arXiv subjects

Bryony Nickson

Publications and source records attributed to Bryony Nickson.

10 recordsLinked to original sources

arXiv2026

JWST telemetry combined with active coronagraphy: raw contrast predictions for exoplanet imaging with the Habitable Worlds Observatory

We provide a quantification of the technological gap between the James Webb Space Telescope (JWST) and the Habitable Worlds Observatory (HWO) for the goal of exo-Earth imaging around Sun-like stars at the $10^{-10}$ raw contrast level. We use JWST's in-flight telemetry of the primary segmented mirror to simulate a JWST-like telescope equipped with a modern coronagraph instrument, inspired by the Roman Space Telescope (RST) Coronagraphic Instrument (CGI), featuring an Apodized Pupil Lyot Coronagraph and active deformable mirror wavefront control on a segmented, unobstructed, off-axis telescope. We show that it can achieve around $10^{-10}$ raw contrast for very bright stars (brighter than magnitude 4) for fast control frequencies of 100 Hz, but that this level of control still lacks sufficient signal to correct JWST-amplitude errors for fainter stars. We show that an improvement of a factor of ten in wavefront stability is sufficient to extend this capability to a $10^{-10}$ raw contrast across all considered control frequencies (1 Hz to 100 Hz), assuming no reaction wheel vibrations, for stars up to a magnitude of 11. These results establish a new quantitative benchmark linking JWST's demonstrated thermo-mechanical stability to HWO's requirements, showing that active wavefront control relaxes the structural stability demands on the observatory, and identifying wavefront stability as the critical technological gap that must be closed for HWO to achieve its exo-Earth imaging goals.

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arXiv2026

Tradeoff between segment density and IWA for high-contrast imaging of exoplanets with a large segmented space mission

Imaging Earth-like exoplanets with coronagraphs on future large segmented space telescopes such as the Habitable Worlds Observatory requires contrasts down to $10^{-10}$ at separations below 100 mas, imposing segment phasing control down to a few picometers. We evaluate how this constraint can be relaxed by optimizing telescope and instrument design, quantifying the impact on performance stability under segment phasing aberrations. We propose a system-level approach, adjusting the primary mirror segmentation and the focal-plane mask size (inner working angle). We compare the passive robustness to segment phasing errors across systems, and the ability of a Zernike low-order wavefront sensor to reconstruct aberrations and recover target performance. Increasing the focal-plane mask radius or decreasing segment count improves both passive robustness and sensor reconstruction: Increasing the mask radius from 3.5 to 6.5{\lambda}/D relaxes phasing constraints by up to a factor 4 near the IWA, and reducing the segment count from 85 (5 rings) to 7 (1 ring) relaxes them by up to a factor 2; The same mask radius increase also doubles, on average, the sensor's sensitivity to photon noise across segment piston, tip, and tilt modes. To conclude, jointly optimizing the segmentation scheme and mask size, so the low-order PSD envelope is blocked by the mask, can significantly relax phasing requirements, complementing active correction, with direct implications for HWO.

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arXiv2026

JWST Spectra Indicate a Large Mass of Postshock Dust Formed by SN 2010jl

We present new JWST mid-IR spectra and ground-based optical spectra of the lingering source at the position of SN 2010jl, which was a relatively nearby superluminous Type IIn supernova having strong interaction with circumstellar material (CSM). Early-time data showed evidence of dust, interpreted as either pre-existing CSM dust, or as newly formed dust in the SN ejecta and post-shock region. At 13 yr post explosion, JWST reveals a strong MIR excess from warm dust, with broad features at 10-15 $\mu$m. Our analysis reveals a minimum dust mass of $>$0.11 $M_{\odot}$, and a more likely value of 0.2 $M_{\odot}$ or more because the dust is optically thick. This is among the largest masses of SN-produced dust yet measured without far-IR/submm data, and greatly exceeds SN 2010jl's dust mass inferred around 2-3 yr post-explosion. Ground-based optical spectra confirm the presence of a young massive cluster at the SN position, and confirm that blueshifted line profiles persisting until the latest epochs arise from dust formed in the post-shock region. The warmest dust emitting in the MIR is likely to be the same post-shock dust causing the blueshift. The JWST spectrum also reveals silicate absorption, which may arise from cool SN ejecta dust along the line of sight to the receding shock. The large mass of post-shock dust in SN 2010jl suggests that strong CSM interaction promotes efficient dust production, where the new post-shock dust will survive. If strongly interacting SNe are common in the early Universe, this may contribute significantly to dust seen in infant galaxies.

