scholarly journals Unveiling the Nature of INTEGRAL Objects: a Review

2014 ◽  
Vol 1 (1) ◽  
pp. 240-245
Author(s):  
Pietro Parisi
Keyword(s):  
Ir Spectroscopy ◽  
Energy Range ◽  
Southern Hemisphere ◽  
Cross Correlation ◽  
Active Galaxies ◽  
X Ray ◽  
The Real ◽  
Real Nature ◽  
X Ray Binaries

Since its launch in October 2002, the <em>INTEGRAL</em> observatory has improved our knowledge of the hard X-ray sky above 20 keV, carrying out more than ten years of observations in the energy range from 5 keV to 8 MeV. The most recently published <em>INTEGRAL</em>/IBIS surveys listed more than seven hundred sources in the 20-100 keV band. Most of these objects are either Active Galaxies (AGNs) or X-ray binaries; a fraction of both classes is made of highly absorbed sources, often associated with dim optical counterparts. Despite the big eort in the identication process, a large part of these IBIS objects (~25% of them) still remains unclassied. Cross-correlation with archival catalogues and/or multiwaveband follow-up observations are of invaluable help to identify and properly classify this unknown objects, but only optical or IR spectroscopy with ground based telescopes in the Northern and Southern Hemisphere can reveal the real nature of these objects. In this work we report on source types that we nd among the unidentied objects in the most recent <em>INTEGRAL</em> surveys.

scholarly journals Spectroscopy of Stellar X-ray Sources in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 305-312
Author(s):  
J. B. Hutchings
Keyword(s):  
Black Hole ◽  
Magellanic Cloud ◽  
Active Galaxies ◽  
Magellanic Clouds ◽  
Dwarf Stars ◽  
X Ray ◽  
Preliminary Comparison ◽  
The Galaxy ◽  
Optical Identifications ◽  
X Ray Binaries

In the Magellanic Clouds, about 75 candidate stellar X-ray sources have been detected. Most of these positions have now been investigated and optical identifications made for ~ 50%. The majority of sources are foreground dwarf stars or background active galaxies. Detailed investigations exist for 3 SMC sources and 6 LMC sources. It is possible to make a preliminary comparison with the population of galactic X-ray sources. The Magellanic Cloud X-ray binaries have a number of unique or remarkable properties and the most important ones are presented and discussed. These include the most rapid pulsars (SMC X-1, 0538–66), the possible precessing disk in LMC X-4, and the black hole candidates LMC X-3, LMC X-1. The properties of these objects relate to the evolution of stars in the Magellanic Clouds and how it differs from the Galaxy.

scholarly journals The Clustering Properties of Intermediate X-ray Luminosity AGN at z ~ 3

2009 ◽  
Vol 5 (S267) ◽  
pp. 261-261
Author(s):  
Harold Francke ◽  
Eric Gawiser ◽  
Paulina Lira ◽  
Leopoldo Infante ◽  
Keyword(s):  
Clustering Analysis ◽  
Cross Correlation ◽  
Selection Method ◽  
Active Galaxies ◽  
High Mass ◽  
Optical Data ◽  
X Ray ◽  
Lyman Break Galaxies ◽  
X Ray Imaging ◽  
Halo Masses

We present clustering results for AGN jointly selected to have optical and X-ray data at z ~ 3 in the ECDF-S field. Using Chandra X-ray imaging and UVR optical colors from MUSYC photometry, we selected a sample of 58 z ~ 3 AGN candidates. From the optical data we also selected 1385 Lyman break galaxies (LBG) in the range 2.8 < z < 3.8 with R < 25.5 mag. From optical spectroscopy, we have also determined redshifts and AGN types and estimated the UV and X-ray luminosities for the set of active galaxies selected by this method. We performed autocorrelation and cross-correlation analyses and present here our results for the clustering amplitudes and dark matter (DM) halo masses of each sample. The clustering analysis yields median DM halo masses of log M/M⊙ = 11.9±0.2 for the LBG sample, and log M/M⊙ = 12.9+0.4−0.9 for the sample of AGN. This shows that the active supermassive black holes (SMBHs) targeted by this selection method tend to sit in galaxies more massive than the typical population of UV–continuum selected galaxies, although showing much less clustering than SDSS quasars at the same redshift. Additionally, the expected evolution of the DM halos in ΛCDM cosmology implies that today these z ~ 3 SMBHs are hosted by group-sized halos, with masses log M/M⊙ = 14.1+0.3−0.2, at the high-mass end of the distribution of LBG DM halo descendants at z = 0.

