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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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. P.; DeHolton, K. Leonard; Leszczy?ska, A.; Liao, J.; Lincetto, M.; Liu, Y. T.; Liubarska, M.; Love, C.; Lu, L.; Lucarelli, F.; Luszczak, W.; Lyu, Y.; Madsen, J.; Magnus, E.; Mahn, K. B. M.; Makino, Y.; Manao, E.; Mancina, S.; Mand, A.; Sainte, W. Marie; Mari?, I. C.; Marka, S.; Marka, Z.; Marsee, M.; Martinez-Soler, I.; Maruyama, R.; Mayhew, F.; McNally, F.; Mead, J. V.; Meagher, K.; Mechbal, S.; Medina, A.; Meier, M.; Merckx, Y.; Merten, L.; Mitchell, J.; Montaruli, T.; Moore, R. W.; Morii, Y.; Morse, R.; Moulai, M.; Mukherjee, T.; Naab, R.; Nakos, M.; Naumann, U.; Necker, J.; Negi, A.; Neste, L.; Neumann, M.; Niederhausen, H.; Nisa, M. U.; Noda, K.; Noell, A.; Novikov, A.; Pollmann, A. Obertacke; O'Dell, V.; Olivas, A.; Orsoe, R.; Osborn, J.; O'Sullivan, E.; Palusova, V.; Pandya, H.; Park, N.; Parker, G. K.; Parrish, V.; Paudel, E. N.; Paul, L.; Heros, C. Pérez de los; Pernice, T.; Peterson, J.; Pizzuto, A.; Plum, M.; Pontén, A.; Popovych, Y.; Rodriguez, M. Prado; Pries, B.; Procter-Murphy, R.; Przybylski, G. T.; Pyras, L.; Raab, C.; Rack-Helleis, J.; Rad, N.; Ravn, M.; Rawlins, K.; Rechav, Z.; Rehman, A.; Resconi, E.; Reusch, S.; Rhode, W.; Riedel, B.; Rifaie, A.; Roberts, E. J.; Robertson, S.; Rodan, S.; Rongen, M.; Rosted, A.; Rott, C.; Ruhe, T.; Ruohan, L.; Safa, I.; Saffer, J.; Salazar-Gallegos, D.; Sampathkumar, P.; Sandrock, A.; Santander, M.; Sarkar, S.; Sarkar, S.; Savelberg, J.; Savina, P.; Schaile, P.; Schaufel, M.; Schieler, H.; Schindler, S.; Schlickmann, L.; Schlüter, B.; Schlüter, F.; Schmeisser, N.; Schmidt, T.; Schneider, J.; Schröder, F. G.; Schumacher, L.; Schwirn, S.; Sclafani, S.; Seckel, D.; Seen, L.; Seikh, M.; Seo, M.; Seunarine, S.; Myhr, P. A. Sevle; Shah, R.; Shefali, S.; Shimizu, N.; Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.; Søgaard, A.; Soldin, D.; Soldin, P.; Sommani, G.; Spannfellner, C.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stürwald, T.; Stuttard, T.; Sullivan, G. W.; Taboada, I.; Ter-Antonyan, S.; Terliuk, A.; Thiesmeyer, M.; Thompson, W. G.; Thwaites, J.; Tilav, S.; Tollefson, K.; Tönnis, C.; Toscano, S.; Tosi, D.; Trettin, A.; Elorrieta, M. A. Unland; Upadhyay, A. K.; Upshaw, K.; Vaidyanathan, A.; Valtonen-Mattila, N.; Vandenbroucke, J.; Eijndhoven, N. van; Vannerom, D.; Santen, J. van; Vara, J.; Varsi, F.; Veitch-Michaelis, J.; Venugopal, M.; Vereecken, M.; Carrasco, S. Vergara; Verpoest, S.; Veske, D.; Vijai, A.; Walck, C.; Wang, A.; Weaver, C.; Weigel, P.; Weindl, A.; Weldert, J.; Wen, A. Y.; Wendt, C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.; Williams, D. R.; Witthaus, L.; Wolf, M.; Wrede, G.; Xu, X. W.; Yanez, J. 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.
