Studies of gamma-ray transitions in 146Eu

1976 ◽  
Vol 54 (2) ◽  
pp. 197-204 ◽  
Author(s):  
P. Sen ◽  
M. Kingman ◽  
H. Bakhru ◽  
N. Cue
Keyword(s):  
High Resolution ◽  
Level Scheme ◽  
Gamma Ray ◽  
X Rays ◽  
Accurate Evaluation ◽  
X Ray ◽  
Correlation Studies ◽  
Γ Rays ◽  
Γ Ray

The decay of 146Gd to levels of 146Eu has been studied using high resolution X-ray and γ-ray detectors. γ–γ directional correlation studies, using X and γ-ray Ge(Li) detectors, were made to assign the spins of the low lying states in 146Eu. γ–γ coincidence experiments with two Ge(Li) detectors and between Eu X rays and γ rays were performed to pin down the levels of 146Eu. On the basis of these measurements, Jπ of 4−, 3−, 2−, and 1− have been assigned respectively to the ground, 115.66, 230.51, and 385.11 keV states in 146Eu. More accurate evaluation of the E2 admixtures in the M1 transitions, 114.85, 115.66, and 154.60 keV, have been obtained. Based on the above results a tentative level scheme for 146Eu has been proposed.

scholarly journals Gamma-ray-emitting narrow-line Seyfert 1 galaxies: the Swift view

2020 ◽  
Vol 496 (2) ◽  
pp. 2213-2229 ◽  
Author(s):  
F D’Ammando
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Optical Emission ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Relativistic Jet ◽  
Photon Index ◽  
Γ Ray ◽  
Lower Variability

ABSTRACT We report the analysis of all Swift observations available up to 2019 April of γ-ray-emitting narrow-line Seyfert 1 galaxies (NLSy1). The distribution of X-ray luminosities (and fluxes) indicates that the jet radiation significantly contributes to their X-ray emission, with Doppler boosting making values higher than other radio-loud NLSy1. The 0.3–10 keV photon indices are on average harder with respect to radio-quiet and radio-loud NLSy1, confirming a dominant jet contribution in X-rays. However, the lower variability amplitude with respect to blazars and the softening of the spectrum in some periods suggests that also the corona radiation contributes to the X-ray emission. In optical and ultraviolet (UV) significant flux changes have been observed on daily, weekly, and monthly time-scale, providing a clear indication of the significant contribution of the jet radiation in this part of spectrum. A strong correlation between X-ray, UV, and optical emission and simultaneous flux variations have been observed in 1H 0323+342, SBS 0846+513, PMN J0948+0022 as expected in case the jet radiation is the dominant mechanism. Correlated multiband variability favours the jet-dominated scenario also in FBQS J1644+2619 and PKS 2004−447. The summed X-ray Telescope spectra of 1H 0323+342, SBS 0846+513, PMN J0948+0022, and FBQS J1644+2619 are well fitted by a broken power law with a break around 2 keV. The spectrum above 2 keV is dominated by the non-thermal emission from a beamed relativistic jet, as suggested by the hard photon index. A Seyfert-like feature like the soft X-ray excess has been observed below 2 keV, making these γ-ray-emitting NLSy1 different from typical blazars.

scholarly journals Centaurus A: Hard X-ray and High-Energy Gamma-Ray Light Curve Correlation

Galaxies ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 44 ◽  
Author(s):  
Isak Davids ◽  
Markus Böttcher ◽  
Michael Backes
Keyword(s):  
Light Curve ◽  
High Energy ◽  
Electromagnetic Spectrum ◽  
X Rays ◽  
X Ray ◽  
Correlation Studies ◽  
High Energy Gamma ◽  
Energy Gamma ◽  
Γ Rays ◽  
Centaurus A

Centaurus A, powered by a 55 million solar mass supermassive black hole, has been intensively monitored in all accessible wavelength ranges of the electromagnetic spectrum. However, its very-high energy gamma ( γ ) ray flux (TeV photons), obtained from H.E.S.S. is relatively faint, hampering detailed light curve analyses in the most energetic energy band. Yet, the extensive long-term light curve data from Fermi-LAT and Swift-BAT (hard X-rays) allows for cross-correlation studies. We find a hint that X-ray emission from Centaurus A precedes the γ rays by 25 ± 125 days. If this lag is real and related to a γ γ absorption effect in the broad-line region (BLR) around the central source, we can constrain the size of the BLR using light-travel time arguments. These are first results of extended light curve correlation studies between high-energy γ rays and X-rays from Centaurus A.

