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 The Sources of the Hard X-Ray Background

1996 ◽  
Vol 168 ◽  
pp. 263-270
Author(s):  
Giancarlo Setti ◽  
Andrea Comastri
Keyword(s):  
Energy Spectrum ◽  
Energy Density ◽  
Energy Flux ◽  
Large Fraction ◽  
Power Laws ◽  
Prima Facie ◽  
Folding Energy ◽  
Hard Component ◽  
X Ray ◽  
X Ray Background

The hard component (3 keV – ~ MeV) of the X-ray background (XRB) comprises the largest portion, ~ 90%, of the overall XRB intensity. The observed isotropy (the entire Galaxy is transparent above 3 keV) provides aprima facieevidence of its prevailing extragalactic nature. A large fraction (~ 75%) of the energy flux falls in the 3 – 100 keV band, the corresponding energy density being ≃ 5×10−5eV cm−3, of which 50% is confined to the narrower 3 – 20 keV band. Although the energy flux carried by the XRB is relatively small compared to other extragalactic backgrounds, it was soon realized that it cannot be accounted for in terms of sources and processes confined to the present epoch. An analysis of the combined observed spectra (Gruber 1992) concludes that, while a thermal bremsstrahlung with an e-folding energy = 41.13 keV accurately fits the data up to 60 keV, above this energy the sum of two power laws is required with normalizations such that at 60 keV the spectral index is ~ 1.6, gradually flattening to ~ 0.7 at MeV energies. It should also be noted that below 10 keV the XRB energy spectrum is well represented by a power law of index α = 0.4 (I∝E−α).

scholarly journals The AGN Content of Hard X-ray Surveys

2002 ◽  
Vol 184 ◽  
pp. 235-244 ◽  
Author(s):  
Andrea Comastri ◽  
Cristian Vignali ◽  
Marcella Brusa
Keyword(s):  
Optical Properties ◽  
Optical Observations ◽  
X Ray ◽  
Normal Galaxies ◽  
X Ray Background ◽  
X Ray Absorption ◽  
Multiwavelength Observations

AbstractMultiwavelength observations of the hard X-ray selected sources discovered by BeppoSAX, Chandra and XMM-Newton surveys have significantly improved our knowledge of the AGN population. The increasing number of X-ray obscured AGN so far discovered confirms the prediction of those AGN synthesis models for the X-ray background based on the Unified scheme. However, follow-up optical observations of hard X-ray selected sources indicate that their optical properties are quite varied and the simple relations between optical and X-ray absorption are by no means without exception. Moreover there is evidence of a substantial number of luminous X-ray sources hosted by apparently normal galaxies. In this paper the results obtained from multiwavelength observations of hard X-ray selected sources discovered by BeppoSAX and XMM-Newton are presented and briefly discussed.

scholarly journals Small-Scale Fluctuations and Anisotropies in the 1–3 keV X-Ray Background

1990 ◽  
Vol 139 ◽  
pp. 408-409
Author(s):  
X. Barcons ◽  
A. C. Fabian
Keyword(s):  
Spatial Distribution ◽  
Probability Distribution ◽  
Proportional Counter ◽  
Flux Distribution ◽  
Small Scale ◽  
X Ray ◽  
Deep Survey ◽  
X Ray Background ◽  
Einstein Observatory ◽  
Source Number

The spatial distribution of the 1–3 keV X-ray background (XRB) in five Einstein Observatory Imaging Proportional Counter fields has been analyzed. The autocorrelation function does not exceed 9% on scales ~5′. The observed count probability distribution is then used to check the source number-flux distribution at faint levels. Agreement with the Einstein Observatory deep survey is obtained. A cutoff in the number-flux distribution for a Euclidean population of sources at a flux approximately one-half of the deep survey limit, previously suggested by Hamilton and Helfand (1987), is also inferred.

Optical Follow-Up Observations of the ASCA Large Sky Survey

1998 ◽  
Vol 188 ◽  
pp. 465-466
Author(s):  
M. Akiyama ◽  
K. Ohta ◽  
T. Yamada ◽  
Y. Ueda ◽  
T. Takahashi ◽  
...  
Keyword(s):  
Clusters Of Galaxies ◽  
X Ray ◽  
Sigma Level ◽  
Sky Survey ◽  
X Ray Background ◽  
Band Survey

To reveal the origin of the cosmic X-ray background (CXB) in the hard band, we are now conducting a wide (~ 7 deg2) and deep (~ 1 × 10−13 erg sec−1 cm−2 in the 2-10 keV band) survey with the ASCA (the ASCA Large Sky Survey, hereafter LSS). We have detected 83 sources above 4 sigma level in the 0.7-10 keV band with the GIS and resolved ~30% of the CXB in the 2-10 keV band into discrete sources (Ueda 1996). AGNs (type 1 and type 2) and clusters of galaxies are expected to be major contributers to these X-ray sources.

