High-Resolution Radio Imaging of Young Supernovae: SN 1979C, SN 1986J, and SN 2001gd

The high resolution obtained through the use of VLBI gives an unique opportunity to directly observe the interaction of an expanding radio supernova with its surrounding medium. We present here results from our VLBI observations of the young supernovae SN 1979C, SN 1986J, and SN 2001gd.

We present the results of observations of the radio emission from SN 2001gd in NGC5033 from 2002 February 8 through 2006 September 25. The data were obtained using the VLA at wavelengths of 1.3 cm (22.4 GHz), 2 cm (14.9 GHz), 3.6 cm (8.4 GHz), 6 cm (4.9 GHz), and 20 cm (1.5 GHz), with one upper limit at 90 cm (0.3 GHz). In addition, one detection has been provided by the GMRT at 21 cm (1.4 GHz). SN 2001gd was discovered in the optical well past maximum light, so that it was not possible to obtain many of the early radio measurements that are important for estimating the local CSM properties. Only at 20 cm were turn-on data available. However, our analysis and fitting of the radio light curves, along with the assumption that the Type IIb SN 2001gd resembles the much better studied Type IIb SN 1993J, enables us to describe the radio evolution as being very regular through day ~550 and consistent with a nonthermal-emitting model with a thermal absorbing CSM. The presence of SSA at early times is implied by the data, but determination of the exact relationship between the SSA component from the emitting region and the free-free absorption component from the CSM is not possible, as there are insufficient early measurements to distinguish between models. After day ~550, the radio emission exhibits a dramatically steeper decline rate, which, assuming similarity to SN 1993J, can be described as an exponential decrease with an e-folding time of 500 days. We interpret this abrupt change in the radio flux density decline rate as implying a transition of the shock front into a more tenuous region of circumstellar material. A similar change in radio evolution has been seen earlier in other SNe, such as SN 1988Z, SN 1980K, and SN 1993J.

We give an overview of circumstellar interaction in young radio supernovae, as seen through the eyes of Very-long-baseline interferometry (VLBI) observations. The resolution attained by such observations (≲ 1 mas) is a powerful tool to probe the interaction that takes place after a supernova goes off. The direct imaging of supernovae has permitted, among other things, to estimate the deceleration of their expansion, and to obtain information on the ejecta and circumstellar density profiles. Unfortunately, only a handful of radio supernovae are close and bright enough as to permit their study with VLBI. We present here results from our high-resolution observations of the nearby radio supernovae SN 1979C, SN 1986J, SN 1993J, and SN 2001gd.

view Abstract Citations (167) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio Emission from Supernovae. II. SN 1986J: A Different Kind of Type II Weiler, Kurt W. ; Panagia, Nino ; Sramek, Richard A. Abstract SN 1986J is the most luminous radio supernova (RSN) which has ever been discovered, being more than 3 times brighter than SN 1979C. We present extensive new radio observations for the period from 1986 May through 1988 December at the five VLA wavelengths of 90, 20, 6, 2, and 1.3 cm. All other known radio data from the literature are also collected to assemble almost 100 measurements of the source. These are analyzed and are found to be poorly described by the external, thermal absorbing screen model which has been very successful for all previously known radio supernovae. However, a slightly more complex model allowing for the possibility of mixed thermal absorbers and nonthermal emitters is found to describe the overall properties of the radio emission from SN 1986J quite well. We are also able to estimate the properties of an external absorbing medium and apparently observe small variations in the optical depth of this external medium. The implications of these new radio data in terms of the mass loss from the presupernova star, the ejected mass in the supernova explosion, and the probable main-sequence mass of the progenitor star are all discussed. In particular, we find M_dot_ ~ 2.4 x 10^-4^ M_sun_ yr^-1^, M(ejecta) >= 1.9 M_sun_, and 20 M_sun_ < M(progenitor) < 30 M_sun_. Also, the available data at optical wavelengths are reconsidered, showing that SN 1986J could have been "normally" bright at maximum light (M_v_ ~ -18 mag) and still have gone undetected. Considering all of these data, we conclude that SN 1986J represents a relatively rare subclass of Type II supernovae produced by massive progenitors. We also speculate that in SN l986J we may be observing the birth of an object like the Crab Nebula--a plerion. Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/169444 Bibcode: 1990ApJ...364..611W Keywords: Radio Astronomy; Radio Emission; Radio Sources (Astronomy); Stellar Radiation; Supernovae; Light Curve; Radio Observation; Radio Spectra; Very Large Array (Vla); Astrophysics; RADIATION MECHANISMS; STARS: INDIVIDUAL ALPHANUMERIC: SN 1986J; STARS: RADIO RADIATION; STARS: SUPERNOVAE full text sources ADS | data products SIMBAD (6) NED (4) Related Materials (1) Part 1: 1989ApJ...336..421W