A recoiling supermassive black hole in a powerful quasar
(2025-01-30) Chiaberge, Marco; Morishita, Takahiro; Boschini, Matteo; Bianchi, Stefano; Capetti, Alessandro; Castignani, Gianluca; Gerosa, Davide; Konishi, Masahiro; Koyama, Shuhei; Kushibiki, Kosuke; Lambrides, Erini; Meyer, Eileen T.; Motohara, Kentaro; Stiavelli, Massimo; Takahashi, Hidenori; Tremblay, Grant R.; Norman, Colin
Supermassive black holes (SMBH) are thought to grow through accretion of matter and mergers. Models of SMBH mergers have long suffered the final parsec problem, where SMBH binaries may stall before energy loss from gravitational waves (GW) becomes significant, leaving the pair unmerged. Direct evidence of coalesced SMBH remains elusive. Theory predicts that GW recoiling black holes can occur following a black hole merger. Here we present decisive spectroscopic evidence that the gas bound to the SMBH in the spatially offset quasar 3C 186 is blue-shifted relative to the host galaxy. This is exclusively explained by the GW recoil super-kick scenario. This confirmation of the ejection process implies that the final parsec problem is resolved in nature, providing evidence that even the most massive black holes can merge.
Towards enhanced precision in thermometry with nonlinear qubits
(IOP, 2025-01-29) Deffner, Sebastian
Quantum thermometry refers to the study of measuring ultra-low temperatures in quantum systems. The precision of such a quantum thermometer is limited by the degree to which temperature can be estimated by quantum measurements. More precisely, the maximal precision is given by the inverse of the quantum Fisher information. In the present analysis, we show that quantum thermometers that are described by nonlinear Schrödinger equations allow for a significantly enhanced precision, that means larger quantum Fisher information. This is demonstrated for a variety of pedagogical scenarios consisting of single and two-qubits systems. The enhancement in precision is indicated by non-vanishing quantum speed limits, which originate in the fact that the thermal, Gibbs state is typically not invariant under the nonlinear equations of motion.
The S-PLUS 12-band photometry as a powerful tool for discovery and classification: ten cataclysmic variables in a proof-of-concept study
(2025-01-27) Oliveira, Raimundo Lopes de; Araujo, Amanda S. de; Krabbe, Angela C.; Oliveira, Claudia L. Mendes de; Mukai, Koji; Gutierrez-Soto, Luis A.; Kanaan, Antonio; Eleuterio, Romualdo; Fernandes, Marcelo Borges; Quispe-Huaynasi, Fredi; Schoenell, William; Ribeiro, Tiago
Multi-band photometric surveys provide a straightforward way to discover and classify astrophysical objects systematically, enabling the study of a large number of targets at relatively low cost. Here we introduce an alternative approach to select Accreting White Dwarf (AWD) candidates following their spectral energy distribution, entirely supported by the twelve photometric bands of the Southern Photometric Local Universe Survey (S-PLUS). The method was validated with optical spectroscopic follow-up with the Gemini South telescope which unambiguously established ten systems as cataclysmic variables (CVs), alongside Swift X-ray observations of four of them. Among the ten CVs presented here are those that may be low-luminosity intermediate polars or WZ Sge-type dwarf novae with rare outbursts, two subclasses that can be easily missed in time-domain and X-ray surveys, the two methods currently dominating the discovery of new CVs. Our approach based on S-PLUS provides an important, complementary tool to uncover the total population of CVs and the complete set of its subclasses, which is an important step towards a full understanding of close binary evolution, including the origin of magnetic fields in white dwarfs and the physics of accretion. Finally, we highlight the potential of S-PLUS beyond AWDs, serving other surveys in the characterization of their sources.
Topological X-states in a quantum impurity model
(2025-01-26) Cavalcante, M. F.; Bonança, Marcus V. S.; Miranda, Eduardo; Deffner, Sebastian
Topological qubits are inherently resistant to noise and errors. However, experimental demonstrations have been elusive as their realization and control is highly complex. In the present work, we demonstrate the emergence of topological X-states in the long-time response of a locally perturbed quantum impurity model. The emergence of the double-qubit state is heralded by the lack of decay of the response function as well as the out-of-time order correlator signifying the trapping of excitations, and hence information in local edge modes.
