UMBC Physics Department

Permanent URI for this collectionhttp://hdl.handle.net/11603/57

The mission of the Department of Physics at UMBC is based on three pillars: education, research and service to society. We strive to provide outstanding educational opportunities, through instruction and research, for undergraduate physics majors seeking preparation for graduate school or entry into the workforce. We also aim to train graduate students to be leaders in their field of research. Our research goal is to grow and sustain internationally recognized research groups in atmospheric physics, astrophysics, condensed matter physics and quantum optics and information science. Through our teaching of physics to non-science and non-physics majors and through our Physics for Secondary Education Teachers program, we provide professional service to the university community and the State.

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Observable-based reformulation of time-delay interferometry
(2025-02-16) Yamamoto, Kohei; Reinhardt, Jan Niklas; Hartwig, Olaf
Spaceborne gravitational-wave observatories utilize a post-processing technique known as time-delay interferometry (TDI) to reduce the otherwise overwhelming laser frequency noise by around eight orders of magnitude. While, in its traditional form, TDI considers the spacecraft as point masses, recent studies have enhanced this simplified scenario by incorporating more realistic metrology chain models, which include onboard optical, electronic, and digital delays. These studies have updated the TDI algorithm to include onboard delays obtained from pre-launch and in-flight calibrations. Conversely, the processing scheme presented in this article naturally treats onboard delays as part of the TDI combinations: instead of having separate calibration stages, it directly expresses all delays appearing in the algorithm in terms of onboard measurements, especially pseudo-random-noise ranging (PRNR) measurements. The only onboard delays that need to be corrected in our processing scheme are PRNR delays in the digital domain, which are determined by commandable digital-signal-processing parameters; hence, they can be easily managed in post-processing. Furthermore, our processing scheme does not require a prior interspacecraft clock synchronization, and it automatically corrects for potential relative drifts between the clocks driving local phase measurement systems. The proposed observable-based processing scheme significantly strengthens the bond between TDI and the real metrology system.
No-go theorem for environment-assisted invariance in non-unitary dynamics
(2025-03-13) Sone, Akira; Touil, Akram; Maeda, Kenji; Cappellaro, Paola; Deffner, Sebastian
We elucidate the requirements for quantum operations that achieve environment-assisted invariance (envariance), a symmetry of entanglement. While envariance has traditionally been studied within the framework of local unitary operations, we extend the analysis to consider non-unitary local operations. First, we investigate the conditions imposed on operators acting on pure bipartite entanglement to attain envariance. We show that the local operations must take a direct-sum form in their Kraus operator representations, establishing decoherence-free subspaces. Furthermore, we prove that the unitary operation on the system's subspace uniquely determines the corresponding unitary operator on the environment's subspace. As an immediate consequence, we demonstrate that environment-assisted shortcuts to adiabaticity cannot be achieved through non-unitary operations. In addition, we identify the requirements that local operations must satisfy to ensure that the eternal black hole states remain static in AdS/CFT.
Multispectral Land Surface Reflectance Reconstruction Based on Non-Negative Matrix Factorization: Bridging Spectral Resolution Gaps for GRASP TROPOMI BRDF Product in Visible
(MDPI, 2025-03-17) Hou, Weizhen; Liu, Xiong; Wang, Jun; Chen, Cheng; Xu, Xiaoguang
In satellite remote sensing, mixed pixels commonly arise in medium- and low-resolution imagery, where surface reflectance is a combination of various land cover types. The widely adopted linear mixing model enables the decomposition of mixed pixels into constituent endmembers, effectively bridging spectral resolution gaps by retrieving the spectral properties of individual land cover types. This study introduces a method to enhance multispectral surface reflectance data by reconstructing additional spectral information, particularly in the visible spectral range, using the TROPOMI BRDF product generated by the Generalized Retrieval of Atmosphere and Surface Properties (GRASP) algorithm. Employing non-negative matrix factorization (NMF), the approach extracts spectral basis vectors from reference spectral libraries and reconstructs key spectral features using a limited number of wavelength bands. The comprehensive test results show that this method is particularly effective in supplementing surface reflectance information for specific wavelengths where gas absorption is strong or atmospheric correction errors are significant, demonstrating its applicability not only within the 400–800 nm range but also across the broader spectral range of 400–2400 nm. While not a substitute for hyperspectral observations, this approach provides a cost-effective means to address spectral resolution gaps in multispectral datasets, facilitating improved surface characterization and environmental monitoring. Future research will focus on refining spectral libraries, improving reconstruction accuracy, and expanding the spectral range to enhance the applicability and robustness of the method for diverse remote sensing applications.
