A5019203618- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Superconducting and THz Device Technology
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Pulsars and Gravitational Waves Research
- Molecular Spectroscopy and Structure
- Neutrino Physics Research
- Gyrotron and Vacuum Electronics Research
- Scientific Research and Discoveries
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Dark Matter and Cosmic Phenomena
- Precipitation Measurement and Analysis
- Mechanics and Biomechanics Studies
Universidade de São Paulo
2012-2023
Museu de Astronomia e Ciências Afins
2018
Universidad Nacional Autónoma de México
2009-2014
Universidade Cidade de São Paulo
2011-2012
Institute of Astrophysics and Space Sciences
2009
University of Lisbon
2009
Instituto de Geofísica y Astronomía
2003-2009
Valongo Observatory
2009
National Observatory
1980-2009
Centro Brasileiro de Pesquisas Físicas
2009
BL Lacertae is the prototype of Lac class active galactic nuclei, exhibiting intensive activity on parsec (pc) scales, such as intense core variability and multiple ejections jet components. In particular, in previous works existence precession motions pc-scale has been suggested. this work we revisit issue, investigating temporal changes observed right ascension declination offsets knots terms our relativistic jet-precession model. The seven free parameters model were optimized via a...
Abstract The recent discovery of a roughly simultaneous periodic variability in the light curves BL Lac object PG 1553+113 at several electromagnetic bands represents first case such odd behavior reported literature. Motivated by this, we analyzed 15 GHz interferometric maps parsec-scale radio jet to verify presence possible counterpart this variability. We used Cross-entropy statistical technique obtain structural parameters Gaussian components present source. kinematically identified seven...
The Perseus galaxy cluster is known to present multiple and misaligned pairs of cavities seen in X-rays, as well twisted kiloparsec-scale jets at radio wavelengths; both morphologies suggest that the active galactic nucleus (AGN) jet subject precession. In this work, we performed three-dimensional hydrodynamical simulations interaction between a precessing AGN warm intracluster medium plasma, whose dynamics are coupled Navarro–Frenk–White dark matter gravitational potential. inflates become...
view Abstract Citations (50) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS More Solar Models and Neutrino Fluxes Abraham, Zulema ; Iben, Icko, Jr. Ve present neutrino fluxes from a sequence of solar models that differ one another in regard to opacity, equation state, nuclear cross-section factors. Using current estimates the relevant input parameters, we obtain capture rates range between 3 10 times most recent result Davis neutrino-capture...
VLBI observations have shown that the parsec-jet of 3C 345 is formed by several components, ejected from core with superluminal velocities and travelling along bent trajectories on plane sky. We interpret differences in velocity position angle among different features at formation time as result parsec-scale precession relativistic jet calculate aperture cone, between cone axis line sight Lorentz factor associated bulk motion. assumed a period 10.1 yr, which one B-band light curve long-term...
We show that it is possible to explain the physical origin of jet precession in active galactic nuclei (AGNs) through misalignment between rotation axes accretion disk and Kerr black hole. apply this scenario quasars, Seyfert galaxies also Galactic Center hole Sgr A*, for which signatures either or have been found. The formalism adopted parameterized by ratio period mass can be used put constraints properties as well spin those systems.
The Bardeen-Petterson general relativistic effect has been suggested as the mechanism responsible for precession in some accretion disk systems. Here we examine separately four mechanisms (tidal, irradiative, magnetic, and Bardeen-Petterson) that can lead to warping precession. We use a sample of eight X-ray binaries active galactic nuclei (AGNs) present signatures and/or their disks explore viability different mechanisms. For SMC X-1 4U 1907+09, all provide periods compatible with those...
Strong evidence for the presence of a warped Keplerian accretion disc in NGC4258 (M 106) has been inferred from kinematics water masers detected at sub-parsec scales. Assuming power-law and using constraints on parameters derived observational data, we have analyzed relativistic Bardeen-Petterson effect driven by Kerr black hole as potential physical mechanism responsible warping. We found that radius is comparable to or smaller than inner maser (independent allowed value spin parameter)....
We present a map of the spiral structure Galaxy, as traced by molecular CS emission associated with IRAS sources which are believed to be compact HII regions. The line velocities used determine kinematic distances sources, in order investigate their distribution galactic plane. This allows us use 870 objects trace arms, number larger than that previous studies based on classical distance ambiguity distances, when it exists, is solved different procedures, including latitude and an analysis...
In the past few decades detailed observations of radio and X-ray emission from massive binary systems revealed a whole new physics present in such systems. Both thermal non-thermal components this indicate that most radiation at these bands originates shocks. O B-type stars Wolf–Rayet (WR) supersonic winds that, when colliding, emit largely due to free–free radiation. The emissions are synchrotron inverse Compton processes, respectively. case, magnetic fields expected play an important role...
A model of a precessing jet obtained from radio data was used to explain the optical light curve OVV quasar 3C 279. The geometrical parameters and bulk motion were position angles, velocities, epoch formation superluminal features in jet. As consequence, provides Doppler factor time dependence. This reached its maximum value at which very strong fast flare observed. Therefore, large increases emission wavelengths could be result beaming, as approaches minimum separation line sight. Fast...