The formation of a core collapse supernovae (SNe) results in a fast (but non- or mildly-relativistic) shock wave expanding outwards into the surrounding medium. The medium itself is likely modified due to the stellar mass-loss from the massive star progenitor, which may be Wolf-Rayet stars (for Type Ib/c SNe), red supergiant stars (for type IIP and perhaps IIb and IIL SNe), or some other stellar type. The wind mass-loss parameters determine the density structure of the surrounding medium. Combined with the velocity of the SN shock wave, this regulates the shock acceleration process. In this article we discuss the essential parameters that control the particle acceleration and gamma-ray emission in SNe, with particular reference to the Type IIb SN 1993J. The shock wave expanding into the high density medium leads to fast particle acceleration, giving rise to rapidly-growing plasma instabilities driven by the acceleration process itself. The instabilities grow over intraday timescales. This growth, combined with the interplay of non-linear processes, results in the amplification of the magnetic field at the shock front, which can adequately account for the magnetic field strengths deduced from radio monitoring of the source. The maximum particle energy can reach, and perhaps exceed, 1 PeV, depending on the dominant instability. The gamma-ray signal is found to be heavily absorbed by pair production process during the first week after the outburst. We derive the time dependent particle spectra and associated hadronic signatures of secondary particles (gamma-ray, leptons and neutrinos) arising from proton proton interactions. We find that the Cherenkov Telescope Array (CTA) should be able to detect objects like SN 1993J above 1 TeV. We predict a low neutrino flux above 10 TeV, implying a detectability horizon with current or planned neutrino telescopes of 1 Mpc.

We review advances in VLBI observations of radio supernovae not considered in earlier reviews [1] [2] [3], in particular of supernovae SN 1979C, SN 1986J, SN 1993J, and SN2004et. SN 1979C is a supernova in practically free expansion. SN 1986J displays in its center an inverted spectrum compact source likely associated to the yet undetected pulsar or rest of star collapse. SN 1993J is a supernova in self‐similar expansion. However, it shows an enhanced deceleration at 6cm due to the characteristics of the radio emission in the shell. SN 2004et's asymmetric structure is interpreted as that of an expanding shell with 2 hot spots. For SN 2004et, the synchrotron self‐absorption seems to be negligible compared to circumstellar free‐free absorption.

Radio and X-ray studies of young supernovae probe the interaction between the supernova shock waves and the surrounding medium and give clues to the nature and past of the progenitor star. Here we discuss the early emission from type Ic SN 2002ap and argue that repeated Compton boosting of optical photons by hot electrons presents the most natural explanation of the prompt X-ray emission. We describe the radio spectrum of another type Ic SN 2003dh (GRB030329) obtained with combined GMRT and VLA data. We report on the low frequency radio monitoring of SN 1995N and our objectives of distinguishing between competing models of X-ray emission from this SN and the nature of its progenitor by X-ray spectroscopy. Radio studies on SN 2001gd, SN 2001ig and SN 2002hh are mentioned.

