scholarly journals 4 Years of Radio to X-ray Observations of 3C 273

1989 ◽  
Vol 134 ◽  
pp. 112-113
Author(s):  
T.J.-L. Courvoisier ◽  
E. I. Robson ◽  
A. Blecha ◽  
P. Bouchet
Keyword(s):  
Near Infrared ◽  
Optical Emission ◽  
Light Curves ◽  
Physical Parameters ◽  
List Type ◽  
Type Number ◽  
Rapid Variability ◽  
X Ray ◽  
Model Independent ◽  
Ir Emission

The quasar 3C273 has been repeatedly observed at radio, mm, IR, optical, UV and X-ray frequencies since December 1983. A complex pattern of continuum variations has been discovered, which can be used to provide model independent physical parameters, and to constrain different models. The main features revealed by our set of observations are: (i)A flux decrease by 40% in the 2–10 kev flux in 20 days in early 1984 (Courvoisier et al. 1987).(ii)Differences between the X-ray light curves at 0.5 keV and 2–10 keV.(iii)A drop in the mm to mid-IR emission by factors 2–4 in early 1986, while the near infrared flux remained stable (Robson et al. 1986).(iv)A decrease in the ultraviolet intensity of ∼40% in about 6 months in 1987 (Ulrich, Courvoisier and Wamsteker 1988).(v)Rapid variability in the infrared and optical emission on timescales as short as one day in 1988 (Courvoisier et al. 1988 and Robson, Courvoisier and Bouchet this conference).

Fluorescence effects in quantitative microprobe analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 188-189
Author(s):  
S.J.B. Reed
Keyword(s):  
Microprobe Analysis ◽  
Depth Distribution ◽  
Exciting Radiation ◽  
Primary Radiation ◽  
List Type ◽  
Type Number ◽  
Computing Power ◽  
X Ray ◽  
Fluorescent Radiation

Characteristic fluorescenceThe theory of characteristic fluorescence corrections was first developed by Castaing. The same approach, with an improved expression for the relative primary x-ray intensities of the exciting and excited elements, was used by Reed, who also introduced some simplifications, which may be summarized as follows (with reference to K-K fluorescence, i.e. K radiation of element ‘B’ exciting K radiation of ‘A’):1.The exciting radiation is assumed to be monochromatic, consisting of the Kα line only (neglecting the Kβ line).2.Various parameters are lumped together in a single tabulated function J(A), which is assumed to be independent of B.3.For calculating the absorption of the emerging fluorescent radiation, the depth distribution of the primary radiation B is represented by a simple exponential.These approximations may no longer be justifiable given the much greater computing power now available. For example, the contribution of the Kβ line can easily be calculated separately.

Interactive multiple area spectrum integration (MASI)

1994 ◽  
Vol 52 ◽  
pp. 942-943
Author(s):  
John A. Hunt ◽  
Richard D. Leapman ◽  
David B. Williams
Keyword(s):  
Image Processing ◽  
Low Dose ◽  
Routine Analysis ◽  
Reference Image ◽  
Area Spectrum ◽  
List Type ◽  
Type Number ◽  
Image Processor ◽  
X Ray ◽  
Scanning Path

Interactive MASI involves controlling the raster of a STEM or SEM probe to areas predefined byan integration mask which is formed by image processing, drawing or selecting regions manually. EELS, x-ray, or other spectra are then acquired while the probe is scanning over the areas defined by the integration mask. The technique has several advantages: (1) Low-dose spectra can be acquired by averaging the dose over a great many similar features. (2) MASI can eliminate the risks of spatial under- or over-sampling of multiple, complicated, and irregularly shaped objects. (3) MASI is an extremely rapid and convenient way to record spectra for routine analysis. The technique is performed as follows:Acquire reference imageOptionally blank beam for beam-sensitive specimensUse image processor to select integration mask from reference imageCalculate scanning path for probeUnblank probe (if blanked)Correct for specimen drift since reference image acquisition

scholarly journals Hydrodynamic Models of Solar and Stellar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 289-298
Author(s):  
Giovanni Peres
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Light Curves ◽  
Physical Parameters ◽  
The Sun ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Stellar Flares