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arXiv2026

CATKit2-HCI: a collaborative framework for advancing high-contrast coronagraph testbeds

High-contrast exoplanet imaging requires dedicated laboratory testbeds for the development and validation of coronagraph architectures, wavefront sensing and control methods, calibration strategies, and system-level observing concepts. These testbeds often share similar software needs, yet many tools are developed independently at each institution. The CATKit2-High-Contrast-Imaging collaboration, or CATKit2-HCI, addresses this gap by providing a shared software framework for reusable HCI infrastructure. Built on top of CATKit2, an open-source hardware control and synchronization framework originally developed for the High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed at the Space Telescope Science Institute, CATKit2-HCI provides the collaborative layer for HCI-specific algorithms, calibration tools, diagnostics, visualization, and performance metrics. The collaboration currently includes multiple coronagraph testbeds in the United States and Europe. Its goals are to reduce duplicated software development, improve code quality through shared review, enable more direct comparison of results across facilities, and facilitate the movement of students, postdoctoral researchers, and collaborators between laboratories. We describe the motivation, architecture, collaboration model, shared technical capabilities, and early cross-testbed examples of CATKit2-HCI as a framework for accelerating coronagraph technology development.

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arXiv2026

Impact of segmented deformable mirrors on high-contrast testbeds for exoplanet imaging with future large space telescopes: contrast stability assessment on the HiCAT bench

We investigate the stability of a segmented deformable mirror (DM) on high-contrast testbeds and its impact on the images produced with coronagraphs. Segmented apertures are promising to obtain large primary mirrors for future missions with starlight suppression capabilities. Cophased at the sub-nanometer level, segments can be slightly misaligned by small drifts, proving harmful for exoplanet observations. We study the impact of misalignments on contrast using the High-contrast Imager for Complex Aperture Telescopes (HiCAT), a testbed which includes a 37-segment DM and produces coronagraphic images with 2.5e-8 contrast in narrowband light. Temporal wavefront errors due to the segmented DM are estimated with a Zernike wavefront sensor. Our in-lab results show aberrations at the sub-nanometer level, proving encouraging for contrast stability studies. We then use a digital twin of HiCAT to simulate coronagraphic images with an initial 0.5e-8 contrast and the segments in flat position. By injecting known perturbations on the segments, we observe a contrast degradation by a factor of 2.5, nearly corresponding to the typical contrast observed on HiCAT. These results highlight the importance of segment cophasing sensing and control strategies to ensure the required contrasts for exo-Earth imaging with a large segmented aperture for the Habitable Worlds Observatory mission.

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arXiv2025

Very Late-Time JWST and Keck Spectra of the Oxygen-Rich Supernova 1995N

We present new {\it JWST}/MIRI MRS and Keck spectra of SN 1995N obtained in 2022--2023, more than 10,000 days after the supernova (SN) explosion. These spectra are among the latest direct detections of a core-collapse SN, both through emission lines in the optical and thermal continuum from infrared dust emission. The new infrared data show that dust heating from radiation produced by the ejecta interacting with circumstellar matter is still present, but greatly reduced from when SN 1995N was observed by the {\it Spitzer Space Telescope} and {\it WISE} in 2009/2010 and 2018, when the dust mass was estimated to be 0.4 M(Sun). New radiative-transfer modeling suggests that the dust mass and grain size may have increased between 2010 and 2023. The new data can alternatively be well fit with a dust mass of 0.4 M(Sun) and a much reduced heating source luminosity. The new late-time spectra show unusually strong oxygen forbidden lines, stronger than the H-alpha emission. This indicates that SN 1995N may have exploded as a stripped-envelope SN which then interacted with a massive H-rich circumstellar shell, changing it from intrinsically Type Ib/c to Type IIn. The late-time spectrum results when the reverse shock begins to excite the inner H-poor, O-rich ejecta. This change in the spectrum is rarely seen, but marks the start of the transition from SN to SN remnant.

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arXiv2024

JWST/MIRI Observations of Newly Formed Dust in the Cold, Dense Shell of the Type IIn SN 2005ip

Dust from core-collapse supernovae (CCSNe), specifically Type IIP SNe, has been suggested to be a significant source of the dust observed in high-redshift galaxies. CCSNe eject large amounts of newly formed heavy elements, which can condense into dust grains in the cooling ejecta. However, infrared (IR) observations of typical CCSNe generally measure dust masses that are too small to account for the dust production needed at high redshifts. Type IIn SNe, classified by their dense circumstellar medium (CSM), are also known to exhibit strong IR emission from warm dust, but the dust origin and heating mechanism have generally remained unconstrained because of limited observational capabilities in the mid-IR. Here, we present a JWST/MIRI Medium Resolution Spectrograph (MRS) spectrum of the Type IIn SN 2005ip nearly 17 years post-explosion. The Type IIn SN 2005ip is one of the longest-lasting and most well-studied SNe observed to date. Combined with a Spitzer mid-IR spectrum of SN 2005ip obtained in 2008, this data set provides a rare 15-year baseline, allowing for a unique investigation of the evolution of dust. The JWST spectrum shows a new high-mass dust component ($\gtrsim0.08$ M$_{\odot}$) that is not present in the earlier Spitzer spectrum. Our analysis shows dust likely formed over the past 15 years in the cold, dense shell (CDS), between the forward and reverse shocks. There is also a smaller mass of carbonaceous dust ($\gtrsim0.005$ M$_{\odot}$) in the ejecta. These observations provide new insights into the role of SN dust production, particularly within the CDS, and its potential contribution to the rapid dust enrichment of the early Universe.

