scholarly journals Correlated X-ray and Millimetre Variability of the Blazar 3C273

1994 ◽  
Vol 159 ◽  
pp. 193-196 ◽  
Author(s):  
I M McHardy ◽  
I Papadakis ◽  
C M Leach ◽  
E I Robson ◽  
W Junor ◽  
...  
Keyword(s):  
Power Law ◽  
Soft Component ◽  
Hard Component ◽  
X Ray ◽  
Simple Extrapolation

We present the results of X-ray and millimetre monitoring of the blazar 3C273 at 1–2 day intervals over the period 12 December 1992 to 24 January 1993. No large flares are seen in this period but variations in both wavebands of ∼ 30% on few day timescales are apparent. The ROSAT PSPC X-ray spectrum consists of 2 power-law components with the harder component dominating above 0.5 keV. There is very little correlation between the variability of the soft and hard components. The soft component does not correlate with the millimetre variations, but the hard component correlates reasonably well and leads the millimetre variations by about 10 days. These results show that the hard X-ray component cannot be a simple extrapolation of the millimetre/IR synchrotron component but may be explained as a self-Compton component in a shocked jet.

scholarly journals 3.10. X-ray constraints on accretion and starburst processes in galactic nuclei

1998 ◽  
Vol 184 ◽  
pp. 109-110
Author(s):  
A. Ptak ◽  
P. Serlemitsos ◽  
T. Yaqoob ◽  
R. Mushotzky ◽  
Y. Terashima ◽  
...  
Keyword(s):  
Power Law ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Soft Component ◽  
Short Term ◽  
Hard Component ◽  
X Ray ◽  
Ngc 6946 ◽  
Process Elements ◽  
Low Activity

Although the galaxies in our sample are heterogenous in their optical classifications (LLAGN: M51, NGC 3147, NGC 4258; LINER: NGC 3079, NGC 3310, NGC 3998, NGC 4579, NGC 4594; starburst: M82, NGC 253, NGC 3628, NGC 6946), they are fit well by a “canonical” spectrum with a hot, optically-thin thermal component with T ~ 8 × 106 K and an absorbed (NH ~ 1022 cm−2) power-law with an energy index α ~ 0.7–0.8. Both the “soft” component, most likely due to SN or superwind-heated ISM, and the “hard” power-law, most likely due to a micro-AGN and/or blackhole candidates, appear to be common in low-activity galaxies. If the soft component is associated with a superwind outflow, than ~ 10% of the X-ray emission is due to “swept-up” ISM rather than superwind emission. The abundance of Fe relative to α-process elements tends to be sub-solar, possibly due to dust-depletion and/or type-II SN enrichment. The lack of short-term variability in the hard component suggests that if it is due to an AGN, then the mode of accretion is probably fundamentally different from “normal” Seyfert galaxies.

scholarly journals Hardness Ratio in Evolving Low-Mass X-ray Binary Systems

1987 ◽  
Vol 125 ◽  
pp. 199-199
Author(s):  
J. Shaham ◽  
M. Tavani
Keyword(s):  
Neutron Star ◽  
Accretion Disk ◽  
Binary Systems ◽  
Spectral Component ◽  
Soft Component ◽  
Hard Component ◽  
X Ray ◽  
Low Mass ◽  
Additional Support ◽  
X Ray Binaries

Spectral observations of low-mass X-ray binaries (LMXBs) show that the soft component usually dominates over the hard one. These results provide additional support to an interpretation based on models of LMXBs in which the neutron star while, on the average, spinning up, is also experiencing a spinning down torque. Under these conditions, a fraction of the luminosity associated with the gravitational release of energy on the surface of the accreting neutron star may manifest itself as luminosity originating in the inner part of the accretion disk. It is probably possible to separate the two contributions; the stellar luminosity can be associated with the hard component of the spectrum and the disk luminosity, related to the exchange of energy due to the torque between the rapidly spinning neutron star and the accretion disk, can be associated with the soft spectral component.

