scholarly journals The auto and cross angular power spectrum of the Cas A supernova remnant in radio and X-ray

2021 ◽  
Author(s):  
Preetha Saha ◽  
Somnath Bharadwaj ◽  
Susmita Chakravorty ◽  
Nirupam Roy ◽  
Samir Choudhuri ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Power Law ◽  
Supernova Remnant ◽  
Strongly Correlated ◽  
Mhd Turbulence ◽  
Angular Power Spectrum ◽  
X Ray ◽  
Shock Interactions ◽  
Cas A ◽  
Thermal Bremsstrahlung

Abstract The shell type supernova remnant (SNR) Cas A exhibits structures at nearly all angular scales. Previous studies show the angular power spectrum (Cℓ) of the radio emission to be a broken power law, consistent with MHD turbulence. The break has been identified with the transition from 2D to 3D turbulence at the angular scale corresponding to the shell thickness. Alternatively, this can also be explained as 2D inverse cascade driven by energy injection from knot-shock interactions. Here we present Cℓ measured from archival VLA 5GHz (C band) data, and Chandra X-ray data in the energy ranges A = 0.6 − 1.0  keV and B = 4.2 − 6.0  keV, both of which are continuum dominated. The different emissions all trace fluctuations in the underlying plasma and possibly also the magnetic field, and we expect them to be correlated. We quantify this using the cross Cℓ between the different emissions. We find that X-ray B is strongly correlated with both radio and X-ray A, however X-ray A is only very weakly correlated with radio. This supports a picture where X-ray A is predominantly thermal bremsstrahlung whereas X-ray B is a composite of thermal bremsstrahlung and non-thermal synchrotron emission. The various Cℓ measured here, all show a broken power law behaviour. However, the slopes are typically shallower than those in radio and the position of the break also corresponds to smaller angular scales. These findings provide observational inputs regarding the nature of turbulence and the emission mechanisms in Cas A.

scholarly journals X-Ray Observations of GRS 1915+105

1997 ◽  
Vol 163 ◽  
pp. 709-710 ◽  
Author(s):  
J. Greiner ◽  
B.A. Harmon ◽  
W.S. Paciesas ◽  
E.H. Morgan ◽  
R.A. Remillard
Keyword(s):  
Power Law ◽  
Count Rate ◽  
Monitoring Data ◽  
Detector Response ◽  
X Ray ◽  
Spectral Fitting ◽  
Spectral Components ◽  
Best Fit ◽  
Intensity Evolution ◽  
Thermal Bremsstrahlung

After the discovery of GRS 1915+105 (Castro-Tirado et al. 1992) we obtained pointed ROSAT observations every six months (12 until now). The flux in the ROSAT (0.1–2.4 keV) band is strikingly different from the simultaneous BATSE (25–50 keV) flux which was obtained by integrating the best fit power law (Fig. 1). Motivated by the different intensity evolution in the soft and hard X-ray band we have selected BATSE monitoring data collected simultaneously to ROSATdata and performed joint spectral fitting with XSPEC. As a result, we never got an acceptable fit (see Fig. 2): The BATSE power law (upper dotted line) is too steep to match the ROSAT band, and even allowing for an increased absorbing column (lower dotted line) does not solve the problem. Alternatively, neither a thermal bremsstrahlung fit (solid line) nor a power law fit (lower dash-dot line) to the ROSAT data match the BATSE flux. The upper dash-dot line is a -2.5 powerlaw which would match the BATSE data while giving too much 1–2 keV emission. A similar, but less stringent result is obtained when folding the best fit BATSE power law models with the HRI detector response to compare the expected count rate with the observed one. We therefore conclude that the spectrum during all simultaneous ROSAT/BATSE observations seemingly consists of two different spectral components.

scholarly journals XMM-Newton and Fermi/LAT view on the supernova remnant 3C434.1

2019 ◽  
Vol 631 ◽  
pp. A179
Author(s):  
V. Doroshenko ◽  
D. Malyshev ◽  
G. Pühlhofer ◽  
B. Dincel ◽  
M. Sasaki ◽  
...  
Keyword(s):  
Power Law ◽  
Supernova Remnant ◽  
X Rays ◽  
Significant Excess ◽  
X Ray ◽  
Thermal Origin

