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R Ophiuchi, A Mira-Type Variable Star
Vikas AgteyEmily BerrymanCaroline Fletcher
Linda GongAaron McNeely
Dan Walsh
University of Notre Dame QuarkNet
Center
Summer, 2013
Advisor: Dr. Dan Karmgard
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Astrophysics Group Projects
• Major projects:– Variable star photometry– Asteroid astrometry (IASC)– General stargazing, telescope use,
astrophotography• Outreach: Solar observing for Sensing the
Cosmos; Observatory visit for iLED• Field Trips: Adler Planetarium, Kalamazoo Air
Zoo, Joshua Tree Museum
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Variable Stars
• Stars that change brightness over time• Project: Measure the brightness (magnitude)
of one or more variable stars• Collect and submit data to the American
Association of Variable Star Observers (AAVSO)
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CCD Photometry
• Photometry: The measurement of the brightness of stars
• Use telescope and CCD camera to determine the brightness of variable stars
• Values estimated in “magnitude”
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CCD & Telescope
• Telescope: Celestron CPC 1100, 11-inch Schmidt-Casssegrain reflector, located at Morrison Observatory, Notre Dame
• CCD: SBIG ST8-XE• Software:
– CCDSoft: Take and combine images
– MaximDL: Photometry tool to measure stellar magnitudes
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+
=
Raw images Flat fields Dark fields
Image for photometry
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Estimating Magnitude
• For our unknown variable star, we compare its brightness to nearby stars of known magnitude (arrows) contained within the CCD image area
• Use MaximDL software to perform magnitude measurements
• Submitted magnitude measurements to AAVSO (observer MMAE)
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R
R
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AAVSO Screenshot
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R Ophiuchi• We selected R Ophiuchi, a variable star in the
constellation Draco• R Ophiuchi is a “Mira-type” or long-peroid
variable star• Star changes on average from magnitude 7 to
13.8 over a period of 10 months (306.5 days)• R Ophiuchi was predicted to peak around
June 20 (Sky & Telescope, July 2013)
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R Oph
Ophiuchus
Newsworthy in 2011 [click]
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AAVSO Star Chart
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R Ophiuchi Results
Date Time Magnitude* Uncertainty**
6/21 12:34 am 7.80 0.00172
6/29 1:44 am 8.30 0.02274
7/10 11:28 pm 8.26 0.00263
7/14 1:24 am 8.16 0.00104
7/18 11:46 pm 8.13 0.00053
*7—13.8
**1/SNR
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R Ophiuchi Light Curve
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SS Cygni• SS Cygni, a well-known variable star in the
constellation Cygnus• Cataclysmic variable (dwarf nova class)• Magnitude 12.2 to 8.3• Outburst every 4-10 weeks, duration of 1-2
weeks• Consists of red dwarf and white dwarf in fast
orbit (6.5 hours)• Newsworthy [click]
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SS Cygni Results
Date Time Magnitude* Uncertainty**
7/14 10:06 pm 12.136 0.0168
7/18 11:09 pm 12.233 0.01149
*7—13.8
**1/SNR
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SS Cygni Light Curve
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Barnard’s Star
• One of the nearest stars to earth (6 LY)• Exhibits greatest proper motion of any star• Project: Take images of Barnard’s Star each
summer, record its proper motion
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Barnard’s StarJuly 2013
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Asteroid Astrometry
• Goal: Measure the position of known asteroids
• Provide reports of asteroid position to the Minor Planet Center
• We worked as a group within the International Asteroid Search Collaboration (IASC)
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Procedure
• Obtain CCD images of predicted NEO asteroid positions
• Stack images, search for moving objects using Astrometrica software
• Prepare reports in a standard format, submit to Dr. Patrick Miller at IASC
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Weather
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Sensing the Cosmos
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L to R: Emily, Vikas, & Linda
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Field Trips