scholarly journals Comptel Observations of X-Ray Binaries

1996 ◽  
Vol 158 ◽  
pp. 277-278
Author(s):  
A. F. Iyudin
Keyword(s):  
Energy Range ◽  
Gamma Ray ◽  
Plasma Temperature ◽  
Time History ◽  
Spectral Model ◽  
Broad Line ◽  
X Ray ◽  
History Of ◽  
X Ray Binaries ◽  
Best Fit

The COMPTEL experiment on the Compton Gamma-Ray Observatory measures γ–radiation in the energy range from 0.75 to 30 MeV [10]. X-ray binaries form one category of potential γ-ray sources. Up to now only two X-ray binaries, Cyg X-l and Nova Per, have been seen by COMPTEL.Cyg X-l. Preliminary results were reported by [6] and indicate that (i) there was no evidence for any hardening of the spectrum near lMeV, (ii) the plasma temperature suggested by a Wien spectral model was much higher than that implied by hard X-ray observations. This latter conclusion seems to require a revision in the standard spectral model for Cyg X-l.The α–ray flux from Cyg X-l is constant up to several MeV. The time history of the flux in the 0.75… 2.0 MeV energy range shows that there are no significant variations near 1 MeV. The average photon spectrum derived from all observations up to 1994 July shows evidence for significant emission extending well above 2 MeV, with a data point in the 2…5 MeV range at 4.3 σ significance. However, the observed flux near 1 MeV is significantly below that reported by HEAO-3 and several other balloon observations [6]. The COMPTEL spectral data show a broad line-like feature around ~ 4 MeV with the best fit of a single power law plus Gaussian. If we assume that the Gaussian represents a single broadened nuclear line of 12C*, then the width of 1.38 MeV demands a temperature of ~ 2 1012 K [7].

scholarly journals Non-linear X-ray variability in X-ray binaries and active galaxies

2005 ◽  
Vol 359 (1) ◽  
pp. 345-362 ◽  
Author(s):  
P. Uttley ◽  
I. M. McHardy ◽  
S. Vaughan
Keyword(s):  
Active Galaxies ◽  
X Ray ◽  
Non Linear ◽  
X Ray Binaries

scholarly journals New simulation of QSO X-ray heating during the Cosmic Dawn

2017 ◽  
Vol 12 (S333) ◽  
pp. 34-38
Author(s):  
Hannah E. Ross ◽  
Keri Dixon ◽  
Ilian Iliev ◽  
Garrelt Mellema
Keyword(s):  
Radiative Transfer ◽  
Large Volume ◽  
Intergalactic Medium ◽  
Temperature Fluctuations ◽  
High Mass ◽  
X Ray ◽  
First Time ◽  
X Ray Binaries ◽  
Skewness And Kurtosis

AbstractThe upcoming radio interferometer Square Kilometre Array is expected to directly detect the redshifted 21-cm signal from the Cosmic Dawn for the first time. In this era temperature fluctuations from X-ray heating of the neutral intergalactic medium can impact this signal dramatically. Previously, in Ross et al. (2017), we presented the first large-volume, 244 h-1 Mpc=349 Mpc a side, fully numerical radiative transfer simulations of X-ray heating. This work is a follow-up where we now also consider QSO-like sources in addition to high mass X-ray binaries. Images of the two cases are clearly distinguishable at SKA1-LOW resolution and have RMS fluctuations above the expected noise. The inclusion of QSOs leads to a dramatic increase in non-Gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm signal. We conclude that this increased non-Gaussianity is a promising signature of early QSOs.

scholarly journals The variable radio counterpart of Swift J1858.6-0814

2020 ◽  
Vol 496 (4) ◽  
pp. 4127-4140 ◽  
Author(s):  
J van den Eijnden ◽  
N Degenaar ◽  
T D Russell ◽  
D J K Buisson ◽  
D Altamirano ◽  
...  
Keyword(s):  
Time Scales ◽  
Radio Spectrum ◽  
Electromagnetic Spectrum ◽  
Very Large Array ◽  
X Ray ◽  
Geometric Origin ◽  
Optical Wavelengths ◽  
X Ray Binaries ◽  
Variable Radio

