scholarly journals Radio Emission from SN 1987A

1996 ◽  
Vol 145 ◽  
pp. 309-315 ◽  
Author(s):  
L. Staveley-Smith ◽  
R. N. Manchester ◽  
A. K. Tzioumis ◽  
J. E. Reynolds ◽  
D. S. Briggs
Keyword(s):  
Radio Emission ◽  
Radio Observations ◽  
Density Profiles ◽  
Circumstellar Material ◽  
Sn 1987A ◽  
Supernova 1987A ◽  
Radio Outburst ◽  
Post Shock ◽  
Two Phases ◽  
Relativistic Particles

We review the first six years of radio observations of Supernova 1987A. The evolution can be divided into two phases: the initial radio outburst which lasted a few weeks, and the period from mid-1990 to the present, during which the radio emission has steadily increased. Both phases can be explained by a small fraction (0.1-0.5%) of the post-shock thermal energy being converted to energy in relativistic particles and magnetic fields, which give rise to synchrotron radiation. The optical depths, densities and density profiles for the pre-shocked circumstellar material are somewhat different for the two phases, but consistent with models of the density structure of the material within the circumstellar ring. New high-resolution radio observations show that the SN shock front is already at about three-quarters of the radius of the circumstellar ring, and that there exists a bright equatorial component of emission aligned with this ring which is probably due to a polar density gradient in the ‘hourglass’ structure.

Structure in the Radio Remnant of Supernova 1987A

1993 ◽  
Vol 10 (4) ◽  
pp. 331-334 ◽  
Author(s):  
L. Staveley-Smith ◽  
R.N. Manchester ◽  
M.J. Kesteven ◽  
A.K. Tzioumis ◽  
J.E.R. Reynolds
Keyword(s):  
Radio Emission ◽  
Expansion Velocity ◽  
Synchrotron Emission ◽  
Low Density ◽  
Radial Expansion ◽  
X Ray ◽  
Circumstellar Material ◽  
Sn 1987A ◽  
Supernova 1987A ◽  
Compact Array

AbstractThe radio emission associated with SN 1987A appears to be synchrotron emission resulting from the acceleration of electrons at the interface between the outward moving shock wave and clumps of circumstellar material. The Australia Telescope Compact Array is now able to resolve this region, which has dimensions of ~ arcsec, revealing a slight (10%) asphericity in the distribution of the low density gas within the [OIII] circumstellar ring. Assuming that the radio emission arises from a region just behind the shock front, we deduce a mean radial expansion velocity, from 1987 to 1992, of 29 200 kms. First observed contact of the shock with the [OIII] circumstellar ring could occur as early as mid-1993, depending on the deceleration in the intervening gas. This will probably be closely followed by shock-excited optical lines, a strong X-ray outburst and a further increase in the radio emission.

AT Monitoring of SNR 1987A

1991 ◽  
Vol 9 (1) ◽  
pp. 108-108
Author(s):  
L. Staveley-Smith ◽  
R. N. Manchester ◽  
M. J. Kesteven
Keyword(s):  
Radio Emission ◽  
High Velocity ◽  
High Sensitivity ◽  
Circumstellar Material ◽  
Sn 1987A ◽  
Upper Limit ◽  
Compact Array

AbstractThe prompt radio emission associated with SN 1987A appeared and disappeared within the space of a few days. The next radio emission is expected as the high velocity ejecta expand into the circumstellar material. The evidence from the timing of the initial UV-flash is that this stage may occur shortly. We have therefore begun to monitor the field around SNR 1987A at high sensitivity with the Australia Telescope Compact Array. At λ6cm, an upper limit to the radio emission of 180μJy has been obtained. Continued observations are planned.