Signal Processing of Images for Convective Boundary Layer Height Estimation from Radar (SPICER) and multi-instrument verification
(IEEE, 2025-01-13) Porta, Delia Tatiana Della; Demoz, Belay
The study of the planetary boundary layer (PBL) is one of the main topics of the atmospheric community. The current study presents a new algorithm for PBL height determination using a publicly available but unexplored data source, the Weather Service Radar (WSR-88D). The diurnal evolution of the PBL is also known as Convective Boundary Layer (CBL), key in the study of convection and precipitation. This paper presents the Signal Processing of Images for Convective Boundary Layer Height Estimation (SPICER) algorithm that can automatically detect the CBL Height (CBLH) for all of the 159 radar locations across the United States during clear days. The present work is the first step to applying SPICER to a network of Next Generation Radars (NEXRAD) with continuous countrywide coverage. With the possible combination with the Automated Surface Observing System network (ASOS), a source of ceilometer profile data, a validated dataset of CBLH estimates can be expected soon. The algorithm treats averaged differential reflectivity vs range as an image and applies filtering plus Canny edge detection to estimate the CBLH. In addition, another algorithm is presented to automate the detection of the mixing layer height (MLH), a proxy for CBLH from Raman Lidar and a 915 MHz wind profiler. A comparison of CBLH estimates vs widely used methods in meteorology (Radiosondes, Raman Lidar, ceilometer, 915 MHz wind profiler, and Doppler Lidar-based derived Value-Added Product (VAP) ) is performed to validate the NEXRAD detected CBLH using SPICER. The SPICER algorithm shows over 0.9 correlation with radiosonde measurements.
Effectiveness of Ultrathin Al2O3 Capping by Atomic Layer Deposition on the Stability of Single Quantum Dots
(2024-01-01) Sarkar, Yasir; Pelton, Matthew; Physics; Physics
Quantum dots (QDs) possess the capability to function as single photon sources, and their size-dependent optical properties offer a broad range of applications in nanophotonics. However, photo-bleaching and oxidation lead to the degradation of QDs at room temperature, presenting one of the main obstacles to applications. Here, we enhance the stability of single core-shell QDs at room temperature and shield them from the air by using 0.5, 0.7, and 1nm thick capping layers of Al2O3 deposited via atomic layer deposition (ALD). This also enables tip-enhanced strong coupling (TESC) spectroscopy by allowing the formation of a subnanometer plasmonic cavity between a nano-optical antenna and a metal film below the QD. After being exposed to a continuous-wave laser beam of 2.01 mW power for 3.5 hours, photoluminescence (PL) microscopy of QDs under the 0.5nm capping layer demonstrated no reduction in fluorescent QD number compared to a 51% reduction in the number of fluorescent QDs in a sample without such protection. This protection method opens up new possibilities for increasing the fluorescent lifetime of other types of QDs, such as less stable perovskite quantum dots and studying the effect of new capping materials on emitter-plasmon coupling.
Investigating the Properties of Transition Metal-Based Thin Films
(2024-01-01) Chowdhary, Nimarta Kaur; Gougousi, Theodosia; Physics; Physics
Transition metal-based thin films, including oxides and nitrides, are widely studied due to their diverse properties and applications. Among these materials, transition metal oxides (TMOs) are known for their wide-band gaps, high refractive indices, and high transparency in the visible spectrum. Due to their low cost, low toxicity, and high natural abundance, efforts are being made to modify these materials for broader application range, such as visible light absorption. Developing optimal methods for producing and characterizing transition metal-based films remains an ongoing challenge. This research investigates the growth and properties of transition metal-based films using complementary thin film deposition approaches: atomic layer deposition (ALD), and physical vapor deposition (PVD). In this work, ALD thin films were grown by varying parameters such as deposition temperature and purge time. The resulting properties were analyzed using X-ray photoelectron spectroscopy (XPS) for chemical states and composition, Fourier transform infrared spectroscopy (FTIR) for bonding and crystal structure, spectroscopic ellipsometry (SE), and ultraviolet-visible spectroscopy (UV-Vis) foroptical properties, and four-point probe (4PP) for electrical conductivity. This project used a new method of adjusting the ALD deposition process to determine the optical functions, providing a complete picture of the observed properties. ALD-grown hafnium oxide (HfO2) and titanium dioxide (TiO2), grown from similar amine precursors, (X[((CH3)2N)4])X=Hf, Ti with comparable deposition conditions exhibit completely different properties. The properties of ALD TiO2 films are shown to be highly dependent on the processing conditions, particularly in the temperature range within the ‘ALD window’. These films incorporate metallic, carbon, and water-based impurities, resulting in variable optical constants at 633 nm (n = 1.7 – 2.4, k = 0.2 – 1.2) and a wide conductivity range (1000 – 30000 S/m). The properties of the ALD TiO2 films are benchmarked between PVD-grown TiOxNy and PVD TiO2 films, providing further insight into the observed behavior. Conversely, the ALD HfO2 films only incorporate carbon and water-based impurities. The resulting optical constants at 633 nm (n = 1.9 – 2.1, k = 0) and conductivity (400 – 1000 S/m) do not strongly depend on the processing conditions. The results highlight that the underlying ALD chemistry and reaction pathways are significantly more complex than is currently understood and cannot be generalized, even for similar materials. Future investigations require combined experimental, theoretical, and computational approaches. By systematically studying thin film growth using this approach, this research establishes pathways for applications in precursor design, photovoltaics, transparent conductive oxides and optoelectronics.