scholarly journals N49: The Site of a Gamma-ray Burst. Preliminary Results from X-ray Observations

1983 ◽  
Vol 101 ◽  
pp. 573-577
Author(s):  
G. Pizzichini ◽  
T. L. Cline ◽  
U. D. Desai ◽  
B. J. Teegarden ◽  
W. D. Evans ◽  
...  
Keyword(s):  
High Resolution ◽  
Supernova Remnant ◽  
Gamma Ray ◽  
Large Magellanic Cloud ◽  
X Rays ◽  
Radio Image ◽  
Gamma Ray Burst ◽  
X Ray ◽  
Preliminary Results ◽  
Einstein Observatory

The error box of the unusual Gamma-Ray Burst of March 5, 1979 falls completely inside the optical and radio image of the Supernova Remnant N49 in the Large Magellanic Cloud. This region was observed twice in x-rays with the High Resolution Imager of the Einstein Observatory, six weeks and nearly two years after the Gamma-Ray Burst. We show the comparison between the two observations.

HIGH-RESOLUTION STUDIES OF GAMMA-RAY SPECTRA USING LITHIUM-DRIFT GERMANIUM GAMMA-RAY SPECTROMETERS

1964 ◽  
Vol 42 (11) ◽  
pp. 2286-2331 ◽  
Author(s):  
G. T. Ewan ◽  
A. J. Tavendale
Keyword(s):  
High Resolution ◽  
Gamma Ray ◽  
High Energy ◽  
Factors Affecting ◽  
Γ Rays ◽  
Γ Ray

This paper describes the use of germanium lithium-drift p-i-n diodes as high-resolution γ-ray spectrometers. With these spectrometers we have obtained γ-ray resolutions of 2.05 keV at 122 keV, 4.0 keV at 1333 keV, and 5.5 keV at 2614 keV. Using the detectors as pair spectrometers for high-energy γ rays, we have obtained a resolution of 9.8 keV on a 7.6-MeV γ ray. The factors affecting the resolution of the detectors are discussed. Fano factors of ~0.4 have been observed. Efficiency curves are given for a 2.5 cm2 × 3.5 mm detector and for a 5 cm2 × 8 mm detector.The detectors have been used to make high-resolution studies of the complex γ-ray spectra from sources of 131Cs, 161Pm, 153Gd, 156Eu, 159Gd, 177Yb, and 226Ra. Results are reported for the energies and intensities of the γ rays observed in these studies.

scholarly journals The X-ray Spectral Properties for Gamma-ray Loud Blazars

2003 ◽  
Vol 214 ◽  
pp. 299-302
Author(s):  
Ben-Zhong Dai
Keyword(s):  
Correlation Analysis ◽  
Gamma Ray ◽  
X Rays ◽  
Spectral Indices ◽  
Bl Lac Objects ◽  
X Ray ◽  
Weighted Analysis ◽  
Spectrum Radio ◽  
Γ Ray ◽  
Weighted Correlation

We selected a sample of bright γ-ray (E>100 MeV) blazars whose X-rays in 0.1–10.0 keV band are observed by ROSAT and other X-ray satellites, and make a detailed spectral analysis between the soft (0.1–2.0 keV) and hard band (2.0–10.0keV) as well as between X-ray and γ-ray properties using both un-weighted and weighted analysis methods. Our results indicate: (i) there are significant anti-correlations of the spectral indices between soft X-rays and γ-rays, and between hard X-ray and γ-ray of flat-spectrum radio quasars (FSRQs) and BL Lac objects; (ii) in the X-ray band, the correlation is confusing, there is positive correlation of the spectral indices between soft and hard X-ray band using weighted correlation analysis, but this correlation is negative using un-weighted correlation analysis.

scholarly journals X-ray spectroscopy of the γ-ray brightest nova V906 Car (ASASSN-18fv)