We report on XMM-Newton observations of the supernova remnant (SNR) 3C434.1 (G94.0+1.0), the first in X-rays since the ROSAT era. Our analysis confirms the thermal origin of the observed extended X-ray emission, whose morphology appears more complex than previously reported. In particular, part of the shell shows a significantly harder spectrum which is consistent with a power law, and it is, therefore, likely of non-thermal origin. Motivated by these finding, we revisited the GeV observations of the field taken with the Fermi observatory. A significant excess associated with the remnant was detected, which is likely associated with non-thermal X-ray emission from part of the shell. The analysis of the Fermi data resulted in the serendipity discovery of GeV emission from the nearby SNR G093.7-00.2. Finally, we searched for a possible compact remnants within the shell, however, no obvious candidates could be identified due to the fairly large positional uncertainties.

scholarly journals HESS J1858+020: A GeV-TeV source possibly powered by cosmic rays from SNR G35.6-0.4

2021 ◽  
Vol 646 ◽  
pp. A114
Author(s):  
Y. Cui ◽  
Y. Xin ◽  
S. Liu ◽  
P. H. T. Tam ◽  
G. Pühlhofer ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Cosmic Rays ◽  
Power Law ◽  
Supernova Remnant ◽  
Observational Evidence ◽  
X Ray ◽  
Multi Wavelength ◽  
Northern Edge ◽  
Cloud Complex ◽  
Hadronic Model

Context. The supernova remnant (SNR) G35.6−0.4 shows a non-thermal radio shell, however, no γ-ray or X-ray counterparts have been found for it thus far. One TeV source, HESS J1858+020, was found near the SNR and this source is spatially associated with some clouds at 3.6 kpc. Aims. To attain a better understanding of the origin of HESS J1858+020, we further investigate the association between SNR cosmic rays (CRs) and the clouds through the Fermi-LAT analysis and hadronic modeling. Methods. We performed the Fermi-LAT analysis to explore the GeV emission in and around the SNR. We explored the SNR physics with previously observed multi-wavelength data. We built a hadronic model using runaway CRs of the SNR to explain the GeV-TeV observation. Results. We found a hard GeV source (SrcX2) that is spatially coincident with both HESS J1858+020 and a molecular cloud complex at 3.6 kpc. In addition, a soft GeV source (SrcX1) was found at the northern edge of the SNR. The GeV spectrum of SrcX2 connects well with the TeV spectrum of HESS J1858+020. The entire γ-ray spectrum ranges from several GeV up to tens of TeV and it follows a power-law with an index of ~2.15. We discuss several pieces of observational evidence to support the middle-aged SNR argument. Using runaway CRs from the SNR, our hadronic model explains the GeV-TeV emission at HESS J1858+020, with a diffusion coefficient that is much lower than the Galactic value.

scholarly journals XMM-Newton spectrum of the magnetar CXOU J171405.7–381031

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Haruka Watanabe ◽  
Aya Bamba ◽  
Shinpei Shibata ◽  
Eri Watanabe
Keyword(s):  
Power Law ◽  
Time Variation ◽  
Supernova Remnant ◽  
Component Model ◽  
Time Variability ◽  
Spectral Parameters ◽  
X Ray ◽  
Two Component ◽  
Photon Index ◽  
Higher Temperature

Abstract We observe the magnetar CXOU J171405.7−381031 with XMM-Newton and obtain the most reliable X-ray spectral parameters for this magnetar. After removing the flux from the surrounding supernova remnant CTB 37B, the radiation of CXOU J171405.7−381031 is best described by a two-component model, consisting of a blackbody and power law. We obtain a blackbody temperature of $0.58^{+0.03}_{-0.03}$ keV, a photon index of $2.15^{+0.62}_{-0.68}$, and an unabsorbed 2–10 keV band flux of $2.33^{+0.02}_{-0.02} \times 10^{-12}$ erg cm−2 s−1. These new parameters enable us to compare CXOU J171405.7−381031 with other magnetars, and it is found that the luminosity, temperature, and photon index of CXOU J171405.7−381031 are aligned with the known trend among the magnetar population with a slightly higher temperature, which could be caused by its young age. All magnetars with a spin-down age of less than 1000 yr show time variation or bursts except for CXOU J171405.7−381031. We explore the time variability for six observations between 2006 and 2015, but there is no variation larger than ∼10%.