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arXiv2024

High-contrast imager for complex aperture telescopes (HiCAT): 8. Dark zone demonstration with simultaneous closed-loop low-order wavefront sensing and control

We present recent laboratory results demonstrating high-contrast coronagraphy for the future space-based large IR/Optical/Ultraviolet telescope recommended by the Decadal Survey. The High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed aims to implement a system-level hardware demonstration for segmented aperture coronagraphs with wavefront control. The telescope hardware simulator employs a segmented deformable mirror with 37 hexagonal segments that can be controlled in piston, tip, and tilt. In addition, two continuous deformable mirrors are used for high-order wavefront sensing and control. The low-order sensing subsystem includes a dedicated tip-tilt stage, a coronagraphic target acquisition camera, and a Zernike wavefront sensor that is used to measure and correct low-order aberration drifts. We explore the performance of a segmented aperture coronagraph both in static operations (limited by natural drifts and instabilities) and in dynamic operations (in the presence of artificial wavefront drifts added to the deformable mirrors), and discuss the estimation and control strategies used to reach and maintain the dark-zone contrast using our low-order wavefront sensing and control. We summarize experimental results that quantify the performance of the testbed in terms of contrast, inner/outer working angle and bandpass, and analyze limiting factors.

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arXiv2024

High-contrast imager for complex aperture telescopes (HiCAT): 11. System-level demonstration of the Apodized Pupil Lyot Coronagraph with a segmented aperture in air

We present the final results of the Apodized Pupil Lyot Coronagraph (APLC) on the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed, under NASA's Strategic Astrophysics Technology program. The HiCAT testbed was developed over the past decade to enable a system-level demonstration of coronagraphy for exoplanet direct imaging with the future Habitable Wolds Observatory. HiCAT includes an active, segmented telescope simulator, a coronagraph, and metrology systems (Low-order and Mid-Order Zernike Wavefront Sensors, and Phase Retrieval camera). These results correspond to an off-axis (un-obscured) configuration, as was envisioned in the 2020 Decadal Survey Recommendations. Narrowband and broadband dark holes are generated using two continuous deformable mirrors (DM) to control high order wavefront aberrations, and low-order drifts can be further stabilized using the LOWFS loop. The APLC apodizers, manufactured using carbon nanotubes, were optimized for broadband performance and include the calibrated geometric aperture. HiCAT is, to this date, the only testbed facility able to demonstrate high-contrast coronagraphy with a truly segmented aperture, as is required for the Habitable World Observatory, albeit limited to ambient conditions. Results presented here include $6\times 10^{-8}$ (90% CI) contrast in 9% bandpass in a 360 deg dark hole with inner and outer working angles of $4.4 λ/D_{pupil}$ and $11 λ/D_{pupil}$ . Narrowband contrast (3% bandpass) reaches $2.4\times 10^{-8}$ (90% confidence interval).

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arXiv2022

JWST/NIRCam Coronagraphy: Commissioning and First On-Sky Results

In a cold and stable space environment, the James Webb Space Telescope (JWST or "Webb") reaches unprecedented sensitivities at wavelengths beyond 2 microns, serving most fields of astrophysics. It also extends the parameter space of high-contrast imaging in the near and mid-infrared. Launched in late 2021, JWST underwent a six month commissioning period. In this contribution we focus on the NIRCam Coronagraphy mode which was declared "science ready" on July 10 2022, the last of the 17 JWST observing modes. Essentially, this mode will allow to detect fainter/redder/colder (less massive for a given age) self-luminous exoplanets as well as other faint astrophysical signal in the vicinity of any bright object (stars or galaxies). Here we describe some of the steps and hurdles the commissioning team went through to achieve excellent performances. Specifically, we focus on the Coronagraphic Suppression Verification activity. We were able to produce firm detections at 3.35$μ$m of the white dwarf companion HD 114174 B which is at a separation of $\simeq$ 0.5" and a contrast of $\simeq$ 10 magnitudes ($10^{4}$ fainter than the K$\sim$5.3 mag host star). We compare these first on-sky images with our latest, most informed and realistic end-to-end simulations through the same pipeline. Additionally we provide information on how we succeeded with the target acquisition with all five NIRCam focal plane masks and their four corresponding wedged Lyot stops.

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