John Henning and Kevin Rykoski were quick and patient in responding to my multitude of computer and electronic requests, often made in the middle of the night. I have to give special thanks to Efrain Hernandez for all the great conversations in the hallways and the sunny encouragement.
The Problems of Atmospheric Turbulence
Left panel: On a short time scale (≈0.1 s), the light from the star breaks down into small 'speckles', indicated by the red arrows. The effectiveness of the corrections depends on the brightness of the reference star, the frequency of the correction and many other parameters.
Science with Adaptive Optics
AO imaging of the solar surface has revealed many details about the role of magnetic fields in the mechanics of the photosphere and insights into the applicability of Kolmogorov turbulence, from the size scales of small jet-like features to ubiquitous grains (Goode et al., 2010) . . In densely populated fields with hundreds of reference stars, such as the galactic center, the accuracy of the proper motion has allowed extremely precise measurements of the mass of the Milky Way's central black hole and the distribution of stars around it with great precision.
Adaptive Optics on Small Telescopes
Resolution: Almost all current AO systems in the world operate in the IR bands. The corresponding increase in the required brightness of the reference star encourages the use of a laser guide star to prevent the sky coverage from shrinking to unusable limits.
Theory Interlude
The angular scale of the decorrelation (θ0) is where the RMS error in the phase of the wavefront is one radian and is given by,. 1.8) An isoplanatic patch is the radius at which the applied correction is still reasonably valid, so the reference wavefront measurement and the science target must be within this patch. Right panel: Inside the instrument, the dichroic sends laser light to the wavefront sensor (WFS), which sends appropriate commands to the deformable mirror (DM), which corrects the wavefront deformation and forms a diffraction-limited image on the science camera.
Inner Workings of Adaptive Optics
The slopes measured at each lenslet can be numerically integrated to form an estimate of the wavefront. The tip-tilt of the wavefront is transferred to the TTM to reduce the stroke requirement on the DM.
Hardware Design and Construction
Mounting the laser projector on the south side of the telescope using a mounting adapter. When mounted on a telescope, the optical axis of the telescope is perpendicular to the image plane.
Atmospheric Dispersion Corrector
When the prisms are opposite (Case 'c'), the dispersion of the prisms cancel each other, leading to zero correction. When the prisms are aligned (case 'a'), the dispersions of the prisms are summed, doubling the total dispersion.
Software Architecture
This was done by bouncing the laser beam off the front surface of the prism (which by design was normal to the optical axis) when it was mounted. Setting up error conditions and error handling functions is the biggest task for system automation. Appendix C (adapted from an internal report written in April 2010) includes full details of the implementation of the AO control system.
Robo-AO Operations
Check internal alignment: At the beginning of each run, the internal alignment (registration) of the deformable mirror, the field stop and the wavefront sensor is checked. In July 2013, an automatic download of the wavefront sensor focus measurements to the telescope focusing was implemented. The left panel shows the shape of the deformable mirror (orange circle; top left panel), the wavefront sensor image (grey ring; top right panel) and the visible camera image (bottom panel image).
Introduction
Basic Characterization
The Robo-AO pipeline averages the flux in each image frame (acquired at 8.9 Hz), so these were counts collected in 0.112 s. Sergi Hildebrandt compared Robo-AOi0 band images of the globular cluster M15 taken by Robo-AO in May 2012 and downscaled by me with Hubble Space Telescope (HST) images of the same field. 207 stars crossed between the Robo-AO image and the HST image were used to calculate the distortion of the Robo-AO image.
AO Performance
Wavefront Error Wavefront Error (WFE) is the most fundamental measure of an optical system's performance. As the name suggests, this is the width of the image at half peak intensity (after the background has been subtracted). The FWHM achieved by an AO system cannot be precisely related to the WFE or the Strehl ratio, as it depends on the spatial distribution of the WFE.
Robo-AO Performance
Left panel: Robo-AO image of a faint star (r0∼16 mag) with a sharp noise peak in the center. In Figure 3.9 we show the 5−σ contrast (i.e. the difference in magnitudes between the primary and a hypothetical companion star that can be detected with a significance of 5−σ) as a function of the radius from the primary for two stars observed in SDSSg0 ,r0,i0, andz0 filters. The tip-tilt reference, typically the brightest star in the field, may be off-center.
Seeing and Turbulence Profiles at Palomar
Characterization and monitoring of seeing and turbulence at the observatory is thus an important activity supporting future instrument development. These line-limited observations are the most accurate direct estimate of the total turbulence at the time of the AO observation. The power spectra of the Zernike coefficients corrected by the deformable mirror (blue) and in the residuals measured by the wavefront sensor (green) are plotted.