scholarly journals Modelling the Soft X-ray Excess in E1615+061

1994 ◽  
Vol 159 ◽  
pp. 317-317
Author(s):  
M. Bałucińska-Church ◽  
L. Piro ◽  
H. Fink ◽  
F. Fiore ◽  
M. Matsuoka ◽  
...  
Keyword(s):  
Power Law ◽  
Column Density ◽  
High Energy ◽  
X Rays ◽  
Hard Component ◽  
X Ray ◽  
Simple Power ◽  
High Energy Tail ◽  
Photon Index ◽  
Best Fit

SummaryWe report results of an international UV – X-ray campaign in 1990–1992 involving the IUE, Rosat and Ginga satellites to observe E1615+061, a Seyfert 1 galaxy with peculiar spectral and intensity behaviour over the last 20 years. The source has been found to be stable in its medium state during the observations. The Ginga (1–20 keV) spectrum of E1615+061 is adequately represented by a simple power law with a photon index α = 1.8 ± 0.1. However, α ∼ 2, as expected for the intrinsic power law component in a reflection model, cannot be ruled out statistically. The Rosat PSPC (0.1–2 keV) spectra collected during the All Sky Survey and the AO-1 phase can be well-described by a simple power law (α = 2.2 ± 0.1) with cold absorber (NH = 3.5 ± 0.3 · 10λ20 H/cmλ2). Both the photon index being significantly different than that obtained from the Ginga spectrum and the column density being smaller than the galactic column (NH ∼ 4.2 · 10λ20 H/cmλ2) give an indication of a soft excess over and above the hard component seen in the Ginga spectrum. E1615+061 has been observed with IUE in 1990 and in 1992. The source was stable and the colour excess E(B-V) derived from the data = 0.1 is in good agreement with that expected from the galactic absorption.To parameterise the soft excess we fitted the Rosat data with a two-component model consisting of a power law, and a blackbody or thermal bremsstrahlung, with a single galactic absorption term. The column density and the slope of the power law were kept constant. The blackbody temperature was 80 ± 6 eV and 63 ± 12 eV for photon index equal to 1.8 and 2.0, respectively, whereas the bremsstrahlung temperature was 220 ± 40 eV and 115 ± 30 eV for the two cases.An attempt to model the soft excess seen in the Rosat PSPC spectrum has been made assuming that the soft excess is the high energy tail of a disc spectrum which peaks in the UV part of the spectrum. Additionally it was assumed that there is a hard component contributing to the spectrum from UV to X-rays with parameters as described by the Ginga spectrum. The best fit parameters: the mass of the central source and the mass accretion rate were around 5 ± 1 · 10λ6 M⊙ and 0.2 ± 0.04 M⊙/yr, respectively.Our modelling shows that the soft X-ray excess can be described (χredλ2 < 1.2) as the high energy tail of an accretion disk spectrum if the intrinsic power law is quite steep (α = 2). The main contribution to the residuals in the Rosat PSPC range comes from 0.3–0.6 keV, with a tendency for these residuals to increase when the slope gets flatter. The accretion luminosity is ∼ 6.5 · 10λ44 erg/s for the best fit parameters, i.e. about the Eddington luminosity.

Observations of SN 1987A from Ginga

1988 ◽  
Vol 7 (4) ◽  
pp. 479-485
Author(s):  
H. Inoue
Keyword(s):  
Energy Spectrum ◽  
Time Variable ◽  
Soft Component ◽  
X Rays ◽  
Hard Component ◽  
X Ray ◽  
Sn 1987A

AbstractResults of the observations of SN 1987A from Ginga are presented. The first detection of X-rays from the SN 1987A was July, 1987. The energy spectrum is quite unnusual for any of the known classes of X-ray sources, and apparently consists of two seperate components; a soft and a hard component. The soft component is significantly time-variable, and also showed a flarelike increase in January, 1988. Whereas, the intensity of the hard component has remained fairly stationary for more than 300 days. The origins of the two components are also discussed.

scholarly journals X-Ray Observation of SN1987A from Ginga

1988 ◽  
Vol 108 ◽  
pp. 399-405
Author(s):  
Y. Tanaka
Keyword(s):  
Energy Spectrum ◽  
Time Variable ◽  
Soft Component ◽  
Hard Component ◽  
X Ray

