Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · astro-ph/0204176

The broad band X-ray spectrum of the black hole candidate GRS1758-258

Lara Sidoli·Sandro Mereghetti
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present the results of a BeppoSAX observation of the black hole candidate GRS1758-258 carried out in 1997, while the source was in its low/hard state. The X-ray spectrum, simultaneously observed over the broad energy range from 0.1 to 200 keV, can be well described by a Comptonized emission model with electron temperature kT_e = 31.4 keV and optical depth of 4.0 (spherical geometry), although a cut-off power-law and a reflection model cannot be excluded. Additionally, a broad iron line at 6.4 keV with equivalent width EW = 67 eV has been marginally detected. The 0.1-200 keV luminosity is 1.4x10^37 erg/s for an assumed distance of 8 kpc. The soft and hard luminosities are such that the source falls inside the so-called "burster box". No evidence for a soft excess is present.

Explore related subjects

astro-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Lara Sidoli, Sandro Mereghetti. 2002-04-10. The broad band X-ray spectrum of the black hole candidate GRS1758-258. https://doi.org/10.1051/0004-6361%3A20020546

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2024

Deformation procedure for scalar fields in cosmology

This work offers an extension of the deformation procedure introduced in field theory to the case of standard cosmology in the presence of real scalar field in flat space-time. The procedure is shown to work for many models, which give rise to several different cosmic scenarios, evolving under the presence of first-order differential equations which solve the corresponding equations of motion very appropriately.

astro-ph↗
arXiv2023

Dark Energy is the Cosmological Quantum Vacuum Energy of Light Particles-The Axion and the Lightest Neutrino

We uncover the general mechanism producing the dark energy(DE). This is only based on well known quantum physics and cosmology. We show that the observed DE originates from the cosmological quantum vacuum of light particles which provides a continuous energy distribution able to reproduce the data. Bosons give positive contributions to the DE while fermions yield negative contributions. As usual in field theory, ultraviolet divergences are subtracted from the physical quantities. The subtractions respect the symmetries of the theory and we normalize the physical quantities to be zero for the Minkowski vacuum. The resulting finite contributions to the energy density and the pressure from the quantum vacuum grow as log a(t) where a(t) is the scale factor, while the particle contributions dilute as 1/a^3(t), as it must be for massive particles. The DE equation of state P = w(z)H turns to be w(z)<-1 with w(z) asymptotically reaching the value -1 from below.A scalar particle can produce the observed DE through its quantum cosmological vacuum provided:(i)its mass is of the order of 10^{-3} eV = 1 meV,(ii) it is very weakly coupled and (iii) it is stable on the time scale of the age of the universe. The axion vacuum thus appears as a natural candidate. The neutrino vacuum (especially the lightest mass eigenstate) can give negative contributions to the DE. We find that w(z=0) is slightly below -1 by an amount ranging from [-1.5 10^{-3}] to [-8 10^{-3}] and we predict the axion mass to be in the range between 4 and 5 meV. We find that the universe will expand in the future faster than the de Sitter universe, as an exponential in the square of the cosmic time. DE arises from the quantum vacua of light particles in FRW cosmological space time in an analogous way to the Casimir effect in Minkowski spacetime with non trivial boundaries.

astro-ph↗