The Transient Universe: AY 250 Spring 2007 Existing Transient Surveys: Optical II: Robot Telescopes...
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Transcript of The Transient Universe: AY 250 Spring 2007 Existing Transient Surveys: Optical II: Robot Telescopes...
The Transient Universe: AY 250 Spring 2007
Existing Transient Surveys:Optical II:
Robot Telescopes
Geoff Bower
The Transient Universe: AY 250 Spring 2007
Contemporaneous Optical Burst with Gamma-Ray Burst
GRB 990123
Akerlof et al 1999
The Transient Universe: AY 250 Spring 2007
Contemporaneous Optical Burst
• GRB 990123– Fluence 99.6
percentile in gamma-rays
• Z=1.6• 5 x 10^49 erg s^-1 at
t=47 s– Most luminous optical
event ever
• Many similar events predicted
• Burst trigger• +4 seconds ---
message with position arrives in LANL
• +10 seconds --- first observation begins (but software error fails)
• +22 seconds --- first good integration
The Transient Universe: AY 250 Spring 2007
ROTSE-I
• 4 x 35mm cameras with 2k x 2k CCDs
• 16 x 16 deg^2 FOV• 14” pixels• 3 sec slew time to
anywhere on the sky• Limiting magnitude of 15• Robotic operations• LANL• Based on military goals of
Strategic Defense Initiative to track missiles
• $200k
The Transient Universe: AY 250 Spring 2007
ROTSE-III
• 4 stations– GRB follow-up at any
time
• 4 x 0.45m aperture• 16 x 16 deg^2 FOV• 18 mag limit
• Designed to fit in a shipping container
The Transient Universe: AY 250 Spring 2007
Other GRB Follow-Up with ROTSE
•No detections•Optical emission not strongly correlated with gamma-ray emission
Akerlof 2000
The Transient Universe: AY 250 Spring 2007
GRB 021211
Li et al 2003
RAPTORKAIT
105s 179s
259s 9600s
Many optically “dark” bursts have been missed by late observations
The Transient Universe: AY 250 Spring 2007
Stereoscopic Vision
• 38 km separation
• Parallax of 1 pixel at distance of Moon
• Rejects space junk, satellites, aircraft, meteors
• Reduces false triggers by orders of magnitude
The Transient Universe: AY 250 Spring 2007
ROTSE-III Search for Untriggered BurstsNo New Transient Classes
1.74 deg^2 yr
Brighter than 17.5 mag for 30 minutes
52 deg^2 yr
Slowly decaying transients such as CVs
4 CVs discovered 0.1 deg^-2 yr-1
Rykoff et al 2005
The Transient Universe: AY 250 Spring 2007
ROTSE-III Transient
• Light curve recalls classical nova– Abs. mag = -8 D=1 Mpc– But no host galaxy
• Dwarf nova– Subgroup of CVs– Resembles SU Uma-
type DNe
Rau et al 2006
The Transient Universe: AY 250 Spring 2007
Northern Sky Variability Survey
• ROTSE-I all sky data• 14 million objects• 1 year• 100-500
observations/object • 8 < mag < 15.5
The Transient Universe: AY 250 Spring 2007
Finding Variable Stars in NSVS
• 2000 deg^2• 10 < m < 15.5• 1781 new periodic
variables• 90% are newly
identified• 0.2% of all stars
variable above 0.1m• 5% of total NSVS• Akerlof et al 2000
The Transient Universe: AY 250 Spring 2007
Many Variable Types Automatically Identified
RR Lyrae AB RR Lyrae C
Delta Scuti Eclipsing
The Transient Universe: AY 250 Spring 2007
Use of Periodic Stars as Galactic Distance Indicators
• RR Lyrae detected from 0.7 to 7 kpc
• Tight period-luminosity relationship
• Periods less than 1 day
• Delta Scuti stars• Periods less than 1 day • Less luminous
The Transient Universe: AY 250 Spring 2007
Machine learning identifications
• Working on LPVs– AGB stars undergoing
pulsations– Mira (M)
• Longer periods– Semiregular (SR)
• Periods < 1 y– Irregular (L)
• Data available– Period– Amplitude– 3 colors
• Use training method for separating variables
The Transient Universe: AY 250 Spring 2007
Confusion Matrix
• 90% of training data used to construct basis
• 10% of training data used to estimate confusion
Classification accuracy 87%
The Transient Universe: AY 250 Spring 2007
Support Vector Machine
• Transform data into higher dimensional space
• Identify hyper-planes that create class boundaries
• Maximize the margin– Orthogonal distance between class boundary
and points closest to the boundary