AbstractAn unusual hard X-ray source was discovered in an error box of 0.2° × 0.3° including SN1987A from the X-ray astronomy satellite Ginga. The energy spectrum is quite unusual for any known classes of X-ray source, and apparently consists of two separate components, a soft component and a very hard component. This source is considered to be identified with SN1987A. The X-ray emergence occurred in July, 1987, or possibly even earlier. The soft component is significantly time-variable and also showed a flare-like increase in January, 1988, while the intensity of the hard component has remained relatively unchanged for more than 200 days.

scholarly journals ASCA observation of Henize 2-10

1999 ◽  
Vol 193 ◽  
pp. 523-525
Author(s):  
Youichi Ohyama ◽  
Yoshiaki Taniguchi
Keyword(s):  
Soft Component ◽  
Hard Component ◽  
X Ray ◽  
Hot Gas

We present results of X-ray spectroscopy of the prototypical Wolf-Rayet galaxy Henize 2–10 with ASCA. We find that the X-ray spectrum is best described by a model with soft (kT ≃ 0.7 keV) and hard (kT ≃ 3.9 keV) components. The soft component is attributed to the hot gas associated with the superwind, and the hard component with a collection of the young sources (young SNRs and HMXBs) associated with the starburst.

scholarly journals X-ray evidence for wind-wind collision in the Wolf-Rayet binary V444 Cygni

1999 ◽  
Vol 193 ◽  
pp. 398-399
Author(s):  
Jun Yokogawa ◽  
Katsuji Koyama ◽  
Yoshitomo Maeda ◽  
Steve L. Skinner
Keyword(s):  
Soft Component ◽  
X Rays ◽  
Plasma Model ◽  
Temperature Plasma ◽  
Absorption Column ◽  
Hard Component ◽  
Eclipsing Binary ◽  
X Ray ◽  
The Individual ◽  
Two Temperature

We present results on the eclipsing binary V444 Cyg (WN5+O6) with the X-ray satellite ASCA. The observations were performed at orbital phases 0.0, 0.25 and 0.5 (the 06 star is in front at phase 0.5 and vice versa at phase 0.0). Two-temperature plasma model could reproduce X-ray spectra in each phase. The temperature of the soft component is lower (kT ≃ 0.6 keV), which is attributed to the individual O6/WN5 stars. The temperature of the hard component is higher (kT ≃ 2 keV), which exhibited phase-related time-variabilities in absorption column NH and luminosity LX; NH was maximal at phase 0.0 while LX was minimal at phase 0.5. These variabilities are consistent with the scenario that X-rays are emitted from plasma heated-up by wind-wind collision near the surface of the O6 star.

scholarly journals XMM-Newton observations of the symbiotic recurrent nova T CrB: evolution of X-ray emission during the active phase

2019 ◽  
Vol 489 (2) ◽  
pp. 2930-2940 ◽  
Author(s):  
Svetozar A Zhekov ◽  
Toma V Tomov
Keyword(s):  
Active Phase ◽  
Soft Component ◽  
X Rays ◽  
Rotational Period ◽  
Hard Component ◽  
X Ray ◽  
Quiescent Phase ◽  
Recurrent Nova ◽  
First Time ◽  
Thin Plasma

ABSTRACT We present an analysis of the XMM-Newton observations of the symbiotic recurrent nova T CrB, obtained during its active phase which started in 2014–2015. The XMM-Newton spectra of T CrB have two prominent components: a soft one (0.2–0.6 keV), well represented by blackbody emission, and a heavily absorbed hard component (2–10 keV), well matched by optically-thin plasma emission with high temperature (kT ≈ 8 keV). The XMM-Newton observations reveal evolution of the X-ray emission from T CrB in its active phase. Namely, the soft component in its spectrum is decreasing with time, while the opposite is true for the hard component. Comparison with data obtained in the quiescent phase shows that the soft component is typical only for the active phase, while the hard component is present in both phases but it is considerably stronger in the quiescent phase. Presence of stochastic variability (flickering) on time-scales of minutes and hours is confirmed both in X-rays and UV (UVM2 filter of the XMM-Newton optical monitor). On the other hand, periodic variability of 6000–6500 s is found for the first time in the soft X-ray emission (0.2–0.6 keV) from T CrB. We associate this periodic variability with the rotational period of the white dwarf in this symbiotic binary.

