A5049154731- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- SAS software applications and methods
- Astrophysics and Star Formation Studies
- High-Energy Particle Collisions Research
- Stellar, planetary, and galactic studies
- Atomic and Molecular Physics
- Particle Detector Development and Performance
- Mechanics and Biomechanics Studies
- Advanced X-ray Imaging Techniques
- Radio Astronomy Observations and Technology
- Cosmology and Gravitation Theories
- Adaptive optics and wavefront sensing
- Radiology practices and education
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Autoimmune Bullous Skin Diseases
- Advanced X-ray and CT Imaging
- Optical Systems and Laser Technology
- CCD and CMOS Imaging Sensors
University of America
2024
Catholic University of America
2024
Deleted Institution
2021-2024
University of Maryland, Baltimore County
2020-2024
Goddard Space Flight Center
2020-2024
Indian Statistical Institute
2024
University of Maryland, Baltimore
2024
University of Maryland Center for Environmental Science
2024
Center for Astrophysics Harvard & Smithsonian
2024
University of California, San Diego
2018-2020
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...
We present results from a homogeneous analysis of the broad-band 0.3–10 keV CCD resolution as well soft X-ray high-resolution grating spectra hard flux-limited sample 26 Seyfert galaxies observed with XMM–Newton. Our goal is to characterize warm absorbers (WAs) along line sight active nucleus. significantly detect WAs in 65 per cent sources. are consistent being at least half nearby Universe, agreement previous estimates. find gap distribution ionization parameter range 0.5 < log ξ 1.5 which...
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...
The nearby type-II AGN 1ES1927+654 went through a violent changing-look (CL) event beginning December 2017 during which the optical and UV fluxes increased by four magnitudes over few months, broad emission lines newly appeared in optical/UV. By July 2018 X-ray coronal had completely vanished, only to reappear months later. In this work we report evolution of radio, optical, X-rays from pre-flare state mid-2021 with new archival data Very Long Baseline Array (VLBA), European VLBI Network,...
Abstract We report observations of the optical counterpart long gamma-ray burst GRB 221009A. Due to extreme rarity being both nearby ( z = 0.151) and highly energetic E γ ,iso ≥ 10 54 erg), 221009A offers a unique opportunity probe connection between massive star core collapse relativistic jet formation across very broad range -ray properties. Adopting phenomenological power-law model for afterglow host galaxy estimates from high-resolution Hubble Space Telescope imaging, we use Bayesian...
Abstract We present the second NuSTAR and XMM-Newton extragalactic survey of JWST north ecliptic pole (NEP) time-domain field (TDF). The first NEP-TDF had 681 ks total exposure time executed in cycle 5 2019 2020. This survey, acquired from 2020 to 2022 6, adds 880 time. overall is most sensitive date, a 60 sources were detected above 95% reliability threshold. constrain hard X-ray number counts, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi>...
We have conducted an extensive X-ray spectral variability study of a sample 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to the neutral intrinsic obscuration along line sight investigate properties location dominant component X-ray-obscuring gas. observations are sensitive absorption columns $N_{\rm H} \sim 10^{20.5-24} {\rm cm^{-2}}$ fully- partially-covering and/or lowly-ionized gas on timescales spanning days well over decade....
Abstract We present Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Alert Telescope (Swift-BAT) searches for gamma-ray/X-ray counterparts to gravitational-wave (GW) candidate events identified during the third observing run of Advanced LIGO Virgo detectors. Using Fermi-GBM onboard triggers subthreshold gamma-ray burst (GRB) candidates found in ground analyses, Targeted Search Untargeted Search, we investigate whether there are any coincident GRBs associated with GWs. also search...
This paper is a sequel to the extensive study of warm absorber (WA) in X-rays carried out using high resolution grating spectral data from XMM-Newton satellite (WAX-I). Here we discuss global dynamical properties as well energetics WA components detected WAX sample. The slope density profile ($n\propto r^{-\alpha}$) estimated linear regression ionization parameter $\xi$ and column $N_H$ sample $\alpha=1.236\pm 0.034$. We find that clouds possibly originate result photo-ionised evaporation...
The UV to X-ray continuum of active galactic nuclei (AGN) is important for maintaining the ionisation and thermal balance warm absorbers (WAs). However, spectra in sensitive energy range $\sim \,13.6 -300 \ev$ are unobservable due Galactic extinction. Moreover, many AGN show soft excess emission varying strength $0.1-2\kev$ band whose origin still highly debated. This soft-excess connects bump unobserved region $13.6 \ev$. Here we investigate effect assumed physical model on flux part...
Abstract We have carried out an extensive X-ray spectral analysis of a sample galaxies exhibiting molecular outflows (MOX sample) to characterize the properties and investigate effect active galactic nuclei (AGNs) on dynamical (MOs). find that bolometric correction ( L 2–10 keV / AGN ) these sources ranges from ∼10 −4.5 10 −0.5 , with ∼70% below −2 implying weak emission relative luminosity ). However, upper limit <?CDATA ${L}_{2-10\mathrm{keV},12\mu {\rm{m}}}$?> obtained 12 μ m flux,...
