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


Contemporaneous Optical Burst with Gamma-Ray Burst

GRB 990123

Akerlof et al 1999


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


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


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


Other GRB Follow-Up with ROTSE

•No detections•Optical emission not strongly correlated with gamma-ray emission

Akerlof 2000


GRB 021211

Li et al 2003

RAPTORKAIT

105s 179s

259s 9600s

Many optically “dark” bursts have been missed by late observations


Swift UVOT observations of GRB 050319

Swift-diamonds


A Handful of Early Detections

Jelinek et al 2006


Vestrand 2006


Wide & Narrow Views

Vestrand 2006


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


Vestrand 2006


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


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


Northern Sky Variability Survey

• ROTSE-I all sky data• 14 million objects• 1 year• 100-500

observations/object • 8 < mag < 15.5


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


Many Variable Types Automatically Identified

RR Lyrae AB RR Lyrae C

Delta Scuti Eclipsing


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


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


Long Period Variables

Wozniak et al 2004


Training Set

MiraLPV


Classified Stars


Confusion Matrix

• 90% of training data used to construct basis

• 10% of training data used to estimate confusion

Classification accuracy 87%


3 Class IdentificationTraining Set

MiraLPVCarbon


Actual Classification


Confusion Matrix


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


Summary

• Robot telescopes for rapid follow-up

• Robot telescopes for surveys

• Machine learning, automatic classification is critical

the transient universe: ay 250 spring 2007 existing transient surveys: optical ii: robot telescopes...

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