Temperature-Dependent Properties of Atomic Layer Deposition-Grown TiO2₂Thin Films
(Wiley, 2025-01-07) Chowdhary, Nimarta Kaur; Gougousi, Theodosia
This study investigates the presence of titanium oxynitride bonds in titanium dioxide (TiO₂) thin films grown by atomic layer deposition (ALD) using tetrakis dimethyl amino titanium (TDMAT) and water at temperatures between 150 and 350 °C and its effect on the films’ optical and electrical properties. Compositional analysis using X-ray photoelectron spectroscopy (XPS) reveals increased incorporation of oxynitride bonds as the process temperature increases. Furthermore, depth profile data demonstrates an increase in the abundance of this type of bonding from the surface to the bulk of the films. Ultraviolet-visible spectroscopy (UV-vis) measurements correlate increased visible light absorption for the films with elevated oxynitride incorporation. The optical constants (n, k) of the films show a pronounced dependence on the process temperature that is mirrored in the film conductivity. The detection of oxynitride bonding suggests a secondary reaction pathway in this well-established ALD process chemistry, that may impact film properties. These findings indicate that the choice of process chemistry and conditions can be used to optimize film properties for optoelectronic applications.
Multi-wavelength observations of a jet launch in real time from the post-changing-look Active Galaxy 1ES 1927+654
(2025-01-04) Laha, Sibasish; Meyer, Eileen T.; Sadaula, Dev R.; Ghosh, Ritesh; Sengupta, Dhrubojyoti; Masterson, Megan; Shuvo, Onic Islam; Guainazzi, Matteo; Ricci, Claudio; Begelman, Mitchell C.; Philippov, Alexander; Mbarek, Rostom; Hankla, Amelia M.; Kara, Erin; Panessa, Francesca; Behar, Ehud; Zhang, Haocheng; Pacucci, Fabio; Pal, Main; Ricci, Federica; Villani, Ilaria; Bisogni, Susanna; Franca, Fabio La; Bianchi, Stefano; Bruni, Gabriele; Oates, Samantha; Hahn, Cameron; Nicholl, Matt; Cenko, S. Bradley; Chattopadhyay, Sabyasachi; Gonzalez, Josefa Becerra; Acosta-Pulido, J. A.; Rakshit, Suvendu; Svoboda, Jiri; Gallo, Luigi; Ingram, Adam; Kakkad, Darshan
We present results from a high cadence multi-wavelength observational campaign of the enigmatic changing look AGN 1ES 1927+654 from May 2022- April 2024, coincident with an unprecedented radio flare (an increase in flux by a factor of $\sim 60$ over a few months) and the emergence of a spatially resolved jet at $0.1-0.3$ pc scales (Meyer et al. 2024). Companion work has also detected a recurrent quasi-periodic oscillation (QPO) in the $2-10$ keV band with an increasing frequency ($1-2$ mHz) over the same period (Masterson et al., 2025). During this time, the soft X-rays ($0.3-2$ keV) monotonically increased by a factor of $\sim 8$, while the UV emission remained near-steady with $<30\%$ variation and the $2-10$ keV flux showed variation by a factor $\lesssim 2$. The weak variation of the $2-10$ keV X-ray emission and the stability of the UV emission suggest that the magnetic energy density and accretion rate are relatively unchanged, and that the jet could be launched due to a reconfiguration of the magnetic field (toroidal to poloidal) close to the black hole. Advecting poloidal flux onto the event horizon would trigger the Blandford-Znajek (BZ) mechanism, leading to the onset of the jet. The concurrent softening of the coronal slope (from $\Gamma= 2.70\pm 0.04$ to $\Gamma=3.27\pm 0.04$), the appearance of a QPO, and low coronal temperature ($kT_{e}=8_{-3}^{+8}$ keV) during the radio outburst suggest that the poloidal field reconfiguration can significantly impact coronal properties and thus influence jet dynamics. These extraordinary findings in real time are crucial for coronal and jet plasma studies, particularly as our results are independent of coronal geometry.
