Keywords

The 2.5 m wide-field and high-resolution solar telescope (WeHoST) is currently under developing for solar observations. WeHoST aims to achieve high-resolution observations over a super-wide field of view (FOV) of 5' × 5', and a desired resolution of 0.3''. To meet the scientific requirements of WeHoST, the ground-layer adaptive optics (GLAO) with a specially designed wave front sensing system is as the primary consideration. We introduce the GLAO configuration, particularly the wave front sensing scheme. Utilizing analytic method, we simulate the performance of both classical AO and GLAO systems, optimize the wave front sensing system, and evaluate GLAO performance in terms of PSF uniformity and correction improvement across whole FOV. The results indicate that, the classical AO will achieve diffraction-limited resolution; the suggested GLAO configuration will uniformly improve the seeing across the full 5' × 5' FOV, reducing the FWHM across the axis FOV to less than 0.3'' (λ ≥ 705 nm, r₀ ≥ 11 cm), which is more than two times improvement. The specially designed wave front sensor schedule offers new potential for WeHoST's GLAO, particularly the multi-FOV GLAO and the flexibility to select the detected area. These capabilities will significantly enhance the scientific output of the telescope.

With the development of cutting-edge multi-object spectrographs, fiber positioners located in the focal plane are being scaled down in size, and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors. However, the small electrical time constant of such coreless motors poses a challenge, as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky. To overcome this challenge, it is advised to increase the Pulse Width Modulation (PWM) frequency as much as possible to mitigate the effects of the current fluctuation. This must be done while ensuring adequate resolution of the PWM generator. By employing a voltage open-loop field-oriented control based on a modulation frequency of 1 MHz, the drive current only costs 25 mA under a 3.3 V power supply. The sine degree of phase current is immaculate, and the repeat positioning accuracy can reach 2 μm. Moreover, it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board, especially in size-sensitive applications. This device has been developed under the new generation of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope.

For the public having a better understanding of solar activities, the Educational Adaptive-optics Solar Telescope (EAST) was built in July 2021 and is located at the Shanghai Astronomy Museum. The EAST consists of a 65 cm aperture solar telescope with a 177-element adaptive optics system and two-channel high resolution imaging system at the Hα and TiO bands, in addition to three full disk solar telescopes at Ca K, Hα and TiO bands equipped on the tube of the main telescope. In this paper, the configuration of the EAST is described. Its performance and on-sky observational results are presented. The EAST, to our knowledge, is the most advanced solar telescope for the popularization of science in the world. Due to its excellent performance, the data acquired by the EAST can also be used for research on solar physics and space weather prediction.

The Kepler Space Telescope observed over 15,000 stars for asteroseismic studies. Of these, 75% of dwarfs (and 8% of giants) were found to show anomalous behavior, such as suppressed oscillations (low amplitude) or no oscillations at all. The lack of solar-like oscillations may be a consequence of multiplicity, due to physical interactions with spectroscopic companions or due to the dilution of oscillation amplitudes from "wide" (AO detected; visual) or spectroscopic companions introducing contaminating flux. We present a search for stellar companions to 327 of the Kepler asteroseismic sample, which were expected to display solar-like oscillations. We used direct imaging with Robo-AO, which can resolve secondary sources at ∼015, and followed up detected companions with Keck AO. Directly imaged companion systems with both separations of ≤05 and amplitude dilutions >10% all have anomalous primaries, suggesting these oscillation signals are diluted by a sufficient amount of excess flux. We also used the high-resolution spectrometer ESPaDOnS at the Canada–France–Hawai'i Telescope to search for spectroscopic binaries. We find tentative evidence for a higher fraction of spectroscopic binaries with high radial velocity scatter in anomalous systems, which would be consistent with previous results suggesting that oscillations are suppressed by tidal interactions in close eclipsing binaries.

We present photometric properties of six small (radii <100 km) satellites of Uranus based on 32 H-band (1.49–1.78μm) images taken on 2015 August 29 from the Keck II Telescope on Maunakea, Hawaii with the near-infrared camera NIRC2 coupled to the adaptive optics system. The sub-observer latitude of our observations was 32°, i.e., we view much of the satellites' north poles, in contrast to the 1986 Voyager measurements. We derive reflectivities based on mean-stacking measurements of these six minor moons of Uranus. We find that the small satellites are significantly brighter than in previous observations, which we attribute to albedo variations between hemispheres. We also search for Mab, a small satellite with an unknown surface composition, orbiting between Puck and Miranda. Despite the significantly improved signal-to-noise ratio we achieved, we could not detect Mab. We suggest that Mab is more similar to Miranda, an icy body, than to the inner rocky moons. Assuming Mab is spherical with a radius of 6 km, as derived from Hubble Space Telescope (HST) observations if its reflectivity is ∼0.46, we derive a 3σ upper limit to its reflectivity [I/F] of 0.14 at 1.6 μm.

