Researching Magnetic Activity Cycles in Spotted Stars

By: Craig Cissel, Michael Preston, Ross Silver, Dr. Milingo

Our work this summer with Dr. Milingo has been filled with many exciting and educational experiences. I will break down our summer into three parts: data analysis, the observing run in Arizona, and community outreach.

Data analysis:

Our research goal was to find rotation periods and long-term activity cycle periods of selected stars in the cluster NGC 6811. We can determine this by using the image analysis program MIRA to perform photometry on our stars. We were looking for variations in brightness caused by spots on the star. The spots are an indication of magnetic activity in the star. We can use many years of data to see how the spots change and determine what the star’s activity cycle is.

NGC 6811

Figure 1: Our star cluster, NGC 6811.

In our day to day work, we mostly did image reduction and analysis using 5 years of images of NGC 6811 taken from the National Undergraduate Research Observatory (NURO). We extracted the difference in instrumental magnitude between our target star and a check star, whose brightness does not vary, and constructed light curves to determine the rotational periods. Then we put the data into a period finding routine to find our long-term activity cycle periods.

Observing at NURO:

NURO is located in Flagstaff, AZ. The NURO consortium consists of ~12 institutions and provides hands-on research opportunities specifically for undergraduates. The NURO telescope is the 0.8m which is part of Lowell Observatory. Our observing run was probably the highlight of our summer. We left on June 21st and came back on the 29th. When we landed in Phoenix at 10 am MST, it was a chilly 105º F. We then took the scenic route up to Flagstaff through Sedona. A few days later we went back to Sedona for lunch. It is one of the most beautiful places I have ever seen.

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Figure 2: Two pictures of the scenery in Sedona, AZ.

            But this trip was not just for sight-seeing, we had work to do. We had 5 nights at the 0.8m telescope. Our work nights consisted of us showing up to the observatory around 6:45 pm, about an hour before sunset. We would open up the dome and take special images called flats and biases that we would later use to calibrate our NGC 6811 images. At the end of twilight, we would finish our focus routine and start taking images. We needed to refocus the telescope every hour due to the changes in temperature. While observing there is plenty of down time; we had many ways to entertain ourselves, including: binging Netflix, reading, watching anime, playing cards against humanity, or going outside to sit on a lounge chair and admire the night sky. We could see the sky so clearly because Flagstaff is the world’s first international dark sky city, http://www.flagstaffdarkskies.org/international-dark-sky-city/ . We continued until about 4 am because that’s when astronomical twilight started. Then we finished up with our shut down procedures. We would get home and go to sleep around 5 am. Then we could sleep until about 1 or 2 in the afternoon and relax or go out into town and explore before it was time to go to work again.

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Figure 3: The top pictures shows the dome that holds the 31” telescope. The bottom picture is our lab group standing to the right of the telescope.

Our trip was filled with a lot of delicious food. We went to In N’ Out and Smashburger for burgers and milkshakes, Salsa Brava for tacos, and our celebratory dinner was at Texas Roadhouse for steaks. We hiked in Oak Creek Canyon which provided us with even more beautiful scenery. On our last full day of the trip, we went to see the Grand Canyon. We took a lot of pictures, but they could never fully capture the essence of the place.

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Figure 4: The top shows our hike in Oak Creek Canyon. The bottom shows our lab group standing at the south rim of the Grand Canyon.

Community Outreach:

We spent part of our summer at the Gettysburg College Observatory, located on the northwest corner of campus. The 16” telescope is designed for use as a research-grade instrument for faculty and student projects, but the observatory is also used for public education and outreach. We held two open houses this summer: one during alumni weekend and one for the XSIG students. To prepare for an open house, we would come up with a list of objects that would be visible that night to show our guests and we studied the night sky so we could point out constellations and objects of interest. Unfortunately, there was about 80% cloud cover for the XSIG open house, which taught us to get used to clouds as we have no control over the weather. On cloudy nights, we bring our guests into the observatory and give them a tour of the classroom, the warm room, and the dome. We spent time learning about the history of the observatory and how the telescope and computers work so that we can teach the people how everything functions. These nights are always fun no matter what weather we have and we hope that we can do this more frequently during the school year.

We also created an astrominute for the community. An astrominute is a one-minute summary of what will be visible in the night sky that month in a certain part of the world and is aired on the radio. We wrote the script, recorded it, and layered it in Garageband. Thank you to Mark Drew, the advisor of the college radio station WZBT, who aired it on the radio and thanks to Ian Clarke, the director of the Hatter Planetarium, for assisting us with the music.

We started another project in the observatory that we hope to conclude this semester. Our 16” telescope does not have an eyepiece; the light goes directly into a CCD camera because it is used for research projects. It is difficult to pack a lot of people into our tiny warm room to show them what the telescope is pointing at, so we installed a large terminal screen out in the classroom that is connected to our 3” telescope that was previously used as an autoguider. An autoguider is a device on the telescope that tracks a bright star in the direction of our image and makes small adjustments to keep the star centered in the frame. The telescope then mimics these movements to prevent the image from drifting during a prolonged exposure. But our new CCD comes with a built in autoguider, so we can use the small 3” telescope to make it much easier for people to see what our telescope is looking at while in operation.

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Figure 5: Our group going to Wine and Spirits to get beverages to entertain our alumni.

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