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1. First Resolution of Microlensed Images of a Binary-lens Event

   https://doi.org/10.3847/1538-4357/ad90b9  

   Wu, Zexuan; Dong, Subo; Mérand, A; Kochanek, Christopher S; Mróz, Przemek; Shangguan, Jinyi; Christie, Grant; Tan, Thiam-Guan; Bensby, Thomas; Bland-Hawthorn, Joss; et al (December 2024, The Astrophysical Journal)

   Abstract We resolve the multiple images of the binary-lens microlensing event ASASSN-22av using the GRAVITY instrument of the Very Large Telescope Interferometer (VLTI). The light curves show weak binary-lens perturbations, complicating the analysis, but the joint modeling with the VLTI data breaks several degeneracies, arriving at a strongly favored solution. Thanks to precise measurements of the angular Einstein radiusθ_E= 0.724 ± 0.002 mas and microlens parallax, we determine that the lens system consists of two M dwarfs with masses ofM₁= 0.258 ± 0.008M_⊙andM₂= 0.130 ± 0.007M_⊙, a projected separation ofr_⊥= 6.83 ± 0.31 au, and a distance ofD_L= 2.29 ± 0.08 kpc. The successful VLTI observations of ASASSN-22av open up a new path for studying intermediate-separation (i.e., a few astronomical units) stellar-mass binaries, including those containing dark compact objects such as neutron stars and stellar-mass black holes. 

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2. The Carousel Lens: A Well-modeled Strong Lens with Multiple Sources Spectroscopically Confirmed by VLT/MUSE

   https://doi.org/10.3847/1538-4357/ad65d3  

   Sheu, William; Cikota, Aleksandar; Huang, Xiaosheng; Glazebrook, Karl; Storfer, Christopher; Agarwal, Shrihan; Schlegel, David J; Suzuki, Nao; Barone, Tania M; Bian, Fuyan; et al (September 2024, The Astrophysical Journal)

   Over the past few years alone, the lensing community has discovered thousands of strong lens candidates, and spectroscopically confirmed hundreds of them. In this time of abundance, it becomes pragmatic to focus our time and resources on the few extraordinary systems, in order to most efficiently study the Universe. In this paper, we present such a system: DESI-090.9854-35.9683, a cluster-scale lens atz_l= 0.49, with seven observed lensed sources around the core, and additional lensed sources further out in the cluster. From the number and the textbook configuration of the lensed images, a tight constraint on the mass potential of the lens is possible. This would allow for detailed analysis on the dark and luminous matter content within galaxy clusters, as well as a probe into dark energy and high-redshift galaxies. We present our spatially resolved kinematic measurements of this system from the Very Large Telescope Multi Unit Spectroscopic Explorer, which confirm five of these source galaxies (in ascending order, atz_s= 0.962, 0.962, 1.166, 1.432, and 1.432). With previous Hubble Space Telescope imaging in the F140W and F200LP bands, we also present a simple flux-based lens model consisting of two power-law profiles that, for a cluster lens, well models the five lensed arc families with redshifts. We determine the mass to beM(<θ_E) = 4.78 × 10¹³M_⊙for the primary mass potential. From the model, we extrapolate the redshift of one of the two source galaxies not yet spectroscopically confirmed to be at $z_{\mathrm{s}}={4.52}_{-0.71}^{+1.03}$. 

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3. Single atom trapping in a metasurface lens optical tweezer

   https://doi.org/10.48550/arXiv.2110.11559  

   Hsu, T-W; Zhu, W.; Thiele, T.; Brown, M.O.; Papp, S.B.; Agrawal, A.; Regal, C.A. (July 2022, ArXivorg)

   Optical metasurfaces of sub-wavelength pillars have provided new capabilities for the versatile definition of the amplitude, phase, and polarization of light. In this work we demonstrate that an efficient dielectric metasurface lens can be used to trap and image single neutral atoms. We characterize the high numerical aperture optical tweezers using the trapped atoms and compare to numerical computations of the metasurface lens performance. We predict future metasurfaces for atom trapping can leverage multiple ongoing developments in metasurface design and enable multifunctional control in complex experiments with neutral-atoms arrays. 

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4. Tunable liquid lens for three-photon excitation microscopy

   https://doi.org/10.1364/BOE.516956  

   Gilinsky, Samuel_D; Jung, Diane_N; Futia, Greg_L; Zohrabi, Mo; Welton, Tarah_A; Supekar, Omkar_D; Gibson, Emily_A; Restrepo, Diego; Bright, Victor_M; Gopinath, Juliet_T (April 2024, Biomedical Optics Express)

   We demonstrate a novel electrowetting liquid combination using a room temperature ionic liquid (RTIL) and a nonpolar liquid, 1-phenyl-1-cyclohexene (PCH) suitable for focus-tunable 3-photon microscopy. We show that both liquids have over 90% transmission at 1300 nm over a 1.1 mm pathlength and an index of refraction contrast of 0.123. A lens using these liquids can be tuned from a contact angle of 133 to 48° with applied voltages of 0 and 60 V, respectively. Finally, a three-photon imaging system including an RTIL electrowetting lens was used to image a mouse brain slice. Axial scans taken with an electrowetting lens show excellent agreement with images acquired using a mechanically scanned objective. 

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5. TDCOSMO: XIV. Practical techniques for estimating external convergence of strong gravitational lens systems and applications to the SDSS J0924+0219 system

   https://doi.org/10.1051/0004-6361/202346093  

   Wells, Patrick; Fassnacht, Christopher D.; Rusu, C. E. (August 2023, Astronomy & Astrophysics)

   Context.Time-delay cosmography uses strong gravitational lensing of a time-variable source to infer the Hubble constant. The measurement is independent from both traditional distance ladder and CMB measurements. An accurate measurement with this technique requires considering the effects of objects along the line of sight outside the primary lens, which is quantified by the external convergence (κ_ext). In absence of such corrections,H₀will be biased towards higher values in overdense fields and lower values in underdense fields. Aims.We discuss the current state of the methods used to account for environment effects. We present a new software package built for this kind of analysis and others that can leverage large astronomical survey datasets. We apply these techniques to the SDSS J0924+0219 strong lens field. Methods.We infer the relative density of the SDSS J0924+0219 field by computing weighted number counts for all galaxies in the field, and comparing to weighted number counts computed for a large number of fields in a reference survey. We then compute weighted number counts in the Millennium Simulation and compare these results to infer the external convergence of the lens field. Results.Our results show the SDSS J0924+0219 field is a fairly typical line of sight, with medianκ_ext = −0.012 and standard deviationσ_κ = 0.028. 

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