Evolution of the radio spectrum of Cassiopeia A from long-term observations. Observations at 290 and 927 MHz

Vinyaikin, E. N.

doi:10.1134/s1063772907020023

Cited by 10 publications

(7 citation statements)

References 6 publications

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“…At 1405 MHz, this corresponds to a fading rate of 0.670 ± 0.019 %/yr, which is consistent with our initial finding of 0.62±0.12 %/yr (Reichart & Stephens 2000). This is also consistent with the finding of Vinyaikin (2007a), who measured a fading rate of 0.67 ± 0.04 %/yr between 1977 and 2004 at the nearby frequency of 927 MHz using the 10-meter diameter radio telescope at Staraya Pustyn' Radio Astronomy Observatory in Russia. However, all of these measurements are inconsistent with the fading rate measured during the epoch of the Baars et al (1977) data: 0.93 ± 0.04 %/yr at 1405 MHz as measured by Baars et al (1977), or 0.886 ± 0.021 %/yr at 1405 MHz as we have remeasured it, in §4.1.…”

supporting

confidence: 92%

“…priors also applied, these two-and three-segment, rebrightening models are favored at the 6.8σ (∆ χ 2 = 49.8, ∆ν = 2) and 6.3σ (∆ χ 2 = 50.4, ∆ν = 4) credible levels, respectively. Vinyaikin (2006), Vinyaikin (2007a), and Vinyaikin (2014) (and references therein) observed Cas A and Cyg A between the two primary epochs considered in this paper, and at a variety of frequencies. We did not include these data in our analysis, because the scatter of these data (compared to their measured uncertainties) suggests that systematics might be an issue, and we do not know enough about these telescopes to model possible systematics (e.g., as we did in §3).…”

Section: Average Fading Model and Fitmentioning

confidence: 67%

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The fading of Cassiopeia A, and improved models for the absolute spectrum of primary radio calibration sources

Trotter

Reichart

Egger

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Based on five years of observations with the 40-foot telescope at Green Bank Observatory (GBO), Reichart & Stephens (2000) found that the radio source Cassiopeia A had either faded more slowly between the mid-1970s and late 1990s than Baars et al. (1977) had found it to be fading between the late 1940s and mid-1970s, or that it had rebrightened and then resumed fading sometime between the mid-1970s and mid-1990s, in L band (1.4 GHz). Here, we present 15 additional years of observations of Cas A and Cyg A with the 40-foot in L band, and three and a half additional years of observations of Cas A, Cyg A, Tau A, and Vir A with GBO's recently refurbished 20-meter telescope in L and X (9 GHz) bands. We also present a more sophisticated analysis of the 40-foot data, and a reanalysis of the Baars et al. (1977) data, which reveals small, but non-negligible differences. We find that overall, between the late 1950s and late 2010s, Cas A faded at an average rate of 0.670 ± 0.019 %/yr in L band, consistent with Reichart & Stephens (2000). However, we also find, at the 6.3σ credible level, that it did not fade at a constant rate. Rather, Cas A faded at a faster rate through at least the late 1960s, rebrightened (or at least faded at a much slower rate), and then resumed fading at a similarly fast rate by, at most, the late 1990s. Given these differences from the original Baars et al. (1977) analysis, and given the importance of their fitted spectral and temporal models for flux-density calibration in radio astronomy, we update and improve on these models for all four of these radio sources. In doing so, we additionally find that Tau A is fading at a rate of 0.102 +0.042 −0.043 %/yr in L band.

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supporting

confidence: 92%

Section: Average Fading Model and Fitmentioning

confidence: 67%

The fading of Cassiopeia A, and improved models for the absolute spectrum of primary radio calibration sources

Trotter

Reichart

Egger

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…In order to construct a broadband SED, we used results from the literature, except for the GeV band where we analyzed public data from the LAT instrument on the Fermi satellite. The radio fluxes were measured at the DKR-1000 radio telescope of the Pushchino Radio Astronomy Observatory (Vitkevich & Kalachev 1965;Artyukh et al 1967) and at the Staraya Pustyn' Radio Astronomy Observatory and taken from Vinyaikin (2006;2007), at the frequencies 38, 151.5, 290, and 927 MHz for the epoch 2005.5. An additional Very Large Array (VLA) 1 flux at 74 MHz corresponding to the epoch 2005.2 was included (Helmboldt & Kassim 2009).…”