Millihertz Oscillations Near the Innermost Orbit of a Supermassive Black Hole
(2025-01-03) Masterson, Megan; Kara, Erin; Panagiotou, Christos; Alston, William N.; Chakraborty, Joheen; Burdge, Kevin; Ricci, Claudio; Laha, Sibasish; Arcavi, Iair; Arcodia, Riccardo; Cenko, S. Bradley; Fabian, Andrew C.; Garc韆, Javier A.; Giustini, Margherita; Ingram, Adam; Kosec, Peter; Loewenstein, Michael; Meyer, Eileen T.; Miniutti, Giovanni; Pinto, Ciro; Remillard, Ronald A.; Sadaula, Dev R.; Shuvo, Onic Islam; Trakhtenbrot, Benny; Wang, Jingyi
Recent discoveries from time-domain surveys are defying our expectations for how matter accretes onto supermassive black holes (SMBHs). The increased rate of short-timescale, repetitive events around SMBHs, including the newly-discovered quasi-periodic eruptions (QPEs), are garnering further interest in stellar-mass companions around SMBHs and the progenitors to mHz frequency gravitational wave events. Here we report the discovery of a highly significant mHz Quasi-Periodic Oscillation (QPO) in an actively accreting SMBH, 1ES 1927+654, which underwent a major optical, UV, and X-ray outburst beginning in 2018. The QPO was first detected in 2022 with a roughly 18-minute period, corresponding to coherent motion on scales of less than 10 gravitational radii, much closer to the SMBH than typical QPEs. The period decreased to 7.1 minutes over two years with a decelerating period evolution ($\ddot{P} > 0$). This evolution has never been seen in SMBH QPOs or high-frequency QPOs in stellar mass black holes. Models invoking orbital decay of a stellar-mass companion struggle to explain the period evolution without stable mass transfer to offset angular momentum losses, while the lack of a direct analog to stellar mass black hole QPOs means that many instability models cannot explain all of the observed properties of the QPO in 1ES 1927+654. Future X-ray monitoring will test these models, and if it is a stellar-mass orbiter, the Laser Interferometer Space Antenna (LISA) should detect its low-frequency gravitational wave emission.
XRISM reveals low non-thermal pressure in the core of the hot, relaxed galaxy cluster Abell 2029
(APJ, 2025-01-09) XRISM Collaboration; Boissay-Malaquin, Rozenn; Hamaguchi, Kenji; Hayashi, Takayuki; Mukai, Koji; Pottschmidt, Katja; Tamura, Keisuke; Yaqoob, Tahir
We present XRISM Resolve observations of the core of the hot, relaxed galaxy cluster Abell 2029. We find that the line-of-sight bulk velocity of the intracluster medium (ICM) within the central 180 kpc is at rest with respect to the Brightest Cluster Galaxy, with a 3-sigma upper limit of |v_bulk| < 100 km/s. We robustly measure the field-integrated ICM velocity dispersion to be sigma_v = 169 +/- 10 km/s, obtaining similar results for both single-temperature and two-temperature plasma models to account for the cluster cool core. This result, if ascribed to isotropic turbulence, implies a subsonic ICM with Mach number M_3D ~ 0.21 and a non-thermal pressure fraction of 2%. The turbulent velocity is similar to what was measured in the core of the Perseus cluster by Hitomi, but here in a more massive cluster with an ICM temperature of 7 keV, the limit on non-thermal pressure fraction is even more stringent. Our result is consistent with expectations from simulations of relaxed clusters, but it is on the low end of the predicted distribution, indicating that Abell 2029 is an exceptionally relaxed cluster with no significant impacts from either a recent minor merger or AGN activity.