Ghost imaging—its physics and application [Invited]
(Chinese Optics Letters, 2024-07-01) Shih, Yanhua
Since its first experimental demonstration, “ghost imaging” has attracted much attention, perhaps not only because of its interesting physics but also because of its attractive application. This review article discusses the physics and application of ghost imaging: (1) emphasizes the nonlocal two-photon interference nature of ghost imaging, including detailed analysis and calculations; (2) introduces three types of applications with unique advantages of ghost imaging, including a light detection and ranging device with imaging ability, namely, an Imaging Lidar or ILidar system; a turbulence-resistant, or turbulence-free, imaging technology; and a vibration-resistant X-ray microscope of high resolving capability. This article is prepared for a Special Issue of Chinese Optics Letters, intended for general audiences, especially young researchers and students who are interested in ghost imaging.
Experimental Demonstration of Turbulence-resistant Lidar via Quantum Entanglement
(2024-05-14) Joshi, Binod; Fitelson, Michael M.; Shih, Yanhua
We report a proof-of-principle experimental demonstration of a turbulence-resistant quantum Lidar system. As a key technology for sensing and ranging, Lidar has drawn considerable attention for a study from quantum perspective, in search of proven advantages complementary to the capabilities of conventional Lidar technologies. Environmental factors such as strong atmospheric turbulence can have detrimental effects on the performance of these systems. We demonstrate the possibility of turbulence-resistant operation of a quantum Lidar system via two-photon interference of entangled photon pairs. Additionally, the reported quantum Lidar also demonstrates the expected noise resistance. This study suggests a potential high precision timing-positioning technology operable under turbulence and noise.
Developing Advanced Cloud Retrievals for PACE: Building a Joint Spectro-Polarimetric Cloud Microphysics Retrieval
(NASA, 2024-12) Miller, Daniel J.; Meyer, Kerry; Platnick, Steven E.; Zhang, Zhibo; Ademakinwa, Adeleke; Sinclair, Kenneth; Alexandrov, Mikhail; Geogdzhayev, Igor; van Diedenhoven, Bastiaan
Developing a Lagrangian Frame Transformation on Satellite Data to Study Cloud Microphysical Transitions in Arctic Marine Cold Air Outbreaks
(2025-03-13) Seppala, Hannah; Zhang, Zhibo; Zheng, Xue
Arctic marine cold air outbreaks (CAOs) generate distinct and dynamic cloud regimes due to intense air-sea interactions. To understand the temporal evolution of CAO cloud properties and compare different CAO events, a Lagrangian perspective is particularly useful. We developed a novel technique that enables the conversion of inherently Eulerian satellite data into a Lagrangian framework, combining the broad spatiotemporal coverage of satellite observations with the advantages of Lagrangian tracking. This technique was applied to eight CAO cases associated with a recent field campaign. Our results reveal a striking contrast among the cases in terms of cloud-top phase transitions, providing new insights into the evolution of CAO cloud properties.
Artifact: Defining and Analyzing Smart Device Passive Mode
(HAL, 2025-03-17) Badolato, Christian; Kullman, Kaur; Papadakis, Nikolaos; Bhatt, Manav; Bouloukakis, Georgios; Engel, Don; Yus, Roberto
This artifact paper presents a guide for the Smart Home IoT Passive Mode Analysis tool and dataset to perform network traffic analysis (NTA) on smart home IoT devices in passive mode. The repository includes: 1) scripts and configurations for processing network traffic capture files and extracting the relevant information; 2) output data files for the experiments conducted; and 3) a link to the raw network capture dataset. The dataset contains 12GB of passive mode traffic from 32 devices across 3 testbeds; between 71 and 196 hours of traffic is present for each device.
An X-ray view of the Cataclysmic Variable V902 Mon: Discovery of an X-ray eclipse
(2025-02-14) Islam, Nazma; Mukai, Koji
V902 Mon is one of a few eclipsing Intermediate Polars (IPs), and show deep eclipses in the optical lightcurves. The presence of a strong Fe Kα fluorescence line in its X-ray spectrum and its low X-ray flux compared to other IPs suggests significant absorption, most likely from an accretion disk. In an observation carried out using the Nuclear Spectroscopic Telescope Array (NuSTAR), we confirm the presence of an X-ray eclipse in the energy resolved lightcurves, coincident with the optical AAVSO/CV-band lightcurves. Broadband X-ray spectral analysis using NuSTAR and XMM-Newton observations confirm a strong absorption N H ∼10 ²³ cm⁻² local to the source, along with a high equivalent width of about 0.7 keV for a Fe Kα fluorescence line. We interpret this using a model similar to an Accretion Disk Corona source, which have a very high inclination and the compact object is heavily obscured by the body of the accretion disk. We propose that the primary X-rays from the accretion column in V902 Mon is hidden from our direct view at all times by the accretion disk. In this scenario, the observed scattered X-rays indicate substantial absorption of direct X-rays by the accretion disk. Additionally, a strong Fe fluorescence line suggests reprocessing of the radiation by a more extended region, such as the pre-shock region, which could be located a few white dwarf radii above the orbital plane.
