Sky Survey of High-Energy Cosmic X-Rays and Spectra of the Sources in the Crab Nebula and Cygnus

1968 ◽  
Vol 151 ◽  
pp. 21 ◽  
Author(s):  
G. W. Clark ◽  
W. H. G. Lewin ◽  
W. B. Smith
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Rays ◽  
Sky Survey ◽  
The Crab Nebula

Sky survey of high-energy cosmic X-rays and spectral information on sources in the Crab nebula, Cygnus, and Scorpius

1968 ◽  
Vol 46 (10) ◽  
pp. S409-S413 ◽  
Author(s):  
Walter H. G. Lewin ◽  
George W. Clark ◽  
William B. Smith
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Rays ◽  
Coma Cluster ◽  
X Ray ◽  
Sky Survey ◽  
Upper Limits ◽  
Intensity Ratios ◽  
The Crab Nebula ◽  
Made In

A complete X-ray survey of the northern sky has been made in the energy range 20–100 keV. Spectra are given for Cyg X-1 and Tau X-1. Intensity ratios (Cyg X-1/Tau X-1) of 0.84 ± 0.10 and 1.30 ± 0.25 were derived in the 20–70 keV range from data obtained on July 19, 1966 and February 13, 1967, respectively. Observations on Sco X-1 and the Coma cluster show upper limits which are quite different from results reported by other groups.

scholarly journals High-energy X rays from the Crab Nebula

1966 ◽  
Vol 71 (13) ◽  
pp. 3261-3264 ◽  
Author(s):  
R. C. Haymes ◽  
W. L. Craddock
Keyword(s):  
Crab Nebula ◽  
High Energy ◽  
X Rays ◽  
The Crab Nebula

scholarly journals Hard Cosmic X-Ray Sources

1973 ◽  
Vol 55 ◽  
pp. 51-73 ◽  
Author(s):  
L. E. Peterson
Keyword(s):  
Supernova Remnants ◽  
Galactic Center ◽  
Galactic Plane ◽  
Crab Nebula ◽  
X Rays ◽  
X Ray ◽  
Sky Survey ◽  
Upper Limits ◽  
Observational Status ◽  
The Crab Nebula

A review of the observational status of X-ray sources detected in the 20 ⋍ 500 keV range is presented. Of the approximately 115 sources listed in the March 1972 edition of the UHURU 2–6 keV sky survey catalog, about 15 sources have been studied in hard X-rays. Most of the data have been obtained from balloons, although the OSO-3, and more recently the OSO-7, have contributed. With the exception of CEN A, the SMC, and possibly M-87, all the sources detected at higher energies are galactic and heavily concentrated in the galactic plane. The Crab Nebula has been measured to about 500 keV in continuous emission and a component at the ⋍ 33 ms pulsar period comprising about 20% of the total emission has been detected to ∼10 MeV. Objects such as SCO-1 and CYG-2 are characterized by an exponential spectrum, which varies over a 10 min. time scale about a factor of two, and a flatter spectrum extending to above 40 keV which exhibits independent variability. Objects such as CYG-1 and possibly CYG-3 have a multi-component power law spectrum extending to over 100 keV, and may vary many factors over a period of weeks. Other sources generally not yet identified with optical or radio candidates, located in the Galactic Center and the Centaurus/Crux region also show considerable variability, and in one case may have been detected to nearly 500 keV. Only upper limits at about 2 × 10−4 photon (cm2 s keV)−1 in the 20–50 keV range exist for most supernova remnants and extragalactic sources.

scholarly journals An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state

2020 ◽  
Vol 496 (3) ◽  
pp. 3912-3928
Author(s):  
MAGIC Collaboration: V A Acciari ◽  
S Ansoldi ◽  
L A Antonelli ◽  
A Arbet Engels ◽  
A Babić ◽  
...  
Keyword(s):  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac ◽  
Very High Energy ◽  
Γ Ray ◽  
Using Data ◽  
The Crab Nebula

