Transcript AAS08 - Caltech Optical Observatories

CAMERA
Compact Automated MEMS Rayleigh Adaptive
Optics System
C. Baranec, S. Kulkarni, R. Dekany, N. Law, E. Ofek, M. Kasliwal, V. Velur, & A. Ramaprakash (IUCAA)
Overview
Rapidly develop and deploy low cost adaptive
optics (AO) system for 1-3 meter telescopes:
Lab Testbed
a)
•Use low-risk technologies
•Ease of use, fully robotic
•Emphasis on high observing efficiency
New astronomical science capability:
•Allocate large amounts of time to
diffraction-limited astronomy, previously
not possible
•Integrated visible and near IR science
instruments
The gravitational lens HE 1113-0641 [2]. In V: HST image. In g':
Seeing-limited discovery image, taken in exceptional seeing.
High angular resolution observations were required to confirm
the lens properties, search for the lens galaxy and
photometrically separate the images. Observations taken in
standard seeing would have failed to resolve this lens.
AO Performance
New Science Capability
Extensive surveys (1000++ objects)
•Stellar, sub-stellar companion searches
•Lensed quasars (300-700 new over a 9
month period of intermittent observing)
•Asteroid binarity
Rapid transient characterization
•Respond to transients identified by other
systems (e.g. PTF, Catalina Sky Survey,
PanSTARRs)
•Rapid near-IR photometry
Time-domain astronomy
•Long term, high-resolution monitoring
•Solar system objects, repeating transients,
orbits
Astrometry
•Dedicated system to optimize stability
•High H-Strehl improves precision
Testbed closed loop at 120 Hz:
Fully remote operation, including simulated
queue scheduled observations
Swift J1955+2614, one of the strangest transients of recent
years [3-5]. This galactic transient was discovered in the galactic
plane by the Swift Gamma-Ray-Burst detector satellite. Followup observations revealed an extremely complex (and still poorly
understood) light curve, followed by rapid fading. Since stellar
crowding was significant, LGS-AO observations were required to
separate the transient light from surrounding stars. (Left): The
transient during emission. (Right): the transient location after
emission ceased. Note the 1” scale bar; clearly, accurate
photometry of this very interesting source required high-angularresolution observations. CAMERA could easily perform similar
observations within minutes of initial detection.
Design
•Compact - WFS and science cameras fit on
0.5 x 0.5 m breadboard
•120” field of view
•12X12 Boston Micromachines MEMS DM
•Shack-Hartmann WFS (CCD39)
•355nm Rayleigh LGS (similar systems FAA
approved), packaged in secondary hub
•IR and visible tip/tilt sensors
•IR and science detectors
•Automated operation
Example error budget for CAMERA under different seeing
conditions (r0) and for different zenith angles (z) assuming an onaxis mV=17 star for tip-tilt sensing and on-axis science target.
FWHM at H < 0.26” in even the 75% worst
seeing conditions
CAMERA at the 200”!?!
•The CAMERA adaptive optics system can be
replicated and potentially deployed at the 200” with a
focus on improving energy concentration for existing
instrumentation such as DoubleSpec and TripleSpec.
Calculated H-band Strehl ratios for CAMERA under the various
observing conditions presented above for different visual
magnitudes of on-axis tip-tilt star.
Supernova 2006GY [1], the second-most luminous supernova
ever recorded. Lick AO observations were required to separate
the supernova from its host galaxy and ascertain if it was simply
AGN variability. The AO observations rapidly confirmed the
nature of the transient and gave vital information: position in the
host galaxy and a light curve resolved from the bright galaxy
nucleus. The ability to quickly and inexpensively perform such
observations is growing ever more important as surveys begin to
find many potentially interesting transients every night.
5
”
Provides a 1.5 m telescope the H sensitivity
of a 4 m telescope
Band Compared to 1.5 m
J
0.35
H
0.14
Compared to 4 m
2.51
1.02
Ratio of CAMERA enhanced integration time for the same SNR
ratio vs. seeing limited telescopes
• COO is currently investigating this new type of AO
for increasing the SNR and resolution of
spectroscopic astronomy.
References
[1] N. Smith, et al., “SN 2006gy: Discovery of the Most Luminous Supernova Ever Recorded,
Powered by the Death of an Extremely Massive Star like nu Carinae,” Astrophysical Journal,
666, 1116–1128, 2007.
[2] J. A. Blackburne, L. Wisotzki, and P. L. Schechter, “HE 1113-0641: The Smallest
Separation Gravitational Lens Identified by a Ground-based Optical Telescope,” ArXiv eprints, 710, October 2007.
[3] A. Stefanescu, et al., “Very fast optical flaring from a possible new Galactic magnetar,”
Nature, 455, 503-505, 2008.
[4] A. J. Castro-Tirado, et al., “Flares from a candidate Galactic magnetar suggest a missing
link to dim isolated neutron stars,” Nature, 455, 506-509, 2008.
[5] M. M. Kasliwal, et al., “GRB 070610: A Curious Galactic Transient,” Astrophysical Journal,
678, 1127–1135, 2008.
Palomar Science Meeting, Pasadena, CA, Apr. 30 – May 1, 2009.