The Elusive Radio Source SN 1987A

1988 ◽  
Vol 7 (4) ◽  
pp. 382-383
Author(s):  
John E. Reynolds ◽  
R.W. Livermore ◽  
David L. Jauncey ◽  
Robert A. Preston ◽  
Samuel Gulkis ◽  
...  
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Neutrino Emission ◽  
Deep Space ◽  
Space Communications ◽  
Sn 1987A ◽  
Radio Outburst

AbstractFollowing the ‘prompt’ radio outburst seen soon after the neutrino emission in SN 1987A (Turtle et al. 1987), we initiated a program to monitor the supernova at the Tidbinbilla Deep Space Communications Complex at 8.4 GHz in a search for radio emission from the expanding remnant. No radio emission has been detected to date (DOY 151, May 30 1988).

Radio Supernova 1987 A

1992 ◽  
Vol 10 (1) ◽  
pp. 38-40 ◽  
Author(s):  
Lewis Ball ◽  
J.G. Kirk
Keyword(s):  
Shock Wave ◽  
Synchrotron Radiation ◽  
Radio Emission ◽  
Density Jump ◽  
Circumstellar Material ◽  
Sn 1987A

AbstractThe reappearance of radio emission from SN 1987A is discussed. We propose a model involving synchrotron radiation from electrons which are accelerated when the expanding supernova shock wave runs into a density jump in the circumstellar material, and which then expand adiabatically.

scholarly journals Initial Radio Observations of SN1987a in the Large Magellanic Cloud

1988 ◽  
Vol 129 ◽  
pp. 189-189
Author(s):  
A. J. Turtle ◽  
D. Campbell-Wilson ◽  
J. D. Bunton ◽  
D. L. Jauncey ◽  
M. J. Kesteven ◽  
...  
Keyword(s):  
Flux Density ◽  
Southern Hemisphere ◽  
Radio Burst ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Radio Observations ◽  
Radio Monitoring ◽  
Supernova 1987A ◽  
Peak Flux ◽  
Radio Outburst

A prompt radio burst has been observed from the supernova 1987a in the Large Magellanic Cloud. Observations were made at 0.843, 1.415, 2.29, and 8.41 GHz. At frequencies around 1 GHz, the peak flux density reached about 150 mJy and occurred within four days of the supernova. This event may be a weak precursor to a major radio outburst of the type previously observed in other extragalactic supernovae. Radio monitoring of the supernova is continuing at each of the above frequencies, and coordination is underway of a southern hemisphere VLBI array to map the radio outburst region as it expands. Differential astrometry carried out on prime-focus plates taken with the Anglo-Australian telescope indicates that the component, star 1, of Sanduleak's star SK-69202 is within 0.05 ± 0.13 arcsec of the supernova.

scholarly journals Spectral Evolution of the X-Ray Remnant of SN 1987A: A High-resolution Chandra HETG Study

2021 ◽  
Vol 922 (2) ◽  
pp. 140
Author(s):  
Aravind P. Ravi ◽  
Sangwook Park ◽  
Svetozar A. Zhekov ◽  
Marco Miceli ◽  
Salvatore Orlando ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Analysis ◽  
Thermal Conditions ◽  
Line Flux ◽  
Spectral Evolution ◽  
X Ray ◽  
Circumstellar Material ◽  
Sn 1987A ◽  
Volume Emission ◽  
Post Shock

Abstract Based on observations with the Chandra X-ray Observatory, we present the latest spectral evolution of the X-ray remnant of SN 1987A (SNR 1987A). We present a high-resolution spectroscopic analysis using our new deep (∼312 ks) Chandra HETG observation taken in 2018 March as well as archival Chandra grating spectroscopic data taken in 2004, 2007, and 2011 with similarly deep exposures (∼170–350 ks). We perform detailed spectral model fits to quantify changing plasma conditions over the last 14 yr. Recent changes in electron temperatures and volume-emission measures suggest that the shocks moving through the inner ring have started interacting with less dense circumstellar material, probably beyond the inner ring. We find significant changes in the X-ray line-flux ratios (among H- and He-like Si and Mg ions) in 2018, consistent with changes in the thermal conditions of the X-ray-emitting plasma that we infer based on the broadband spectral analysis. Post-shock electron temperatures suggested by line-flux ratios are in the range ∼0.8–2.5 keV as of 2018. We do not yet observe any evidence of substantial abundance enhancement, suggesting that the X-ray emission component from the reverse-shocked metal-rich ejecta is not yet significant in the observed X-ray spectrum.

