arXiv subjects

Garreth Ruane

Publications and source records attributed to Garreth Ruane.

At least 19 recordsLinked to original sources

arXiv2026

The Photonic Lantern Nuller: from concept to laboratory and on-sky demonstrations

This thesis work presents the conceptual design and experimental characterization of the Photonic Lantern Nuller instrument, which uses a multimode-to-single-mode demultiplexing waveguide to cancel out starlight while maintaining planet light, allowing for the direct characterization of planets at a telescope's diffraction limit. The PLN was experimentally characterized in the lab, where it was further enhanced using common-path wavefront sensing and control techniques, and then demonstrated on sky at the Subaru Telescope. Highlights include measured in-lab null-depths of $\sim 10^{-4}$ in three out of four ports simultaneously and on-sky null-depths of approximately $\sim 10^{-1}$ (limited by jitter and atmospheric residuals). We provide an overview of these results and discuss avenues for future work.

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arXiv2026

The Roman Coronagraph Community Participation Program: Using the Zernike wavefront sensor for a full characterisation of the Roman Space Telescope and the Coronagraph Instrument

The Roman Space Telescope Coronagraph Instrument (CGI) will demonstrate a series of technologies and techniques to enable the direct detection of reflected-light planets with space-based observatories. Among the several available observing modes and coronagraphic devices embarked in CGI, there is the transmissive dual-path Zernike wavefront sensor (ZWFS) that could be used to directly measure optical aberrations in the system. The dual-path ZWFS is currently unsupported, but in this work we advocate for the commissioning of this unique observing mode. We investigate the sensitivity of the ZWFS using CGI simulator and other tools developed and supported by the Roman community participation program (CPP). This type of analysis is crucial for understanding the stability of the Roman observatory and to prepare the path towards HWO.

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arXiv2026

Investigating the differential limb coupling effect for diffraction-limited spectrographs with PARVI

A promising new architecture for extreme-precision radial velocity (EPRV) spectrographs, hunting for small-amplitude stellar Doppler shifts induced by orbiting planets, is to build diffraction-limited instruments by using single-mode fibers fed by an adaptive optics system. However, the target stars are partially resolved when observing at the diffraction limit, and the resulting RVs are expected to be affected by differential limb coupling (DLC), an effect where the red- and blue-shifted sides of the stellar disk are coupled unequally into the spectrograph, producing an RV error term on the order of m/s for nearby EPRV target stars for the upcoming HISPEC spectrograph for Keck II. We present our efforts to directly measure the RV shifts resulting from DLC for the first time, using the diffraction-limited spectrograph PARVI, in order to verify the expected behavior of DLC and subsequently develop mitigation strategies for HISPEC and other future instruments. We outline an observing strategy designed to produce DLC-induced RV shifts of hundreds of m/s, and describe the execution of this experiment with PARVI. We use these data to characterize the PARVI tip-tilt guide camera and its performance, and have begun analysis of the derived RVs, though this investigation has proven complicated since the RVs are deeply entangled with other instrumental and algorithmic effects.

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arXiv2026

Dimpled scalar vortex coronagraph laboratory demonstration

Achieving the Habitable Worlds Observatory (HWO) goal of 10^-10 contrast at a separation of 3 $\lambda$/D across a 20% bandwidth requires coronagraph focal plane masks with both broadband high contrast performance and high planet throughput. Scalar vortex coronagraphs (SVCs) offer a promising alternative to polarization-sensitive vector vortex designs but face chromatic limitations. This work presents the latest laboratory demonstrations of second-generation scalar vortex prototypes that incorporate radial phase dimples to improve broadband starlight suppression. We compare these new "dimpled" sawtooth masks to previous-generation scalar designs through high-contrast imaging experiments on the In-Air Coronagraph Testbed. Using electric field conjugation, we achieve near testbed-limited contrasts across both narrow (2%) and broadband (10%) spectral ranges. We report the best in-air contrasts achieved to date for scalar vortex masks across narrow and broadband spectral ranges and we also show that the dimpled vortex predicted bench-limited contrast performances for 2%, 10% and 18% bandwidths agree with the measured lab contrasts within a factor of two. These results highlight the potential of topographically achromatized scalar vortex masks as candidates for future space-based high-contrast imaging missions and mark a significant step toward polarization-independent coronagraphs capable of meeting HWO performance requirements.

