scholarly journals NuSTAR measurement of the cosmic X-ray background in the 3–20 keV energy band

2021 ◽  
Vol 502 (3) ◽  
pp. 3966-3975
Author(s):  
Roman Krivonos ◽  
Daniel Wik ◽  
Brian Grefenstette ◽  
Kristin Madsen ◽  
Kerstin Perez ◽  
...  
Keyword(s):  
Energy Range ◽  
Energy Band ◽  
Spectral Shape ◽  
Spatial Modulation ◽  
Photon Statistics ◽  
Telescope Array ◽  
X Ray ◽  
Relative Scatter ◽  
X Ray Background ◽  
Systematic Noise

ABSTRACT We present measurements of the intensity of the cosmic X-ray background (CXB) with the Nuclear Spectroscopic Telescope Array (NuSTAR) telescope in the 3–20 keV energy range. Our method uses spatial modulation of the CXB signal on the NuSTAR detectors through the telescope’s side aperture. Based on the NuSTAR observations of selected extragalactic fields with a total exposure of 7 Ms, we have estimated the CXB 3–20 keV flux to be 2.8 × 10−11 erg s−1 cm−2 deg−2, which is $\sim \! 8{{\ \rm per\ cent}}$ higher than that measured with HEAO-1 and consistent with the INTEGRAL measurement. The inferred CXB spectral shape in the 3–20 keV energy band is consistent with the canonical model of Gruber et al. We demonstrate that the spatially modulated CXB signal measured by NuSTAR is not contaminated by systematic noise and is limited by photon statistics. The measured relative scatter of the CXB intensity between different sky directions is compatible with cosmic variance, which opens new possibilities for studying CXB anisotropy over the whole sky with NuSTAR.

XAFS and X-MCD spectroscopies with undulator gap scan

1998 ◽  
Vol 5 (3) ◽  
pp. 989-991 ◽  
Author(s):  
Andrei Rogalev ◽  
Vincent Gotte ◽  
Jose´ Goulon ◽  
Christophe Gauthier ◽  
Joel Chavanne ◽  
...  
Keyword(s):  
Energy Range ◽  
Absorption Spectroscopy ◽  
Emission Peak ◽  
Photon Statistics ◽  
Wide Energy Range ◽  
X Ray ◽  
Polarization Rate ◽  
Spin Polarized ◽  
Wide Energy ◽  
X Ray Absorption

The first experimental applications of the undulator gap-scan technique in X-ray absorption spectroscopy are reported. The key advantage of this method is that during EXAFS scans the undulator is permanently tuned to the maximum of its emission peak in order to maximize the photon statistics. In X-MCD or spin-polarized EXAFS studies with a helical undulator of the Helios type, the polarization rate can also be kept almost constant over a wide energy range.

scholarly journals Optical Follow-Up Observations of ASCA Lynx Deep Survey

1998 ◽  
Vol 188 ◽  
pp. 471-472
Author(s):  
K. Ohta ◽  
M. Akiyama ◽  
K. Nakanishi ◽  
T. Yamada ◽  
K. Hayashida ◽  
...  
Keyword(s):  
Energy Density ◽  
Energy Band ◽  
X Ray ◽  
Preliminary Results ◽  
Deep Survey ◽  
X Ray Background

Since the bulk of the energy density of the Cosmic X-ray Background (CXB) resides in the harder energy band than that of the ROSAT band (0.5-2 keV) and since the X-ray sources identified in the ROSAT band have X-ray spectra softer than that of the CXB, investigation of nature of the X-ray sources at the harder energy band is indispensable to solve the origin of the CXB. However, only 2-3% of the CXB in the hard band (2-10 keV) had been resolved into discrete sources (Piccinotti et al. 1982, ApJ 253, 485). We present our preliminary results of optical follow-up observations of the ASCA Lynx deep survey.

scholarly journals Evidence for a galactic component of the diffuse X-ray background

1970 ◽  
Vol 37 ◽  
pp. 280-288
Author(s):  
B. A. Cooke ◽  
R. E. Griffiths ◽  
K. A. Pounds
Keyword(s):  
Energy Range ◽  
Low Energy ◽  
Galactic Latitude ◽  
X Ray ◽  
Latitude Dependence ◽  
The Galaxy ◽  
X Ray Background

It is widely believed that the diffuse X-ray background, observed on several occasions over the energy range from 0.25 keV to above 1 MeV has an extragalactic origin. Evidence for this comes from the generally reported isotropy above several keV [1, 2, 3] and the observed galactic latitude dependence at 0.25 keV, believed to result from the interstellar attenuation of these low energy photons in passage through the Galaxy [4, 5].

scholarly journals ASCA Sky Survey Observations and the Cosmic X-Ray Background in 2-10 KeV

1998 ◽  
Vol 188 ◽  
pp. 197-200
Author(s):  
H. Inoue ◽  
T. Takahashi ◽  
Y. Ueda ◽  
A. Yamashita ◽  
Y. Ishisaki ◽  
...  
Keyword(s):  
Energy Range ◽  
Galactic Plane ◽  
Galactic Latitude ◽  
High Galactic Latitude ◽  
X Ray ◽  
Sky Survey ◽  
X Ray Background ◽  
Excess Component ◽  
Highly Uniform

The X-ray background in the energy range above 2 keV is highly uniform except for an excess component along the Galactic plane. The excess along the plane is considered to be associated with our Galaxy, whereas the rest of the emission is believed to be of extragalactic origin. In this paper, the X-ray background at high Galactic latitude is discussed and is designated as the CXB (cosmic X-ray background) to distinguish it from the Galactic origin.