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.

scholarly journals The Twin-Nucleus Merging Galaxy MKN 266

1989 ◽  
Vol 134 ◽  
pp. 452-453
Author(s):  
J.B. Hutchings ◽  
S.G. Neff ◽  
J.H. van Gorkom
Keyword(s):  
Optical Emission ◽  
Physical Parameters ◽  
List Type ◽  
Imaging Data ◽  
Ccd Imaging ◽  
Spatially Resolved ◽  
The Galaxy ◽  
Extended Complex ◽  
Double Nucleus ◽  
Narrow Bands

We present results of observations of the double-nucleus galaxy Markarian 266 (NGC 5256) from 3 principal sources. These are 1:CCD imaging with the Canada-France-Hawaii telescope in broad and narrow bands. These indicate that the galaxy has extended, complex, faint outer plumes which indicate that a recent merger has occurred. The narrow-band images reveal remarkable knotty structure of the [O III] emitting gas, extending over the whole central part of the galaxy. This is not seen in Hα (see figure 1).2:21cm imaging with the VLA, covering velocity space near that of the optical nuclei. The continuum image reveals resolved triple structure, with the two outer peaks coincident with the optical nuclei. The 21cm velocity profiles indicate the presence of considerable H I absorption near the optical emission line velocities.3:Spatially resolved optical spectroscopy with the DAO 1.8m telescope. These data reveal the details of the [O III] velocity field and some of the physical parameters of the gas. The complexity and extended nature of the gas explains some conflicting redshift measurements in the literature. Together with the imaging data, we derive estimates of nuclear reddening and luminosity.

Mixed-morphology supernova remnants: the case of SNR 0520–69.4 in the Large Magellanic Cloud

2020 ◽  
Vol 499 (3) ◽  
pp. 4213-4222
Author(s):  
I Ramírez-Ballinas ◽  
J Reyes-Iturbide ◽  
P Ambrocio-Cruz ◽  
R Gabbasov ◽  
M Rosado
Keyword(s):  
Supernova Remnants ◽  
Plasma Temperature ◽  
Optical Emission ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Physical Parameters ◽  
X Ray ◽  
Hot Plasma ◽  
Observatory Data ◽  
Fabry Perot

ABSTRACT We present observations in X-ray and optical emission of the supernova remnant (SNR) 0520–69.4 in the Large Magellanic Cloud. Using XMM–Newton observatory data, we produced images of the diffuse X-ray emission and spectra to obtain the X-ray parameters, such as luminosity and temperature, of hot plasma in the SNR. Diffuse X-ray emission with filled-centre morphology goes beyond the Hα region, suggesting that the hot gas escapes through the pores of the Hα shell. We fitted a model that has a plasma temperature of 1.1 × 107 K for an X-ray thermal luminosity of 3.3 × 1035 erg s−1. However, from Hα and [O iii] Fabry–Perot observations obtained with the Marseille Hα Survey of the Magellanic Clouds and the Milky Way at La Silla, European Southern Observatory, we are able to obtain physical parameters such as the velocity of the shock induced in the cloudlets emitting at optical wavelengths and the electron density of this gas. With the parameters described above, we test the model proposed by White & Long (1991, ApJ, 373, 543) for explaining the mixed-morphology observed.

scholarly journals Large-amplitude late-time radio variability in GRB 151027B

2018 ◽  
Vol 614 ◽  
pp. A29 ◽  
Author(s):  
J. Greiner ◽  
J. Bolmer ◽  
M. Wieringa ◽  
A. J. van der Horst ◽  
D. Petry ◽  
...  
Keyword(s):  
Large Amplitude ◽  
Near Infrared ◽  
Gamma Ray ◽  
Physical Parameters ◽  
Constant Density ◽  
Late Time ◽  
Slow Cooling ◽  
Data Set ◽  
X Ray ◽  
Radio Band