2020 ◽  
Vol 497 (3) ◽  
pp. 2569-2585 ◽  
Author(s):  
Kirill V Sokolovsky ◽  
Koji Mukai ◽  
Laura Chomiuk ◽  
Raimundo Lopes de Oliveira ◽  
Elias Aydi ◽  
...  
Keyword(s):  
White Dwarf ◽  
X Rays ◽  
Radiative Shock ◽  
X Ray ◽  
Classical Novae ◽  
Low Mass ◽  
Γ Rays ◽  
Γ Ray ◽  
X Ray Absorption ◽  
Shock Fronts

ABSTRACT Shocks in γ-ray emitting classical novae are expected to produce bright thermal and non-thermal X-rays. We test this prediction with simultaneous NuSTAR and Fermi/LAT observations of nova V906 Car, which exhibited the brightest GeV γ-ray emission to date. The nova is detected in hard X-rays while it is still γ-ray bright, but contrary to simple theoretical expectations, the detected 3.5–78 keV emission of V906 Car is much weaker than the simultaneously observed >100 MeV emission. No non-thermal X-ray emission is detected, and our deep limits imply that the γ-rays are likely hadronic. After correcting for substantial absorption (NH ≈ 2 × 1023 cm−2), the thermal X-ray luminosity (from a 9 keV optically thin plasma) is just ∼2 per cent of the γ-ray luminosity. We consider possible explanations for the low thermal X-ray luminosity, including the X-rays being suppressed by corrugated, radiative shock fronts or the X-rays from the γ-ray producing shock are hidden behind an even larger absorbing column (NH > 1025 cm−2). Adding XMM–Newton and Swift/XRT observations to our analysis, we find that the evolution of the intrinsic X-ray absorption requires the nova shell to be expelled 24 d after the outburst onset. The X-ray spectra show that the ejecta are enhanced in nitrogen and oxygen, and the nova occurred on the surface of a CO-type white dwarf. We see no indication of a distinct supersoft phase in the X-ray light curve, which, after considering the absorption effects, may point to a low mass of the white dwarf hosting the nova.

scholarly journals High Energy Radiation from Spider Pulsars

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 93 ◽  
Author(s):  
Chung Yue Hui ◽  
Kwan Lok Li
Keyword(s):  
High Energy ◽  
X Rays ◽  
The Novel ◽  
Large Area ◽  
High Energy Radiation ◽  
X Ray ◽  
Compact Binaries ◽  
Low Mass ◽  
Γ Rays ◽  
Γ Ray

The population of millisecond pulsars (MSPs) has been expanded considerably in the last decade. Not only is their number increasing, but also various classes of them have been revealed. Among different classes of MSPs, the behaviours of black widows and redbacks are particularly interesting. These systems consist of an MSP and a low-mass companion star in compact binaries with an orbital period of less than a day. In this article, we give an overview of the high energy nature of these two classes of MSPs. Updated catalogues of black widows and redbacks are presented and their X-ray/ γ -ray properties are reviewed. Besides the overview, using the most updated eight-year Fermi Large Area Telescope point source catalog, we have compared the γ -ray properties of these two MSP classes. The results suggest that the X-rays and γ -rays observed from these MSPs originate from different mechanisms. Lastly, we will also mention the future prospects of studying these spider pulsars with the novel methodologies as well as upcoming observing facilities.

scholarly journals Gamma-ray observations of low-luminosity active galactic nuclei

2020 ◽  
Vol 492 (3) ◽  
pp. 4120-4130 ◽  
Author(s):  
Raniere de Menezes ◽  
Rodrigo Nemmen ◽  
Justin D Finke ◽  
Ivan Almeida ◽  
Bindu Rani
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Detailed Comparison ◽  
Spectral Energy ◽  
X Rays ◽  
Large Area ◽  
Accretion Flow ◽  
Γ Rays ◽  
Γ Ray