Magneto-optics in a van der Waals magnet tuned by self-hybridized polaritons
(Springer Nature, 2023-08) Dirnberger, Florian; Quan, Jiamin; Bushati, Rezlind; Diederich, Geoffrey M.; Florian, Matthias; Klein, Julian; Mosina, Kseniia; Sofer, Zdenek; Xu, Xiaodong; Kamra, Akashdeep; García-Vidal, Francisco J.; Alù, Andrea; Menon, Vinod M.
Controlling quantum materials with light is of fundamental and technological importance. By utilizing the strong coupling of light and matter in optical cavities¹ ² ³, recent studies were able to modify some of their most defining features⁴ ⁵ ⁶. Here we study the magneto-optical properties of a van der Waals magnet that supports strong coupling of photons and excitons even in the absence of external cavity mirrors. In this material-the layered magnetic semiconductor CrSBr-emergent light-matter hybrids called polaritons are shown to substantially increase the spectral bandwidth of correlations between the magnetic, electronic and optical properties, enabling largely tunable optical responses to applied magnetic fields and magnons. Our results highlight the importance of exciton-photon self-hybridization in van der Waals magnets and motivate novel directions for the manipulation of quantum material properties by strong light-matter coupling.
Unifying radiative transfer models in computer graphics and remote sensing, Part II: A differentiable, polarimetric forward model and validation
(Elsevier, 2024-01-03) Salesin, Katherine; Knobelspiesse, Kirk D.; Chowdhary, Jacek; Zhai, Peng-Wang; Jarosz, Wojciech
The constellation of Earth-observing satellites continuously collects measurements of scattered radiance, which must be transformed into geophysical parameters in order to answer fundamental scientific questions about the Earth. Retrieval of these parameters requires highly flexible, accurate, and fast forward and inverse radiative transfer models. Existing forward models used by the remote sensing community are typically accurate and fast, but sacrifice flexibility by assuming the atmosphere or ocean is composed of plane-parallel layers. Monte Carlo forward models can handle more complex scenarios such as 3D spatial heterogeneity, but are relatively slower. We propose looking to the computer graphics community for inspiration to improve the statistical efficiency of Monte Carlo forward models and explore new approaches to inverse models for remote sensing. In Part 2 of this work, we demonstrate that Monte Carlo forward models in computer graphics are capable of sufficient accuracy for remote sensing by extending Mitsuba 3, a forward and inverse modeling framework recently developed in the computer graphics community, to simulate simple atmosphere-ocean systems and show that our framework is capable of achieving error on par with codes currently used by the remote sensing community on benchmark results.
Unifying radiative transfer models in computer graphics and remote sensing, Part I: A survey
(Elsevier, 2023-12-02) Salesin, Katherine; Knobelspiesse, Kirk D.; Chowdhary, Jacek; Zhai, Peng-Wang; Jarosz, Wojciech
The constellation of Earth-observing satellites continuously collects measurements of scattered radiance, which must be transformed into geophysical parameters in order to answer fundamental scientific questions about the Earth. Retrieval of these parameters requires highly flexible, accurate, and fast forward and inverse radiative transfer models. Existing forward models used by the remote sensing community are typically accurate and fast, but sacrifice flexibility by assuming the atmosphere or ocean is composed of plane-parallel layers. Monte Carlo forward models can handle more complex scenarios such as 3D spatial heterogeneity, but are relatively slower. We propose looking to the computer graphics community for inspiration to improve the statistical efficiency of Monte Carlo forward models and explore new approaches to inverse models for remote sensing. In Part 1 of this work, we examine the evolution of radiative transfer models in computer graphics and highlight recent advancements that have the potential to push forward models in remote sensing beyond their current periphery of realism.