scholarly journals The angular power spectrum measurement of the Galactic synchrotron emission using the TGSS survey

2017 ◽  
Vol 12 (S333) ◽  
pp. 157-161
Author(s):  
Samir Choudhuri ◽  
Somnath Bharadwaj ◽  
Sk. Saiyad Ali ◽  
Nirupam Roy ◽  
H. T. Intema ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Power Spectrum ◽  
Point Source ◽  
Power Law ◽  
Point Sources ◽  
Synchrotron Emission ◽  
Angular Power Spectrum ◽  
Spectrum Measurement ◽  
Upper Limit ◽  
Sky Survey

AbstractCharacterizing the diffuse Galactic synchrotron emission (DGSE) at arcminute angular scales is needed to remove this foregrounds in cosmological 21-cm measurements. Here, we present the angular power spectrum (Cℓ) measurement of the diffuse Galactic synchrotron emission using two fields observed by the TIFR GMRT Sky Survey (TGSS). We apply 2D Tapered Gridded Estimator (TGE) to estimate the Cℓ from the visibilities. We find that the residual data after subtracting the point sources is likely dominated by the diffuse Galactic synchrotron radiation across the angular multipole range 240 ≤ ℓ ≲ 500. We fit a power law to the measured Cℓ over this ℓ range. We find that the slopes in both fields are consistent with earlier measurements. For the second field, however, we interpret the measured Cℓ as an upper limit for the DGSE as there is an indication of a significant residual point source contribution.

scholarly journals A study of Kepler supernova remnant: angular power spectrum estimation from radio frequency data

2019 ◽  
Vol 489 (4) ◽  
pp. 5866-5875
Author(s):  
Preetha Saha ◽  
Somnath Bharadwaj ◽  
Nirupam Roy ◽  
Samir Choudhuri ◽  
Debatri Chattopadhyay
Keyword(s):  
Power Spectrum ◽  
Power Law ◽  
Supernova Remnants ◽  
Ambient Medium ◽  
Spectrum Estimation ◽  
Angular Power Spectrum ◽  
Kolmogorov Turbulence ◽  
Wide Range ◽  
L Band ◽  
5 Ghz

ABSTRACT Supernova remnants (SNRs) have a variety of overall morphology as well as rich structures over a wide range of scales. Quantitative study of these structures can potentially reveal fluctuations of density and magnetic field originating from the interaction with ambient medium and turbulence in the expanding ejecta. We have used 1.5 GHz (L band) and 5 GHz (C band) VLA data to estimate the angular power spectrum Cℓ of the synchrotron emission fluctuations of the Kepler SNR. This is done using the novel, visibility-based, Tapered Gridded Estimator of Cℓ. We have found that, for ℓ = (1.9–6.9) × 104, the power spectrum is a broken power law with a break at ℓ = 3.3 × 104, and power-law index of −2.84 ± 0.07 and −4.39 ± 0.04 before and after the break, respectively. The slope −2.84 is consistent with 2D Kolmogorov turbulence and earlier measurements for the Tycho SNR. We interpret the break to be related to the shell thickness of the SNR (0.35 pc) which approximately matches ℓ = 3.3 × 104 (i.e. 0.48 pc). However, for ℓ > 6.9 × 104, the estimated Cℓ of L band is likely to have dominant contribution from the foregrounds while for C band the power-law slope −3.07 ± 0.02 is roughly consistent with 3D Kolmogorov turbulence like that observed at large ℓ for Cas A and Crab SNRs.

scholarly journals Radio Observations of the Supernova Remnant CTB109 (G109.2–1.0)

1983 ◽  
Vol 101 ◽  
pp. 455-458
Author(s):  
V. A. Hughes ◽  
R. H. Harten ◽  
C. Costain ◽  
L. Nelson ◽  
M. R. Viner
Keyword(s):  
Antenna Arrays ◽  
Supernova Remnant ◽  
Galactic Plane ◽  
Radio Observations ◽  
Extended Source ◽  
Radio Observatory ◽  
X Ray ◽  
Close Proximity ◽  
Strong Source ◽  
Cas A