ABSTRACT Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at νs ≥ 1017 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the ground-based γ-ray telescope FACT during a high γ-ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) γ-rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE γ-ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The Γ index of the intrinsic spectrum in the VHE γ-ray band is 2.04 ± 0.12stat ± 0.15sys. We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz.

scholarly journals Time-Domain Astronomy with Swift, Fermi and Lobster

2011 ◽  
Vol 7 (S285) ◽  
pp. 41-46 ◽  
Author(s):  
Neil Gehrels ◽  
Scott D. Barthelmy ◽  
John K. Cannizzo
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Tidal Disruption ◽  
X Ray ◽  
Order Of Magnitude ◽  
New Type ◽  
The Crab Nebula ◽  
High Energy Emission ◽  
Higher Sensitivity

AbstractThe dynamic transient gamma-ray sky is revealing many interesting results, largely due to findings by Fermi and Swift. The list includes new twists on gamma-ray bursts (GRBs), a GeV flare from a symbiotic star, GeV flares from the Crab Nebula, high-energy emission from novae and supernovae, and, within the last year, a new type of object discovered by Swift—a jetted tidal disruption event. In this review we present highlights of these exciting discoveries. A new mission concept called Lobster is also described; it would monitor the X-ray sky at order-of-magnitude higher sensitivity than current missions can.

Detection of High-Energy Gamma Rays from the Crab Nebula

1972 ◽  
Vol 175 ◽  
pp. L117 ◽  
Author(s):  
G. G. Fazio ◽  
H. F. Helmken ◽  
E. O'Mongain ◽  
T. C. Weekes
Keyword(s):  
Gamma Rays ◽  
Crab Nebula ◽  
High Energy ◽  
High Energy Gamma ◽  
Energy Gamma ◽  
The Crab Nebula

VIBRATING NEUTRON STARS

1967 ◽  
Vol 45 (9) ◽  
pp. 2823-2831 ◽  
Author(s):  
Carl J. Hansen ◽  
Sachiko Tsuruta
Keyword(s):  
Neutron Stars ◽  
Storage Capacity ◽  
Vibrational Energy ◽  
Crab Nebula ◽  
X Rays ◽  
Vibrational Heating ◽  
Large Spread ◽  
Vibrational Energies ◽  
The Crab Nebula ◽  
Urca Process

The time variation of some interesting properties of vibrating neutron stars is considered. The models used are based on two nuclear potentials that cover a large spread of possibilities. The modified URCA neutrino process has been assumed to be the major damping mechanism. The calculations are performed both for the case when the vibration energy is partially converted into heat through the URCA process and for the case when this conversion does not take place. It is found that the vibrational energy-storage capacity is extremely model-dependent. The vibrational energies at 1 000 years range from about 1047 to 1050 ergs, which are sufficiently large as a possible energy source for the X rays from the Crab Nebula, ft is shown also that the cooling times of neutron stars will not be significantly increased by the inclusion of the vibrational heating.

Low-energy cosmic X-ray measurements

1969 ◽  
Vol 47 (23) ◽  
pp. 2651-2666 ◽  
Author(s):  
A. J. Baxter ◽  
B. G. Wilson ◽  
D. W. Green
Keyword(s):  
Spectral Analysis ◽  
Energy Range ◽  
Crab Nebula ◽  
Spectral Characteristics ◽  
Low Energy ◽  
Data Recovery ◽  
X Rays ◽  
X Ray ◽  
Recovery System ◽  
The Crab Nebula

An experiment is described to investigate cosmic X rays in the energy range 0.25–12 keV. The data-recovery system and methods of spectral analysis are considered. Results are presented for the energy spectrum of the diffuse X-ray component and its distribution over the northern sky down to 1.6 keV with a limited extension at 0.27 keV.In the energy range 1.6 to 12 keV, the spectrum is represented by:[Formula: see text]although separate analyses indicate a flattening below 4.5 keV to give:[Formula: see text]and[Formula: see text]At the lowest energies, the flux appears to increase more rapidly and exhibits some anisotropy in arrival directions related to the gross galactic structure. Spectral characteristics of the Crab Nebula and Cygnus X-2 have also been determined.

Sign in / Sign up

Export Citation Format

Share Document