussels. This is a much younger university, and its "fortress-style" architecture is very much in line with 1960's buildings on U. of T.'s three campuses. John presented a paper on "Autocorrelation Analysis of Hipparcos Photometry of Short-Period B and A Stars", incorporating project work by students Katrina Au-Yong, Geoffrey Gilmour-Taylor, JoAnne Hosick, Heather Kincaide, Ceci Pang, and Joe Wilson.
(My kids had my hair too; they've never forgiven me. - Ed.)
To celebrate his retirement, Bob decided on some activities that are usually not possible in September because of all the pressures of classes. So, in early September, he attended the Toronto International Film Festival for the first time and saw 35 films in 8 days. He also went on a solo canoe trip to Algonquin Park for the last week in September - the peak of the Autumn colors. Seems like a good way to celebrate. Now, he says, "it will be a delight to get back to work on research without the usual interruptions."
There's not much news to report since the summer is a quiet time of year. With the start of the academic year, we have five new students joining us. Although they have already made themselves comfortable and gotten down to work, we will nevertheless have a welcoming party for them at the end of September. Wayne Barkhouse will be around the department this year as an instructor, and Chris Burns has begun his first year teaching at Swarthmore College in Pennsylvania. Mike Gladders is on his way to Carnegie this fall.
Spirits have been subdued by the shock of the September 11th attacks in the US, although as far as I know none of us lost close family or friends. The second and third-hand accounts we've heard from witnesses are quite disturbing, though, and the uncertainty of everything from flying to an observing run to the state of geopolitics keeps us from being able to forget for too long. Our sympathies are with all those affected by the attacks and the aftermath.
-Rosemary McNaughton
GASA President
p.s. don't forget to start preparing your submissions for this
year's shadow department newsletter...the David Dunlap Droppings. The
"Friend" of the "Editor" will be announced in October.
LUKE CHAMANDY
Originally
from Montreal, I did a BSc in Astrophysics at Queen's. I actually
graduated not last spring, but a year before. Coming from Quebec, I
had only been at Queen's 3 years, one year less than most students,
and wanting to garner the full Kingston/Queen's experience (yeah
right!), and not being sure what I wanted to do with my life, I
enrolled to do a minor in philosophy. During that year, I decided not
to go into astrophysics because I thought I should do something that
actually made a difference, among other reasons. So basically I'm not
sure why I'm here, or even how I got here, but I'm really glad I made
this decision, and I've really enjoyed the time I've spent working
here the past two months. Currently, I'm doing research on the early
stages of neutron stars with Chris Thompson, and I'm enrolled in the
new direct entry PhD program.
BRIAN LEE
My
undergraduate degree in Physics and Astronomy comes from the
University of Victoria. While my place of birth is Vancouver, B.C.,
I've lived almost my entire life in Victoria, B.C. The interaction
between UVic and the Herzberg Institute of Astrophysics yielded a
topic for my undergraduate project research, optics design for a
multi-conjugate adaptive optics testbed, and I hope to continue to
dabble in instrumentation research over the years. However, my main
research interest is the area of solar system formation and evolution,
and for the immediate future, I want to participate in the search for
and characterization of extrasolar planets. To that end, I will be
pursuing my degree under the supervision of Howard Yee. Outside the
office, you are likely to find me either with my nose in a book
(almost any book will do), listening to a classical music station on
the radio, or practicing cooking and baking. I must fatten myself in
preparation for the unfamiliar winter cold!
JOHN LISKA
I obtained
my undergraduate degree from the University of Toronto in the
Astronomy and Physics specialist programme. I have worked on a variety
of different research projects ranging from the study of variable
stars to a QSO survey. I am still undecided on my MSc topic but I am
currently leaning towards gravitational lensing.
PREETHI NAIR
I'm
Preethi. I will be starting my PhD in astronomy this year at U of T
though at present I am still looking for a supervisor. I did my B.Sc
in Physics from the University of Delhi and my masters also in Physics
at IIT (Indian Institute of Technology) Delhi. I worked on applied
optics and holography during my masters. My interest in astronomy was
sparked of by some very good physics teachers and a project which I
had taken at IIA Bangalore. As for my other interests I love food (as
anyone who knows me will be able to tell you). I am a bit obsessive on
board games, especially Scrabble! The one thing that I want to do most
is jump out of a plane...with a parachute of course!
