scholarly journals X-ray bursting activity in the BL Lacertae object PKS 2155-304

1986 ◽  
Vol 119 ◽  
pp. 267-268
Author(s):  
D. Maccagni ◽  
L. Chiappetti ◽  
L. Maraschi ◽  
D. Molteni ◽  
M. Morini ◽  
...  
Keyword(s):  
Exposure Time ◽  
Low Energy ◽  
Medium Energy ◽  
X Ray ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Proportional Counters ◽  
Bursting Activity

The bright BL Lac object PKS 2155-304 (mv=13; z=0.117) was observed with EXOSAT at five epochs (1983 Oct. 31, Nov. 30, 1984 Nov. 6, 7 and 11), for a total of about 30 hours of exposure time. Here we present data and results obtained with the Low Energy (LE) telescopes, in the band 0.05–2. keV, and with the Medium Energy (ME) argon proportional counters in the range 1.–6. keV.

Effects of x-ray exposure on NOR and NAND flash memories during high-resolution 2D and 3D x-ray inspection

2016 ◽  
Vol 2016 (1) ◽  
pp. 000660-000665
Author(s):  
Anju Sharma ◽  
Preeth Sivakumar ◽  
Andrew Feigel ◽  
In Tae Bae ◽  
Lawrence P. Lehman ◽  
...  
Keyword(s):  
Exposure Time ◽  
Flash Memory ◽  
Low Energy ◽  
Memory Devices ◽  
Nand Flash ◽  
Flash Memories ◽  
Tube Voltage ◽  
X Ray ◽  
Data Corruption ◽  
Tube Current

Abstract In this paper, we present a detailed study on the effects of x-ray exposure on data corruption in commercially available NOR and NAND flash memory devices during x-ray inspection with a high-resolution Phoenix Nanomex system from GE. We investigated role of the x-ray tube voltage, tube current, device orientation, x-ray filters and photon energy. We explored the low exposure regime in detail when the first byte errors start occurring and also determined the absorbed dose for 100% byte errors. No data corruption was observed after the normal 2D x-ray inspection and CT scans of the NOR and NAND flash memory devices under study. However, increase in the tube voltage, tube current and/or the x-ray beam size resulted in byte errors which increased exponentially with the exposure time. The byte error rate was found to be much more sensitive to the tube voltage than the tube current. It was also affected by the device orientation with respect to the x-ray beam. The NAND flash memories were found to be more susceptible to data corruption from x-ray exposure than the NOR devices examined in this work. Some NOR devices were irradiated with the monochromatic x-rays from the CHESS synchrotron facility at Cornell University. Of all the photon energies used in this study, 12 keV x-ray irradiation resulted in the highest byte error rate. In this paper, we thus present a direct proof that it is the low-energy photon absorption that plays a major role in introducing bit errors in flash memories. Commonly available low-energy x-ray filters such as Cu and Al foils were found to be effective in preventing data corruption in such devices for long exposure time. Use of lower tube voltage, lower tube current, smaller x-ray spot size, short exposure time and low-energy x-ray filters, is recommended to prevent data corruption during 2D and 3D x-ray inspection of flash memory devices and other semiconductor devices in general.

scholarly journals Discovery of Five New X-ray–Selected BL Lacertae Objects and Three New Quasars

1997 ◽  
Vol 159 ◽  
pp. 423-424
Author(s):  
G.Z. Xie ◽  
W. Brinkmann ◽  
G.W. Cha ◽  
S. Laurent-Muehleisen ◽  
Y.H. Zhang ◽  
...  
Keyword(s):  
Astronomical Observatory ◽  
Bl Lacertae Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lacertae ◽  
Bl Lac

Through combined ROSAT and VLA observations, we have identified 19 BL Lac/quasar candidates. In 1994 December, 1995 January and October, and 1996 January 1996, we obtained spectra of all 19 candidates using the 2.16-m telescope of Beijing Astronomical Observatory. The dispersion used is 195 Å mm−1, which yields a dispersion of about 4.65 Å pixel−1, and the wavelength coverage is 3500–7800 Å. Five of these objects are uniformly featureless, and we identify them as BL Lac objects. Three new quasars are also identified. Table 1 presents VLA positions and redshifts for the 5 new BL Lac objects and three new quasars. By checking them in the NASA/IPAC Extragalactic Database (NED) and Véron-Cetty & Véron’s (1993) Catalogue of Quasars and AGNs, and other recent reports about discovery of new BL Lac objects and quasars, we find that these sources are previously unreported.