SUZAKU VIEW OF POWERFUL GAMMA-RAY QUASARS

2008 ◽  
Vol 17 (09) ◽  
pp. 1483-1489
Author(s):  
JUN KATAOKA
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Shock Acceleration ◽  
Soft Component ◽  
Diffusive Shock Acceleration ◽  
X Ray ◽  
Hard Power ◽  
Photon Index

We present the results from multiwavelength campaigns of three powerful gamma-ray quasars, PKS 1510-089, RBS 315 and Swift J0746.3+2548, recently organized with Suzaku. The Suzaku observation provided one of the highest S/N X-ray spectra ever reported between 0.3 and 50 keV. For these quasars, the X-ray spectrum is well represented by an extremely hard power-law with photon index Γ ≃ 1.2, but is augmented by an additional soft component apparently below 1 keV for PKS 1510-089, whereas a strong deficit of soft photons is observed in RBS 315. We model the broadband spectra of these powerful quasars and argue that the power of the jet is dominated by protons but with the number of electrons/positrons exceeding the number of protons by a factor ≃ 10. We also argue that an extremely hard X-ray spectra may result from a double power-law form of the injected electrons, with the break energy γ br ≃ 1000 corresponding to the anticipated threshold of diffusive shock acceleration.

ROSAT Spectra of Quasars

1994 ◽  
Vol 159 ◽  
pp. 369-369
Author(s):  
P. Bühler ◽  
T.J.-L. Courvoisier ◽  
R. Staubert ◽  
H. Brunner ◽  
G. Lamer
Keyword(s):  
Power Law ◽  
Column Density ◽  
Soft Part ◽  
Black Body ◽  
Soft Component ◽  
X Rays ◽  
Power Law Model ◽  
X Ray ◽  
Power Law Index ◽  
Single Power

X–ray observations of AGN with Einstein, EXOSAT and Ginga have shown, that the spectra of quasars in the energy range 2 to 10 keV can be approximately described by a single power law model with a photon index of 1.7 to 2.0. They also suggested that a soft X-ray excess component (below ≈ 1 keV) is a common feature in many quasars. In order to investigate whether a soft excess is characteristic for a certain class of objects we analysed the data of the pointed ROSAT PSPC observations of the six radio-loud quasars PG0007+106, PKS0135-247, QSO0537-286, QSO0923+392, PG1225+317, 3C273 and the radio-quiet quasar PG0804+761. In a first step the observed spectra were fitted with an absorbed single power law model. The hydrogen column density was fixed to its galactic value and the normalisation at 1 keV and the spectral index α were the free fit parameters. In order to decide whether a soft component is present in a source, the resulting power law index was compared with the hard X-ray power law index (2–10 keV) determined in the past with other instruments. A steep ROSAT PSPC spectrum indicates the presence of an additional soft X–ray component. In four cases (PKS0135-247, PG0804+761, QSO0923+392, 3C273) we find that the spectra in the PSPC band are considerably steeper than the spectra above 2 keV and therefore suggest the presence of a soft excess. In order to quantify the contribution of the soft excess these spectra were successively fitted with a model containing a hard power law component and an additional soft component described either by a power law, thermal bremsstrahlung or black body model. For the other three members of our sample (0007+106, 0537-286, 1225+317) the fitted power law index is not enhanced. This means that no soft component has been detected, but not necessarily that it does not exist. There are two effects which render more difficult the detection of a soft component in ROSAT spectra, the absorption of photons by interstellar material and the shift of the spectra towards lower energies due to the redshift. Both processes have first an effect on the soft part of the observed spectrum and it is therefore evident, that this leads to a decrease of the sensitivity for soft X–rays of the emitted spectrum. For the three quasars in our sample, where no soft excess has been detected, either the column density (0007+106) or the redshift (0537-286, 1225+317) is especially large and therefore an eventually present soft component could have remained undetected. In these cases we calculated upper limits for the strength of such a soft component (P. Bühler et al., to be published in A&A.)

Sign in / Sign up

Export Citation Format

Share Document