AAS HIGH ENERGY ASTROPHYSICS DIVISION MEETING: X-ray Flares Size Up a Neutron Star

Science ◽  
2004 ◽  
Vol 305 (5692) ◽  
pp. 1898b-1899b
Author(s):  
R. Irion
Keyword(s):  
Neutron Star ◽  
High Energy ◽  
High Energy Astrophysics ◽  
X Ray

scholarly journals Introduction

1980 ◽  
Vol 5 ◽  
pp. 621-622
Author(s):  
H. van der Laan
Keyword(s):  
Good Deal ◽  
High Energy ◽  
General Assembly ◽  
High Energy Astrophysics ◽  
Optical Techniques ◽  
X Ray ◽  
Tremendous Progress ◽  
New Material ◽  
General Secretary

In the summer of 1977 the IAU General Secretary requested proposals for Joint Discussions at the XVIIth General Assembly more than two years later. As President of Commission 40 I wrote to other Commission Presidents proposing a J.D. on Extragalactic High Energy Astrophysics. The motivation was as follows, and I quote from my July 22, 1977 letter:“With the current advances in radio and optical techniques and the tremendous progress to be expected from the satellites HEAO-A and HEAO-B, to be launched respectively in the summer of 1977 and 1978, there should be a good deal of new material on high energy astrophysical phenomena in the extragalactic domain by the time of the 1979 General Assembly. Some of this will be of great cosmological significance and all of it will be astrophysically interesting. It is clear that the X-ray satellite results will get a lot of optical and radio follow-up and it therefore seems appropriate that a Joint Discussion of that topic be arranged at that time.”

Commission N°48: High Energy Astrophysics (Astrophysique Des Hautes Energies)

1988 ◽  
Vol 20 (1) ◽  
pp. 671-675
Author(s):  
C.J. Cesarsky ◽  
R.A. Sunyaev ◽  
G.W. Clark ◽  
R. Giacconi ◽  
Vin-Yue Qu ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Supernova Remnants ◽  
Cataclysmic Variables ◽  
Galactic Nuclei ◽  
High Energy ◽  
Clusters Of Galaxies ◽  
High Energy Astrophysics ◽  
X Ray ◽  
X Ray Binaries ◽  
Imaging Telescopes

The european X-ray observatory (EXOSAT), which was launched in 1983 and which finished operations in April 1986, has brought a rich harvest of results in the period 1984-1987, surveyed here. The EXOSAT payload consisted of three sets of instruments: two low energy imaging telescopes (LE:E<2 KeV), a medium-energy experiment (ME:E=l-50KeV) and a gas scintillation proportional counter (GSPC:E=2-20KeV). Over most of the energy range covered, EXOSAT was not more sensitive than its predecessor, the american EINSTEIN satellite. But the EINSTEIN satellite is far from having exhausted the treasures of the X-ray sky. And EXOSAT, thanks to its elliptical 90-hour orbit, had the extra advantage of being able to make long, continuous observations of interesting objects, lasting up to 72 hours. Thus, EXOSAT was very well suited for variability studies, and many of its most important findings are in this area. EXOSAT observations sample a vide range of astrophysical sources: X-ray binaries, cataclysmic variables and active stars; supernova remnants and the interstellar medium; active galactic nuclei, and clusters of galaxies. Among the highlights, let us mention:

scholarly journals The Nature of the Compact Object in the Hard X-Ray Source 4U2206+54

2004 ◽  
Vol 194 ◽  
pp. 208-208
Author(s):  
J. M. Torrejón ◽  
I. Kreykenbohni ◽  
A. Orr ◽  
L. Titarchuk ◽  
I. Negueruela
Keyword(s):  
Neutron Star ◽  
Accretion Disk ◽  
Compact Object ◽  
High Energy ◽  
Energy Data ◽  
X Ray ◽  
Hot Plasma ◽  
Cyclotron Line ◽  
First Time

We present an analysis of archival RXTE and BeppoSAX data of the X-ray source 4U2206+54. For the first time, high energy data (≥ 30 keV) is analyzed. The data is well described by comptonization models in which seed photons with temperatures between 1.1 keV arid 1.5 keV are comptonized by a hot plasma at 50 keV thereby producing a hard tail which extends up to 100 keV. From luminosity arguments it is shown that the area of the soft photons source must be small (r ≈ 1 km) and that the presence of an accretion disk in this system is unlikely. Here we report on the possible existence of a cyclotron line around 30 keV . The presence of a neutron star in the system is strongly favored by the available data.

scholarly journals Accretion heated atmospheres of X-ray bursting neutron stars

2018 ◽  
Vol 619 ◽  
pp. A114 ◽  
Author(s):  
V. F. Suleimanov ◽  
J. Poutanen ◽  
K. Werner
Keyword(s):  
Neutron Star ◽  
Model Atmosphere ◽  
High Energy ◽  
Energy Dissipation Rate ◽  
Chemical Compositions ◽  
Type I ◽  
Coulomb Interactions ◽  
Spectral Evolution ◽  
X Ray ◽  
High Energy Tail