The bulk motion of gas in the core of the Centaurus galaxy cluster
(Nature, 2025-02) Audard, Marc; Awaki, Hisamitsu; Ballhausen, Ralf; Bamba, Aya; Behar, Ehud; Boissay-Malaquin, Rozenn; Brenneman, Laura; Brown, Gregory V.; Corrales, Lia; Costantini, Elisa; Cumbee, Renata; Done, Chris; Dotani, Tadayasu; Ebisawa, Ken; Eckart, Megan E.; Eckert, Dominique; Enoto, Teruaki; Eguchi, Satoshi; Ezoe, Yuichiro; Foster, Adam; Fujimoto, Ryuichi; Fujita, Yutaka; Fukazawa, Yasushi; Fukushima, Kotaro; Furuzawa, Akihiro; Gallo, Luigi; García, Javier A.; Gu, Liyi; Guainazzi, Matteo; Hagino, Kouichi; Hamaguchi, Kenji; Hatsukade, Isamu; Hayashi, Katsuhiro; Hayashi, Takayuki; Hell, Natalie; Hodges-Kluck, Edmund; Hornschemeier, Ann; Ichinohe, Yuto; Ishida, Manabu; Ishikawa, Kumi; Ishisaki, Yoshitaka; Kaastra, Jelle; Kallman, Timothy; Kara, Erin; Katsuda, Satoru; Kanemaru, Yoshiaki; Kelley, Richard; Kilbourne, Caroline; Kitamoto, Shunji; Kobayashi, Shogo; Kohmura, Takayoshi; Kubota, Aya; Leutenegger, Maurice; Loewenstein, Michael; Maeda, Yoshitomo; Markevitch, Maxim; Matsumoto, Hironori; Matsushita, Kyoko; McCammon, Dan; McNamara, Brian; Mernier, François; Miller, Eric D.; Miller, Jon M.; Mitsuishi, Ikuyuki; Mizumoto, Misaki; Mizuno, Tsunefumi; Mori, Koji; Mukai, Koji; Murakami, Hiroshi; Mushotzky, Richard; Nakajima, Hiroshi; Nakazawa, Kazuhiro; Ness, Jan-Uwe; Nobukawa, Kumiko; Nobukawa, Masayoshi; Noda, Hirofumi; Odaka, Hirokazu; Ogawa, Shoji; Ogorzalek, Anna; Okajima, Takashi; Ota, Naomi; Paltani, Stephane; Petre, Robert; Plucinsky, Paul; Porter, Frederick Scott; Pottschmidt, Katja; Sato, Kosuke; Sato, Toshiki; Sawada, Makoto; Seta, Hiromi; Shidatsu, Megumi; Simionescu, Aurora; Smith, Randall; Suzuki, Hiromasa; Szymkowiak, Andrew; Takahashi, Hiromitsu; Takeo, Mai; Tamagawa, Toru; Tamura, Keisuke; Tanaka, Takaaki; Tanimoto, Atsushi; Tashiro, Makoto; Terada, Yukikatsu; Terashima, Yuichi; Trigo, María Díaz; Tsuboi, Yohko; Tsujimoto, Masahiro; Tsunemi, Hiroshi; Tsuru, Takeshi G.; Uchida, Hiroyuki; Uchida, Nagomi; Uchida, Yuusuke; Uchiyama, Hideki; Ueda, Yoshihiro; Uno, Shinichiro; Vink, Jacco; Watanabe, Shin; Williams, Brian J.; Yamada, Satoshi; Yamada, Shinya; Yamaguchi, Hiroya; Yamaoka, Kazutaka; Yamasaki, Noriko Y.; Yamauchi, Makoto; Yamauchi, Shigeo; Yaqoob, Tahir; Yoneyama, Tomokage; Yoshida, Tessei; Yukita, Mihoko; Zhuravleva, Irina; Kondo, Marie; Werner, Norbert; Plšek, Tomáš ; Sun, Ming; Hosogi, Kokoro; Majumder, Anwesh; XRISM collaboration
Galaxy clusters contain vast amounts of hot ionized gas known as the intracluster medium (ICM). In relaxed cluster cores, the radiative cooling time of the ICM is shorter than the age of the cluster. However, the absence of line emission associated with cooling suggests heating mechanisms that offset the cooling, with feedback from active galactic nuclei (AGNs) being the most likely source1,2. Turbulence and bulk motions, such as the oscillating (‘sloshing’) motion of the core gas in the cluster potential well, have also been proposed as mechanisms for heat distribution from the outside of the core3,4. Here we present X-ray spectroscopic observations of the Centaurus galaxy cluster with the X-Ray Imaging and Spectroscopy Mission satellite. We find that the hot gas flows along the line of sight relative to the central galaxy, with velocities from 130 km s⁻¹ to 310 km s⁻¹ within about 30 kpc of the centre. This indicates bulk flow consistent with core gas sloshing. Although the bulk flow may prevent excessive accumulation of cooled gas at the centre, it could distribute the heat injected by the AGN and bring in thermal energy from the surrounding ICM. The velocity dispersion of the gas is found to be only ≲120 km s⁻¹ in the core, even within about 10 kpc of the AGN. This suggests that the influence of the AGN on the surrounding ICM motion is limited in the cluster.
