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 ResultsDate 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