Context. Deriving physical parameters from gamma-ray burst (GRB) afterglow observations remains a challenge, even 20 years after the discovery of afterglows. The main reason for the lack of progress is that the peak of the synchrotron emission is in the sub-mm range, thus requiring radio observations in conjunction with X-ray/optical/near-infrared data in order to measure the corresponding spectral slopes and consequently remove the ambiguity with respect to slow vs. fast cooling and the ordering of the characteristic frequencies. Aims. We have embarked on a multifrequency, multi-epoch observing campaign to obtain sufficient data for a given GRB that allows us to test the simplest version of the fireball afterglow model. Methods. We observed GRB 151027B, the 1000th Swift-detected GRB, with GROND in the optical–near-IR, ALMA in the sub-millimeter, ATCA in the radio band; we combined this with public Swift/XRT X-ray data. Results. While some observations at crucial times only return upper limits or surprising features, the fireball model is narrowly constrained by our data set, and allows us to draw a consistent picture with a fully determined parameter set. Surprisingly, we find rapid, large-amplitude flux density variations in the radio band which are extreme not only for GRBs, but generally for any radio source. We interpret them as scintillation effects, though their extreme nature requires the scattering screen to be at a much smaller distance than usually assumed, multiple screens, or a combination of the two. Conclusions. The data are consistent with the simplest fireball scenario for a blast wave moving into a constant-density medium, and slow-cooling electrons. All fireball parameters are constrained at or better than a factor of 2, except for the density and the fraction of the energy in the magnetic field which has a factor of 10 uncertainty in both directions.

scholarly journals Solar X radiation

1965 ◽  
Vol 23 ◽  
pp. 45-52 ◽  
Author(s):  
C. de Jager
Keyword(s):  
Electromagnetic Radiation ◽  
Gamma Rays ◽  
Electronic Transitions ◽  
List Type ◽  
X Rays ◽  
Type Number ◽  
X Ray ◽  
Image Position ◽  
Electron Shells

X-ray bursts are defined as electromagnetic radiation originating from electronic transitions involving the lowest electron shells; gamma rays are of nuclear origin. Solar gamma rays have not yet been discovered.According to the origin we have : 1.Quasi thermal X-rays, emitted by (a) the quiet corona, (b) the activity centers without flares, and (c) the X-ray flares.2.Non-thermal X-ray bursts; these are always associated with flares.The following subdivision is suggested for flare-associated bursts :

Ferromagnetism and Near-infrared Luminescence in Neodymium and Erbium Doped Gallium Nitride via Diffusion

2009 ◽  
Vol 1183 ◽  
Author(s):  
Melvyn Oliver Luen ◽  
Neeraj Nepal ◽  
Pavel Frajtag ◽  
John Zavada ◽  
Ei Brown ◽  
...  
Keyword(s):  
Room Temperature ◽  
Near Infrared ◽  
Optical Emission ◽  
Diffusion Profile ◽  
Infrared Luminescence ◽  
Erbium Doped ◽  
Nir Emission ◽  
Ir Emission ◽  
Emission Studies ◽  
Secondary Ion

AbstractIn this study, we report on the diffusion of neodymium (Nd) and erbium (Er) into n-type and undoped GaN and subsequent measurements of the room-temperature (RT) magnetic and optical properties. The diffusion profile has been measured via secondary ion mass spectroscopy (SIMS) with rare-earth (RE) concentration yields of up to 1×1018/cm3. The ferromagnetic properties were measured using an alternating gradient magnetometer (AGM) giving a saturation magnetization (Ms) of up to 3.17emu/cm3 for the RE-diffused layer. The photoluminescence (PL) emission of the Nd-diffused and Er-diffused GaN is observable in the near-infrared (NIR) and infrared (IR) regions of the spectrum, respectively. The Nd-diffused GaN samples show NIR emission at 1064nm and 1350nm, while Er-diffused GaN samples have IR emission at 1546nm. This appears to be the first successful result of Nd diffusion doping into GaN crystals, and the first demonstration of above RT ferromagnetism involving GaN diffused with Nd. Details of our ferromagnetic and optical emission studies, related to the RE diffusion into GaN, are presented.