HEATHER CAMERON
When I was younger
I built my own equipment
For science projects.
To study physics
I went to Acadia
From Wolfville, I am.
In the summer time
I worked at D-R-A-O
To study the Sun.
In my free moments
My feet move with a "tap tap"
My background is dance.
In Massey I dwell
One of the four "Astroteers"
Among diverse fields.
Here at U of T
I will do my PhD
In astronomy.
(It looks like the next Tea Poet has arrived. Finally! - Ed.)
by Chris Burns
After reading Mike Gladders' article in the last Doings, I thought I would follow suit and talk a bit about my dive into the "real world", though I decided to go the teaching route rather than the research route (at least for now). Now that I've settled in here at Swarthmore College and gotten to know the faculty on a more personal level, I took the opportunity to ask each of them what aspects of my application made me a good candidate for the position. I figured this would help me in my next round of job applications and interviews. Their answer was universal: I had the most teaching experience.
I was very surprised by this. Surely, the other candidates who had previously taught classes at the undergraduate level would have had more teaching experience than someone fresh out of graduate school! Indeed, after digging a bit more, some of the faculty here admitted that they had not considered my teaching assistantship at Scarborough "real teaching" at first. It was apparently a hotly debated issue during the candidate review meetings. To some, a "teaching assistant" at a large university was synonymous with "grader" or, at best, someone who helped students one-on-one during drop-in sessions. They wanted someone who could lecture effectively to their small classes as well as design problem sets and exams which test the course material.
Letters of support from Charles Dyer and Jim Thompson (Chair of Physical Sciences at Scarborough) made a strong case that teaching assistants at Scarborough were more than graders. That was enough to bring me in for an interview where they had me teach a freshman class. To be honest, I remember very little of those two days, but I guess they liked what they saw because 3 days later, the call came. In the end, they decided I had the equivalent of 5 years of teaching experience.
Nevertheless, I was scared out of my mind in the few days leading up to my first lecture. I was receiving emails addressed to "Professor Burns" from eager students which only served to underline my new responsibilities. I was suffering from the "Imposter Syndrome" now more than I ever had in graduate school. The day finally came and I met my students for the first time. The first thing that hit me was how small the class was: 30 students, which is smaller than a typical tutorial in ASTA03. But by the time I had finished introducing myself, it felt as if everything had fallen into place. Five years of conducting tutorials in front of 30-40 students really pays off and I hadn't realized how much until I was in this situation. Presenting material and getting students to participate had become second nature. In fact, Swarthmore students are so eager to participate that it almost seemed too easy at times.
Of course, there are things which a teaching assistantship won't
teach you. Planning, organizing and having ultimate responsibility
for the course is completely new and is something I will have to get
used to. Nonetheless, conducting tutorials at Scarborough allowed me
to develop a teaching style and provided me with the necessary
experience to launch my career as an educator. So for those of you
thinking of pursuing a more teaching-oriented job, conducting
tutorials is an excellent way to gain experience and get a leg up on
the competition. And for those of you who have already had the
opportunity to teach in tutorials (or equivalent), make sure you
emphasize the teaching aspect in your CVs and get a supporting letter
from the course supervisor. Don't just write down "Teaching
Assistant" or you might be mistaken for a "grader."
By Christopher Tycner
Another Superb Michelson Summer School!
Those who had a chance to read my last year's travel log would know how excited I was to have the opportunity to attend a summer school, held last year in Berkeley, on optical interferometry (see Vol 31, issue #2 of The Doings). Since the last year's summer school was a part of an annual summer school series, naturally I had to apply again. With a bit of luck, I have been accepted again (thank you NASA and JPL).
This year's summer school was held at the Lowell Observatory in Flagstaff, Arizona. The main purpose of the summer school was to teach young scientists (like me) the practical skills needed to use these instruments for scientific work. I do not mean the skills a telescope operator or more appropriately, an interferometer operator is required to possess, since such skills will be different from one instrument to another. I am talking about the general skills one needs to acquire to use such instruments scientifically. Skills related to setting up a successful observing run, understanding the technical limitations of the instrument(s), such us, magnitude limits, sky coverage, exposure times, reduction techniques and interpretations. I do not think it is appropriate for me to write here what I have learned, since that will not interest most of you, but I do want to tell you that the summer school has done an incredible job, on what it was aiming for.