Machine learning based aerosol and ocean color joint retrieval algorithm for multiangle polarimeters over coastal waters
(Optica Publishing Group, 2024-08-05) Aryal, Kamal; Zhai, Peng-Wang; Gao, Meng; Franz, Bryan A.; Knobelspiesse, Kirk; Hu, Yongxiang
NASA's Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, recently launched in February 2024, carries two multiangle polarimeters (MAPs): the UMBC Hyper-Angular Rainbow Polarimeter (HARP2) and SRON Spectropolarimeter for Planetary Exploration One (SPEXone). Measurements from these MAPs will greatly advance ocean ecosystem and aerosol studies as their measurements contain rich information on the microphysical properties of aerosols and hydrosols. The Multi-Angular Polarimetric Ocean coLor (MAPOL) joint retrieval algorithm has been developed to retrieve aerosol and ocean color information, which uses a vector radiative transfer (RT) model as the forward model. The RT model is computationally expensive, which makes processing a large amount of data challenging. FastMAPOL was developed to expedite retrieval using neural networks to replace the RT forward models. As a prototype study, FastMAPOL was initially limited to open ocean applications where the ocean Inherent Optical Properties (IOPs) were parameterized in terms of one parameter: chlorophyll-a concentration (Chla). In this study we further expand the FastMAPOL joint retrieval algorithm to incorporate NN based forward models for coastal waters, which use multi-parameter bio-optical models. In addition, aerosols are represented by six components, i.e., fine mode non absorbing insoluble (FNAI), brown carbon (BrC), black carbon (BC), fine mode non absorbing soluble (FNAS), sea salt (SS) and non-spherical dust (Dust). Sea salt and dust are coarse mode aerosols, while the other components are fine mode. The sizes and spectral refractive indices are fixed for each aerosol component, while their abundances are retrievable. The multi-parameter bio-optical model and aerosol components are chosen to represent the coastal marine environment. The retrieval algorithm is applied to synthetic measurements in three different configurations of MAPs in the PACE mission: HARP2 observations only, SPEXone observations only and combined HARP2 and SPEXone observations. The retrieval results from synthetic measurements show that for aerosol retrieval the SPEXone-only configuration works equally well with the HAPR2-only configuration. On the other hand, for ocean color retrieval the SPEXone instrument provides better information due to its larger spectral coverage. For the surface parameters (wind speed), HARP2 measurements provide better information due to its wide field of view. Combined measurement configuration HARP2+SPEXone performed the best to retrieve all aerosol, ocean color, and surface parameters. We also studied the impact of sun glint to aerosol and ocean color retrievals. The retrieval test revealed that wind speed and absorbing aerosol retrieval improves significantly when including measurements at glint geometries. Furthermore, the retrieval algorithm is equipped with modules for atmospheric correction and bidirectional reflectance distribution (BRDF) correction to obtain the remote sensing reflectance, which enables ocean biogeochemistry studies using the PACE polarimeter data.
Tunable interaction between excitons and hybridized magnons in a layered semiconductor
(Springer Nature, 2022-28-12) Diederich, Geoffrey M.; Cenker, John; Ren, Yafei; Fonseca, Jordan; Chica, Daniel G.; Bae, Youn Jue; Zhu, Xiaoyang; Roy, Xavier; Cao, Ting; Xiao, Di; Xu, Xiaodong
The interaction between distinct excitations in solids is of both fundamental interest and technological importance. One such interaction is the coupling between an exciton, a Coulomb bound electron-hole pair, and a magnon, a collective spin excitation. The recent emergence of van der Waals magnetic semiconductors provides a platform to explore these exciton-magnon interactions and their fundamental properties, such as strong correlation, as well as their photospintronic and quantum transduction applications. Here we demonstrate the precise control of coherent exciton-magnon interactions in the layered magnetic semiconductor CrSBr. We varied the direction of an applied magnetic field relative to the crystal axes, and thus the rotational symmetry of the magnetic system. Thereby, we tuned not only the exciton coupling to the bright magnon, but also to an optically dark mode via magnon-magnon hybridization. We further modulated the exciton-magnon coupling and the associated magnon dispersion curves through the application of uniaxial strain. At a critical strain, a dispersionless dark magnon band emerged. Our results demonstrate an unprecedented level of control of the opto-mechanical-magnonic coupling, and a step towards the predictable and controllable implementation of hybrid quantum magnonics.