In this paper, we report on the observational performance of Swift Ultra-violet/Optical Telescope (UVOT) in response to Gravitational Wave alerts announced by Advanced Laser Interferometer Observatory and Virgo detector during O3 period. We provide strategy for follow-up GW an overview processing analysis candidate optical/UV sources. For period, also a statistical serendipitous sources discovered Swift/UVOT. followed 18 gravitational-wave alerts, with UVOT observing total 424 deg^2. found...
FRB180301 is one of the most actively repeating fast radio bursts (FRBs) which has shown polarization angle changes in its burst emission, an indication for their likely origin magnetosphere a highly-magnetized neutron star. We carried out multi-wavelength campaign with FAST telescope and NICER X-ray observatory to investigate any possible emission temporally coincident bright bursts. The observations took place on 2021 March 4, 9 19. detected five FAST, four were strictly simultaneous...
We have carried out a systematic X-ray spectral analysis of sample low luminosity quasars (LLQSO) to investigate the nature central engines these sources. The optically-selected LLQSO consists close, known bright active galactic nuclei (AGN) which serves as an important link between powerful at higher redshift and local Seyfert galaxies. find that although bolometric luminosities LLQSOs are lower than those by almost order magnitude, their distribution Eddington rate $\lambda_{\rm Edd}$ is...
We have extensively studied the broadband X-ray spectra of source ESO~141--G055 using all available \xmm{} and \nustar{} observations. detect a prominent soft excess below 2 keV, narrow Fe line Compton hump (>10 keV). The origin is still debated. used two models to describe excess: blurred reflection from ionized accretion disk intrinsic thermal Comptonisation model. find that both these explain equally well. confirm we do not any broad in this source, although physical prefer maximally...
We present a detailed study of the ionized environment Seyfert 1 galaxy Mrk 704 using medium- and high-resolution X-ray spectra obtained with long XMM-Newton observation. The 0.3–10 keV continuum, well described by power law (Γ ≈ 1.86) two blackbodies (kT 0.085 0.22 keV), is found to be affected neutral partial covering absorption (NH 1023 cm−2, fraction ≈0.22) warm absorber components. identify low-ionization, ξ ∼ 20 erg cm s−1, high outflow velocity, v 1350 km phase producing O vi Fe...
Abstract 1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years. Here we report the unusual X-ray, UV, and radio source its postflare state (2022 January–2023 May). First, detect increase soft X-ray (0.3–2 keV) flux from 2022 May 2023 almost factor 5, which call bright state. The hard 2–10 keV increased 2, while UV density did not show any significant...
BurstCube is a 6U (10 x 20 30 cm) CubeSat designed to detect gamma-ray bursts (GRBs) and enable multimessenger observations, scheduled launch in early 2024. science informed by the coincident detection of GRB 170817A gravitational wave (GW) 170817, which confirmed compact binary mergers as progenitors for GRBs. Future detections will also provide important context GW measurements - namely constraining neutron star equation state testing fundamental physics, while probing origin prompt...
Abstract The reprocessed X-ray emission from active galactic nuclei is an important diagnostic tool to study the dynamics and geometry of matter surrounding supermassive black holes (SMBHs). We present a broadband (optical-UV hard X-ray) spectral bare Seyfert 1 galaxy, ESO 511–G030, using multi-epoch Suzaku XMM-Newton data 2012 2007, respectively. spectra 511–G030 exhibit UV bump, prominent soft excess below <?CDATA $2\,\mathrm{keV}$?> , relatively broad ( $\sigma...
BurstCube aims to expand sky coverage in order detect, localize, and rapidly disseminate information about gamma-ray bursts (GRBs). is a '6U' CubeSat with an instrument comprised of 4 Cesium Iodide (CsI) scintillators coupled arrays Silicon photo-multipliers (SiPMs) will be sensitive gamma-rays between 50 keV 1 MeV. assist current observatories, such as Swift Fermi, the detection GRBs well provide astronomical context gravitational wave (GW) events detected by LIGO, Virgo, KAGRA. currently...
We have investigated the nature and origin of Fe K emission lines in Mrk~205 using observations with {\it Suzaku} XMM-Newton}, aiming to resolve ambiguity between a broad line multiple unresolved higher ionization. detect presence narrow K$\alpha$ along band Compton reflection hump at energies $E>10 \rm \, keV$. These are consistent reflected hard X-ray photons off thick material $N_{\rm H} \ge 2.15\times 10^{24} cm^{-2}$. In addition we partially covering ionized absorption ionization...
FRB 180916.J0158+65 is one of the nearest, periodically repeating, and actively bursting fast radio burst (FRB) which has been localized to outskirts a spiral galaxy. In this work we study with hard X-ray $14-195$ keV data from Burst Alert Telescope (BAT) on board The Neil Gehrels Swift Observatory. BAT uses coded mask technology giving localization $\lesssim 3$ arc-minute in band, along an accurate background estimation. observing source location survey mode since February 2020....
We have studied the nature and origin of soft X-ray excess detected in interesting changing-look AGN (CLAGN) Mrk~590 using two decades multi-wavelength observations from \xmm{}, \suzaku{}, \swift{} \nustar{}. In light vanishing this CLAGN, we test models, "the warm Comptonization" ionized disk reflection" extensive UV/X-ray spectral analysis. Our main findings are: (1) emission, last observed 2004, vanished 2011, never reappeared any later observations, (2) a significant variability...