Optical variability of 3C 120 is discussed in the framework jet precession. Specifically, we assume that observed long-term periodic produced by emission from an underlying with a time-dependent boosting factor driven The differences apparent velocities different superluminal components milliarcsec can also be explained precession model as being related to changes viewing angle. evolution has been used determine parameters model, which reproduce helical structure seen at large scales. Among...
In this paper we present observations of η Carinae in the 1.3 mm and 7 radio continuum, during 2003.5 low excitation phase. The expected minimum light curves was confirmed at both wavelengths probably due to a decrease number UV photons available ionize gas surrounding binary system. At very well defined peak superimposed on declining flux density. It presented maximum amplitude 29 June 2003 lasted for about 10 days. We show that its origin can be free-free emission from shock formed by...
K-band spectra of young stellar candidates in four Southern hemisphere clusters have been obtained with the Gemini Near-Infrared Spectrograph South. The are associated IRAS sources that colours characteristic ultracompact H ii regions. Spectral types were by comparison observed those a near-infrared (NIR) library; results include spectral classification nine massive stars and seven objects confirmed as background late-type stars. Two studied compatible very hot stars, inferred from presence...
We report observations of $\eta$ Carinae obtained with ALMA in the continuum 100, 230, 280 and 660 GHz 2012 November, a resolution that varied from 2.88" to 0.45" for lower higher frequencies respectively. The source is not resolved, even at highest frequency; its spectrum characteristic thermal bremsstrahlung compact source, but different optically thin wind. recombination lines H42$\alpha$, He42$\alpha$, H40$\alpha$, He40$\alpha$, H50$\beta$, H28$\alpha$, He28$\alpha$, H21$\alpha$...
VLBA high spatial resolution observations of the disk structure active galactic nucleus (AGN) NGC 1068 have recently revealed that kinematics and geometry this AGN is well characterized by an outer H2O maser emission having a compact milliarcsecond- (parsec-) scale structure, which encircling thin rotating inner surrounding ~107 M☉ mass, likely black hole. A curious feature in source occurrence misalignment between parts disk, with galaxy's radio jet being orthogonal to disk. We interpret...
In this paper, we present multiband optical polarimetric observations of the very-high energy blazar PKS 2155−304 made simultaneously with a HESS/Fermi high-energy campaign in 2008, when source was found to be low state. The intense daily coverage data set allowed us study detail temporal evolution emission, and that particle acceleration time-scales are decoupled from changes properties source. We model which emission originates at polarized mm-wave core propose an explanation for lack...
We report on four years of observations 3C 273 at 7 mm obtained with the Itapetinga radio telescope, in Brazil, between 2009 and 2013. detected a flare 2010 March, when flux density increased by 50 per cent reached 35 Jy. After flare, started to decrease values lower than 10 suggest that 7-mm is counterpart γ-ray observed Fermi Large Area Telescope September, which high energies factor its average value. A delay 170 d flares was revealed using discrete correlation function (DCF) can be...
Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into global VLBI network will bring unprecedented sensitivity and transformational leap capabilities for mmVLBI. Building on years pioneering efforts US Europe ongoing Phasing Project (APP), US-led international collaboration with MPIfR-led European contributions, is expected to...
We modelled the He iiλ4686 line profiles observed in η Carinae binary system close to 2003.5 spectroscopic event, assuming that they were formed shocked gas flows at both sides of contact surface by wind–wind collision. used a constant flow velocity and added turbulence form Gaussian distribution. allowed emission from primary secondary shocks but introduced infinite opacity surface, implying only side cone visible observer contributed profile. Using orbital parameters derived 7-mm light...
Evidence of jet precession in many galactic and extragalactic sources has been reported the literature. Much this evidence is based on studies kinematics knots, which depends correct identification components to determine their respective proper motions position angles plane sky. Identification problems related fitting procedures, as well observations poorly sampled time, may influence follow-up consequently might contribute a misinterpretation data. In order deal with these limitations, we...
The bipolar nebula Menzel 3 (Mz 3) was observed as part of the \textit{Herschel} Planetary Nebula Survey (\textit{HerPlaNS}), which used PACS and SPIRE instruments aboard \textit{Herschel Space Observatory} to study a sample planetary nebulae (PNe). In this paper, one series describing \textit{HerPlaNS} results, we report detection H I recombination lines (HRLs) in spectrum Mz 3. Inspection reveals presence 12 HRLs 55 680 $\mu$m range covered by (H11$\alpha$ H21$\alpha$ H14$\beta$). is...
In this paper we use the 7 mm and 1.3 light curves obtained during 2003.5 low excitation phase of eta Carinae system to constrain possible parameters binary orbit. To do that assumed wave emission is produced in a dense disk surrounding system; phase, which occurs close periastron, number ionizing photons decreases, producing dip radio emission. On other hand, due large eccentricity, density shock region at periastron very high plasma optically thick for free-free radiation mm, explaining...
view Abstract Citations (41) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolution of 3C 273 at 10.7 GHz Cohen, M. H. ; Zensus, J. A. Biretta, Comoretto, G. Kaufmann, P. Abraham, Z. The quasar has been observed three epochs spanning 1984.1 - 1985.6. Two new superluminal components, C5 and C7a, are separating from the core with apparent transverse velocity v/c = (8.0±0.2)h-1 (5.1±0.3)h-1. old components C3 C4 may still be recognizable,...