Strain-programmable van der Waals magnetic tunnel junctions
(2023-01-10) Cenker, John; Ovchinnikov, Dmitry; Yang, Harvey; Chica, Daniel G.; Zhu, Catherine; Cai, Jiaqi; Diederich, Geoffrey M.; Liu, Zhaoyu; Zhu, Xiaoyang; Roy, Xavier; Cao, Ting; Daniels, Matthew W.; Chu, Jiun-Haw; Xiao, Di; Xu, Xiaodong
The magnetic tunnel junction (MTJ) is a backbone device for spintronics. Realizing next generation energy efficient MTJs will require operating mechanisms beyond the standard means of applying magnetic fields or large electrical currents. Here, we demonstrate a new concept for programmable MTJ operation via strain control of the magnetic states of CrSBr, a layered antiferromagnetic semiconductor used as the tunnel barrier. Switching the CrSBr from antiferromagnetic to ferromagnetic order generates a giant tunneling magnetoresistance ratio without external magnetic field at temperatures up to ≈ 140 K. When the static strain is set near the phase transition, applying small strain pulses leads to active flipping of layer magnetization with controlled layer number and thus magnetoresistance states. Further, finely adjusting the static strain to a critical value turns on stochastic switching between metastable states, with a strain-tunable sigmoidal response curve akin to the stochastic binary neuron. Our results highlight the potential of strain-programmable van der Waals MTJs towards spintronic applications, such as magnetic memory, random number generation, and probabilistic and neuromorphic computing.
Electrical, optical, and magnetic properties of amorphous yttrium iron oxide thin films and consequences for non-local resistance measurements
(AIP, 2023-06-08) Roos, M. J.; Bleser, S. M.; Hernandez, L.; Diederich, Geoffrey M.; Siemens, M. E.; Wu, M.; Kirby, B. J.; Zink, B. L.
We present magnetic characterization, charge resistivity, and optical photoluminescence measurements on amorphous yttrium iron oxide thin films (a-Y-Fe-O), with supporting comparisons to amorphous germanium (a-Ge) films. We measured magnetic properties with both SQUID magnetometry and polarized neutron reflectometry. These results not only confirm that a-Y-Fe-O is a disordered magnetic material with strong predominantly antiferromagnetic exchange interactions and a high degree of frustration, but also that it is best understood electrically as a disordered semiconductor. As with amorphous germanium, a-Y-Fe-O obeys expectations for variable-range hopping through localized electron states over a wide range of temperature. We also clarify the consequences of charge transport through such a semiconducting medium for non-local voltage measurements intended to probe spin transport in nominally insulating magnetic materials. We further compare non-local resistance measurements made with "quasi-dc" automated current reversal to ac measurements made with a lock-in amplifier. These show that the "quasi-dc" measurement has an effective ac current excitation with frequency up to approximately 22 Hz, and that this effective ac excitation can cause artifacts in these measurements including incorrect sign of the non-local resistance. This comprehensive investigation of non-local resistance measurements in a-Y-Fe-O shows no evidence of spin transport on micrometer length scales, which is contrary to our original work, and in line with more recent investigations by other groups.
VERITAS and multiwavelength observations of the Blazar B3 2247+381 in response to an IceCube neutrino alert
(2025-02-06) Acharyya, Atreya; Adams, Colin B.; Bangale, Priyadarshini; Bartkoske, J. T.; Benbow, Wystan; Buckley, James H.; Chen, Yu; Christiansen, Jodi; Chromey, Alisha; Duerr, Anne; Errando, Manel; Godoy, Miguel E.; Falcone, Abe; Feng, Qi; Foote, Juniper; Fortson, Lucy; Furniss, Amy; Hanlon, William; Hanna, David; Hervet, Olivier; Hinrichs, Claire E.; Holder, Jamie; Humensky, Thomas B.; Jin, Weidong; Johnson, Madalyn N.; Kaaret, Philip; Kertzman, Mary P.; Kherlakian, Maria; Kieda, David; Kleiner, Tobias K.; Korzoun, Mx Nikolas; Krennrich, Frank; Kumar, Sajan; Lang, Mark J.; Lundy, Matthew; McGrath, Conor; Meyer, Eileen T.; Millard, Matthew J.; Millis, John; Mooney, Connor; Moriarty, Patrick; Mukherjee, Reshmi; Ning, Wenmeng; O'Brien, Stephan; Ong, Rene A.; Pohl, Martin; Pueschel, Elisa; Quinn, John; Rabinowitz, Pazit L.; Ragan, Ken; Reynolds, Paul; Ribeiro, Deivid; Roache, Emmet Thomas; Ryan, Jamie L.; Sadeh, Iftach; Sadun, Alberto; Saha, Lab; Santander, Marcos; Sembroski, Glenn H.; Shang, Ruo-Yu; Splettstoesser, Megan; Tak, Donggeun; Talluri, Anjana K.; Tucci, James V.; Valverde, Janeth; Williams, David A.; Wong, Sam L.; Woo, Jooyun; Abbasi, R.; Ackermann, M.; Adams, J.; Agarwalla, S. K.; Aguilar, J. A.; Ahlers, M.; Alameddine, J. M.; Amin, N. M.; Andeen, K.; Argüelles, C.; Ashida, Y.; Athanasiadou, S.; Axani, S. N.; Babu, R.; Bai, X.; V, A. Balagopal; Baricevic, M.; Barwick, S. W.; Bash, S.; Basu, V.; Bay, R.; Beatty, J. J.; Tjus, J. Becker; Beise, J.; Bellenghi, C.