Dynamic Imprints of Colliding-wind Dust Formation from WR 140
(IOP, 2025-01-13) Lieb, Emma P.; Lau, Ryan M.; Hoffman, Jennifer L.; Corcoran, Michael F.; Garcia Marin, Macarena; Gull, Theodore R.; Hamaguchi, Kenji; Han, Yinuo; Hankins, Matthew J.; Jones, Olivia C.; Madura, Thomas I.; Marchenko, Sergey V.; Matsuhara, Hideo; Millour, Florentin; Moffat, Anthony F. J.; Morris, Mark R.; Morris, Patrick W.; Onaka, Takashi; Perrin, Marshall D.; Rest, Armin; Richardson, Noel; Russell, Christopher M. P.; Sanchez-Bermudez, Joel; Soulain, Anthony; Tuthill, Peter; Weigelt, Gerd; Williams, Peredur M.
Carbon-rich Wolf–Rayet (WR) binaries are a prominent source of carbonaceous dust that contribute to the dust budget of galaxies. The "textbook" example of an episodic dust-producing WR binary, WR 140 (HD 193793), provides us with an ideal laboratory for investigating the dust physics and kinematics in an extreme environment. This study is among the first to utilize two separate JWST observations, from Cycle 1 ERS (2022 July) and Cycle 2 (2023 September), to measure WR 140's dust kinematics and confirm its morphology. To measure the proper motions and projected velocities of the dust shells, we performed a novel point-spread function (PSF) subtraction to reduce the effects of the bright diffraction spikes and carefully aligned the Cycle 2 to the Cycle 1 images. At 7.7 μm, through the bright feature common to 16 dust shells (C1), we find an average dust shell proper motion of 390 ± 29 mas yr⁻¹, which equates to a projected velocity of 2714 ± 188 km s⁻¹ at a distance of 1.64 kpc. Our measured speeds are constant across all visible shells and consistent with previously reported dust expansion velocities. Our observations not only prove that these dusty shells are astrophysical (i.e., not associated with any PSF artifact) and originate from WR 140, but also confirm the "clumpy" morphology of the dust shells, in which identifiable substructures within certain shells persist for at least 14 months from one cycle to the next. These results support the hypothesis that clumping in the wind collision region is required for dust production in WR binaries.
Power of simultaneous X-ray and ultraviolet high-resolution spectroscopy for probing outflows in active galactic nuclei
(SPIE, 2024-12) Mehdipour, Missagh; Brenneman, Laura W.; Miller, Jon M.; Costantini, Elisa; Behar, Ehud; Gallo, Luigi; Kaastra, Jelle S.; Laha, Sibasish; Nowak, Michael A.
Black hole accretion in active galactic nuclei (AGN) is coupled to the evolution of their host galaxies. Outflowing winds in AGN can play an important role in this evolution through the resulting feedback mechanism. Multi-wavelength spectroscopy is key for probing the intertwined physics of inflows and outflows in AGN. However, with the current spectrometers, crucial properties of the ionized outflows are poorly understood, such as their coupling to accretion rate, their launching mechanism, and their kinetic power. We discuss the need for simultaneous X-ray and UV high-resolution spectroscopy for tackling outstanding questions on these outflows in AGN. The instrumental requirements for achieving the scientific objectives are addressed. We demonstrate that these requirements would be facilitated by the proposed Arcus Probe mission concept. The multi-wavelength spectroscopy and timing by Arcus would enable us to establish the kinematics and ionization structure of the entire ionized outflow, extending from the vicinity of the accretion disk to the outskirts of the host galaxy. Arcus would provide key diagnostics on the origin, driving mechanism, and energetics of the outflows, which are useful benchmarks for testing various theoretical models of outflows and understanding their impact in AGN.