Exosat Observations of H2252−035: Pulse Phase and Orbital Phase Dependent Low Energy Absorption and Iron Line Emission

1987 ◽  
Vol 93 ◽  
pp. 281-292
Author(s):  
W. Pietsch ◽  
W. Voges ◽  
E. Kendziorra ◽  
M. Pakull
Keyword(s):  
Energy Absorption ◽  
Line Emission ◽  
Low Energy ◽  
Gas Absorption ◽  
X Rays ◽  
Medium Energy ◽  
Iron Line ◽  
X Ray ◽  
Low Energies ◽  
Optical Light Curve

AbstractThe 805 sec pulsing X-ray source H2252−035 has been observed for 7 h on September 14/15 and on September 17, 1983 in X-rays with the low energy telescope and the medium energy detectors of EXOSAT. While below 2 keV the semiamplitude of the 805 s pulses is ~ 100% in the 2.3–7.9 keV band it is only ~ 40%. X-ray dips that are more pronounced in low energies occur simultaneously with the orbital minimum of the optical light curve. The medium energy spectra during dips with respect to the non dip spectrum can be explained by just enhanced cold gas absorption of an additional absorbing column of 2 1022 cm−2. Model spectra for the 805 s minimum have to include a strong iron emission line at 6.55 keV with an equivalent width of 3 keV in addition to a reduced continuum intensity (radiating area) and enhanced low energy absorption.

Low energy X-ray calibration sources for proportional counters using radionuclides

1978 ◽  
Vol 155 (3) ◽  
pp. 435-442 ◽  
Author(s):  
Chizuo Mori ◽  
Hiroshi Noguchi ◽  
Nobuhito Ishigure ◽  
Tamaki Watanabe
Keyword(s):  
Low Energy ◽  
X Ray ◽  
Proportional Counters

A New Method for the Eliminaion of the Wall Effect in Proportional Counter

1976 ◽  
Vol 20 ◽  
pp. 555-563 ◽  
Author(s):  
K. Sipilä ◽  
E. Kiuru
Keyword(s):  
Proportional Counter ◽  
Dead Zone ◽  
Low Energy ◽  
Wall Effect ◽  
Cylindrical Shape ◽  
X Ray ◽  
Detector Pulse ◽  
Proportional Counters ◽  
And Performance ◽  
X Ray Absorption

The wall effect present in the gas-filled proportional counters and the low-energy background caused by it are well-known disadvantages. In this paper a method is presented to define the radial position of a single X-ray absorption in ordinary proportional counters. The method utilizes the variation in detector pulse collection times due to the electron diffusion. This variation can be determined with a specially constructed risetime analyzer which effectively forms a dead zone of cylindrical shape inside the detector. The properties and performance of the method are demonstrated. In the experiment performed the signal to background ratio was improved by a factor of twenty.

scholarly journals The X-Ray Flare of π UMA : Temperature and Emission Measure

1989 ◽  
Vol 104 (2) ◽  
pp. 127-130
Author(s):  
M. Landini ◽  
B.C. Monsignori Fossi
Keyword(s):  
Temperature Gradient ◽  
Power Supply ◽  
Emission Measure ◽  
Low Energy ◽  
Loop Model ◽  
Medium Energy ◽  
Differential Emission Measure ◽  
X Ray ◽  
Spectral Bands

AbstractAn X-ray flare from the star π UMA has been observed by EXOSAT on January 31, 1984. The data were collected using the-Low Energy Experiment and the Medium Energy Experiment, sensitive to the spectral bands 0.04 - 2 Kev and 1-20 Kev (Landini et al. 1986).The temperature and emission measure variations during the flare are deduced under the isothermal assumption. Using a parametrized profile of the differential emission measure, wich is controlled by the conductive flux via the temperature gradient, the comparison with the observed data gives some insight on a “mean loop” model and its power supply.

scholarly journals Broadband study of BL Lac during flare of 2020: Spectral evolution and emergence of HBL component

2021 ◽  
Author(s):  
Raj Prince
Keyword(s):  
Time Lag ◽  
Light Curves ◽  
X Rays ◽  
Spectral Evolution ◽  
X Ray ◽  
Bl Lacertae ◽  
Physical Mechanisms ◽  
Broadband Emission ◽  
Bl Lac ◽  
Astrophysical Neutrinos