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Blaufuss, E.; Bloom, L.; Blot, S.; Bontempo, F.; Motzkin, J. Y. Book; Meneguolo, C. Boscolo; Böser, S.; Botner, O.; Böttcher, J.; Braun, J.; Brinson, B.; Brisson-Tsavoussis, Z.; Brostean-Kaiser, J.; Brusa, L.; Burley, R. T.; Butterfield, D.; Campana, M. A.; Caracas, I.; Carloni, K.; Carpio, J.; Chattopadhyay, S.; Chau, N.; Chen, Z.; Chirkin, D.; Choi, S.; Clark, B. A.; Coleman, A.; Coleman, P.; Collin, G. H.; Connolly, A.; Conrad, J. M.; Corley, R.; Cowen, D. F.; Clercq, C. De; DeLaunay, J. J.; Delgado, D.; Deng, S.; Desai, A.; Desiati, P.; Vries, K. D. de; Wasseige, G. de; DeYoung, T.; Diaz, A.; Díaz-Vélez, J. C.; Dierichs, P.; Dittmer, M.; Domi, A.; Draper, L.; Dujmovic, H.; Durnford, D.; Dutta, K.; DuVernois, M. A.; Ehrhardt, T.; Eidenschink, L.; Eimer, A.; Eller, P.; Ellinger, E.; Mentawi, S. El; Elsässer, D.; Engel, R.; Erpenbeck, H.; Esmail, W.; Evans, J.; Evenson, P. A.; Fan, K. L.; Fang, K.; Farrag, K.; Fazely, A. R.; Fedynitch, A.; Feigl, N.; Fiedlschuster, S.; Finley, C.; Fischer, L.; Fox, D.; Franckowiak, A.; Fukami, S.; Fürst, P.; Gallagher, J.; Ganster, E.; Garcia, A.; Garcia, M.; Garg, G.; Genton, E.; Gerhardt, L.; Ghadimi, A.; Girard-Carillo, C.; Glaser, C.; Glüsenkamp, T.; Gonzalez, J. G.; Goswami, S.; Granados, A.; Grant, D.; Gray, S. J.; Griffin, S.; Griswold, S.; Groth, K. M.; Guevel, D.; Günther, C.; Gutjahr, P.; Ha, C.; Haack, C.; Hallgren, A.; Halve, L.; Halzen, F.; Hamacher, L.; Hamdaoui, H.; Minh, M. Ha; Handt, M.; Hanson, K.; Hardin, J.; Harnisch, A. A.; Hatch, P.; Haungs, A.; Häußler, J.; Helbing, K.; Hellrung, J.; Hermannsgabner, J.; Heuermann, L.; Heyer, N.; Hickford, S.; Hidvegi, A.; Hill, C.; Hill, G. C.; Hmaid, R.; Hoffman, K. D.; Hori, S.; Hoshina, K.; Hostert, M.; Hou, W.; Huber, T.; Hultqvist, K.; Hünnefeld, M.; Hussain, R.; Hymon, K.; Ishihara, A.; Iwakiri, W.; Jacquart, M.; Jain, S.; Janik, O.; Jansson, M.; Jeong, M.; Jin, M.; Jones, B. J. P.; Kamp, N.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.; Kardum, L.; Karg, T.; Karl, M.; Karle, A.; Katil, A.; Katz, U.; Kauer, M.; Kelley, J. L.; Khanal, M.; Zathul, A. Khatee; Kheirandish, A.; Kiryluk, J.; Klein, S. R.; Kobayashi, Y.; Kochocki, A.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Köpke, L.; Kopper, C.; Koskinen, D. J.; Koundal, P.; Kowalski, M.; Kozynets, T.; Krieger, N.; Krishnamoorthi, J.; Krishnan, T.; Kruiswijk, K.; Krupczak, E.; Kumar, A.; Kun, E.; Kurahashi, N.; Lad, N.; Gualda, C. Lagunas; Lamoureux, M.; Larson, M. J.; Lauber, F.; Lazar, J. 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P.; Yildizci, E.; Yoshida, S.; Young, R.; Yu, F.; Yu, S.; Yuan, T.; Zegarelli, A.; Zhang, S.; Zhang, Z.; Zhelnin, P.; Zilberman, P.; Zimmerman, M.; Drake, Pablo; Spira-Savett, Elizabeth; Lusen, Piatra; Mori, Kaya
While the sources of the diffuse astrophysical neutrino flux detected by the IceCube Neutrino Observatory are still largely unknown, one of the promising methods used towards understanding this is investigating the potential temporal and spatial correlations between neutrino alerts and the electromagnetic radiation from blazars. We report on the multiwavelength target-of-opportunity observations of the blazar B3 2247+381, taken in response to an IceCube multiplet alert for a cluster of muon neutrino events compatible with the source location between May 20, 2022 and November 10, 2022. B3 2247+381 was not detected with VERITAS during this time period. The source was found to be in a low-flux state in the optical, ultraviolet and gamma-ray bands for the time interval corresponding to the neutrino event, but was detected in the hard X-ray band with NuSTAR during this period. We find the multiwavelength