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

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

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)

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”

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

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)

R

R

AAVSO Screenshot

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)

R Oph

Ophiuchus

Newsworthy in 2011 [click]

AAVSO Star Chart

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

R Ophiuchi Light Curve

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]

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

SS Cygni Light Curve

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

Barnard’s StarJuly 2013

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)

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

Weather

Clear Sky Charts [click]

Sensing the Cosmos

L to R: Emily, Vikas, & Linda

Field Trips