The supernova remnant G109.2–1.0 was discovered at λ49cm by Hughes, Harten and van den Bergh (1981) during a survey of part of the Galactic plane. The northern part of it had been detected previously as the non-thermal radio source CTB109 by Wilson and Bolton (1960), and by Raghava Roa et al (1965), but the extended low brightness of the source and its close proximity to the very strong source Cas A, from which it is separated by ∼5′, excluded it from any further detailed study. It was discovered independently at X-ray wavelengths by Gregory and Fahlman (1980). Recently, the original WSRT radio observations have been found to be in error as a result of applying the CLEAN procedure to an extended source, and since the object appears to contain an X-ray pulsar (Fahlman and Gregory, 1981), it was decided to carry out a more detailed and extensive mapping of the remmant using different antenna arrays and frequencies. This paper describes the results obtained at λ49cm and λ21cm using the Westerbork Synthesis Radio Telescope (WSRT), at λ21cm using the aperture synthesis array at the Dominion Radio Astrophysical Observatory (DRAO) and at λ4.6cm using the 46m telescope of the Algonquin Radio Observatory (ARO). Thus, data has been obtained from three completely independent telescopes, using completely independent data reduction systems. Of importance is the fact that not only have wavelengths been chosen such that the larger dimensions of the array give a reasonable angular resolution of ≤1′, but also that the smallest spacing enables the larger angular dimensions of the remnant to be observed. This paper presents some of the results and a brief interpretation.

scholarly journals Locating the TeV γ-rays from the shell regions of Cassiopeia A

2013 ◽  
Vol 9 (S296) ◽  
pp. 380-381
Author(s):  
Lab Saha ◽  
Tulun Ergin ◽  
Pratik Majumdar ◽  
Mustafa Bozkurt
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Supernova Remnant ◽  
X Ray ◽  
Cassiopeia A ◽  
Young Supernova Remnant ◽  
Multi Wavelength ◽  
Flux Level ◽  
Γ Rays ◽  
Different Parts

AbstractWe have analyzed Chandra X-ray data from different parts of the shell of young supernova remnant (SNR) in the energy range of 0.7 - 8 keV. We observed that X-ray flux level varies over different shell regions of the source. Implications of X-ray observation will be discussed here. We also analyzed Fermi-LAT data in the energy range 0.5 - 50 GeV for the source. The differential spectrum obtained in this way fits with simple power-law. We also present here multi-wavelength modeling of the source considering archival radio and TeV data along with Chandra and Fermi-LAT data.

scholarly journals Theoretical ideas concerning X-ray sources

1967 ◽  
Vol 31 ◽  
pp. 463-467 ◽  
Author(s):  
Geoffrey R. Burbidge
Keyword(s):  
Energy Source ◽  
Synchrotron Radiation ◽  
Crab Nebula ◽  
Line Spectrum ◽  
X Ray ◽  
Hot Gas ◽  
Cas A ◽  
The Crab Nebula ◽  
Thermal Bremsstrahlung

Several possible mechanisms for the emission of galactic X-ray sources are briefly reviewed. Synchrotron radiation is probably responsible for the X-ray emission from the Crab Nebula and from Cas A. The source Sco X-1 probably radiates by thermal bremsstrahlung in a cloud at 50 × 106°K, associated with an old nova. The energy source of the hot gas in such a model, and the conditions for formation of the line spectrum are considered.

scholarly journals X-ray, Optical and UV Observations of the Young Supernova Remnant in the Irregular Galaxy NGC 4449

1983 ◽  
Vol 101 ◽  
pp. 579-582
Author(s):  
W. P. Blair ◽  
R. P. Kirshner ◽  
P. F. Winkler ◽  
J. C. Raymond ◽  
R. A. Fesen ◽  
...  
Keyword(s):  
Supernova Remnant ◽  
Massive Star ◽  
Irregular Galaxy ◽  
Reverse Shock ◽  
X Ray ◽  
Young Supernova Remnant ◽  
Cas A

A powerful young supernova remnant (SNR) similar to Cas A has recently been discovered in the irregular galaxy NGC 4449. We have obtained X-ray, optical and ultraviolet data which allow us to investigate possible models for this object and estimate its age. Several lines of argument indicate a massive star of order 25 M⊙ as the precursor to this remnant. If the x-ray emission is attributed to a reverse shock in the ejecta, the remnant should be ∼ 120 years old.

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