Abstract BL Lacertae (BL Lac) is categorized as TeV blazar and considered as a possible source of astrophysical neutrinos. In 2020, the brightest X-ray flare ever detected from it. A detailed study can answer many puzzling questions related to multiband emissions and fast-flux variability often seen in this kind of source. We have performed the temporal and spectral analysis of the brightest flare. The variability is characterized by the fractional variability amplitude and the variability time. We found that the source has crossed all its previous limits of flux and reached to a maximum ever seen from it in optical and X-rays. It is highly variable in X-rays with fractional variability above 100 per cent (1.8397±0.0181) and the fastest variability time of 11.28 hours within a day. The broadband light curves correlation with X-ray suggest a time lag of one day. A broadband SED modeling is pursued to understand the possible physical mechanisms responsible for broadband emission. Modeling requires two emission regions located at two different sites to explain the low and high flux states. A significant spectral change is observed in the optical-UV and X-ray spectrum during the high state, which eventually leads to shifts in the location of the synchrotron peak towards higher energy, suggesting an emergence of a new HBL component.

X-ray Emission of Low-Energy-Peaked BL Lacertae Objects

2009 ◽  
Author(s):  
Jill M. Randall ◽  
Eric S. Perlman ◽  
Sebastian Heinz ◽  
Eric Wilcots
Keyword(s):  
Low Energy ◽  
Bl Lacertae Objects ◽  
X Ray ◽  
Bl Lacertae

scholarly journals EXOSAT Observations of Flux and Spectral Variability in the Seyfert Galaxy NGC5548

1989 ◽  
Vol 134 ◽  
pp. 177-178
Author(s):  
G. Branduardi-Raymont
Keyword(s):  
Seyfert Galaxy ◽  
Low Energy ◽  
High State ◽  
Medium Energy ◽  
Spectral Variability ◽  
Proportional Counters ◽  
Order Of Magnitude

The Seyfert galaxy NGC5548 was observed with EXOSAT 12 times between February 1984 and March 1986. The bottom panel of Fig. 1 shows the lightcurves obtained with the Low Energy telescope and CMA detector and the Medium Energy proportional counters. The CMA flux doubled in a month at the beginning of the EXOSAT coverage, and was down by more than an order of magnitude 15 months later; the source was again in a high state in January and March 1986. The ME lightcurve mirrors that of the CMA, with L2–6 keV varying between 1 and 5 × 1043 erg s−1.

scholarly journals X-Ray Emission Lines: Present and Future Experiments

1997 ◽  
Vol 159 ◽  
pp. 1-19
Author(s):  
H. Kunieda
Keyword(s):  
Line Profile ◽  
Line Emission ◽  
Low Noise ◽  
Low Energy ◽  
X Rays ◽  
Rapid Variability ◽  
Line Energy ◽  
X Ray ◽  
Proportional Counters ◽  
Ccd Detectors

AbstractAfter 34 years of X-ray astronomical observations, we approach the time when we will be able to explore AGN using line spectroscopy with newly developed technology and methods. In the beginning, X-rays from AGN were observed using proportional counters in a sort of photometric way, allowing us to determine that the continuum is a power law. This result suggested a predominance of non-thermal emission mechanisms in AGN. Rapid variability on time scales as short as 1000 seconds implied a small size for the X-ray emitting region, of order 1014cm, which is 3 orders of magnitude smaller than the optical emission-line regions.The first detection of line emission from AGN was the Fe-K line by the GINGA satellite. The line energy was 6.4 keV and its equivalent width was about 150 eV in Seyfert 1 galaxies. Detection became possible by use of large-area, low-noise proportional counters. The Fe-K line emission is important in X-ray astronomy because iron is rather abundant and this line is isolated in energy from neighboring lines.The Fe-K line profile has been examined with the CCD detectors on board ASCA. Many Seyfert 1 galaxies exhibit a broad-line profile of more than 1 keV width with an asymmetric tail on the low-energy side. This is explained as the fluorescence line from a relativistic accretion disk around a black hole, which is broadened by the Doppler motion and distorted by the strong gravitational field. The CCD detectors also revealed the absorption edges of warm material in the line of sight, which is ionized by the strong emission from AGN.In the next decade, new spectrometers will be launched which can perform spectroscopy with E/dE > 100: AXAF in 1998, XMM in 1999, and Astro-E in 2000. Dispersive spectrometers on board AXAF and XMM will be powerful tools for low-energy lines, while the calorimeter on board Astro-E will examine the Fe-K line profile. Spectral resolution E/dE of several hundred will reveal the intensity ratio of satellite and resonance lines. This will give us physical parameters, such as the density and absolute size of surrounding matter. We hope that the structure of the nucleus will be more deeply understood using X-ray spectroscopy with new instruments, and we will come close to the level of optical spectroscopy, which has worked well in the study of the outskirts of AGN.

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