A5068724023- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Pulsars and Gravitational Waves Research
- Neutrino Physics Research
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Gyrotron and Vacuum Electronics Research
- High-pressure geophysics and materials
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Radio Wave Propagation Studies
- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Geophysics and Gravity Measurements
- Relativity and Gravitational Theory
- Phase Equilibria and Thermodynamics
- Precipitation Measurement and Analysis
College of New Jersey
2015-2024
Aryabhatta Research Institute of Observational Sciences
2019-2021
Universidade de São Paulo
2019
Kavli Institute for Particle Astrophysics and Cosmology
2017
National Centre for Radio Astrophysics
1993-2012
Georgia State University
2002-2011
Institute for Advanced Study
2008-2009
Princeton University
2001-2004
Princeton Public Schools
2000
Indian Institute of Astrophysics
1995
ABSTRACT In a previous paper, we reported evidence for quasi-periodicities in the Transiting Exoplanet Survey Satellite (TESS) light curves of BL Lacerate and two other blazars found serendipitously Sloan Digital Sky (SDSS) active galactic nuclei catalogue. this work, find tentative quasi-periodic features TESS observations five sources fourth catalogue Fermi–Large Area Telescope sources: J090453.4−573503, J2345−1555, B0422+004, J002159.2−514028, B0537−441. We analysed these that extracted...
view Abstract Citations (182) References (61) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accretion Disk Models for Optical and Ultraviolet Microvariability in Active Galactic Nuclei Mangalam, Arun V. ; Wiita, Paul J. We describe Scenarios rapid, low-amplitude UV optical variability AGNs through phenomenologically modeled asymmetries on accretion disks, which can represent perturbations arising from magnetic, gravitational, other instabilities. The...
We present the results of a periodicity search 20 intra-day variable optical light curves blazar S5 0716+714, selected from database 102 spanning over three years. use wavelet analysis technique along with randomization test and find strong candidates for nearly periodic variations in eight curves, probabilities ranging 95% to >99%. This is first good evidence periodic, or more precisely, quasi-periodic, components any blazar. Such flux changes support idea that some active galactic nuclei...
Over the course of three hours on 27 December 2008 we obtained optical (R-band) observations blazar S5 0716+714 at a very fast cadence 10 s. Using several different techniques find fluctuations with an approximately 15-minute quasi-period to be present in first portion that data > 3 sigma confidence level. This is fastest QPO has been claimed observed any wavelength. While this insufficient strongly constrain models for such fluctuations, presence short timescale when source not low state...
Abstract We present the results of our power spectral density analysis for BL Lac object OJ 287, utilizing Fermi -LAT survey at high-energy γ -rays, Swift -XRT in X-rays, several ground-based telescopes and Kepler satellite optical, radio GHz frequencies. The light curves are modeled terms continuous-time autoregressive moving average (CARMA) processes. Owing to inclusion data, we were able construct first time optical variability spectrum a blazar without any gaps across ∼6 dex temporal Our...
Since 2016 October, the active galaxy PKS 2247-131 has undergone a gamma-ray outburst, which we studied using data obtained with Fermi Gamma-ray Space Telescope. The emission arises from relativistic jet in 2247-131, as an optical spectrum only shows few weak absorption lines, typical of BL Lacertae sub-class blazar class galactic nuclei. Here report ~34.5 day quasi-periodic oscillation (QPO) after initial flux peak outburst. Compared to one-year time-scale QPOs, previously identified...
Abstract We report the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in blazar OJ 287. In binary black hole model, it is associated with an impact secondary accretion disk primary. Our multifrequency observing campaign was set up to search for such signature based prediction made 8 yr earlier. The first I -band results have already been reported by Kishore et al. (2024). Here we combine these data our monitoring R -band. There big change – spectral index 1.0 ± 0.1...
view Abstract Citations (124) References (73) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spiral Shocks in Accretion Disks As a Contributor to Variability Active Galactic Nuclei Chakrabarti, Sandip K. ; Wiita, Paul J. We simulate the variations emission from accretion disks subjected nonaxisymmetric tidal perturbations generated by masses within or passing through disk, using two-dimensional hydrodynamics code. shocks can form, fragment, and reform on...
We report a possible detection of an ~4.6-hour quasi-periodic oscillation (QPO) in the 0.3-10 keV emission high-energy peaked blazar PKS 2155-304 from 64 ks observation by XMM-Newton EPIC/pn detector. identify total modulation ~5% light curve and confirm that nominal period periodogram, structure function wavelet analyses. The limited duration allows capture only 3.8 cycles this thus precludes very strong claim for QPO, despite nominally high (>3 sigma) statistical significance. briefly...
view Abstract Citations (102) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutrino Emission by the Pair, Plasma, and Photo Processes in Weinberg-Salam Model Schinder, Paul J. ; Schramm, David N. Wiita, Margolis, Steven H. Tubbs, L. The results of numerical integrations rates emissivities photo, pair, plasma neutrino emission mechanisms theory weak interaction are presented. range densities from 10 to 14th g/cu cm temperature 8th 11th K...