Here are some general details of how the summer school has accomplished its goals and I personally think more summer schools should follow in its footsteps, whenever it is possible, and appropriate of course.
The school was five days long and it started on the first day with a general introduction to both the school itself, and the science that was covered on subsequent days. Half of the day was also used for guided tours of the interferometric facilities nearby, at the Navy Prototype Optical Interferometer (NPOI). The second, third, and fourth day had the same general structure, but they concentrated on different astrophysical topics and interferometers. The three astrophysical themes were, angular measurements of variable stars like Miras, synthesis imaging of stellar systems like Wolf Rayet stars, and on the third day the interferometric studies of binary systems were discussed. The above topics were also discussed in the context of different interferometers, thus they did not concentrate solely on NPOI.
What made this summer school so incredible was the practical component present in each of the three days. Each day started with a morning session on the astrophysical introduction to one of the subjects listed above, including the scientific motivation behind the study. Then the theory behind the apparatus was presented which was followed with a practical session, where every person attending the summer school had a chance to use one of the laptops that were provided by the organizers, and software package provided by the presenting team, to apply the new ideas they have learned in a semi-controlled environment. The format of the software packages ranged from an online type tutorials to fully functional reduction packages used in real scientific projects. There was time to make mistakes, ask for help and get things right. Personally, I learn much, much more in such an environment than in a simple lecture style format. The afternoon session were structured in a very similar manner. The summer school concluded on the fifth day with a summary of what we have learned and with more examples of current research being conducted on optical interferometers such as NPOI.
I have returned from the summer school with a much different view
on what I would now consider a superb summer school. I only hope that
other summer schools can do the same, whenever such a format would
enhance the student learning. And as always, I recommend to any
graduate student to go and attend summer schools that relate to his or
hers line of study.
by Michael Allen
Evening tours of the DDO were very successful this year. Between April 28 and Sept 29 we attracted exactly 2100 visitors, which is 50% of capacity. Thanks and congratulations are due to the tour guides. Also, thanks to our two volunteers, Mel Blake from York, and Rob Chan, who is in grade 10 this year. Lastly, I publicly thanked members of the RASC for their participation during their meeting in October, and do so again here - the presence of RASC people and telescopes really enhances the tours.
The month-by-month breakdown is as follows:
| Month | Visitors | % of Capacity |
|---|---|---|
| Apr/May | 245 | 27% |
| June | 266 | 44% |
| July | 560 | 47% |
| August | 596 | 66% |
| September | 433 | 82% |
| Total | 2100 | 50% |
The tours benefitted from (1) the completion of the Hillsview Drive construction project, (2) a very wide distribution of promotional material, and (3) word of mouth. In the later months, especially September, there were a number of group reservations that filled up each and every week, so that on some weeks we were forced to turn people away. Also, the mini-drought at the end of the summer brought many clear nights (as Jim and Heide will tell you!); a weekly breakdown clearly shows that more people come out when the weather is good. Of course, the excellent presentations by our grad students and post-docs helped sustain the word of mouth campaign.
Those of you connected with the tours know that there is room for improvement. In the next few weeks I will be re-writing (NOT a mere revision) the tour guide manual. I encourage you to send in suggestions (or demands?).
The above chart excludes Thursday morning tours for schools, which run from Sept to April. These tours are usually fully booked, and an individual school can bring anywhere from 10 to 70 people.
There are two more programs which bring people to DDO. One is the Fall Lecture Series, which this year will run in November and which has attracted about 20 people. And lastly, people occasionally come for filming. This summer alone has seen a commercial production of "Ace Lightning and the Carnival of Doom" (BBC/Alliance-Atlantis), plus documentary-style programs from Shaw TV, SPACE The Imagination Station, and CBC Sportsworld.
All in all, the public keeps us pretty busy, and we're happy to
have it this way.
The following list of papers is not necessarily comprehensive. For others, refer to:
Barkhouse, W. A.;West, M. J.;Bothun, G. D. . Globular cluster population of Hickson compact group 22a and 90c. July 26, 2001. Preprint No. 2001-0007
Kerton, C. R.;Martin, P. G. A fast technique for the creation of large scale high-resolution IRAS (HIRES) beam-matched images. May 02, 2001. Preprint No. 2001-0006
Lee, S.-W. NGC 5775: anatomy of a disk-halo interface. August 20, 2001. Preprint No. 2001-0008