SummaryRadio and X-ray studies of young supernovae probe the interaction between the supernova shock waves and the surrounding medium and give clues to the nature and past of the progenitor star. Here we discuss the early emission from type Ic SN 2002ap and argue that repeated Compton boosting of optical photons by hot electrons presents the most natural explanation of the prompt X-ray emission. We describe the radio spectrum of another type Ic SN 2003dh (GRB030329) obtained with combined GMRT and VLA data. We report on the low frequency radio monitoring of SN 1995N and our objectives of distinguishing between competing models of X-ray emission from this SN and the nature of its progenitor by X-ray spectroscopy. Radio studies on SN 2001gd, SN 2001ig and SN 2002hh are mentioned.

Spectroscopic and photometric observations of the nearby Type Ia Supernova (SN Ia) SN 2014J are presented. Spectroscopic observations were taken -8 to +10 d relative to B-band maximum, using FRODOSpec, a multi-purpose integral-field unit spectrograph. The observations range from 3900 AA to 9000 AA. SN 2014J is located in M82 which makes it the closest SN Ia studied in at least the last 28 years. It is a spectrosopically normal SN Ia with high velocity features. We model the spectra of SN 2014J with a Monte Carlo (MC) radiative transfer code, using the abundance tomography technique. SN 2014J is highly reddened, with a host galaxy extinction of E(B-V)=1.2 (R_V=1.38). It has a $\Delta$m_15(B) of 1.08$\pm$0.03 when corrected for extinction. As SN 2014J is a normal SN Ia, the density structure of the classical W7 model was selected. The model and photometric luminosities are both consistent with B-band maximum occurring on JD 2456690.4$\pm$0.12. The abundance of the SN 2014J behaves like other normal SN Ia, with significant amounts of silicon (12% by mass) and sulphur (9% by mass) at high velocities (12300 km s$^{-1}$) and the low-velocity ejecta (v<6500 km s$^{-1}$) consists almost entirely of $^{56}$Ni.

In this work we present data from observations with the MAGIC telescopes of SN 2014J detected in January 21 2014, the closest Type Ia supernova since Imaging Air Cherenkov Telescopes started to operate. We probe the possibility of very-high-energy (VHE; $E\geq100$ GeV) gamma rays produced in the early stages of Type Ia supernova explosions. We performed follow-up observations after this supernova explosion for 5 days, between January 27 and February 2 in 2014. We search for gamma-ray signal in the energy range between 100 GeV and several TeV from the location of SN 2014J using data from a total of $\sim5.5$ hours of observations. Prospects for observing gamma-rays of hadronic origin from SN 2014J in the near future are also being addressed. No significant excess was detected from the direction of SN 2014J. Upper limits at 95$\%$ confidence level on the integral flux, assuming a power-law spectrum, d$F/$d$E\propto E^{-\Gamma}$, with a spectral index of $\Gamma=2.6$, for energies higher than 300 GeV and 700 GeV, are established at $1.3\times10^{-12}$ and $4.1\times10^{-13}$ photons~cm$^{-2}$s$^{-1}$, respectively. For the first time, upper limits on the VHE emission of a Type Ia supernova are established. The energy fraction isotropically emitted into TeV gamma rays during the first $\sim10$ days after the supernova explosion for energies greater than 300 GeV is limited to $10^{-6}$ of the total available energy budget ($\sim 10^{51}$ erg). Within the assumed theoretical scenario, the MAGIC upper limits on the VHE emission suggest that SN 2014J will not be detectable in the future by any current or planned generation of Imaging Atmospheric Cherenkov Telescopes.