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arXiv2026

Model validation and tolerancing of scalar vortex masks in the High Contrast Imaging Testbed (HCIT) facility

The Habitable Worlds Observatory (HWO) mission will require coronagraphs capable of suppressing starlight at the $\sim 10^{-10}$ contrast level to directly image exo-Earths. High contrast achromatic coronagraphic masks are the missing critical component to achieving this. Vortex coronagraphs, particularly scalar vortex designs with an achromatic focal plane mask, offer key advantages. While all vortex coronagraph varieties provide high throughput, a small inner working angle, and rejection of low-order aberrations, the scalar approach enables dual-polarization observation in a single optical path. This simplifies instrument design and increases transmission by maintaining light from the planet in two orthogonal polarization states. In this work we test scalar vortex masks and investigate their contrast limitations. We perform phase metrology to assess the mask defects and manufacturing deviations and use it to refine the coronagraphic model used for electric field conjugation (EFC) algorithms and end-to-end simulations. We also measure the impact of model-mismatch with EFC by varying model parameters including clocking angle, and central wavelength in laboratory demonstrations. Finally, we validate our scalar vortex models against experimental results from the High Contrast Imaging Testbed (HCIT) facility at JPL by finding good agreement between lab and simulated performance. This ultimately helps to benchmark simulated contrast predictions for future scalar vortex coronagraph designs for HWO.

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arXiv2025

Revealing the accelerating wind in the inner region of the colliding-wind binary WR 112

Colliding winds in massive binaries generate X-ray-bright shocks, synchrotron radio emission, and sometimes even dusty "pinwheel" spirals. We report the first X-ray detections of the dusty WC+O binary system WR 112 from Chandra and Swift, alongside 27 years of VLA/ATCA radio monitoring and new diffraction-limited Keck images. Because we view the nearly circular orbit almost edge-on, the colliding-wind zone alternates between heavy Wolf-Rayet wind self-absorption and a near-transparent O-star wind foreground each 20-yr orbit, producing phase-locked radio and X-ray variability. This scenario leads to a prediction that the radio spectral index is flatter from a larger non-thermal contribution around the radio intensity maximum, which is indeed observed. Existing models that assume a single dust-expansion speed fail to reproduce the combined infrared geometry and radio light curve. Instead, we require an accelerating post-shock flow that climbs from near-stationary to ~1350 km/s in about one orbital cycle, naturally matching the infrared spiral from about 5" down to within 0.1", while also fitting the phase of the radio brightening. These kinematic constraints supply critical boundary conditions for future hydrodynamic simulations, which can link hot-plasma cooling, non-thermal radio emission, X-ray spectra, and dust formation in a self-consistent framework. WR 112 thus joins WR 140, WR 104, and WR 70-16 (Apep) as a benchmark system for testing colliding-wind physics under an increasingly diverse range of orbital architectures and physical conditions.

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arXiv2025

Flight masks of the Roman Space Telescope Coronagraph Instrument

Over the past two decades, thousands of confirmed exoplanets have been detected. The next major challenge is to characterize these other worlds and their stellar systems. Much information on the composition and formation of exoplanets and circumstellar debris disks can only be achieved via direct imaging. Direct imaging is challenging because of the small angular separations (< 1 arcsec) and high star-to-planet flux ratios such as ~1e9 for a Jupiter analog or ~1e10 for an Earth analog in the visible. Atmospheric turbulence prohibits reaching such high flux ratios on the ground, so observations must be made above the Earth's atmosphere. The Nancy Grace Roman Space Telescope (Roman), planned to launch in late 2026, will be the first space-based observatory to demonstrate high-contrast imaging with active wavefront control using its Coronagraph Instrument. The instrument's main purpose is to mature the various technologies needed for a future flagship mission to image and characterize Earth-like exoplanets. These technologies include two high-actuator-count deformable mirrors, photon-counting detectors, two complementary wavefront sensing and control loops, and two different coronagraph types. In this paper, we describe the complete set of flight masks in the Roman Coronagraph Instrument, their intended combinations, and how they were laid out, fabricated, and measured.

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arXiv2025

High-order wavefront sensing and control for the Roman Coronagraph Instrument (CGI): architecture and measured performance

The Nancy Grace Roman Space Telescope (``Roman'') is a 2.4m space telescope scheduled for a 2026 launch. The Coronagraph Instrument (CGI) on Roman is a technology-demonstration instrument with a coronagraph and, for the first time in space, deformable mirrors and active wavefront control. This paper walks through the algorithmic and system-level architecture of the HOWFSC implementation for CGI, including the use of ground-in-the-loop (GITL) operations to support computationally-expensive operations, and reports on instrument performance measured during thermal vacuum testing in instrument integration and test. CGI achieved better than $5\times10^{-8}$ total raw contrast with two independent coronagraph architectures covering 3-9 and 6-20 $\lambda/D$ between them and a $360^{\circ}$ dark hole on each. The contrast limits appear to be driven by time available for testing, and do not appear to represent a floor in the achievable performance of CGI in flight.

