Observations of soft X-rays : upper limits on the flux from SN 1972e and measurements of the diffuse background in Centaurus.

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

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Structural and functional adaptations in the athlete’s heart

The ESC Textbook of Sports Cardiology ◽

10.1093/med/9780198779742.003.0002 ◽

2019 ◽

pp. 9-20

Author(s):

Antonio Pelliccia ◽

Stefano Caselli

Keyword(s):

Functional Assessment ◽

Cardiovascular Imaging ◽

Athlete’S Heart ◽

Cardiac Remodelling ◽

X Rays ◽

Physiological Limits ◽

Upper Limits ◽

Vast Literature ◽

Systematic Training ◽

Athlete's Heart

Cardiac changes in athletes have been described for more than a century, with initial observations derived by chest percussion and chest X-rays. Recent advances in cardiovascular imaging have allowed morphological and functional assessment of cardiac remodelling associated with systematic training, and consequently over the last decades a vast literature has been assembled focused on the constellation of alterations known as ‘athlete’s heart’. This chapter provides means for understanding the determinants, extent, and upper limits of cardiovascular adaptation in athletes. A detailed overview of all cardiac chambers is provided to help the physician to recognize the physiological limits of cardiovascular remodelling.

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‘Local’ Theories of the X-Ray Background

Symposium - International Astronomical Union ◽

10.1017/s0074180900100440 ◽

1973 ◽

Vol 55 ◽

pp. 258-275 ◽

Cited By ~ 2

Author(s):

James E. Felten

Keyword(s):

Intergalactic Medium ◽

Galactic Plane ◽

Cosmic Ray ◽

Seyfert Galaxies ◽

X Rays ◽

Statistical Fluctuations ◽

Galactic Emission ◽

Diffuse Background ◽

The Galaxy ◽

X Ray Background

Recent theories of the origins of diffuse-background X-rays are reviewed, with emphasis on theories of the soft flux in the galactic plane and at the poles. This is probably partly galactic and partly extragalactic in origin. Failure to observe absorption by the Small Magellanic Cloud and by galactic gas in neighboring directions may be due to sources in the Cloud and to statistical fluctuations in galactic emission and absorption. Several models for numerous low-luminosity sources in the Galaxy are available. True ‘diffuse’ emission seems unnecessary. Absorption by Galactic gas seems to agree roughly with theory. The soft extragalactic component may arise in a hot intergalactic medium.The existence of a ‘diffuse’ galactic-plane excess in 1–100 keV is in some doubt. Low-luminosity sources may contribute to this as well.For isotropic X-rays in 1 keV – 1 MeV, superposition theories involving clusters of galaxies, Seyfert galaxies, etc. over a cosmological path length are now roughly viable. Simple ‘metagalactic’ Compton theories seem excluded if the break at 40 keV is sharp, but this is now in doubt. A very hot intergalactic medium at T ≈ 3 × 108 K would give the possibility of a sharp break.A recent upper limit on the line source strength of 100-MeV photons in the galactic plane may create some difficulties for cosmic-ray theory. The spectral shape of π-γ photons has become a matter of theoretical dispute.

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Soft X-rays from the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900004605 ◽

1970 ◽

Vol 37 ◽

pp. 406-407

Author(s):

M. J. Rees

Keyword(s):

Galactic Plane ◽

Galactic Latitude ◽

X Rays ◽

Indirect Methods ◽

X Ray ◽

Background Data ◽

Diffuse Background ◽

The Galaxy ◽

X Ray Background ◽

Significant Flux

Below 1 keV, analyses of X-ray background data are complicated by galactic absorption effects, which cause the received intensity to vary with galactic latitude. Bowyer et al. (1968) observed that the diffuse background did not fall off as rapidly as was expected towards the galactic plane. One plausible interpretation of their data would be to suppose that a significant flux of soft X-rays emanates from the disc itself. I wish to discuss what could be inferred about the latter component from improved observations of its latitude-dependence, and by indirect methods.

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An Instrument to Study the Diffuse EUV Astronomical Background

International Astronomical Union Colloquium ◽

10.1017/s0252921100036630 ◽

1996 ◽

Vol 152 ◽

pp. 611-616 ◽

Cited By ~ 1

Author(s):

S. Bowyer ◽

J. Edelstein ◽

M. Lampton ◽

L. Morales ◽

J. Perez Mercader ◽

...