spectral energy distribution is well described using a simple one-zone leptonic synchrotron self-Compton radiation model. Moreover, assuming the neutrinos originate from hadronic processes within the jet, the neutrino flux would be accompanied by a photon flux from the cascade emission, and the integrated photon flux required in such a case would significantly exceed the total multiwavelength fluxes and the VERITAS upper limits presented here. The lack of flaring activity observed with VERITAS, combined with the low multiwavelength flux levels, and given the significance of the neutrino excess is at 3σ level (uncorrected for trials), makes B3 2247+381 an unlikely source of the IceCube multiplet. We conclude that the neutrino excess is likely a background fluctuation.
COSP-RTTOV-1.0: Flexible radiation diagnostics to enable new science applications in model evaluation, climate change detection, and satellite mission design
(45692) Shaw, Jonah K.; Swales, Dustin J.; Desouza-Machado, Sergio; Turner, David D.; Kay, Jennifer E.; Schneider, David P.
Infrared spectral radiation fields observed by satellites make up an information-rich, multi-decade record with continuous coverage of the entire planet. As direct observations, spectral radiation fields are also largely free from uncertainties that accumulate during geophysical retrieval and data assimilation processes. Comparing these direct observations with earth system models (ESMs), however, is hindered by definitional differences between the radiation fields satellites observe and those generated by models. Here, we present a flexible, computationally efficient tool called COSP-RTTOV for simulating satellitelike radiation fields within ESMs. Outputs from COSP-RTTOV are consistent with instrument spectral response functions and orbit sampling, as well as the physics of the host model. After validating COSP-RTTOV's performance, we demonstrate new constraints on model performance enabled by COSP-RTTOV. We show additional applications in climate change detection using the NASA AIRS instrument, and observing system simulation experiments using the NASA PREFIRE mission. In summary, COSP-RTTOV is a convenient tool for directly comparing satellite radiation observations with ESMs. It enables a wide range of scientific applications, especially when users desire to avoid the assumptions and uncertainties inherent in satellite-based retrievals of geophysical variables or in atmospheric reanalysis.
BatAnalysis -- A Comprehensive Python Pipeline for Swift BAT Time-Tagged Event Data Analysis
(2025-02-01) Parsotan, Tyler; Palmer, David M.; Ronchini, Samuele; Delaunay, James; Tohuvavohu, Aaron; Laha, Sibasish; Lien, Amy; Cenko, S. Bradley; Krimm, Hans; Markwardt, Craig
The Swift Burst Alert Telescope (BAT) is a coded aperture gamma-ray instrument with a large field of view that was designed to detect and localize transient events. When a transient is detected, either on-board or externally, the BAT saves time-tagged event (TTE) data which provides the highest quality information of the locations of the photons on the detector plane and their energies. This data can be used to produce spectra, lightcurves, and sky images of a transient event. While these data products are produced by the Swift Data Center and can be produced by current software, they are often preset to certain time and energy intervals which has limited their use in the current time domain and multi-messenger environment. Here, we introduce a new capability for the BatAnalysis python package to download and process TTE data under an open-source pythonic framework that allows for easy interfacing with other python packages. The new capabilities of the BatAnalysis software allows for TTE data to be used by the community in a variety of advanced customized analyses of astrophysical sources which BAT may have TTE data for, such as Fast Radio Bursts (FRBs), Gamma-ray Bursts (GRBs), Low Mass X-ray Binaries (LMXB), Soft Gamma-ray Repeaters, magnetars, and many other sources. We highlight the usefulness of the BatAnalysis package in analyzing TTE data produced by an on-board GRB trigger, a FRB external trigger, a sub-threshold detection of the LMXB EXO 0748-676, and an external trigger of a GRB that BAT detected during a slew.

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