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arXiv2025

Implicit Electric Field Conjugation with the Photonic Lantern Nuller

The Photonic Lantern Nuller (PLN) is an instrument concept designed to characterize exoplanets within a single beam-width from its host star. The PLN leverages the spatial symmetry of a mode-selective photonic lantern (MSPL) to create nulled ports, which cancel out on-axis starlight but allow off-axis exoplanet light to couple. The null-depths are limited by wavefront aberrations in the system as well as by imperfections in the lantern. We show that the implicit electric field conjugation algorithm can be used to reduce the stellar coupling through the PLN by orders of magnitude while maintaining the majority of the off-axis light, leading to deeper null depths (~10^{-4}) and thus higher sensitivity to potential planet signals. We discuss a theory for the tradeoff we observed between the different ports, where iEFC improves the nulls of some ports at the expense of others, and show that targeting one port alone can lead to deeper starlight rejection through that port than when targeting all ports at once. We also observe different levels of stability depending on the port and discuss the implications for practically implementing this technique for science observations.

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arXiv2025

JWST/NIRCam Coronagraphic Search for Hidden Planets in the HD~163296 Protoplanetary Disk

HD~163296 is a Herbig Ae/Be star with multiple signposts of on-going planet formation on its disk, such as prominent rings and gaps, as well as kinematic features as identified by previous ALMA observations. We carried out JWST/NIRCam coronagraphic imaging using the F410M and F200W NIRCam filters, with the goal of detecting the emission from the putative young planets in this system. Our F410M observations did not detect the putative planets at the predicted locations of the ALMA velocity kinks, but detected a point-like source candidate at a separation of $\approx0\farcs75$ and a position angle of $\approx231\fdg4$ that is unlikely a background star because of the measured flux in the F410M filter and the detection limit in the F200W filter. These data achieved unprecedented contrast levels at $\sim4~\micron$ at stellocentric separations $\rho\gtrsim0\farcs8$. This allowed us to derive stringent constraints at the outer velocity kink ($\Delta {\rm F410M}=15.2~{\rm mag}$) on the mass of the putative planet with or without a circumplanetary disk, and considering different possible initial entropies for the planet.

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arXiv2025

Technical description and performance of the phase II version of the Keck Planet Imager and Characterizer

The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for the Keck II Adaptive Optics (AO) system and the NIRSPEC spectrograph to enable diffraction limited, high resolution (R>30000) spectroscopy of exoplanets and low mass companions in the K and L bands. Phase I consisted of single mode fiber injection/extraction units (FIU/FEU) used in conjunction with a H band pyramid wavefront sensor. The use of single mode fibers provides a gain in stellar rejection, a substantial reduction in sky background, and an extremely stable line spread function in the spectrograph. Phase II, deployed and commissioned in 2022, brought a 1000 actuator deformable mirror, beam shaping optics, a vortex mask, and other upgrades to the FIU/FEU. An additional service mission in 2024 extended operations down to y band, delivered an atmospheric dispersion corrector, and provided access to two laser frequency combs. KPIC phase II brings higher planet throughput, lower stellar leakage and many new observing modes which extend its ability to characterize exoplanets at high spectral resolution, building on the success of phase I. In this paper we present a description of the final phase II version of KPIC, along with results of system level laboratory testing and characterization showing the instrument's phase II throughput, stability, repeatability, and other key performance metrics prior to delivery and during installation at Keck. We outlined the capabilities of the various observing modes enabled by the new modules as well as efforts to compensate for static aberrations and non common path errors at Keck, which were issues that plagued phase I. Finally, we show results from commissioning.

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arXiv2025

HD 206893 B at High Spectral Resolution with the Keck Planet Imager and Characterizer (KPIC)

We present an atmospheric characterization and orbital analysis of HD 206893 B, an exceptionally red, L/T-transition substellar companion in a multiplanetary system, via Keck Planet Imager and Characterizer (KPIC) high-resolution (R $\sim$ 35,000) K-band spectroscopy. Using PHOENIX atmospheric models in a forward-model framework that fits the spectrum of the companion and diffracted starlight simultaneously, we detect HD 206893 B at $>8\sigma$ significance via cross-correlation in two epochs. We find an effective temperature for the companion of $1634^{+72}_{-38}$ K and a log(g) of $4.55^{+0.17}_{-0.22}$. Only accounting for statistical uncertainties, we measure the carbon-oxygen ratio (C/O) of this companion to be $0.57 \pm 0.02$, or near-solar while assuming solar metallicity. The C/O ratio we measure fits the tentative trend of $>4 M_{Jup}$ companions having near-solar C/O ratios while less massive companions have greater-than-solar C/O ratios. Using substellar evolution models, we find an age of $112^{+36}_{-22}$ Myr, a mass of $22.7^{+2.5}_{-1.7} M_{Jup}$, and a radius of $1.11 \pm 0.03 R_{Jup}$ for this companion. We also use KPIC radial velocity data to fit the orbit of HD 206893 B and analyze the orbital stability of this system. We find that the orbital stability is relatively independent of the mass of HD 206893 B, and favors an orbital configuration where B and its interior planetary companion, HD 206893 c, are co-planar. The measured C/O ratio coupled with the current architecture of the system cannot rule out a core accretion scenario, nor a disk fragmentation scenario regarding the formation pathway of HD 206893 B.