Context. Observations of radio emission from young core-collapse supernovae (CCSNe) allow one to study the history of the pre-supernova stellar wind, trace the density structure of the ejected material, and probe the magnetohydrodynamics that describe the interaction between the two, as the forward shock expands into the circumstellar medium. The radio shell of supernova SN 1993J has been observed with very long baseline interferometry (VLBI) for ∼20 years, giving one of the most complete pictures of the evolution of a CCSN shock. However, different results about the expansion curve and properties of the radio-emitting structure have been reported by different authors, likely due to systematics in the data calibration and/or model assumptions made by each team. Aims. We aim to perform an analysis of the complete set of VLBI observations of SN 1993J that accounts for different instrumental and source-intrinsic effects, in order to retrieve robust conclusions about the shock expansion and physics in SN 1993J. Methods. We have explored the posterior probability distribution of a complete data model, using a technique based on Markov chains. Our model accounts for antenna calibration effects, as well as different kinds of radio-emission structures for the supernova. Results. The posterior parameter distributions strongly favor a spherical shell-like radio structure with a nonuniform radial intensity profile, with a broad brightness distribution that peaks close to or just above the region where the contact discontinuity is expected to be located. Regarding the shell expansion, the full dataset can be well described using one single deceleration parameter, β ∼ 0.80, being the shell outer radius R ∝ tβ. There is clear evidence of a relative widening of the shell width beyond day 2600−3300 after the explosion, which is due to an increased deceleration of the inner shell boundary. This is similar to findings previously reported by other authors. Conclusions. The radial intensity profile and the late evolution of the shell suggest a scenario in which the magnetic field is amplified mainly by the Rayleigh-Taylor instability, which emanates from the contact discontinuity. Furthermore, the increased deceleration of the inner boundary indicates that the reverse shock enters a region of the ejecta at around 3000 days, where the density distribution is substantially flatter. Such a weakening of the reverse shock can also explain the achromatic break in the radio light curves, which occurs at the same time. The deduced radial intensity distribution for SN 1993J is quite similar to that observed in the spatially well-resolved supernova remnant Cassiopeia A.

Recent works have studied the late-time light curves of Type Ia supernovae (SNe Ia) when these were older than 500 days past B-band maximum light. Of these, SN 2014J, which exploded in the nearby galaxy M82, was studied with the Advanced Camera for Surveys onboard the Hubble Space Telescope (HST) by Yang et al. Here, I report complementary photometry of SN 2014J taken with the HST Wide Field Camera 3 when it was ∼360–1300 days old. My F555W measurements are consistent with the F606W measurements of Yang et al., but the F438W measurements are ∼1 mag fainter than their F475W measurements. I corroborate their finding that, even though SN 2014J has spatially resolved light echoes, its photometry is not contaminated by an unresolved echo. Finally, I compare the F438W and F555W light curves of SN 2014J to those of the other late-time SNe Ia observed to date and show that more intrinsically luminous SNe have slower light curve decline rates. This is consistent with the correlation claimed by Graur et al., which was based on a comparison of pseudo-bolometric light curves. By conducting a direct comparison of the late-time light curves in the same filters, I remove any systematic uncertainties introduced by the assumptions that go into constructing the pseudo-bolometric light curves, thus strengthening the Graur et al. claim.