ABSTRACT The majority of the activity around nearby (z ≈ 0) supermassive black holes is found in low-luminosity active galactic nuclei (LLAGN), the most of them being classified as low-ionization nuclear emission regions. Although these sources are well studied from radio up to X-rays, they are poorly understood in γ-rays. In this work, we take advantage of the all sky-surveying capabilities of the Large Area Telescope on board Fermi Gamma-ray Space Telescope to study the whole Palomar sample of LLAGN in γ-rays. Precisely, the four radio-brightest LLAGN in the sample are identified as significant γ-ray emitters, all of which are recognized as powerful Fanaroff–Riley I galaxies. These results suggest that the presence of powerful radio jets is of substantial importance for observing a significant γ-ray counterpart even if these jets are misaligned with respect to the line of sight. We also find that most of the X-ray-brightest LLAGN do not have a significant γ-ray and strong radio emission, suggesting that the X-rays come mainly from the accretion flow in these cases. A detailed analysis of the spectral energy distributions (SEDs) of NGC 315 and NGC 4261, both detected in γ-rays, is provided where we make a detailed comparison between the predicted hadronic γ-ray emission from a radiatively inefficient accretion flow (RIAF) and the γ-ray emission from a leptonic jet-dominated synchrotron self-Compton (SSC) model. Both SEDs are better described by the SSC model, while the RIAF fails to explain the γ-ray observations.

scholarly journals Comparative intranight optical variability of X-ray and γ-ray-detected narrow-line Seyfert 1 galaxies

2020 ◽  
Vol 493 (3) ◽  
pp. 3642-3655 ◽  
Author(s):  
Vineet Ojha ◽  
Hum Chand ◽  
Gopal Krishna ◽  
Sapna Mishra ◽  
Krishan Chand
Keyword(s):  
Duty Cycle ◽  
High Energy ◽  
Minor Role ◽  
Optical Variability ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Γ Rays ◽  
Γ Ray ◽  
A Minor

ABSTRACT In a systematic program to characterize the intranight optical variability (INOV) of different classes of narrow-line Seyfert 1 (NLSy1s) galaxies, we report here the first comparative INOV study of NLSy1 sets detected in the X-ray and γ-ray bands. Our sample consists of 18 sources detected in X-rays but not in γ-rays (hereafter x_NLSy1s) and seven sources detected in γ-rays (hereafter g_NLSy1s), out of which five are detected also in X-rays. We have monitored these two sets of NLSy1s, respectively, in 24 and 21 sessions of a minimum of 3-h duration each. The INOV duty cycles for these two sets are found to be 12 per cent and 53 per cent, respectively (at a 99 per cent confidence level). In the set of 18 x_NLSy1s, INOV duty cycle is found to be zero for the 13 radio-quiet members (monitored in 14 sessions) and 43 per cent for the five radio-loud members (10 sessions). The latter is very similar to the aforementioned duty cycle of 53 per cent found here for the set of g_NLSy1s (all of which are radio-loud). Thus, it appears that the radio-loudness level is the prime factor behind the INOV detection and the pattern of the high-energy radiation plays only a minor role.

Cryogenic high-resolution X-ray spectrometers for SR-XRF and microanalysis

1998 ◽  
Vol 5 (3) ◽  
pp. 515-517 ◽  
Author(s):  
M. Frank ◽  
C. A. Mears ◽  
S. E. Labov ◽  
L. J. Hiller ◽  
J. B. le Grand ◽  
...  
Keyword(s):  
High Resolution ◽  
Energy Resolution ◽  
Superconducting Tunnel Junction ◽  
Semiconductor Detectors ◽  
X Rays ◽  
X Ray ◽  
Sr Xrf ◽  
Demonstration Experiment ◽  
Near Future ◽  
Stj Detector

Experimental results are presented obtained with a cryogenically cooled high-resolution X-ray spectrometer based on a 141 × 141 µm Nb-Al-Al2O3-Al-Nb superconducting tunnel junction (STJ) detector in an SR-XRF demonstration experiment. STJ detectors can operate at count rates approaching those of semiconductor detectors while still providing a significantly better energy resolution for soft X-rays. By measuring fluorescence X-rays from samples containing transition metals and low-Z elements, an FWHM energy resolution of 6–15 eV for X-rays in the energy range 180–1100 eV has been obtained. The results show that, in the near future, STJ detectors may prove very useful in XRF and microanalysis applications.

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