scholarly journals Some possible implications of the radio emission of Sco X-1

1970 ◽  
Vol 37 ◽  
pp. 257-259
Author(s):  
P. A. Feldman ◽  
J. I. Silk
Keyword(s):  
Radio Emission ◽  
Thermal Model ◽  
Radio Spectrum ◽  
X Rays ◽  
Plasma Component ◽  
Radiation Mechanism ◽  
Similar Time ◽  
X Ray ◽  
Infrared Continuum ◽  
Thin Plasma

Recent observations of radio emission from Sco X-1 at centimeter wavelengths by Andrew and Purton (1968) and by Ables (1969) have added an important new dimension to the study of galactic X-ray sources. We have considered two alternative interpretations of the radio emission from this object. First, we discuss whether it is possible to attribute the radio emission of Sco X-1 to thermal bremsstrahlung from an optically thin plasma at a temperature of 15 to 20 keV. This interpretation would have the merit of relating the radio properties to the existence of a hot, flaring plasma component whose presence has been invoked to explain the observations of hard X-rays (≳ 35 keV) from this object (Peterson and Jacobson, 1966, Buselli et al., 1968, Riegler et al., 1968, Riegler, 1969, Agrawal et al., 1969a, McCracken, 1969). That the 6-cm radio emission and the hard X-radiation should be found to vary by similar amounts over similar time scales lends this hypothesis a certain appeal. However, the measurement at 11 cm of flux density amounting to ≈0.07 flux units (1 flux unit ≡ ≡ 10−23 erg cm−2 sec−1 Hz−1) reported at this Symposium by McCracken makes it virtually untenable to regard the radio emission of Sco X-1 as arising from thermal origins. Excessive optical and infrared continuum radiation would be produced; moreover, the shape of the radio spectrum is inconsistent with any conceivable thermal model. An explanation for the radio emission of Sco X-1 must therefore be sought in terms of some non-thermal radiation mechanism.

scholarly journals X-ray Observations of Crab-Like Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 321-328
Author(s):  
R. H. Becker
Keyword(s):  
Spatial Distribution ◽  
Kinetic Energy ◽  
Radio Emission ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
Crab Nebula ◽  
Radio Spectrum ◽  
X Rays ◽  
X Ray ◽  
Evolutionary Connection

On the basis of extensive radio surveys of the galactic plane, approximately 140 sources of diffuse radio emission have been classified as supernova remnants (SNR). Using spectral index and spatial distribution as the primary selection criteria, these have been subdivided into two groups, “shell” and “Crab-like”. In each case, the radio emission is assumed to be of non-thermal origin. The two distinct morphologies arise from two distinct energy sources. For shell remnants, the energy is drawn from the reservoir of kinetic energy in the expanding shock front; in Crab-like remnants, the energy is drawn from the rotational kinetic energy of a central stellar remnant.These two classes of remnants differ significantly in their x-ray emission. With few exceptions, radio shell remnants emit thermal x-rays from shock heated gas which is itself distributed in a shell. Crab-like sources (as defined by their radio properties) emit synchrotron x-rays in a centrally-peaked spatial distribution. Presumably, the x-ray emission from these objects is an extension of the radio spectrum. Crab-like sources have a high probability of containing a compact (unresolved) source of x-ray emission which in analogy to the Crab Nebula, is identified as the central stellar remnant.The general absence of either compact x-ray sources or Crab-like diffuse nebulae within shell sources indicates that active pulsars are not usually formed in SN events which eventually form shell sources. However, there are several examples of remnants which share both shell and Crab-like characteristics so we cannot rule out an evolutionary connection between these two classes of SNR.

scholarly journals A unified accretion-ejection paradigm for black hole X-ray binaries

2019 ◽  
Vol 626 ◽  
pp. A115 ◽  
Author(s):  
G. Marcel ◽  
J. Ferreira ◽  
M. Clavel ◽  
P.-O. Petrucci ◽  
J. Malzac ◽  
...  
Keyword(s):  
Radio Emission ◽  
Accretion Disk ◽  
Ad Hoc ◽  
Emission Model ◽  
X Rays ◽  
Temperature Plasma ◽  
X Ray ◽  
Fitting Procedure ◽  
High Level ◽  
X Ray Binaries