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arXiv2024

Efficiently Searching for Close-in Companions around Young M Dwarfs using a Multi-year PSF Library

We present Super-RDI, a unique framework for the application of reference star differential imaging (RDI) to Keck/NIRC2 high-contrast imaging observations with the vortex coronagraph. Super-RDI combines frame selection and signal-to-noise ratio (S/N) optimization techniques with a large multi-year reference point spread function (PSF) library to achieve optimal PSF subtraction at small angular separations. We compile a $\sim$7000 frame reference PSF library based on a set of 288 new Keck/NIRC2 $L'$ sequences of 237 unique targets acquired between 2015 and 2019 as part of two planet-search programs, one focusing on nearby young M dwarfs and the other targeting members of the Taurus star-forming region. For our dataset, synthetic companion injection-recovery tests reveal that frame selection with the mean-squared error (MSE) metric combined with KLIP-based PSF subtraction using 1000-3000 frames and $<$500 principal components yields the highest average S/N for injected synthetic companions. We uniformly reduce targets in the young M-star survey with both Super-RDI and angular differential imaging (ADI). For the typical parallactic angle rotation of our dataset ($\sim$10$^\circ$), Super-RDI performs better than a widely used implementation of ADI at separations $\lesssim$0.4" ($\approx$5 $λ$/$D$) gaining an average of 0.25 mag in contrast at 0.25" and 0.4 mag in contrast at 0.15". This represents a performance improvement in separation space over RDI with single-night reference star observations ($\sim$100 frame PSF libraries) applied to a similar Keck/NIRC2 dataset in previous work. We recover two known brown dwarf companions and provide detection limits for 155 targets in the young M-star survey. Our results demonstrate that increasing the PSF library size with careful selection of reference frames can improve the performance of RDI with the Keck/NIRC2 vortex coronagraph in $L'$.

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arXiv2024

Revisiting the Borde-Traub focal plane wavefront estimation technique for exoplanet direct imaging

Direct imaging of exoplanets relies on complex wavefront sensing and control architectures. In addition to fast adaptive optics systems, most of the future high-contrast imaging instruments will soon be equipped with focal plane wavefront sensing algorithms. These techniques use the science detector to estimate the static and quasi-static aberrations induced by optical manufacturing defects and system thermal variations. Pair-wise probing (PWP) has been the most widely used, especially for space-based application and will be tested at contrast levels of ~1e-9 on-sky along with the future coronagraph instrument onboarding the Roman Space Telescope. This algorithm leans on phase diversities applied on the deformable mirror that are recorded in pairs. A minimum of two pairs of probes are required per bandwidth. An additional unprobed image is also recorded to verify the convergence rate of the correction. Before PWP, Borde & Traub proposed a similar algorithm that takes advantage of the unprobed image in the estimation process to get rid of the pair diversity requirement. In this work, we theoretically show that this latter technique should be more efficient than PWP when the convergence time is not limited by photon noise. We then present its performance and practical limitations on coronagraphic testbeds at JPL and exhibit a first on-sky control of non-common path aberrations with such method on VLT/SPHERE.

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arXiv2024

RV measurements of directly imaged brown dwarf GQ Lup B to search for exo-satellites