LP 600 SDSS z 0
Possible Improvements to Robo-AO
The advantage of LBWFS is that it provides real-time feedback to the AO control system. The LBWFS prevents this by adjusting the position of the WFS to be conjugated to the sodium laser. The centroiding sensitivity of the laser spot in the WFS subaperture is proportional to the peak intensity (or equivalent Strehl) of the spots in the image.
Introduction
Conveniently, a majority of the young stars in sparse star-forming regions such as Taurus are binaries (Ghez et al.,1993;Simon et al.,1995)1. Kraus et al.(2011) found that 2/3 to 3/4 of all stars in the Taurus star-forming region were multiples with a log-flat separation distribution between 3 and 5000 AU. Kraus et al.(2011) suggest that this may be due to dynamical disruptions of multiple star systems in dense young clusters and sparse old clusters.
Observations and Data Analysis
Robo-AO is the world's first AO system to routinely observe in the visible wavelengths. Originally, a sample of 100 systems in the Taurus-Auriga region and 150 systems in the Upper Scorpius-Ophiuchus region were proposed for observation in semester 2013A. However, due to time constraints, we made 148 observations of 37 systems in the Taurus-Auriga region and 117 observations of 30 systems in the Upper Scorpius-Ophiuchus region.
Data Reduction and Analysis
The residuals created by subtracting the PSF estimate from the image were used to estimate the flux of the secondary. We plan to measure the opening flux of the primary star from the PSF estimate and of the secondary star in the residual image. They noted that the measured fluxes were consistently lower than the original fluxes of the planets.
Future Work
Introduction
We present the results in Section 5.4 and in Section 5.5 we discuss the importance of our proper motion measurements.
Targets
- SGR 1806−20
- SGR 1900+14
- AXP 1E 2259+586
- AXP 4U 0142+61
- SGR 0501+4516
- AXP 1E 1841−045
Our photometric measurements show a factor of three variations in the brightness of the same object (Section 5.4.1). They obtained two KS-band AO observations of the same field around SGR 1900+14 with the VLT NACO instrument in March and July 2006. Neither source in the error circle has been definitively identified as the magnetar counterpart.
Observations and Analysis
- NIRC2
However, there are small errors in the setting of the field rotator as well as tracking errors. We calculated the rotation angle and the plate scale of the image at each epoch with respect to the reference image. From the rotation curve, we calculate the Galactic proper motion ~µGal = [µα, µδ]Gal of objects at different distances (1 kpc≤r ≤20 kpc) in the direction (l, b) of the magnetar flowing with the Galactic .
Results
- SGR 1806−20
- SGR 1900+14
- SGR 0501+4516
- AXP 1E 1841−045
The size of the ellipse indicates the positional uncertainty that corresponds to the uncertainty in the proper motion measurement. Stars 2–7 (except 5) are highlighted. The zero point of the H-band image has a systematic uncertainty of ~0.5 mag, which would essentially only change the scale of the x-axis. The position of the putative counterpart of SGR 1900+14 (blue diamond), traced to 6 kyr, is marked by the solid ellipse (red in the online version).
Discussion
The proper motions are corrected for the motion of the Milky Way according to Tendulkar et al. This is in very good agreement with the mean and standard deviation of the normal pulsar population (Hobbs et al., 2005). This is in good agreement with the tangential velocities of the pulsar population, which is measured to be 211 km s−1 (Hobbs et al., 2005) with a standard deviation of ∼100 km s−1.
Epilogue and Future Work
Disks around Magnetars van Paradijs et al.(1995) first suggested that a supernova reentry disk could explain the X-ray luminosity of AXPs through accretion without inducing an extremely strong magnetic field. A number of authors (most recently Tr¨umper et al., 2013) improved this model for AXPs to explain the OIR emission as thermal emission from disc heated by high-energy radiation from the magnetar. 2006); Wang & Kaspi (2008) showed that the optical to mid-IR spectral energy distribution (SED) of AXP 4U 0142+61 (see Fig. 5.22 ) fits a two-component model well; a power-law component likely originating in the magnetosphere of the magnetar and a thermal blackbody component consistent with a heated disk in the 2.2–24µm range. Currently, there is no evidence for the presence or absence of a recursion disk around AXPs.
Journal Publications
Conference Proceedings and Other
In this section, we will move on to deriving the calculations for the ADC rotation angle positions. We need to know the angle between the image axis and the parallax vector so that we can rotate the ADC axes to match the parallax angle. We also calculate the maximum rates of change of parallax angle: (in deg/sec) Maximum rotation rate for parallax angle = 0.067 deg/sec.