Context. Transient X-ray binaries (XrB) exhibit very different spectral shapes during their evolution. In luminosity-color diagrams, their behavior in X-rays forms q-shaped cycles that remain unexplained. In Paper I, we proposed a framework where the innermost regions of the accretion disk evolve as a response to variations imposed in the outer regions. These variations lead not only to modifications of the inner disk accretion rate ṁin, but also to the evolution of the transition radius rJ between two disk regions. The outermost region is a standard accretion disk (SAD), whereas the innermost region is a jet-emitting disk (JED) where all the disk angular momentum is carried away vertically by two self-confined jets. Aims. In the previous papers of this series, it has been shown that such a JED–SAD disk configuration could reproduce the typical spectral (radio and X-rays) properties of the five canonical XrB states. The aim of this paper is now to replicate all X-ray spectra and radio emission observed during the 2010–2011 outburst of the archetypal object GX 339-4. Methods. We used the two-temperature plasma code presented in two previous papers (Papers II and III) and designed an automatic ad hoc fitting procedure that for any given date calculates the required disk parameters (ṁin,rJ) that fit the observed X-ray spectrum best. We used X-ray data in the 3–40 keV (RXTE/PCA) spread over 438 days of the outburst, together with 35 radio observations at 9 GHz (ATCA) dispersed within the same cycle. Results. We obtain the time distributions of ṁin(t) and rJ(t) that uniquely reproduce the X-ray luminosity and the spectral shape of the whole cycle. In the classical self-absorbed jet synchrotron emission model, the JED–SAD configuration also reproduces the radio properties very satisfactorily, in particular, the switch-off and -on events and the radio-X-ray correlation. Although the model is simplistic and some parts of the evolution still need to be refined, this is to our knowledge the first time that an outburst cycle is reproduced with such a high level of detail. Conclusions. Within the JED–SAD framework, radio and X-rays are so intimately linked that radio emission can be used to constrain the underlying disk configuration, in particular, during faint hard states. If this result is confirmed using other outbursts from GX 339-4 or other X-ray binaries, then radio could be indeed used as another means to indirectly probe disk physics.

scholarly journals The X-ray Spectra of High Redshift Quasars

1989 ◽  
Vol 134 ◽  
pp. 161-166
Author(s):  
Claude R. Canizares ◽  
Julia L. White
Keyword(s):  
High Redshift ◽  
Radio Spectrum ◽  
Clear Correlation ◽  
X Rays ◽  
Spectral Parameters ◽  
X Ray ◽  
Systematic Uncertainties ◽  
Two Component ◽  
X Ray Background ◽  
Single Power

We present mean spectral parameters for various ensembles of quasars observed with the Einstein Observatory Imaging Proportional Counter (IPC). Our sample contains 71 optically or radio selected quasars with 0.1 < z < 3.5, Galactic NH < 1021 cm−2, total counts of 30 −500, and IPC gain < 19. Quasars are grouped into ensembles according to radio properties (Flat Radio Spectrum [FRS], Steep Radio Spectrum [SRS] or Radio Quiet [RQ]), and either redshift or X-ray luminosity, lx. We find a clear correlation between radio properties and α. FRS quasars have α∼0.4, SRS quasars have α∼0.7 and RQ quasars have α ∼1–1.4. There is no evidence for a dependence of α on z nor, for the FRS and SRS ensembles, on lx over nearly three decades. FRS quasars with 2.0 < z < 3.5 have just as flat mean spectra as those with low z, implying that a single power law, which is flatter than the canonical one with α ∼ 0.65, continues into the 1–10 keV band (in which the observed softer X-rays were emitted). Unfortunately, the results for high redshift and high lx RQ quasars are ambiguous because of systematic uncertainties in the ensemble means. Thus we cannot test the two-component spectral hypothesis of Wilkes and Elvis for these objects. SRS X-ray spectra could be steeper than FRS spectra because of the mixing of two components, although a single intrinsically steeper spectrum is easier to reconcile with the absence of z dependence. The uncertainty in a for RQ quasars with high z leaves open the important question of their contribution to the cosmic X-ray background.

scholarly journals Cygnus X-3: Orbital Modulation in X-Rays and Radio

2004 ◽  
Vol 194 ◽  
pp. 216-216 ◽  
Author(s):  
L. Hjalmarsdotter ◽  
P. J. Hakala ◽  
O. Vilhu ◽  
D. C. Hannikainen ◽  
M. McCollough ◽  
...  
Keyword(s):  
Radio Emission ◽  
Monitoring Data ◽  
X Rays ◽  
X Ray ◽  
Orbital Modulation

The orbital modulation of the X-ray and radio emission of Cyg X-3 was studied using monitoring data from CGRO/BATSE, RXTE/ASM, GBI and the Ryle telescope as well as recent INTEGRAL observations. The depth of the X-ray modulation was found to be the same at X-ray energies ranging from 1.5 up to at least 20 keV, but the shape of the lightcurves changes gradually with energy. No modulation was found in radio.

