Disks and things

Paddling has been wearing me out. We have practice every day for about an hour and half. On Thursday and Friday last week we paddled 4.5 and 3.5 miles respectively and now we’ve gotten into to doing half mile sprints. I have gotten to the point where whileI’m not horribly sore the next day which is really satisfying it still takes a lot out of me. Our regatta is this Sunday and then that’s the end of it. It’s been a ton of fun be out on the bay every day but I’m looking forward to be back to normal energy levels.

I spoke with Bernadette again on Monday. I updated her on the papers I have been reading and the conversation I had with Vladimir. She was particularly interested in the Grinin paper that proposed the binarity of RR Tau. I need to email her the reference so she can take a look at it. I have a few questions on that paper and it would be good if she can answer them.

For most of our conversation we talked about what kind of data I want to get focusing on what wavelength region I should be interested in. In her 2002 paper Bernadette detected about 15 features over a large wavelength range. We decided we wanted to focus on a smaller wavelength range, and thus less features, so we can get higher resolution data. My job is to play with the Integration Time Calculator and decide the observing parameters: the best grating, wavelength range, etc…Then I’m going to write the proposal for time despite the fact that it doesn’t need to be submitted until August when RR Tau finally comes back up. I’ve never written a proposal before so it seems best to start as soon as possible so I can get feedback and make sure everything is correct so when it’s time of submission I can do it immediately.

Bernadette sent me a research statement she wrote a few years back about some high resolution spectra of RR Tau she obtained but never published.

Two Fe II lines overlaid in velocity space.

In the statement Bernadette reiterates the key point made in her 2002 paper, that the spectral signature of RR Tau changes with continuum variations. When the star is at its brightest there are strong metallic absorption lines and at its dimmest there are faint metal emission lines that are associated with the stellar photosphere and an optically-thin disk atmosphere respectively. Understanding this is completely tied to understanding the nature of the obscuring material. What is it made of? How does it move? Evolve? What is it’s structure?

The general outline of discerning the fundamentals of the obscuring material is to use the characteristics of the light curve with spectral information to constrain models which has been fairly rudimentary. I think it will be a real step up to use narrow band filters along with spectroscopy. Also, depending on the resolution we’re able to obtain we might be able to resolve the disk in greater detail than what has been previously managed.


There haven’t been any updates lately since I’ve been busy and tired with paddling. I’ve been reading a lot of fun papers and had another conversation with Bernadette but I haven’t felt up to writing about them. But here is a picture of the boat we paddle in, it’s very cool.

Sprinted a mile today in this. Picture by Joe.

First Steps in Monitoring RR Tau

When I’m busy my life becomes a positive feedback loop as I do more things not only my ability but my desire to do those things increases. I’ve been busy these last couple of weeks with my normal work coming to an end. There is some sense of urgency to get as much done before I’m done. But also, getting my RR Tau project off the ground while maintaining this site as documentation.

AND I just joined a novice outrigger canoe racing team with Petra and Joe. We have a race in two weeks with practice every day. Holy cow is it fun though.

Conversely, the opposite also tends to be true. When I have nothing to do it’s very easy for me slip into a hole of naps and cake making/eating. I had last Friday off because it was Good and I managed to surprise myself in how much I was able to get done. Most of it consisted of a nice back-and-forth between Vladimir and me.

I mentioned in my previous post Bernadette and I were curious if MMO had been monitoring RR Tau since the paper was published last fall so I emailed Vladimir to ask. He responded saying that they stopped monitoring RR Tau, they’ve moved on to white dwarfs and binary systems, but that he would be willing to continue monitoring the star if I had a solid, new idea that would warrant the effort. He also expressed doubts on my ability to get time on Gemini.

It was good to have someone question the merits of the project because I really needed to think of the best way to justify it. Vladimir seemed to be coming around to the idea but he was right in pointing out that this cannot just be a monitoring project. There has to be an underlying astrophysical idea that guides the project. I’ve got the beginnings of that with my focus on the [O I] line and trying to associate that with the long term variability but I want to go much deeper. I really need to read more papers that go into the physics of dust and gas evolution in stellar environments so I can get a better idea of what direction I should look in.