Diffuse X-ray background measurements in the energy range 2?18 keV

1971 ◽  
Vol 10 (1) ◽  
pp. 150-155 ◽  
Author(s):  
A. S. Prakasarao ◽  
D. P. Sharma ◽  
U. B. Jayanthi ◽  
U. R. Rao
Keyword(s):  
Energy Range ◽  
X Ray ◽  
X Ray Background

scholarly journals Cosmic X-ray Background from Self-absorbed Low Luminosity AGNs

1990 ◽  
Vol 115 ◽  
pp. 276-280
Author(s):  
Jonathan E. Grindlay ◽  
Michael Luke
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Energy ◽  
Spectral Shape ◽  
Density Evolution ◽  
Background Spectrum ◽  
Asymptotic Spectrum ◽  
X Ray ◽  
Energy Cutoff ◽  
X Ray Background

AbstractA model is proposed for the origin of the diffuse cosmic x-ray background whereby it is primarily due to the contribution of low luminosity active galactic nuclei which are increasingly self-absorbed at low luminosities. Strong self-absorption for low luminosity objects allows the observed background spectrum to be flatter in the ~2-20 keV band than the asymptotic spectrum, assumed to have mean index γ ~ -0.7 up to a high energy cutoff at ~125 keV. The model can account for the spectral shape and intensity of the background spectrum, as well as its possible fluctuations, if the AGN undergo modest density evolution and the bulk of the CXB arises from AGNs at redshifts z ~ 1-3. The model can be tested with AXAF observations of low luminosity AGNs at 5-10 keV and sensitive new hard x-ray observations.

Using IRAS Cirrus to Look for X-Ray Shadowing with ROSAT

1990 ◽  
Vol 139 ◽  
pp. 465-466
Author(s):  
Helen J. Walker ◽  
Alan W. Harris ◽  
Timothy J. Sumner
Keyword(s):  
Energy Range ◽  
Wide Field ◽  
Satellite Mission ◽  
X Ray ◽  
Conflicting Evidence ◽  
X Ray Background

The ROSAT X-ray satellite mission and its X-ray telescope (XRT) are described by Trümper (1984). The characteristics of the Wide Field Camera (WFC) on ROSAT and its potential for studies of the soft X-ray background (SXRB) are discussed by Harris, Sumner, and Walker (1989, this volume). The energy range covered by the WFC is 0.06 keV to 0.21 keV (60 Å to 200 Å), whilst the XRT covers the higher energy range from 0.2 keV to 2 keV. Observations performed to date in this field have given rise to conflicting evidence on the location and nature of the 106 K gas, which is presumed to be the origin of the observed emission (see references in Harris, Sumner, and Walker, 1989, this volume).

scholarly journals Origin of the cosmic X-ray background: (Invited discourse)

1970 ◽  
Vol 37 ◽  
pp. 352-371
Author(s):  
G. Setti ◽  
M. J. Rees
Keyword(s):  
Energy Band ◽  
Black Body ◽  
Relativistic Electrons ◽  
Intergalactic Gas ◽  
Satisfactory Explanation ◽  
X Ray ◽  
The Galaxy ◽  
Simple Extrapolation ◽  
X Ray Background ◽  
Natural Way

In this paper we review the theories which have been proposed to account for the extra-galactic X-ray background. Although there is still no detailed theory, one may devise reasonable models which account in a natural way both for the intensity and the spectral shape over the whole energy band, provided that cosmological evolutionary effects are included. A model based on Compton scattering of cosmic black body photons by relativistic electrons in radio sources at large redshifts (z ≳ 4) seems to give the most satisfactory explanation. However, the data are not yet good enough to discriminate against alternative models.A discussion of the recent observations in the soft X-ray region (< 1 keV), and their relevance to the physics of interstellar and intergalactic gas, is given. The available data are somewhat confusing, but it seems that this part of the spectrum may still be consistent with a simple extrapolation of the non-thermal spectrum at higher energies, though various workers have claimed the detection of a new component probably due to hot intergalactic gas. If this interpretation is correct one may deduce interesting conclusions about the state of ionization and composition of the intergalactic gas, because of the importance of the absorption effects in this energy band.Also it appears that the Galaxy is more transparent than one would deduce from 21-cm observations. However, due to the lack of observational data, no firm conclusions can be reached.

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