High-energy radiation from natural lightning observed in coincidence with a VHF Lightning Interferometer

2020 ◽  
Author(s):  
Michele Urbani ◽  
Joan Montanyà ◽  
Oscar Van der Velde ◽  
Jesús Alberto López
Keyword(s):  
High Energy ◽  
Strong Absorption ◽  
X Rays ◽  
Coverage Area ◽  
Radiation Mechanism ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Cloud To Ground Lightning ◽  
Energy Emissions

&lt;p&gt;In the last two decades, it has been discovered that lightning strikes can emit high-energy radiation.&lt;br&gt;In particular, a phenomenon has been observed from space called &quot;Terrestrial Gamma-ray Flash'' (TGF), which consists of an intense burst of gamma radiation that can be produced during thunderstorms. This phenomenon has met with considerable interest in the scientific community and its mechanism is still not fully understood. Nowadays several satellites for astrophysics like AGILE and FERMI are able to detect and map TGFs and specific instruments like the ASIM detector on the ISS are studying this phenomenon from space.&lt;br&gt;In the atmosphere, the high-energy radiation undergoes a strong absorption exponentially proportional to the air density which makes it more difficult to detect TGFs on the ground. Nonetheless, ground measurements were conducted and observed that even in cloud-to-ground lightning high-energy radiation were produced. In particular, the works of Moore et al. [2001] and Dwyer et al. [2005] highlight two lightning processes in which the X-ray emission could be produced: downward negative stepped leader and dart leader. Currently, it is not clear if the emissions revealed on the ground and the TGFs observed in space are essentially the same phenomenon or how these phenomena are related. For these reasons, it is particularly interesting to study high-energy emissions also from ground instruments because, despite the strong absorption of the high-energy radiation, ground observations can reach a better accuracy in time and space and provide crucial information to investigate the origin and conditions under which these emissions occur.&lt;br&gt;A privileged instrument for this research is the VHF Lightning Interferometer, a system of antennas that allows you to map lightning through the very high frequency (VHF) emission. Due to the high resolution of this instrument, should be possible to locate the origin of the high-energy emissions and hopefully provide a better understanding of the radiation mechanism.&lt;br&gt;The aim of this research is, therefore, to develop a 3D interferometry system to identify as accurately as possible the origin and the conditions in which the X-ray emission occurs in cloud-to-ground lightning and investigate the relation of the VHF emissions with the TGFs.&lt;br&gt;Recently an observation campaign was conducted in Colombia with two VHF Lightning Interferometers and two X-rays detectors. This interferometry system was installed in the coverage area of a Lightning Mapping Array (LMA) and LINET to take advantage of the complementary information that these lightning location networks could provide. At the moment, about 15 lightning events with X-ray emissions were observed, including five X-ray bursts from downward negative leaders and two emissions from dart leaders. Further studies and analysis of the collected data are still ongoing.&lt;/p&gt;

scholarly journals The MAVERIC Survey: Variable Jet-accretion Coupling in Luminous Accreting Neutron Stars in Galactic Globular Clusters

2021 ◽  
Vol 923 (1) ◽  
pp. 88
Author(s):  
Teresa Panurach ◽  
Jay Strader ◽  
Arash Bahramian ◽  
Laura Chomiuk ◽  
James C. A. Miller-Jones ◽  
...  
Keyword(s):  
Black Holes ◽  
Neutron Star ◽  
Radio Emission ◽  
Neutron Stars ◽  
Globular Clusters ◽  
Radio Continuum ◽  
X Rays ◽  
X Ray ◽  
Galactic Globular Clusters ◽  
X Ray Binaries

Abstract Accreting neutron stars in low-mass X-ray binaries show outflows—and sometimes jets—in the general manner of accreting black holes. However, the quantitative link between the accretion flow (traced by X-rays) and outflows and/or jets (traced by radio emission) is much less well understood for neutron stars than for black holes, other than the general observation that neutron stars are fainter in the radio at a given X-ray luminosity. We use data from the deep MAVERIC radio continuum survey of Galactic globular clusters for a systematic radio and X-ray study of six luminous (L X > 1034 erg s−1) persistent neutron star X-ray binaries in our survey, as well as two other transient systems also captured by our data. We find that these neutron star X-ray binaries show an even larger range in radio luminosity than previously observed. In particular, in quiescence at L X ∼ 3 × 1034 erg s−1, the confirmed neutron star binary GRS 1747–312 in Terzan 6 sits near the upper envelope of the black hole radio/X-ray correlation, and the persistently accreting neutron star systems AC 211 (in M15) and X1850–087 (in NGC 6712) show unusual radio variability and luminous radio emission. We interpret AC 211 as an obscured “Z source” that is accreting at close to the Eddington limit, while the properties of X1850–087 are difficult to explain, and motivate future coordinated radio and X-ray observations. Overall, our results show that neutron stars do not follow a single relation between inflow and outflow, and confirm that their accretion dynamics are more complex than for black holes.