We present observations of 50 pairs of redshift z ≈ 0.2 star-forming galaxies and background quasars. These sightlines probe the circumgalactic medium (CGM) out to half the virial radius, and we describe the circumgalactic gas kinematics relative to the reference frame defined by the galactic disks. We detect halo gas in Mg ii absorption, measure the equivalent-width-weighted Doppler shifts relative to each galaxy, and find that the CGM has a component of angular momentum that is aligned with the galactic disk. No net counter-rotation of the CGM is detected within 45° of the major axis at any impact parameter. The velocity offset of the circumgalactic gas correlates with the projected rotation speed in the disk plane out to disk radii of roughly 70 kpc. We confirm previous claims that the Mg ii absorption becomes stronger near the galactic minor axis, and we show that the equivalent width correlates with the velocity range of the absorption. We cannot directly measure the location of any absorber along the sightline, but we explore the hypothesis that individual velocity components can be associated with gas orbiting in the disk plane or flowing radially outward in a conical outflow. We conclude that centrifugal forces partially support the low-ionization gas and galactic outflows kinematically disturb the CGM producing excess absorption. Our results firmly rule out schema for the inner CGM that lack rotation and suggest that angular momentum as well as galactic winds should be included in any viable model for the low-redshift CGM.

We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey. This subsample includes six detected planets and three brown dwarfs; from these detections and our contrast curves we infer the underlying distributions of substellar companions with respect to their mass, semimajor axis, and host stellar mass. We uncover a strong correlation between planet occurrence rate and host star mass, with stars M_* > 1.5 M_⊙ more likely to host planets with masses between 2 and 13M_Jup and semimajor axes of 3–100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semimajor axis (a) for planet populations around high-mass stars (M_* > 1.5 M_⊙) of the form ${d}^{2}N/({dm}\,{da})\propto {m}^{\alpha }\,{a}^{\beta }$, finding α = −2.4 ± 0.8 and β = −2.0 ± 0.5, and an integrated occurrence rate of ${9}_{-4}^{+5}$% between 5–13M_Jup and 10–100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with ${0.8}_{-0.5}^{+0.8}$% of stars hosting a brown dwarf companion between 13–80M_Jup and 10–100 au. Brown dwarfs also appear to be distributed differently in mass and semimajor axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semimajor axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of short-period giant planets from the radial velocity method, our results are consistent with a peak in occurrence of giant planets between ∼1 and 10 au. We discuss how these trends, including the preference of giant planets for high-mass host stars, point to formation of giant planets by core/pebble accretion, and formation of brown dwarfs by gravitational instability.

The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM), enabling interferometric resolution in complement to its coronagraphic capabilities. The NRM operates both in spectroscopic (integral field spectrograph, henceforth IFS) and polarimetric configurations. NRM observations were taken between 2013 and 2016 to characterize its performance. Most observations were taken in spectroscopic mode, with the goal of obtaining precise astrometry and spectroscopy of faint companions to bright stars. We find a clear correlation between residual wavefront error measured by the adaptive optic system and the contrast sensitivity by comparing phase errors in observations of the same source, taken on different dates. We find a typical 5σ contrast sensitivity of (2–3) × 10⁻³ at ∼λ/D. We explore the accuracy of spectral extraction of secondary components of binary systems by recovering the signal from a simulated source injected into several data sets. We outline data reduction procedures unique to GPI's IFS and describe a newly public data pipeline used for the presented analyses. We demonstrate recovery of astrometry and spectroscopy of two known companions to HR 2690 and HD 142527. NRM+polarimetry observations achieve differential visibility precision of σ ∼ 0.4% in the best case. We discuss its limitations on Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects for future upgrades. We summarize lessons learned in observing with NRM in spectroscopic and polarimetric modes.

We used high-resolution optical Hubble Space Telescope/WFC3 and multiconjugate adaptive optics assisted GEMINI GeMS/Gemini South Adaptive Optics Imager observations in the near-infrared (NIR) to investigate the physical properties of the globular cluster (GC) NGC 6569 in the Galactic bulge. We have obtained the deepest purely NIR color–magnitude diagram published so far for this cluster using ground-based observations, reaching K_s ≈ 21.0 mag (two magnitudes below the main-sequence turn-off point). By combining the two data sets secured at two different epochs, we determined relative proper motions for a large sample of individual stars in the center of NGC 6569, allowing a robust selection of cluster member stars. Our proper motion analysis solidly demonstrates that, despite its relatively high metal content, NGC 6569 hosts some blue horizontal branch stars. A differential reddening map has been derived in the direction of the system, revealing a maximum color excess variation of about $\delta E(B-V)\sim 0.12$ mag in the available field of view. The absolute age of NGC 6569 has been determined for the first time. In agreement with the other few bulge GCs with available age estimates, NGC 6569 turns out to be old, with an age of about 12.8 Gyr, and a typical uncertainty of 0.8–1.0 Gyr.