scholarly journals Complex optical/UV and X-ray variability in Seyfert 1 galaxy Mrk 509

2021 ◽  
Vol 38 ◽  
Author(s):  
Neeraj Kumari ◽  
Main Pal ◽  
Sachindra Naik ◽  
Arghajit Jana ◽  
Gaurava K. Jaisawal ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Timing Analysis ◽  
Optical Emission ◽  
Light Curves ◽  
Thermal Component ◽  
X Ray ◽  
Uv Emission ◽  
Average Spectrum ◽  
Entire Duration ◽  
Using Data

Abstract We performed a detailed spectral and timing analysis of a Seyfert 1 galaxy Mrk 509 using data from the Neil Gehrels Swift observatory that spanned over $\sim$ 13 years between 2006 and 2019. To study the variability properties from the optical/UV to X-ray emission, we used a total of 275 pointed observations in this work. The average spectrum over the entire duration exhibits a strong soft X-ray excess above the power law continuum. The soft X-ray excess is well described by two thermal components with temperatures of kT $_{\rm BB1}\sim$ 120 eV and kT $_{\rm BB2}\sim$ 460 eV. The warm thermal component is likely due to the presence of an optically thick and warm Comptonizing plasma in the inner accretion disk. The fractional variability amplitude is found to be decreasing with increasing wavelength, i.e., from the soft X-ray to UV/optical emission. However, the hard X-ray (2–8 keV) emission shows very low variability. The strength of the correlation within the UV and the optical bands (0.95–0.99) is found to be stronger than the correlation between the UV/optical and X-ray bands (0.40–0.53). These results clearly suggest that the emitting regions of the X-ray and UV/optical emission are likely distinct or partly interacting. Having removed the slow variations in the light curves, we find that the lag spectrum is well described by the 4/3 rule for the standard Shakura–Sunyaev accretion disk when we omit X-ray lags. All these results suggest that the real disk is complex, and the UV emission is likely reprocessed in the accretion disk to give X-ray and optical emission.

scholarly journals A new catalogue of quasi-stellar objects

1986 ◽  
Vol 119 ◽  
pp. 51-52
Author(s):  
A. Hewitt ◽  
G. Burbidge
Keyword(s):  
Seyfert Galaxies ◽  
List Type ◽  
Type Number ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Similar Information ◽  
Quasi Stellar Objects ◽  
Objective Prism

We have prepared a new catalogue of QSOs and BL Lac objects containing approximately 3400 entries. A complete update of the Hewitt-Burbidge (1980) catalogue has been made with approximately another 2000 objects with known redshifts added. The references to discovery, magnitudes, redshifts, color, spectra and polarimetry have been updated for the objects listed in 1980, and complete new references are included for the new objects. In addition to the basic optical information, the new catalogue also contains X-ray, radio and infrared information for all objects. Absorption redshifts are listed when they are available. A supplementary catalogue which is now in preparation will contain similar information for objects described variously as Seyfert galaxies, N systems and AGNs. In doubtful cases we have used the operational dividing line ƶ = 0.1. All objects with ƶ < 0.1 are put in the supplementary catalogue unless their discoverers have unambiguously defined them as QSOs. With approximately twice as many objects included it is interesting to note that: a)There are still very few genuine BL Lac objects, ∼100.b)The largest number of additions has come from identifications using the objective prism-grism techniques.

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