scholarly journals Inverse-Compton scattering in the resolved jet of the high-redshift quasar PKS J1421−0643

2020 ◽  
Vol 497 (1) ◽  
pp. 988-1000 ◽  
Author(s):  
D M Worrall ◽  
M Birkinshaw ◽  
H L Marshall ◽  
D A Schwartz ◽  
A Siemiginowska ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Redshift ◽  
Lorentz Factor ◽  
High Energy ◽  
Radio Spectrum ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Jet Power

ABSTRACT Despite the fact that kpc-scale inverse-Compton (iC) scattering of cosmic microwave background (CMB) photons into the X-ray band is mandated, proof of detection in resolved quasar jets is often insecure. High redshift provides favourable conditions due to the increased energy density of the CMB, and it allows constraints to be placed on the radio synchrotron-emitting electron component at high energies that are otherwise inaccessible. We present new X-ray, optical, and radio results from Chandra, HST, and the VLA for the core and resolved jet in the z = 3.69 quasar PKS J1421−0643. The X-ray jet extends for about 4.5 arcsec (32 kpc projected length). The jet’s radio spectrum is abnormally steep and consistent with electrons being accelerated to a maximum Lorentz factor of about 5000. Results argue in favour of the detection of iC X-rays for modest magnetic field strength of a few nT, Doppler factor of about 4, and viewing angle of about 15°, and predict the jet to be largely invisible in most other spectral bands including the far- and mid-infrared and high-energy gamma-ray. The jet power is estimated to be about 3 × 1046 erg s−1 which is of order a tenth of the quasar bolometric power, for an electron–positron jet. The jet radiative power is only about 0.07 per cent of the jet power, with a smaller radiated power ratio if the jet contains heavy particles, so most of the jet power is available for heating the intergalactic medium.

scholarly journals LSI +61°303: A Pulsar Wind Nebula in a Binary?

2004 ◽  
Vol 218 ◽  
pp. 219-220
Author(s):  
D. A. Leahy
Keyword(s):  
Radio Emission ◽  
Gamma Rays ◽  
Confining Pressure ◽  
Rapid Expansion ◽  
Photon Flux ◽  
Relativistic Electrons ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton ◽  
Pulsar Wind

LSI +61°303 outbursts are modeled as a pulsar wind nebula expanding inside the environment provided by the Be companion star's stellar wind and photon flux. A set of equations describing the system is developed and solved numerically for representative sets of parameters. Emission in X-rays through gamma-rays is due to inverse Compton emission from relativistic electrons around the pulsar. The radio emission is due to synchrotron emission of varying optical depth, which yields a varying spectral index. The peak of X-ray emission is near periastron and the peak of the radio emission is near apastron, due to reduced confining pressure on the relativistic electron cloud and its subsequent rapid expansion.

scholarly journals Extended X-ray emission in PKS 1718−649

2018 ◽  
Vol 612 ◽  
pp. L4 ◽  
Author(s):  
T. Beuchert ◽  
A. Rodríguez-Ardila ◽  
V. A. Moss ◽  
R. Schulz ◽  
M. Kadler ◽  
...  
Keyword(s):  
Large Scale ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Effective Area ◽  
Radio Spectrum ◽  
Host Galaxy ◽  
X Rays ◽  
Radio Structure ◽  
X Ray ◽  
Close Proximity

PKS 1718−649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718−649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton, we are able to study the detailed physics of the environment of PKS 1718−649. Not only can we confirm that the bulk of the ≲kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate.

scholarly journals Search for Nonthermal X-Rays from Supernova Remnant Shells

1998 ◽  
Vol 188 ◽  
pp. 117-120
Author(s):  
R. Petre ◽  
J. Keohane ◽  
U. Hwang ◽  
G. Allen ◽  
E. Gotthelf
Keyword(s):  
Radio Emission ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Cosmic Ray ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Nonthermal Radio ◽  
Cosmic Ray Acceleration ◽  
Nonthermal Radio Emission

The suggestion that the shocks of supernova remnants (SNR's) are cosmic ray acceleration sites dates back more than 40 years. While observations of nonthermal radio emission from SNR shells indicate the ubiquity of GeV cosmic ray production, there is still theoretical debate about whether SNR shocks accelerate particles up to the well-known “knee” in the primary cosmic ray spectrum at ~3,000 TeV. Recent X-ray observations of SN1006 and other SNR's may have provided the missing observational link between SNR shocks and high energy cosmic ray acceleration. We discuss these observations and their interpretation, and summarize our ongoing efforts to find evidence from X-ray observations of cosmic ray acceleration in the shells of other SNR's.

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