Conditions needed for generation of type II radio emission in the interplanetary space

2021 ◽  
Author(s):  
Immanuel Christopher Jebaraj ◽  
Athanasios Kouloumvakos ◽  
Jasmina Magdalenic ◽  
Alexis Rouillard ◽  
Vratislav Krupar ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Radio Emission ◽  
Interplanetary Space ◽  
Region Of Interest ◽  
Type Ii ◽  
Radio Observations ◽  
Wave Parameters ◽  
First Results ◽  
Radio Signature

<p>Eruptive events such as Coronal mass ejections (CMEs) and flares cangenerate shock waves. Tracking shock waves and predicting their arrival at Earth is a subject of numerous space weather studies. Ground-based radio observations allow us to locate shock waves in the low corona while space-based radio observations provide us opportunity to track shock waves in the inner heliosphere. We present a case study of CME/flare event, associated shock wave and its radio signature, i.e. type II radio burst.</p><p>In order to analyze the shock wave parameters, we employed a robust paradigm. We reconstructed the shock wave in 3D using multi-viewpoint observations and modelled the evolution of its parameters using a 3D MHD background coronal model produced by the MAS (Magnetohydrodynamics Around a Sphere).</p><p>To map regions on the shock wave surface, possibly associated with the electron acceleration, we combined 3D shock modelling results with the 3D source positions of the type II burst obtained using the radio triangulation technique. We localize the region of interest on the shock surface and examine the shock wave parameters to understand the relationship between the shock wave and the radio event. We analyzed the evolution of the upstream plasma characteristics and shock wave parameters during the full duration of the type II radio emission. First results indicate that shock wave geometry and its relationship with shock strength play an important role in the acceleration of electrons responsible for the generation of type II radio bursts.</p>

scholarly journals Some Observations of Shell-type Galactic Radio Sources

1967 ◽  
Vol 20 (3) ◽  
pp. 297 ◽  
Author(s):  
ER Hill
Keyword(s):  
Radio Emission ◽  
Spherical Symmetry ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Milky Way ◽  
Radio Sources ◽  
Radio Observations ◽  
Shell Type ◽  
Rosette Nebula ◽  
Galactic Radio

Radio evidence for two new supernova remnants in the Southern Milky Way is presented. Some new observations of the known supernova remnant, source 1439-62, and of the Rosette nebula, a shell source but not a supernova remnant, are also presented. The problem of finding model shells to fit the radio observations is considered and it is shown that the radio emission from 1439-62 is unlikely to originate in a shell with spherical symmetry.

scholarly journals Jupiter's Radiation Belts and Upper Atmosphere

1974 ◽  
Vol 65 ◽  
pp. 375-383
Author(s):  
Joseph J. Degioanni ◽  
John R. Dickel
Keyword(s):  
Radio Emission ◽  
Radiation Belts ◽  
Upper Atmosphere ◽  
Mixing Ratio ◽  
Frequency Range ◽  
Emission Data ◽  
High Energies ◽  
Isotropic Distribution ◽  
Relativistic Particles ◽  
Flat Distribution

Models of Jupiter's radiation belts have been constructed to determine the distribution of particles and their energies which will produce the observed decimetric radio emission. Data on the spectrum and the variation of emission with Jovian longitude have been used to show that the relativistic particles have a nearly isotropic distribution with high energies (of order 100 MeV) within 2 Jovian radii and a very flat distribution in the equatorial plane of low energy particles further out in the magnetosphere.Subtraction of the emission predicted by this model from the total radio emission shows that the thermal contribution in the frequency range between 3000 and 10000 MHz is somewhat less than had been previously expected. (The brightness temperature of the planetary disk is 180 K at 3000 MHz, for example.) This suggests that the ammonia mixing ratio in Jupiter's upper atmosphere may be as high as 0.002.

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