A5032324842- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Black Holes and Theoretical Physics
- Microwave Imaging and Scattering Analysis
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Astrophysics and Star Formation Studies
- Electrical and Bioimpedance Tomography
- Mechanics and Biomechanics Studies
- Pulsars and Gravitational Waves Research
- Hemodynamic Monitoring and Therapy
- Relativity and Gravitational Theory
- History and Developments in Astronomy
- Atmospheric Ozone and Climate
University of Maryland, Baltimore County
2023-2025
United States Naval Observatory
2022-2024
George Mason University
2021-2023
Western Illinois University
2021
University of Dhaka
2016
Abstract We present multifrequency (5–345 GHz) and multiresolution radio observations of 1ES 1927+654, widely considered one the most unusual extreme changing-look active galactic nuclei (CL-AGNs). The source was first designated a CL-AGN after an optical outburst in late 2017 has since displayed considerable changes X-ray emission, including destruction rebuilding corona 2019–2020. Radio prior to 2023 show faint compact typical radio-quiet AGN. Starting February, 1927+654 began exhibiting...
Abstract We present results from a high-cadence multiwavelength observational campaign of the enigmatic changing-look active galactic nucleus 1ES 1927+654 2022 May to 2024 April, coincident with an unprecedented radio flare (an increase in flux by factor ∼60 over few months) and emergence spatially resolved jet at 0.1–0.3 pc scales. Companion work has also detected recurrent quasi-periodic oscillation (QPO) 2–10 keV band increasing frequency (1–2 mHz) same period. During this time, soft...
We present results from a high cadence multi-wavelength observational campaign of the enigmatic changing look AGN 1ES 1927+654 May 2022- April 2024, coincident with an unprecedented radio flare (an increase in flux by factor $\sim 60$ over few months) and emergence spatially resolved jet at $0.1-0.3$ pc scales (Meyer et al. 2024). Companion work has also detected recurrent quasi-periodic oscillation (QPO) $2-10$ keV band increasing frequency ($1-2$ mHz) same period (Masterson al., 2025)....
We present $4-12$ GHz in-band spectral energy distributions with accompanying 6 and 10 imaging results for a volume-complete sample ($<40$ Mpc) of hard X-ray selected active galactic nuclei (AGNs) observed the Karl G. Jansky Very Large Array (VLA) in its A-array configuration. Despite expectations, only 12 out 25 these targets have been detected by Long Baseline (VLBA) at milliarcsecond resolution our previous studies, we aim to understand nature why circumnuclear radio emission resolves...
Abstract We present results from the Very Long Baseline Array multifrequency (1.6, 4.4, 8.6, and 22 GHz), high-sensitivity (∼25 μ Jy beam −1 ), subparsec-scale (<1 pc) observations spectral energy distributions for a sample of 12 local active galactic nuclei (AGNs), subset our previous volume-complete with hard-X-ray (14–195 keV) luminosities above 10 42 erg s , out to distance 40 Mpc. All sources presented here were detected in C (4.4 GHz) X (8.6 bands, 75% L band (1.6 50% K (22 GHz)....
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), garnering further interest in stellar-mass companions SMBHs and progenitors to mHz frequency gravitational wave events. Here we report discovery a highly significant Quasi-Periodic Oscillation (QPO) an actively accreting...
Accurately determining the black hole mass ($M_\mathrm{BH}$) in active galactic nuclei (AGN) is crucial to constraining their properties and studying evolution. While direct methods yield reliable measurements of $M_\mathrm{BH}$ unobscured type 1 AGN, where dynamics stellar or gas components can be directly observed, only indirect applied vast majority heavily absorbed 2 which represent most AGN population. Since it difficult evaluate accuracy precision these methods, we utilize nearby X-ray...
Abstract We present the first results from Karl G. Jansky Very Large Array (VLA) observations as a part of Fundamental Reference Active Galactic Nucleus (AGN) Monitoring Experiment, program to understand relationship between AGN accretion physics and wavelength-dependent position function time. With this VLA survey, we investigate radio properties volume-complete sample 25 hard X-ray-selected AGNs using in its wideband mode. observed targets A-array configuration at 4–12 GHz with all...