GQ Lup B is one of the few substellar companions with a detected cicumplanetary disk, or CPD. Observations of the CPD suggest the presence of a cavity, possibly formed by an exo-satellite. Using the Keck Planet Imager and Characterizer (KPIC), a high contrast imaging suite that feeds a high resolution spectrograph (1.9-2.5 microns, R$\sim$35,000), we present the first dedicated radial velocity (RV) observations around a high-contrast, directly imaged substellar companion, GQ Lup B, to search for exo-satellites. Over 11 epochs, we find a best and median RV error of 400-1000 m/s, most likely limited by systematic fringing in the spectra due to transmissive optics within KPIC. With this RV precision, KPIC is sensitive to exomoons 0.6-2.8% the mass of GQ Lup B ($\sim 30 M_{\text{Jup}}$) at separations between the Roche limit and $65 R_{\text{Jup}}$, or the extent of the cavity inferred within the CPD detected around GQ Lup B. Using simulations of HISPEC, a high resolution infrared spectrograph planned to debut at W.M. Keck Observatory in 2026, we estimate future exomoon sensitivity to increase by over an order of magnitude, providing sensitivity to less massive satellites potentially formed within the CPD itself. Additionally, we run simulations to estimate the amount of material that different masses of satellites could clear in a CPD to create the observed cavity. We find satellite-to-planet mass ratios of $q > 2 \times 10^{-4}$ can create observable cavities and report a maximum cavity size of $\sim 51 \, R_{\text{Jup}}$ carved from a satellite.

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arXiv2024

Fringing analysis and forward modeling of Keck Planet Imager and Characterizer (KPIC) spectra

The Keck Planet Imager and Characterizer (KPIC) combines high contrast imaging with high resolution spectroscopy (R~35,000 in K band) to study directly imaged exoplanets and brown dwarfs in unprecedented detail. KPIC aims to spectrally characterize substellar companions through measurements of planetary radial velocities, spins, and atmospheric composition. Currently, the dominant source of systematic noise for KPIC is fringing, or oscillations in the spectrum as a function of wavelength. The fringing signal can dominate residuals by up to 10% of the continuum for high S/N exposures, preventing accurate wavelength calibration, retrieval of atmospheric parameters, and detection of planets with flux ratios less than 1% of the host star. To combat contamination from fringing, we first identify its three unique sources and adopt a physically informed model of Fabry-Perot cavities to apply to post-processed data. We find this strategy can effectively model the fringing in observations of A0V/F0V stars, reducing the residual systematics caused by fringing by a factor of 2. Next, we wedge two of the transmissive optics internal to KPIC to eliminate two sources of fringing and confirm the third source as the entrance window to the spectrograph. Finally, we apply our previous model of the Fabry-Perot cavity to new data taken with the wedged optics to reduce the amplitude of the residuals by a factor of 10.

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arXiv2024

A Survey of Protoplanetary Disks Using the Keck/NIRC2 Vortex Coronagraph

Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations of protoplanetary disks in the millimeter continuum have shown a variety of radial gaps, cavities, and spiral features. These substructures may be signposts for ongoing planet formation, and therefore these systems are promising targets for direct imaging planet searches in the near-infrared. To this end, we present results from a deep imaging survey in the $L'$-band (3.8 $μ$m) with the Keck/NIRC2 vortex coronagraph to search for young planets in 43 disks with resolved features in the millimeter continuum or evidence for gaps/central cavities from their spectral energy distributions. Although we do not detect any new point sources, using the vortex coronagraph allows for high sensitivity to faint sources at small angular separations (down to ${\sim}$0$^{\prime\prime}$.1), allowing us to place strong upper limits on the masses of potential gas giant planets. We compare our mass sensitivities to the masses of planets derived using ALMA observations, and while we are sensitive to $\sim$1 M$_{Jup}$ planets in the gaps in some of our systems, we are generally not sensitive to planets of the masses expected from the ALMA observations. In addition to placing upper limits on the masses of gas giant planets that could be interacting with the dust in the disks to form the observed millimeter substructures, we are also able to map the micron-sized dust as seen in scattered light for 8 of these systems. Our large sample of systems also allows us to investigate limits on planetary accretion rates and disk viscosities.

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arXiv2024

Comparative laboratory study of electric field conjugation algorithms

Future space telescope coronagraph instruments hinge on the integration of high-performance masks and precise wavefront sensing and control techniques to create dark holes essential for exoplanet detection. Recent advancements in wavefront control algorithms might exhibit differing performance depending on the coronagraph used. This research investigates three model-free and model-based algorithms in conjunction with either a vector vortex coronagraph or a scalar vortex coronagraph under identical laboratory conditions: pairwise probing with electric field conjugation, the self-coherent camera with electric field conjugation, and implicit electric field conjugation. We present experimental results in narrowband and broadband light from the In-Air Coronagraph Testbed at the Jet Propulsion Laboratory. We find that model-free dark hole digging methods achieve comparable broadband contrasts to model-based methods, and highlight the calibration costs of model-free methods compared to model-based approaches. This study also reports the first time that electric field conjugation with the self-coherent camera has been applied for simultaneous multi-subband correction with a field stop. This study compares the advantages and disadvantages of each of these wavefront sensing and control algorithms with respect to their potential for future space telescopes.

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