Some thermonuclear (type I) X-ray bursts at the neutron star surfaces in low-mass X-ray binaries take place during hard persistent states of the systems. Spectral evolution of these bursts is well described by the atmosphere model of a passively cooling neutron star when the burst luminosity is high enough. The observed spectral evolution deviates from the model predictions when the burst luminosity drops below a critical value of 20–70% of the maximum luminosity. The amplitude of the deviations and the critical luminosity correlate with the persistent luminosity, which leads us to suggest that these deviations are induced by the additional heating of the accreted particles. We present a method for computation of the neutron star atmosphere models heated by accreted particles assuming that their energy is released via Coulomb interactions with electrons. We computed the temperature structures and the emergent spectra of the atmospheres of various chemical compositions and investigate the dependence of the results on the velocity of accreted particles, their temperature and the penetration angle. We show that the heated atmosphere develops two different regions. The upper one is the hot (20–100 keV) corona-like surface layer cooled by Compton scattering, and the deeper, almost isothermal optically thick region with a temperature of a few keV. The emergent spectra correspondingly have two components: a blackbody with the temperature close to that of the isothermal region and a hard Comptonized component (a power law with an exponential decay). Their relative contribution depends on the ratio of the energy dissipation rate of the accreted particles to the intrinsic flux from the neutron star surface. These spectra deviate strongly from those of undisturbed, passively cooling neutron star atmospheres, with the main differences being the presence of a high-energy tail and a strong excess in the low-energy part of the spectrum. They also lack the iron absorption edge, which is visible in the spectra of undisturbed low-luminosity atmospheres with solar chemical composition. Using the computed spectra, we obtained the dependences of the dilution and color-correction factors as functions of relative luminosities for pure helium and solar abundance atmospheres. We show that the helium model atmosphere heated by accretion corresponding to 5% of the Eddington luminosity describes well the late stages of the X-ray bursts in 4U 1820−30.

scholarly journals DIVISION D COMMISSION 44: SPACE AND HIGH-ENERGY ASTROPHYSICS

2015 ◽  
Vol 11 (T29A) ◽  
pp. 219-244
Author(s):  
Christine Jones ◽  
Noah Brosch ◽  
Günther Hasinger ◽  
Matthew G. Baring ◽  
Martin Adrian Barstow ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
High Energy Astrophysics ◽  
X Ray ◽  
Neutrino Detectors ◽  
Gamma Ray Astronomy ◽  
The Hague ◽  
Almost All ◽  
Modern Astronomy

Division XI, the predecessor to Division D until 2012, was formed in 1994 at the IAU General Assembly in The Hague by merging Commission 44 Astronomy from Space and Commission 48 High Energy Astrophysics. Historically, space astrophysics started with the high energy wavelengths (far UV, X-ray, and gamma-ray astronomy) which are only accessible from space. However, in modern astronomy, to study high energy astrophysical processes, almost all wavelengths are used (including gamma-ray, X-ray, UV, optical, infrared, submillimeter and radio). In addition other ground-based facilities, including gravitational wave antennas, neutrino detectors and high-energy cosmic ray arrays are joining in this era of multi-messenger astrophysics, as well as space missions with the primary goals to discover and study exoplanets, are under the umbrella of Division XI.

scholarly journals High Energy Astrophysics and Cosmology

1980 ◽  
Vol 5 ◽  
pp. 753-761
Author(s):  
L. Woltjer
Keyword(s):  
High Energy ◽  
Selection Effects ◽  
High Energy Astrophysics ◽  
X Ray ◽  
Cosmological Tests ◽  
Γ Ray ◽  
X Ray Background ◽  
Galactic Sources

AbstractA brief review is given of cosmological tests based on quasars, of source evolution and of the X-ray background. The cosmological tests are still inconclusive because of the limited material available and the possibility of serious selection effects. Quasars and other extra-galactic sources account for most or all of the background in the 1-10 kev range and very possibly also at higher X- and γ-ray energies.

scholarly journals The X-Ray Large Array

1990 ◽  
Vol 123 ◽  
pp. 439-442
Author(s):  
K. S. Wood ◽  
P. Hertz ◽  
J.P. Norris ◽  
P. F. Michelson
Keyword(s):  
Angular Resolution ◽  
Critical Role ◽  
High Energy ◽  
General Purpose ◽  
Coded Aperture ◽  
Large Array ◽  
High Energy Astrophysics ◽  
X Ray ◽  
Timing Resolution ◽  
Astrophysical Objects

AbstractThere is a conspicuous gap in plans for X-ray timing after the X-ray Timing Explorer (XTE). Timing science has played a critical role in the development of X-ray astronomy. The need now is to move into a new domain of shorter timescales and weaker modulation, one that can be reached only with very large aperture instruments. XLA is an X-ray facility with an aperture substantially greater than 1 m2, nominally 100 m2. Most of this area is devoted to a large array of collimated proportional counters. There is also a ~ 1 m2 coded aperture. It extends observational parameter space by several orders of magnitude in timing resolution, sensitivity to variability, and angular resolution. This will lead to a qualitatively new kind of X-ray astrophysics that can be applied to the study of a broad range of astrophysical objects. XLA is thus both an advanced timing mission and a general purpose facility whose principal uses are in areas that are not well covered in other aspects of the planned High Energy Astrophysics program.

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