I present an investigation into Type Ia Supernovae (SNe Ia). The aim of this investigation is to explain the physics and diversity of SNe Ia, motivated by the fact that, although SNe Ia are known to come from a thermonuclear explosion of a C+O Chandrasekhar mass (Ch-mass) White Dwarf (WD), their exact explosion scenario is one of debate, and their full diversity is not fully understood. As SNe Ia are used as cosmological distance probes, understanding their explosions and progenitors systems in more detail could have important consequences. To examine the diversity of SNe Ia, I first present a large sample analysis of their B and V - band light curves, separated by host galaxy type. A new method for calculating host galaxy extinction is implemented and the width luminosity relation (WLR) is examined. After correction for host galaxy extinction, ‘normal’ SNe Ia (∆m15(B) < 1.6 mag) fill a larger parameter space in the WLR than previously suggested. Even excluding fast declining SNe, ‘normal’ (MB <−18mag) SNeIa from star forming(S- F) and passive galaxies are distinct. This may indicate that various progenitor channels are prevalent in different galaxy types. Furthermore, it was also confirmed that sub- luminous SNe Ia tend to favour passive galaxies, which implies that this subset of SNe Ia come from an older progenitor system. There was a lack of transition SNe Ia in the dataset used in this project. These are SNe Ia with a luminosity between normal and sub-luminous SNe Ia. Understanding transitional SNe Ia is important in determining whether sub-luminous SNe Ia are a totally different population. With the aim of understanding how normal SNe explode, I first turn my attention to SN 2014J. SN 2014J was the closest type Ia in the last 410 years, and it was a once in a life time opportunity to study. Therefore, a detailed spectroscopic and photometric analysis and abundance stratification modelling of SN 2014J is presented. SN 2014J is a spectroscopically normal type Ia SN with a B band decline rate of 0.95 mag, before correction for extinction. It was located in the dusty starburst galaxy M82, and does not follow the average Galactic extinction law of Rv = 3.1. With the knowledge about the diversity of SNe Ia and the ability to carry out de- tailed modelling, SN 1986G was next chosen to be modelled. SN 1986G sits in an interesting area of parameter space in the WLR. It is located in the ‘gap’ between normal and sub-luminous SNe Ia. It has been theorised that sub-luminous SNe Ia come from a different progenitor system than standard SNe Ia. Therefore, understanding SN properties in this ‘gap’ is important for determining at which point SNe Ia properties begin to diverge from the normal scenario. A full abundance tomography modelling of SN 1986G was carried out. It was found that this SN is a low energy Chandrasekhar mass explosion. It had 70% of the energy of a standard W7 model. These findings raise the possibility that only SNe Ia with very large decline rates deviate from a Chandrasekhar mass.

The radio non-detection of two Type Ia supernovae (SNe) SN 2011fe and SN 2014J has been modeled considering synchrotron radiation from shock accelerated electrons in the SN shock fronts. With 10% each of the bulk kinetic energy in electric and magnetic fields, a very low density of the medium around both the SNe has been estimated from the null detection of radio emission, around 1 and 4 years after the explosion of SNe 2014J and 2011fe, respectively. Keeping the fraction of energy in electrons fixed at 10%, a medium with particle density ~ 1cm−3 is found when 1% of the post shock energy is in magnetic fields. In case of a wind medium, the former predicts the mass loss rate Ṁ to be &lt;10−9M⊙ yr−1, and the latter gives an upper limit ~10−9M⊙ yr−1, for wind velocity of 100 kms−1, for both the SNe. The tenuous media obtained from this study favor the double degenerate as well as a spin up/down model for both SNe 2011fe and 2014J.

We investigate line formation processes in Type IIb supernovae (SNe) from 100 to 500 days post-explosion using spectral synthesis calculations. The modeling identifies the nuclear burning layers and physical mechanisms that produce the major emission lines, and the diagnostic potential of these. We compare the model calculations with data on the three best observed Type IIb SNe to-date - SN 1993J, SN 2008ax, and SN 2011dh. Oxygen nucleosynthesis depends sensitively on the main-sequence mass of the star and modeling of the [O I] 6300, 6364 lines constrains the progenitors of these three SNe to the M_ZAMS=12-16 M_sun range (ejected oxygen masses 0.3-0.9 M_sun), with SN 2011dh towards the lower end and SN 1993J towards the upper end of the range. The high ejecta masses from M_ZAMS >= 17 M_sun progenitors give rise to brighter nebular phase emission lines than observed. Nucleosynthesis analysis thus supports a scenario of low/moderate mass progenitors for Type IIb SNe, and by implication an origin in binary systems. We demonstrate how oxygen and magnesium recombination lines may be combined to diagnose the magnesium mass in the SN ejecta. For SN 2011dh, a magnesium mass of of 0.02-0.14 M_sun is derived, which gives a Mg/O production ratio consistent with the solar value. Nitrogen left in the He envelope from CNO-burning gives strong [N II] 6548, 6583 emission lines that dominate over H-alpha emission in our models. The hydrogen envelopes of Type IIb SNe are too small and dilute to produce any noticeable H-alpha emission or absorption after ~150 days, and nebular phase emission seen around 6550 A is in many cases likely caused by [N II] 6548, 6583. Finally, the influence of radiative transport on the emergent line profiles is investigated...(abridged)