ABSTRACT Swift J1858.6-0814 is a transient neutron star X-ray binary discovered in 2018 October. Multiwavelength follow-up observations across the electromagnetic spectrum revealed many interesting properties, such as erratic flaring on minute time-scales and evidence for wind outflows at both X-ray and optical wavelengths, strong and variable local absorption, and an anomalously hard X-ray spectrum. Here, we report on a detailed radio observing campaign consisting of one observation at 5.5/9 GHz with the Australia Telescope Compact Array, and nine observations at 4.5/7.5 GHz with the Karl G. Jansky Very Large Array. A radio counterpart with a flat to inverted radio spectrum is detected in all observations, consistent with a compact jet being launched from the system. Swift J1858.6-0814 is highly variable at radio wavelengths in most observations, showing significant variability when imaged on 3-to-5-min time-scales and changing up to factors of 8 within 20 min. The periods of brightest radio emission are not associated with steep radio spectra, implying they do not originate from the launching of discrete ejecta. We find that the radio variability is similarly unlikely to have a geometric origin, be due to scintillation, or be causally related to the observed X-ray flaring. Instead, we find that it is consistent with being driven by variations in the accretion flow propagating down the compact jet. We compare the radio properties of SwiftJ1858.6-0814 with those of Eddington-limited X-ray binaries with similar X-ray and optical characteristics, but fail to find a match in radio variability, spectrum, and luminosity.

scholarly journals Optical follow-up of new Small Magellanic Cloud wing Be/X-ray binaries

2007 ◽  
Vol 381 (4) ◽  
pp. 1561-1568 ◽  
Author(s):  
M. P. E. Schurch ◽  
M. J. Coe ◽  
K. E. McGowan ◽  
V. A. McBride ◽  
D. A. H. Buckley ◽  
...  
Keyword(s):  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
X Ray ◽  
X Ray Binaries

scholarly journals Multiwavelength Search and Studies of Active Galaxies and Quasars

2017 ◽  
pp. 15-38
Author(s):  
Areg Mickaelian
Keyword(s):  
Flux Ratio ◽  
Seyfert Galaxies ◽  
Active Galaxies ◽  
Point Sources ◽  
Physical Parameters ◽  
Stellar Objects ◽  
X Ray ◽  
Ir Sources ◽  
Uv Excess

The Byurakan Astrophysical Observatory (BAO) has always been one of the centres for surveys and studies of active galaxies. Here we review our search and studies of active galaxies during last 30 years using various wavelength ranges, as well as some recent related works. These projects since late 1980s were focused on multiwavelength search and studies of AGN and Starbursts (SB). 1103 blue stellar objects (BSOs) on the basis of their UV-excess were selected using Markarian Survey (First Byurakan Survey, FBS) plates and Markarian’s criteria used for the galaxies. Among many blue stars, QSOs and Seyfert galaxies were found by follow-up observations. 1577 IRAS point sources were optically identified using FBS lowdispersion spectra and many AGN, SB and high-luminosity IR galaxies (LIRG/ULIRG) were discovered. 32 extremely high IR/opt flux ratio galaxies were studies with Spitzer. 2791 ROSAT FSC sources were optically identified using Hamburg Quasar Survey (HQS) lowdispersion spectra and many AGN were discovered by follow-up observations. Fine analysis of emission line spectra was carried out using spectral line decomposition software to establish true profiles and calculate physical parameters for the emitting regions, as well as to study the spectral variability of these objects. X-ray and radio selection criteria were used to find new AGN and variable objects for further studies. We have estimated AGN content of X-ray sources as 52.9%. We have also combined IRAS PSC and FSC catalogs and compiled its extragalactic sample, which allowed us to estimate AGN content among IR sources as 23.7%. Multiwavelength approach allowed revealing many new AGN and SB and obtaining a number of interesting relations using their observational characteristics and physical properties.

scholarly journals Discovery of QPO from X Persei with RXTE

1998 ◽  
Vol 188 ◽  
pp. 368-369
Author(s):  
Toshiaki Takeshima
Keyword(s):  
Pulsation Period ◽  
X Ray ◽  
Binary Pulsar ◽  
X Ray Binaries

X Persei is a Be X-ray binary pulsar with ~835-sec pulsation period. Different from most other Be X-ray binaries, X Persei does not exhibit X-ray outbursts. A binary period of ~580 days has been suggested, but is not confirmed the by follow-up observations.

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