arXiv subjects

Anna Pusack

Publications and source records attributed to Anna Pusack.

3 recordsLinked to original sources

arXiv2026

On-sky capabilities and performance of the Keck All Sky Precision Adaptive Optics system

The Keck All Sky Precision Adaptive optics (KAPA) project upgrades the Keck I adaptive optics system to enable laser tomography using a four laser guide star (LGS) asterism. KAPA is now in operation in both narrow field and wide field modes to optimize correction on-axis or over the science field of view of the camera. The use of four LGSs, in conjunction with a tomographic reconstructor and pseudo open-loop control, leads to a significant reduction in wavefront error. We describe the overall architecture, development of the tomographic algorithm, real-time implementation and preliminary on-sky results here. By comparing the on-sky image quality with that obtained using a single LGS (sLGS) we clearly demonstrate the benefits of laser tomography, a technology which is crucial to the success of the next generation of extremely large telescopes.

astro-ph.IM↗

arXiv2026

A Kinematic Study of Wolf-Rayet Stars at the Galactic Center I: Binary Candidates and Constraints on the Binary Fraction

We report the binary fraction of Wolf-Rayet (WR) stars within 0.5~pc of the Galactic center obtained through the longest time-baseline (1994-2024) kinematic study of this population of stars. The new radial velocity ($v_{z}$) data we present is primarily from the W. M. Keck Observatory, with additional $v_{z}$ measurements from Gemini North Observatory. When combining our new $v_{z}$ measurements with literature measurements, we find $v_{z}$ variations suggesting the presence of a companion for five out of 27 WR stars, of which two are newly identified here (IRS~13E4, S8-181), along with three previously detected binaries (IRS~16SW, IRS~16NE, S4-258). Based on our experimental sensitivity and expected properties of the underlying population, we infer the binary fraction of the WR stars in the Galactic center to be 0.56$\pm$0.18. This is consistent with previous photometric studies of the young stars in the Galactic center, and with the binary fraction of field WR stars. When our results are combined with the results of previous photometric work, we find a binary fraction of 0.69$\pm$0.17 for the WR stars in the Galactic center.

astro-ph.GA↗

arXiv2023

The Galactic Center with Roman

We advocate for a Galactic center (GC) field to be added to the Galactic Bulge Time Domain Survey (GBTDS). The new field would yield high-cadence photometric and astrometric measurements of an unprecedented ${\sim}$3.3 million stars toward the GC. This would enable a wide range of science cases, such as finding star-compact object binaries that may ultimately merge as LISA-detectable gravitational wave sources, constraining the mass function of stars and compact objects in different environments, detecting populations of microlensing and transiting exoplanets, studying stellar flares and variability in young and old stars, and monitoring accretion onto the central supermassive black hole. In addition, high-precision proper motions and parallaxes would open a new window into the large-scale dynamics of stellar populations at the GC, yielding insights into the formation and evolution of galactic nuclei and their co-evolution with the growth of the supermassive black hole. We discuss the possible trade-offs between the notional GBTDS and the addition of a GC field with either an optimal or minimal cadence. Ultimately, the addition of a GC field to the GBTDS would dramatically increase the science return of Roman and provide a legacy dataset to study the mid-plane and innermost regions of our Galaxy.

astro-ph.IM↗