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.

scholarly journals Spin-Resolved Hα Spectroscopy and Photometry of the Intermediate Polar RXJ0558+5353

1996 ◽  
Vol 158 ◽  
pp. 177-178
Author(s):  
S. R. Duck ◽  
M. D. Still ◽  
A. Allan ◽  
K. Horne ◽  
R. W. Hilditch
Keyword(s):  
Optical Spectroscopy ◽  
Orbital Period ◽  
X Ray ◽  
Preliminary Results ◽  
Spin Period ◽  
Spin Modulation ◽  
Sky Survey

RXJ0558+5353 was discovered and classified as an intermediate polar during the ROSAT all-sky survey and subsequent optical follow up programme (Haberl et al. 1994). A further pointed ROSAT observation revealed a spin periodicity of 272.74 s and a soft X-ray component well represented by an absorbed 57 eV blackbody, the spin modulation being due principally to intensity variations of the component (rather than variable absorption). Optical spectroscopy showed the orbital period to be 4.15 h. In this paper we show the true spin period to be 545.4555(8) s (Allan, Horne & Hilditch 1995), twice the published X-ray period, and also discuss preliminary results of the first spin-resolved spectroscopy of RXJ0558+5353.

A Model of the Soft X-Ray Background as a Blast wave Viewed from Inside

1984 ◽  
Vol 81 ◽  
pp. 297-300
Author(s):  
Richard J. Edgar ◽  
Donald P. Cox
Keyword(s):  
Energy Band ◽  
Thermal Conduction ◽  
Ambient Medium ◽  
External Pressure ◽  
The Sun ◽  
Relative Importance ◽  
Energy Bands ◽  
X Ray ◽  
Band Ratios ◽  
X Ray Background

AbstractThe suggestion that the soft x-ray background arises In part from the Sun being inside a large (R ∼ 100 pc) supernova blastwave is examined by producing models of spherical blastwaves. Such models can produce quantitative fits to both surface brightnesses and energy band ratios (for the lowest energy bands) when t ∼ 105 yr, EO = 5 x 1050 ergs, and nO ≃ 0.004 cm-3.Such models can be generalized by varying the relative importance of such factors as thermal conduction, Coulomb heating of electrons, and external pressure; by allowing the explosions to occur In pre-existing cavities with steep density gradients, or by examining the effects of large obstructions or other anlsotroples in the ambient medium.

scholarly journals Ultrasoft X-Ray Background Observations of the Local Interstellar Medium

1984 ◽  
Vol 81 ◽  
pp. 222-225 ◽  
Author(s):  
W.T. Sanders ◽  
S.L. Snowden ◽  
J.J. Bloch ◽  
M. Juda ◽  
K.M. Jahoda ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Energy Band ◽  
Mean Free Path ◽  
Sounding Rocket ◽  
X Rays ◽  
Local Interstellar Medium ◽  
Peak Response ◽  
X Ray ◽  
Band Emission ◽  
X Ray Background

Preliminary results from a May 8, 1984 sounding rocket survey of the soft X-ray background are presented. The X-ray detectors are sensitive to X-rays in three soft X-ray bandpasses: 80-110 eV, 90-188 eV, and 284-532 eV (at 20% of peak response). The lowest energy X-rays in this range have a mean free path of order 1019 cm-2 and provide information about the local interstellar medium. The count rate in the 80-110 eV energy band (the Be band) tracks the 90-188 eV band (the B band) very well, indicating that the same ~1 million degree gas that is responsible for the B band emission may be responsible for the bulk of the Be band X-rays as well. We estimate for the flux in the Be band ~1 photon cm-2 s-1 sr-1 eV-1 , about a factor of four lower than that found by Stern and Bowyer (1979) and Paresce and Stern (1981) over a similar energy band.

scholarly journals The X-Ray Background from Star-Forming Galaxies

1990 ◽  
Vol 139 ◽  
pp. 412-413
Author(s):  
Richard E. Griffiths
Keyword(s):  
Energy Range ◽  
Active Galactic Nuclei ◽  
Surface Density ◽  
Galactic Nuclei ◽  
X Ray ◽  
Star Forming ◽  
Smooth Component ◽  
Spatial Fluctuations ◽  
Deep Survey ◽  
X Ray Background

It has been established observationally that at least 30% of the all-sky X-ray background (XRB) in the energy range of 1–3 keV comes from active galactic nuclei (AGN) in the redshift interval of 0.4 to 1.2 (Griffiths et al. 1983, 1988); it is also quite plausible that AGN contribute half of the XRB in the 1–3 keV range (Morisawa and Takahara 1989). However, analysis of spatial fluctuations in the Einstein deep survey counts (Hamilton and Helfand 1987; Barcons and Fabian 1989) has indicated the presence of a relatively smooth component of the XRB with a corresponding surface density of discrete sources of at least several thousand per square degree.

Near-Infrared Observations of a Type-2 QSO at z = 0.9

1999 ◽  
Vol 186 ◽  
pp. 361-361
Author(s):  
K. Nakanishi ◽  
M. Akiyama ◽  
K. Ohta ◽  
T. Yamada
Keyword(s):  
Optical Spectrum ◽  
Near Infrared ◽  
High Excitation ◽  
Infrared Observations ◽  
X Ray ◽  
High Ionization ◽  
Deep Survey

We report the results of near-infrared observations of a type-2 QSO, AX J08494+4454 at z = 0.9 which was identified in our optical follow-up observations of the ASCA Lynx deep survey. This object has a hard X-ray spectrum with an X-ray luminosity of about 1×1044 erg s−1 in 2–10 keV. The optical spectrum shows high-excitation and high-ionization lines but no significant broad Hβ emission. These properties strongly suggest that this object is a “type-2” QSO (Ohta et al. 1996).

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