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Light Curves of the Dwarf Nova U Gem: A Diagnostic of Accretion Disk Evolution
Larry Molnar
Calvin College
Grand Rapids,
Michigan
Calvin-Rehoboth Twin Telescope Project
• NSF-CCLI funding
• Two 16” OGS telescopes– One in Grand Rapids, MI
• Hands-on experience for students
• Development platform for remote site
– One in Rehoboth, NM (35.5N,108.6W)• Unattended robotic operation
• High throughput
Dwarf Novae
• White dwarf + red dwarf
• Red dwarf fills Roche Lobe
• Angular momentum loss leads to mass transfer via an accretion stream, and formation of an accretion disk
• Disk conditions do not permit steady-state
U Gem
• Brightness: 10-14 magnitude
• Mass ratio: 0.25
• Orbital period: 4.24 hours
• Outburst time scale: 3-4 months
• Inclination: hot spot is eclipsed by red dwarf
10
10.5
11
11.5
12
12.5
13
13.5
14
2453020 2453030 2453040 2453050 2453060 2453070 2453080 2453090
Julian Date
I (m
ag
)
U Gem
12.6
12.7
12.8
12.9
13.0
13.1
13.2
13.3
13.4
13.5
2453078.55 2453078.60 2453078.65 2453078.70 2453078.75 2453078.80 2453078.85
Julian Date [3/13/4]
I (m
ag
)
U Gem
Check 6
10.1
10.3
10.5
10.7
10.9
11.1
11.3
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
Orbital Phase
I (m
ag
)
3/7/4
3/8/4
3/9/4
U Gem
12.8
13
13.2
13.4
13.6
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2
Orbital Phase
I (m
ag
)
1/18/4
3/13/4
3/15/4
3/20/4
U Gem
12.9
13
13.1
13.2
13.3
13.4
-0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20
Orbital Phase
I (m
ag
)
1/18/4
3/13/4
3/15/4
3/20/4
U Gem