Section: Archival Datamentioning

confidence: 99%

Evidence for Cosmic Ray Acceleration in Cassiopeia A

Araya

Cui

2010

ApJ

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Combining archival data taken at radio and infrared wavelengths with stateof-the-art measurements at X-ray and gamma-ray energies, we assembled a broadband spectral energy distribution (SED) of Cas A, a young supernova remnant. Except for strong thermal emission at infrared and X-ray wavelengths, the SED is dominated by non-thermal radiation. We attempted to model the non-thermal SED with a two-zone leptonic model which assumes that the radio emission is produced by electrons that are uniformly distributed throughout the remnant while the non-thermal X-ray emission is produced by electrons that are localized in regions near the forward shock. Synchrotron emission from the electrons can account for data from radio to X-ray wavelengths. Much of the GeV-TeV emission can also be explained by a combination of bremsstrahlung emission and inverse Compton scattering of infrared photons. However, the model cannot fit a distinct feature at GeV energies. This feature can be well accounted for by adding a π 0 emission component to the model, providing evidence for cosmic ray production in Cas A. We discuss the implications of these results.

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“…radio (Baars et al 1977;Anderson et al 1995;Vinyaikin 2007;Helmboldt & Kassim 2009), optical (Reed et al 1995), IR (Smith et al 2009;Delaney el al. 2010), and X-rays (Allen et al 1997;Hwang et al 2004;Helder & Vink 2008;Maeda et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Cassiopeia A (Cas A) is a historically well-known shell type supernova remnant (SNR) observed in almost all wavebands, e.g. radio (Baars et al 1977;Anderson et al 1995;Vinyaikin 2007;Helmboldt & Kassim 2009), optical (Reed et al 1995), IR (Smith et al 2009;Delaney el al. 2010), and X-rays (Allen et al 1997;Hwang et al 2004;Helder & Vink 2008;Maeda et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Origin of gamma-ray emission in the shell of Cassiopeia A

Saha

Ergin

Majumdar

et al. 2014

A&A

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Context. Non-thermal X-ray emission from the shell of Cassiopeia A (Cas A) has been an interesting subject of study, as it provides information about relativistic electrons and their acceleration mechanisms in the shocks. Chandra X-ray observatory revealed the detailed spectral and spatial structure of this SNR in X-rays. The spectral analysis of Chandra X-ray data of Cas A shows unequal flux levels for different regions of the shell, which can be attributed to different magnetic fields in those regions. Additionally, the GeV gamma-ray emission observed by Large Area Telescope on board Fermi Gamma Ray Space Telescope showed that the hadronic processes are dominating in Cas A, a clear signature of acceleration of protons. Aims. To locate the origin of gamma rays based on the X-ray data of the shell of Cas A. We also aim to explain the GeV−TeV gamma-ray data in the context of both leptonic and hadronic scenario. Methods. We modeled the multi-wavelength spectrum of Cas A. We use synchrotron emission process to explain the observed nonthermal X-ray fluxes from different regions of the shell. These result in estimation of the model parameters, which are then used to explain TeV gamma-ray emission spectrum. We also use hadronic scenario to explain both GeV and TeV fluxes simultaneously. Results. Based on this analysis, it has been shown that the southern part of the remnant is bright in TeV gamma rays. We also show that, leptonic model alone cannot explain the GeV−TeV data. Therefore, we need to invoke a hadronic model to explain the observed GeV−TeV fluxes. We found that although pure hadronic model is able to explain the GeV−TeV data, lepto-hadronic model provides the best fit to the data.

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Evolution of the radio spectrum of Cassiopeia A from long-term observations. Observations at 290 and 927 MHz

Cited by 10 publications

References 6 publications

The fading of Cassiopeia A, and improved models for the absolute spectrum of primary radio calibration sources

The fading of Cassiopeia A, and improved models for the absolute spectrum of primary radio calibration sources

Evidence for Cosmic Ray Acceleration in Cassiopeia A

Origin of gamma-ray emission in the shell of Cassiopeia A

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