One of the major problems with Electrical Impedance Tomography (EIT) is lack spatial sensitivity within measured volume. In this paper, distribution tetrapolar impedance measurement system was visualized considering a cylindrical phantom consisting homogeneous and inhomogeneous medium. Previously, analysed analytically only for medium simple geometries found to be complex1,2. However, volume conductors analysis needs done using finite element method (FEM). results based on COMSOL...
Abstract We present follow-up results from the first Fundamental Reference AGN Monitoring Experiment (FRAMEx) X-ray/radio snapshot program of a volume-complete sample local hard X-ray-selected active galactic nuclei (AGNs). Here, we added nine new sources to our previous campaign, two which are detected in 6 cm Very Long Baseline Array (VLBA) observations. also obtained deeper VLBA observations for AGNs not by campaign. recovered three with approximately twice observing sensitivity. In...
ABSTRACT The black hole mass MBH is crucial in constraining the growth of supermassive holes within their host galaxies. Since direct measurements with dynamical methods are restricted to a limited number nearly quiescent nearby galaxies and small minority active galactic nuclei (AGN), we must rely on indirect methods. In this work, utilize an unbiased, volume-limited, hard X-ray selected sample AGN compare reliability some commonly used methods, emphasizing those that can be applied...
We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one the most unusual extreme changing-look active galactic nuclei (CL-AGN). The source was first designated a CL-AGN after an optical outburst in late 2017 has since displayed considerable changes X-ray emission, including destruction rebuilding corona 2019-2020. Radio prior to 2023 show faint compact not for radio-quiet AGN. Starting February 2023, 1927+654 began exhibiting...
ABSTRACT Spectral lines from formaldehyde (H2CO) molecules at cm wavelengths are typically detected in absorption and trace a broad range of environments, diffuse gas to giant molecular clouds. In contrast, thermal emission is rare. previous observations with the 100 m Robert C. Byrd Green Bank Telescope (GBT), we 2 towards NGC 7538 IRS1 – high-mass protostellar object prominent star-forming region our Galaxy. We present further GBT 1 H2CO investigate nature emission. conducted constrain...
Accurately determining the black hole mass ($M_\mathrm{BH}$) in active galactic nuclei (AGN) is crucial to constraining their properties and studying evolution. While direct methods yield reliable measurements of $M_\mathrm{BH}$ unobscured type 1 AGN, where dynamics stellar or gas components can be directly observed, only indirect applied vast majority heavily absorbed 2 which represent most AGN population. Since it difficult evaluate accuracy precision these methods, we utilize nearby X-ray...
We present the first results from Karl G. Jansky Very Large Array (VLA) observations as a part of Fundamental Reference Active Galactic Nucleus (AGN) Monitoring Experiment (FRAMEx), program to understand relationship between AGN accretion physics and wavelength-dependent position function time. With this VLA survey, we investigate radio properties volume-complete sample 25 hard X-ray-selected AGNs using in its wideband mode. observed targets A-array configuration at $4-12$ GHz with all...
We present results from the Very Long Baseline Array (VLBA) multi-frequency (1.6, 4.4, 8.6, 22 GHz), high-sensitivity (~25 microJy beam^-1), sub-parsec scale (<1 pc) observations and Spectral Energy Distributions (SEDs) for a sample of 12 local active galactic nuclei (AGNs), subset our previous volume-complete with hard X-ray (14-195 keV) luminosities above 10^42 erg s^-1, out to distance 40 Mpc. All sources presented here were detected in C (4.4 GHz) X (8.6 bands, 75% L band(1.6 50% K band...
The black hole mass MBH is crucial in constraining the growth of supermassive BHs within their host galaxies. Since direct measurements with dynamical methods are restricted to a limited number nearly quiescent nearby galaxies and small minority active galactic nuclei (AGN), we must rely on indirect methods. In this work, utilize an unbiased, volume-limited, hard X-ray selected sample AGN compare reliability some commonly used methods, emphasising those that can be applied obscured AGN....
We present follow-up results from the first Fundamental Reference AGN Monitoring Experiment (FRAMEx) X-ray/radio snapshot program of a volume-complete sample local hard X-ray-selected active galactic nuclei (AGNs). Here, we added 9 new sources to our previous campaign, two which are detected in 6 cm Very Long Baseline Array (VLBA) observations. also obtained deeper VLBA observations for AGNs not by campaign. recovered 3 with approximately twice observing sensitivity. In contrast lower...