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David Pearson

Publications and source records attributed to David Pearson.

12 recordsLinked to original sources
arXiv2026

Direct Imaging Discovery of Giant Exoplanet $\beta$ Pictoris d: A Decade-Long Game of Hide-and-Seek

We report the direct imaging discovery of a third exoplanet in the $\beta$ Pictoris system. We detect $\beta$ Pictoris d ($\beta$ Pic d) in non-coronagraphic observations obtained with VLT/ERIS as well as multi-epoch archival datasets from JWST/NIRCam and VLT/SPHERE. Astrometric measurements over an 11-year baseline demonstrate that it is consistent with a gravitationally-bound source with orbital motion. Joint multi-planet orbit fits of all three planets in the system yield a semi-major axis of $26.0^{+2.2}_{-6.1}$ au and inclination $89.0^{+0.7}_{-0.6}$ deg for planet d. $\beta$ Pic d has a larger orbital semi-major axis than the other known planets in the system, but is coplanar with the inner two planets, and its orbit is consistent with sculpting the inner edge of the debris disk. $\beta$ Pic d has a contrast of $\Delta L^{\prime}=12.11\pm0.15$ mag, with colors and luminosity that closely match those of 51 Eri b, another exoplanet in the $\beta$ Pictoris moving group. Its VLT/ERIS and JWST/NIRCam colors are distinct from those of free-floating planetary-mass objects of a similar age and temperature. Its red $F410M-F444W$ color indicates strong CO$_2$ absorption in its atmosphere and suggests significant enhancement in metals compared to free-floating objects. From the ATMO hot-start evolutionary models, we estimate an effective temperature of $600^{+45}_{-60}$ K and mass of $2.4\pm0.6$ $M_{\rm Jup}$, which also closely matches similar estimates for 51 Eri b. $\beta$ Pic d is among the lowest-mass exoplanets imaged from the ground. This discovery highlights the deep sensitivity achievable with ground-based imaging in the mid-infrared and the discovery potential of future high-contrast observations with the Extremely Large Telescope.

astro-ph.EP↗
arXiv2025

The SPace-based InterFerometer Feasibility (SPIFF) Project: Enabling Future High-Resolution Astronomy Across the EM Spectrum

A plethora of astronomical science cases can only be achieved with high angular resolution observations, and we can expect the number of these to grow as astronomers are constrained by the size limitations of single-aperture space telescopes, making space-based interferometry inevitable. However, the enabling technologies do not have flight heritage at the system level, and the concept remains immature to much of the community, meaning no direct-detection synthetic-aperture space-based interferometer has yet flown and an opportunity exists for the UK to take a world leading role. Here we propose the SPace-based InterFerometry Feasibility (SPIFF) Project as a program to address both issues simultaneously by: 1) completing a thorough survey of the science cases across the EM spectrum that would directly benefit from, or be impossible without, space-based interferometry; 2) down selecting key requirements via a Science Traceability Matrix mapping exercise; 3) host a workshop for the UK astronomical community to consolidate these findings; 4) build a technology demonstration mission to raise TRL and achieve flight heritage of critical technologies. Such a program positions the UK as the partner of choice for any future NASA or ESA space-based interferometry mission, allowing the UK to lead groundbreaking scientific discoveries, while also directly benefiting the UK industrial base by advancing domestic exportable technologies and building direct synergy with other UK space priorities. Indeed, the UK is uniquely positioned to lead in space-based interferometry, possessing a rare trifecta of domestic strengths: world-class expertise in ground-based interferometry and space-based instrumentation; commercial entities developing mission-critical technologies; and scientists whose research spans the full range of science cases that would benefit directly from space-based interferometry.

astro-ph.IM↗
arXiv2025

High-contrast spectroscopy with the new VLT/ERIS instrument: Molecular maps and radial velocity of the gas giant AF Lep b