Keyword(s):

Dark Matter ◽

Interstellar Medium ◽

Extreme Ultraviolet ◽

Unique Line ◽

Upper Limits ◽

Diffuse Background ◽

Source Mechanisms ◽

New Type

The extreme ultraviolet (EUV) diffuse background is the most poorly known of any of the diffuse astronomical backgrounds. Only upper limits to this flux exist, obtained with spectrometers with very crude (from ≈ 15 to 30 Å) resolution; these limits are generally one to two orders of magnitude larger than the expected sources of cosmic flux. A variety of source mechanisms have been postulated to radiate in this bandpass; the most discussed is the hot phase of the interstellar medium. A speculative possibility is that hot dark matter in the form of massive, radiatively unstable neutrinos in our Galaxy will produce a unique line in this bandpass. We describe an instrument employing a new type of spectrometer which will provide ~5 Å resolution and unprecedented sensitivity for diffuse EUV radiation. The instrument will be carried aboard the newly developed Spanish Minisat satellite.

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Supersoft X-ray nebulae in the Large Magellanic Cloud

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2213 ◽

2020 ◽

Vol 497 (3) ◽

pp. 3234-3250 ◽

Cited By ~ 1

Author(s):

Diego A Farias ◽

Alejandro Clocchiatti ◽

Tyrone E Woods ◽

Armin Rest

Keyword(s):

Interstellar Medium ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

The Other ◽

X Rays ◽

X Ray ◽

Upper Limits ◽

Type Ia ◽

Source Models ◽

Flux Measurements

ABSTRACT Supersoft X-rays sources (SSSs) have been proposed as potential Type Ia supernova (SN Ia) progenitors. If such objects are indeed persistently X-ray luminous and embedded in sufficiently dense interstellar medium (ISM), they will be surrounded by extended nebular emission. These nebulae should persist even long after an SN Ia explosion, due to the long recombination and cooling times involved. With this in mind, we searched for nebular [O iii] emission around four SSSs and three SNRs in the Large Magellanic Cloud, using the 6.5-m Baade telescope at Las Campanas Observatory and the imacs camera. We confirm that, out of the four SSS candidates, only CAL 83 can be associated with an [O iii] nebula. The [O iii] luminosity for the other objects is constrained to ≲17 per cent of that of CAL 83 at 6.8 pc from the central source. Models computed with the photoionization code cloudy indicate that either the ISM densities in the environments of CAL 87, RX J0550.0-7151, and RX J0513.9-6951 must be significantly lower than surrounding CAL 83 or the average X-ray luminosities of these sources over the last ≲10 000 yr must be significantly lower than presently observed, in order to be consistent with the observed luminosity upper limits. For the three SNRs we consider (all with ages <1000 yr), our [O iii] flux measurements together with the known surrounding ISM densities strongly constrain the ionizing luminosity of their progenitors in the last several thousand years, independent of the progenitor channel.

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

Canadian Journal of Physics ◽

10.1139/p68-259 ◽

1968 ◽

Vol 46 (10) ◽

pp. S409-S413 ◽

Cited By ~ 12

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.

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THE FSRQs 3C 279 AND PKS 1510-089: MAGIC LATEST RESULTS AND MULTIWAVELENGTH OBSERVATIONS

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194514601768 ◽

2014 ◽

Vol 28 ◽

pp. 1460176 ◽

Cited By ~ 1

Author(s):

◽

G. DE CANEVA ◽

U. BARRES DE ALMEIDA ◽

E. LINDFORS ◽

K. SAITO ◽

...

Keyword(s):

Spectral Energy Distribution ◽

High Energy ◽

Spectral Energy ◽

X Rays ◽

Spectrum Radio ◽

Upper Limits ◽

Very High Energy ◽

Γ Rays ◽

Differential Flux ◽

Multiwavelength Observations

At very high energy (VHE, E> 100 GeV), we count only three blazars of the flat spectrum radio quasars (FSRQs) type to date. The MAGIC experiment detected all three of them; here we present MAGIC observations of 3C 279 and PKS 1510-089. 3C 279 was observed in 2011, without a significant detection, hence upper limits on the differential flux have been computed. The MAGIC observations of PKS 1510-089 in 2012 were triggered by alerts of high activity states and resulted in a significant detection. MAGIC observations are complemented with simultaneous multiwavelength observations in high energy γ rays, X-rays, optical and radio wavelengths and polarization measurements. With the study of the spectral features and the variability observed, we aim to identify the physical processes responsible for the behavior of this source class. In particular, we propose coherent scenarios, which take into account both the modeling of the spectral energy distribution and the constraints obtained from the lightcurves.

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