I’ve also started to look into the process of applying for time on Gemini. I downloaded the application package and started going through it but I can’t actually apply for anything until RR Tau is above the horizon which isn’t until late August.


I’m always eager for March to end. March is like the Wednesday of the academic year, it’s the middle of the winter holidays and the end of the spring semester. I still feel this way despite not being in school this year. I didn’t take a vacation during Christmas and New Year’s but my Gemini job ends April 30th and I have a blissfully empty summer schedule before I start my last year of school in the fall.

There are many things that I’m excited about this April. The second season of Game of Thrones, it’s no longer March, less than two months now until Joe and I leave Hawaii and go home. But mostly, I’m thrilled about starting to work on my senior thesis. I’m going back to Bennington for my final year after spending a year at UMass so I feel like I need to start early so I have a solid foundation for when I get back.

There is a new full time astronomy and physics professor at Bennington this year, Hugh, who will be my thesis advisor. I haven’t met him but we’ve emailed about the project that I’m interested in. It doesn’t have anything to do with his work which he’s fine with this as long as I can find an expert in the field who is willing to act as a second advisor.

Working at Gemini has been amazing in this regard. I have met so many people who are doing such awesome things in their field. I met Bernadette, who works in the south, at the Hilo Burger Joint during after-soccer drinks while she was visiting Hilo for a few days a couple months ago. Bernadette was the first author of the paper on RR Tau that we at Maria Mitchell based many of our assumptions on for the spectral monitoring program for UXors. 

Of course I had to talk to her. We had actually met the previous year at the AAS meeting in Seattle and she remembered me and my poster. She thought it was good! Over our beers and burgers I told her I wanted to expand on the results of the paper for my senior work, she said that she had high resolution Keck spectra of RR Tau that she never published and the first steps toward collaboration were made.

I sent her my paper the next day and just this week we finally got around to talking again. She’s back in Chile so we polycom’d and it was all very fancy. It ended up being a wonderfully productive conversation, I came in with an idea of what I want to do for my thesis and Bernadette was very helpful in pointing out papers and authors I should look into.

Instead of making you read my paper I’ll summarize it. UXors are a subclass of T Tauri stars. They experience pronounced and non periodic dimming in continuum light. Their mechanism of variability has been disputed for decades now. UXors have had a lot of photometric monitoring done on them but they have not been studied spectroscopically nearly as much. One of the advantages that Bernadette’s project is that she had spectroscopy.

While I was working at Maria Mitchell Observatory Vladimir, the director, developed a method of extracting the H-Alpha line from continuum, my role was to help the development and employment. The method involves two narrowband interference filters: one that is centered at the H-Alpha line and the other that sits in the continuum but overlaps with the H-Alpha lineInterference Filter Set-Up and basically subtracting the flux of the continuum filter from the H-Alpha filter. This meant that we could look at the temporal changes of the H-Alpha emission line and compare it to the evolution of continuum over time.

The insight that this led us to is that while the H-Alpha lives a life separate from continuum on short term time scales they correlate on long time scales (~100 days). This means that there is possibly a second mechanism of variability that has different effects than what causes the short term.

The green dotted lines show long term correlation between light curves.

So, what I want to do for my senior thesis is explore that second mechanism of variability. In Bernadette’s paper she and her co authors claim that the H-Alpha line is not correlated to photometric variability but they didn’t know about what was happening on longer time scales since they were just using spectra.

They also claim that the [O I] forbidden line is not affected by the changes in continuum but I feel that conclusion, like that of H-Alpha, suffers from not knowing about the second driver of variability. I want to see if I can associate the [O I] line with the long term variations. This would be significant because [O I] is indicative of stellar winds. If [O I] relates to long term continuum changes than that might mean that some wind is kicking up dust or the like and obscuring the star.

Bernadette and I talked about applying for telescope time through Gemini’s Poor Weather program. RR Tau is bright enough that we could get good spectra even when RR Tau is at a minimum and Poor Weather is an undersubscribed program so I’m likely to get time on the sky. I also want to email Vladimir about what he’s doing with RR Tau and UXors since I left.

I need to do a review of the literature before Bernadette and I talk again on April 9