The Enhanced Resolution Imager and Spectrograph (ERIS) is the new Adaptive-Optics (AO) assisted Infrared instrument at the Very Large Telescope (VLT). Its refurbished Integral Field Spectrograph (IFS) SPIFFIER leverages a new AO module, enabling high-contrast imaging applications and giving access to the orbital and atmospheric characterisation of super-Jovian exoplanets. We test the detection limits of ERIS and demonstrate its scientific potential by exploring the atmospheric composition of the young super-Jovian AF Lep b and improving its orbital solution by measuring its radial velocity relative to its host star. We present new spectroscopic observations of AF Lep b in $K$-band at $R\sim 11000$ obtained with ERIS/SPIFFIER at the VLT. We reduce the data using the standard pipeline together with a custom wavelength calibration routine, and remove the stellar PSF using principal component analysis along the spectral axis. We compute molecular maps by cross-correlating the residuals with molecular spectral templates and measure the radial velocity of the planet relative to the star. Furthermore, we compute contrast grids for molecular mapping by injecting fake planets. We detect a strong signal from H$_{2}$O and CO but not from CH$_{4}$ or CO$_{2}$. This result corroborates the hypothesis of chemical disequilibrium in the atmosphere of AF Lep b. Our measurement of the RV of the planet yields $\Delta v_{\mathrm{R,P\star}} = 7.8 \pm 1.7$ km s$^{-1}$. This enables us to disentangle the degeneracy of the orbital solution, namely the correct longitude of the ascending node is $\Omega=248^{+0.4}_{-0.7}$ deg and the argument of periapsis is $\omega=109^{+13}_{-21}$ deg. Our results demonstrate the competitiveness of the new ERIS/SPIFFIER instrument for the orbital and atmospheric characterisation of exoplanets at high contrast and small angular separation.

astro-ph.EP↗
arXiv2018

Laboratory Demonstration of an Active Optics System for High-Resolution Deployable CubeSat

In this paper we present HighRes: a laboratory demonstration of a 3U CubeSat with a deployable primary mirror that has the potential of achieving high-resolution imaging for Earth Observation. The system is based on a Cassegrain telescope with a segmented primary mirror composed of 4 petals that form an effective aperture of 300 mm. The design provides diffraction limited performance over the entire field-of-view and allows for a panchromatic ground-sampling distance of less than 1 m at an altitude of 350 km. The alignment and co-phasing of the mirror segments is performed by focal plane sharpening and is validated through rigorous numerical simulations. The opto-mechanical design of the prototype and its laboratory demonstration are described and measurements from the on-board metrology sensors are presented. This data verifies that the performance of the mirror deployment and manipulation systems is sufficient for co-phasing. In addition, it is shown that the mirrors can be driven to any target position with an accuracy of 25 nm using closed-loop feedback between the mirror motors and the on-board metrology.

astro-ph.IM↗
arXiv2018

ERIS: revitalising an adaptive optics instrument for the VLT

ERIS is an instrument that will both extend and enhance the fundamental diffraction limited imaging and spectroscopy capability for the VLT. It will replace two instruments that are now being maintained beyond their operational lifetimes, combine their functionality on a single focus, provide a new wavefront sensing module that makes use of the facility Adaptive Optics System, and considerably improve their performance. The instrument will be competitive with respect to JWST in several regimes, and has outstanding potential for studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS had its final design review in 2017, and is expected to be on sky in 2020. This contribution describes the instrument concept, outlines its expected performance, and highlights where it will most excel.

astro-ph.IM↗
arXiv2013

Algorithms for estimating spectral density functions for periodic potentials on the half line

For Hill's equation on [0,infinity) we prove new characterizations of the spectral function rho(lambda) and the spectral density function f(lambda) based on analysis involving a companion system of first order differential equations in [6,7]. A numerical algorithm is derived and implemented based on coefficient approximation. Results for several examples, including the Mathieu equation, are presented.

math.NA↗
arXiv2013

Estimating Spectral Density Functions for Sturm-Liouville problems with two singular endpoints