How cancer cells globally struggle with a chemotherapeutic insult before succumbing to apoptosis is largely unknown. Here we use an integrated systems-level examination of transcription, translation, and proteolysis understand these events central treatment. As model study myeloma exposed the proteasome inhibitor bortezomib, first-line therapy. Despite robust transcriptional changes, unbiased quantitative proteomics detects production only few critical anti-apoptotic proteins against...
We have measured multiband optical flux and colour variations for a sample of 12 low-energy peaked blazars (LBLs) on short, day-to-month, time-scales. Our contains six BL Lacertae objects (BL Lacs) flat spectrum radio quasars (FSRQs). These photometric observations, made during 2008 September to 2009 June, used five telescopes, one in India four Bulgaria. detected short-term 11 these variability eight them. data indicate that (3C 66A, AO 0235+164, S5 0716+714, PKS 0735+178, OJ 287 3C 454.3)...
We report results from a 1 week multi-wavelength campaign to monitor the BL Lac object S5 0716+714 (on December 9-16, 2009). In radio bands source shows rapid (~ (0.5-1.5) day) intra-day variability with peak amplitudes of up ~ 10 %. The at 2.8 cm leads by about day 6 and 11 cm. This time lag more variations suggests an intrinsic contribution source's intraday cm, while interstellar scintillation (ISS) seems predominate. Large quasi-sinusoidal 0.8 mag were detected in V, R I-bands. X-ray...
We present our optical photometric observations of three TeV blazars, PKS 1510-089, PG 1553+113 and Mrk 501 taken using two telescopes in India, one Bulgaria, Greece Serbia during 2012 - 2014. These covered a total 95 nights with 202 B filter frames, 247 images V band, 817 R band while 229 were the I filter. This work is focused on multi-band flux colour variability studies these blazars diverse timescales which are useful understanding emission mechanisms. studied characteristics above...
We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high synchrotron peaked blazars: 1ES 0229+200, Mrk 421, 501, 1959+650 and PKS 2155-304. Four the blazars showed intraday variability in energy range 3-79 keV. Using an auto correlation function analysis we searched for timescales these LCs found indications several between 2.5 32.8 ks eight a timescale around 8.0 one LC 29.6 57.4 two The other blazars' do not show any evidence shorter than lengths those observations, however,...
We detected a possible quasi-periodic oscillation (QPO) of ~ 71 days in the 0.1 -- 300 GeV gamma-ray Fermi-LAT light curve high redshift flat spectrum radio quasar B2 1520+31. identify and confirm that quasi-period by Lomb Scargle periodogram (LSP), weighted wavelet z-transform (WWZ) analyses. Using this QPO period, assuming it originates from accretion-disc fluctuations at innermost stable circular orbit, we estimate central supermassive black hole mass to range between 5.4 * 10$^{9}$...
We report the detection ($>4\sigma$) of a Quasi-Periodic Oscillation (QPO) in $\gamma$-ray light curve 3C 454.3 along with simultaneous marginal QPO ($>2.4\sigma$) optical curves. Periodic flux modulations were detected both these wavebands dominant period $\sim 47$ days. The lasted for over 450 days (from MJD 56800 to 57250) resulting nine observed cycles which is among highest number periods ever blazar curve. was not well sampled almost half span due daytime transit source, could explain...
We report the results of multiband optical photometric monitoring two well-known blazars, S5 0716+714 and BL Lacertae, carried out during 1996 2000–01 with an aim to study variations on time-scales ranging from minutes hours longer. The light curves were derived relative comparison stars present CCD frames. Night-to-night intensity ≥0.1 mag observed in a campaign about 2 weeks 1996. A good correlation between different bands was found for both inter-night intra-night observations. In all,...
We selected a sample of 24 XMM–Newton light curves (LCs) four high energy peaked blazars, PKS 0548 − 322, ON 231, 1ES 1426+428, and 2155 304. These data comprise continuous LCs 7.67–18.97 hr in length. searched for possible quasi-periodic oscillations (QPOs) intra-day variability (IDV) timescales the these blazars. found likely QPO one LC 304 which was reported elsewhere. In remaining 23 we hints weak QPOs each 231 304, but neither is statistically significant. IDV that ranged from 15.7 to...
We have performed a structure function analysis of the Rossi X-Ray Timing Explorer All-Sky Monitor data to search for variability in 24 blazars using trains that each exceed 12 yr. Although 20 them show nominal periods through this technique, great majority these "periods" are clearly related yearly variations arising from instrument. Nonetheless, an apparently real periodic component about 17 days was detected blazar AO 0235+164 and it confirmed by discrete correlation periodogram analyses....
(Abridged) With the largest homogeneous quasar sample with optical spectra and robust radio morphology classifications assembled to date, we investigate properties unprecedented statistical power. The data consist of 4714 quasars from FIRST S_{20}>2mJy SDSS spectra. Radio classes include core-only (core), core-lobe (lobe), core-jet (jet), lobe-core-lobe (triple), double-lobe. We examine colors radio-morphology subsamples find that core emission unresolved by (on 5" scale) have a redder color...