Overionized plasma in the supernova remnant Sagittarius A East anchored by XRISM observations
(Oxford University Press, 2024-12-26) Boissay-Malaquin, Rozenn; Hamaguchi, Kenji; Hayashi, Takayuki; Mukai, Koji; Pottschmidt, Katja; Tamura, Keisuke; Yaqoob, Tahir; XRISM Collaboration
Sagittarius A East is a supernova remnant with a unique surrounding environment, as it is located in the immediate vicinity of the supermassive black hole at the Galactic center, Sagittarius A*. The X-ray emission of the remnant is suspected to show features of overionized plasma, which would require peculiar evolutionary paths. We report on the first observation of Sagittarius A East with the X-Ray Imaging and Spectroscopy Mission (XRISM). Equipped with a combination of a high-resolution microcalorimeter spectrometer and a large field-of-view CCD imager, we for the first time resolved the Fe xxv K-shell lines into fine structure lines and measured the forbidden-to-resonance intensity ratio to be 1.39 ± 0.12, which strongly suggests the presence of overionized plasma. We obtained a reliable constraint on the ionization temperature just before the transition into the overionization state, of >4 keV. The recombination timescale was constrained to be <8 × 10¹¹ cm⁻³ s. The small velocity dispersion of 109 ± 6 km s⁻¹ indicates a low Fe ion temperature <8 keV and a small expansion velocity <200 km s⁻¹. The high initial ionization temperature and small recombination timescale suggest that either rapid cooling of the plasma via adiabatic expansion from dense circumstellar material or intense photoionization by Sagittarius A∗ in the past may have triggered the overionization.
Extracting the Optical Constants of Partially Absorbing TiO2 ALD Films
(MDPI, 2024-12-12) Chowdhary, Nimarta Kaur; Gougousi, Theodosia
Typical titanium oxide (TiO₂) films are transparent in the visible range, allowing for their index of refraction and thickness to be extracted by single-angle spectroscopic ellipsometry (SE) using a Cauchy model. However, TiO₂ films grown by atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium (IV) (TDMAT) and H₂O at 350 °C absorb in the visible range due to the formation of Ti-O-N/Ti-N bonds. Single-angle SE is inadequate for extracting the optical constants of these films, as there are more unknowns (n, k, d) than measurable parameters (ψ, Δ). To overcome this limitation, we combined SE with transmission (T) measurements, a method known as SE + T. In the process, we developed an approach to prevent backside deposition on quartz substrates during ALD deposition. When applying a B-spline model to SE + T data, the film thicknesses on the quartz substrates closely matched those on companion Si samples measured via standard lithography. The resulting optical constants indicate a reduced refractive index, n, and increased extinction coefficient, k, when compared to purer TiO₂ thin films deposited via a physical vapor deposition (PVD) method, reflecting the influence of nitrogen incorporation on the optical properties.
X-ray properties of coronal emission in radio quiet Active Galactic Nuclei
(2024-12-20) Laha, Sibasish; Ricci, Claudio; Mather, John C.; Behar, Ehud; Gallo, Luigi C.; Marin, Frederic; Mbarek, Rostom; Hankla, Amelia
Active galactic nuclei (AGN) are powerful sources of panchromatic radiation. All AGN emit in X-rays, contributing around ∼5−10% of the AGN bolometric luminosity. The X-ray emitting region, popularly known as the corona, is geometrically and radiatively compact with a size typically ≲10RG (gravitational radii). The rapid and extreme variability in X-rays also suggest that the corona must be a dynamic structure. Decades of X-ray studies have shed much light on the topic, but the nature and origin of AGN corona are still not clearly understood. This is mostly due to the complexities involved in several physical processes at play in the high-gravity, high-density and high-temperature region in the vicinity of the supermassive black hole (SMBH). It is still not clear how exactly the corona is energetically and physically sustained near a SMBH. The ubiquity of coronal emission in AGN points to their fundamental role in black hole accretion processes. In this review we discuss the X-ray observational properties of corona in radio quiet AGN.
Time transfer and clock synchronization with ghost frequency comb
(AIP, 2024-12-10) Joshi, Binod; Smith, Thomas A.; Shih, Yanhua
We report an experimental demonstration of a time transfer and distant clock synchronization scheme based on what we have labeled as a ghost frequency comb, observed from the nonlocal correlation measurements of a laser beam. Unlike a conventional frequency comb, the laser beam used in this work does not consist of a pulse train but instead it is in a continuous-wave operation. The laser beam, consisting of half a million longitudinal cavity modes from a fiber ring laser, is split into two beams, each sent to a distant observer. In their local measurements, both observers observe constant intensity with no pulse structure present. Surprisingly, a pulse train of comb-like, ultra-narrow peaks is observed from their nonlocal correlation function measurement. This observation makes an important contribution to the field of precision spectroscopy, as we show in optical correlation-based nonlocal timing and positioning.

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