In this paper we consider the Sturm-Liouville equation -y"+qy = lambda*y on the half line (0,infinity) under the assumptions that x=0 is a regular singular point and nonoscillatory for all real lambda, and that either (i) q is L_1 near x=infinity, or (ii) q' is L_1 near infinity with q(x) --> 0 as x --> infinity, so that there is absolutely continuous spectrum in (0,infinity). Characterizations of the spectral density function for this doubly singular problem, similar to those obtained in [12] and [13] (when the left endpoint is regular) are established; corresponding approximants from the two algorithms in [12] and [13] are then utilized, along with the Frobenius recurrence relations and piecewise trigonometric - hyperbolic splines, to generate numerical approximations to the spectral density function associated with the doubly singular problem on (0,infinity). In the case of the radial part of the separated hydrogen atom problem, the new algorithms are capable of achieving near machine precision accuracy over the range of lambda from 0.1 to 10000, accuracies which could not be achieved using the SLEDGE software package.

math.NA↗
arXiv2011

The effect of changing electrode metal on solution-processed flexible titanium dioxide memristors

Flexible solution processed memristors show different behaviour dependent on the choice of electrode material. Use of gold for both electrodes leads to switchable WORM (Write Once Read Many times) resistive devices. Use of aluminium for both electrodes increases the richness of behaviour allowing both curved and triangular memristive switching resistance memories. A comparison device with an aluminium bottom electrode and gold top electrode only exhibited significant memristive resistance switching when the aluminium electrode was the cathode, suggesting that the electrode is acting as a source/sink of oxygen anions. When the gold electrode was the cathode this electrode was deformed by oxygen evolution. These results demonstrate that aluminium is helpful for stabilising and promoting memristive behaviour in sol-gel TiO$_2$ devices and that changing electrodes from aluminium to gold creates fundamentally different device characteristics.

cond-mat.mtrl-sci↗
arXiv2005

Current status of the DARPA Quantum Network

This paper reports the current status of the DARPA Quantum Network, which became fully operational in BBN's laboratory in October 2003, and has been continuously running in 6 nodes operating through telecommunications fiber between Harvard University, Boston University, and BBN since June 2004. The DARPA Quantum Network is the world's first quantum cryptography network, and perhaps also the first QKD systems providing continuous operation across a metropolitan area. Four more nodes are now being added to bring the total to 10 QKD nodes. This network supports a variety of QKD technologies, including phase-modulated lasers through fiber, entanglement through fiber, and freespace QKD. We provide a basic introduction and rational for this network, discuss the February 2005 status of the various QKD hardware suites and software systems in the network, and describe our operational experience with the DARPA Quantum Network to date. We conclude with a discussion of our ongoing work.

quant-ph↗
arXiv2004

On the Optimal Mean Photon Number for Quantum Cryptography

The optimal mean photon number (mu) for quantum cryptography is the average photon number per transmitted pulse that results in the highest delivery rate of distilled cryptographic key bits, given a specific system scenario and set of assumptions about Eve's capabilities. Although many experimental systems have employed a mean photon number (mu) of 0.1 in practice, several research teams have pointed out that this value is somewhat arbitrary. In fact, various optimal values for mu have been described in the literature. In this paper we offer a detailed analytic model for an experimental, fiber-based quantum cryptographic system, and an explicit set of reasonable assumptions about Eve's current technical capabilities. We explicitly model total system behavior ranging from physical effects to the results of quantum cryptographic protocols such as error correction and privacy amplification. We then derive the optimal photon number (mu) for this system in a range of scenarios. One interesting result is that mu of approximately 1.1 is optimal for a wide range of realistic, fiber-based QKD systems; in fact, it provides nearly 10 times the distilled throughput of systems that employ a more conventional mu = 0.1, without any adverse affect on system security, as judged against a set of reasonable assumptions about Eve's current capabilities.

quant-ph↗
arXiv2003

Quantum Cryptography in Practice

BBN, Harvard, and Boston University are building the DARPA Quantum Network, the world's first network that delivers end-to-end network security via high-speed Quantum Key Distribution, and testing that Network against sophisticated eavesdropping attacks. The first network link has been up and steadily operational in our laboratory since December 2002. It provides a Virtual Private Network between private enclaves, with user traffic protected by a weak-coherent implementation of quantum cryptography. This prototype is suitable for deployment in metro-size areas via standard telecom (dark) fiber. In this paper, we introduce quantum cryptography, discuss its relation to modern secure networks, and describe its unusual physical layer, its specialized quantum cryptographic protocol suite (quite interesting in its own right), and our extensions to IPsec to integrate it with quantum cryptography.

quant-ph↗