VLBI Observations of SN 1979C and SN 1986J

We summarize our results on multi-epoch VLBI observations of SN 1979C in the galaxy M100 in Virgo, and of SN 1986 in the galaxy NGC 891. From t = 3.7 to 22 yr after the explosion, SN 1979C expands ≽ t m, almost freely, with m = 0.95 ± 0.03. For a total kinetic energy of 3 × 1051 erg, the expansion result requires a mass-loss to wind-velocity ratio for the progenitor of only 1 × 10−5 M⨀ yr−1per 10 km s−1, an order of magnitude smaller than estimated from radio light-curve fitting. We show a first image with slightly discernible structure of the supernova. For SN 1986J we present five images from 1987 to 2002 and show our result on moderately to strongly decelerated expansion with m = 0.71 ± 0.11. We comment on our result of an inversion of the radio spectrum in terms of the emergence of a possible pulsar nebula.

VLBI observations at 5 GHz have revealed that supernova 1979C, in the galaxy M100 in the Virgo cluster, has shell structure. The shell is approximately circular with the 50% contour deviating from a circle by an rms of no more than 8% of the radius. The brightness distribution along the ridge may vary. The position of the center of the shell is at R.A.=12h 22m 58.66758s and decl.=15^o 47' 51.9695 (J2000), with a standard error of 0.8 mas in each of the coordinates. No isolated central component is visible above a flux density limit of ~0.15 mJy which corresponds to an upper limit of ~15 times the corresponding spectral luminosity of the Crab Nebula. The radio lightcurve is clearly falling again and the radio spectrum is now flatter than at earlier times. SN 1979C is only the fourth, and oldest (optically identified) supernova of which a detailed image could be obtained.

A new method of determining extragalactic distances and inferring Ho is presented. The method combines the determinations of radial expansion velocities of supernovae via optical spectroscopy and the determinations of angular expansion velocities via Very Long Baseline Interfer ometry (VLBI). The data of two recent supernovae, SN 1979c in the galaxy M100 and SN 1980k in the galaxy NGC 6946, have been analyzed. We obtained an estimate of the distance, D, to M100 of 11.4αv ≲ D [Mpc] ≲ 24.4αv and a lower limit of the distance to NGC 6946 of D > 2.3αv [Mpc] with the factor av coupling the expansion velocities of the “radiosphere” and the photosphere and being most likely ≲ 1. These distances are equivalent to 100x,1' Ho [km s−1 Mpc−1] ≲ 40α v −1 and Ho < 230α v t-1 1 km s−1 Mpc−1 for the two measurements, respectively.

We report on VLBI measurements of supernova 2014C at several epochs between $t = 384$ and 1057 days after the explosion. SN 2014C was an unusual supernova that initially had Type Ib optical spectrum, but after $t = 130$ d it developed a Type IIn spectrum with prominent H$\alpha$ lines, suggesting the onset of strong circumstellar interaction. Our first VLBI observation was at $t = 384$ d, and we find that the outer radius of SN 2014C was $(6.40 \pm 0.26) \times 10^{16}$ cm (for a distance of 15.1 Mpc), implying an average expansion velocity of $19300 \pm 790$ \kms\ up to that time. At our last epoch, SN 2014C was moderately resolved and shows an approximately circular outline but with an enhancement of the brightness on the W side. The outer radius of the radio emission at $t = 1057$ d is $(14.9 \pm 0.6) \times 10^{16}$ cm. We find that the expansion between $t = 384$ and 1057 d is well described by a constant velocity expansion with $v = 13600 \pm 650$ \kms. SN 2014C had clearly been substantially decelerated by $t = 384$ d. Our measurements are compatible with a scenario where the expanding shock impacted upon a shell of dense circumstellar material during the first year, as suggested by the observations at other wavelengths, but had progressed through the dense shell by the time of the VLBI observations.

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

We have obtained an 8.4 GHz Very Large Array (VLA) A-array map of the starburst galaxy M82 with a resolution Full Width at Half Maximum (FWHM) approximately 0.182 sec. About 50 compact radio sources in the central region of M82 were detected with a peak surface brightness approximately greater than 10(exp -17) W/Hz/sq m/sr. Comparison with previous observations shows that most sources are declining in flux. Three previously visible sources have faded into the background of our map (approximately less than 0.2 mJy/beam), while a few sources, including the second and third brightest radio sources in M82, may have increased slightly in flux over the last decade. No new radio supernova was found. The birth rate of the compact radio sources is estimated to be 0.11 + or - 0.05/yr. We attribute the population of such bright, small supernova remnants (SNRs) in M82 to the high pressure in the central region that can truncate the mass loss during a red supergiant phase or allow dense ionized clouds to be present. The compact radio sources obey a Sigma(radio surface brightness) - D(diameter) relation which is remarkably similar to that followed by supernova remnants in the Galaxy and the Magellanic Clouds and by two of the strongest known extragalactic radio supernovae: SN 1986J and SN 1979C. A least-squares fit to the SNR data gives: Sigma(sub 8.4 GHz) (W/Hz/sq m/sr) = 4.4 x 10(exp -16) D(sub pc)(exp -3.5 +/- 0.1) covering seven orders of magnitude in Sigma. Possible selection effects are discussed and a theoretical discussion of the correlation is presented.

SN 2014C was originally classified as a Type Ib supernova, but at phase ϕ = 127 days, post-explosion strong Hα emission was observed. SN 2014C has since been observed in radio, infrared, optical and X-ray bands. Here we present new optical spectroscopic and photometric data spanning ϕ = 947–2494 days post-explosion. We address the evolution of the broadened Hα emission line, as well as broad [O iii] emission and other lines. We also conduct a parallel analysis of all publicly available multiwavelength data. From our spectra, we find a nearly constant Hα FWHM velocity width of ∼2000 km s−1 that is significantly lower than that of other broadened atomic transitions (∼3000–7000 km s−1) present in our spectra ([O i] λ6300; [O iii] λ λ4959, 5007; He i λ7065; [Ca ii] λ λ7291, 7324). The late radio data demand a fast forward shock (∼10,000 km s−1 at ϕ = 1700 days) in rarified matter that contrasts with the modest velocity of the Hα. We propose that the infrared flux originates from a toroidal-like structure of hydrogen surrounding the progenitor system, while later emission at other wavelengths (radio, X-ray) likely originates predominantly from the reverse shock in the ejecta and the forward shock in the quasi-spherical progenitor He-wind. We propose that the Hα emission arises in the boundary layer between the ejecta and torus. We also consider the possible roles of a pulsar and a binary companion.

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.

We review the possible evolutionary paths from massive stars to explosive endpoints as various types of supernovae associated with Population I and hence with massive stars: Type II-P, Type II-L, Type Ib, Type Ic, and the hybrid events SN 1987K and SN 1993J. We identify SN 1954A as another hybrid event from the evidence for both H and He in its spectrum with velocities nearly the same as SN 1983J. Evidence for ejected 56Ni mass of ∼ 0.07 M⊙ suggests that SN II-P underwent standard iron core collapse, not collapse of an O-Ne-Mg core nor thermonuclear explosion of a C-O core. Most SN II-P presumably arise in single stars or wide binaries of ∼ 10 - 20 M⊙. There may be indirect evidence for duplicity in some cases in the form of strong Ba II lines, such as characterized SN 1987A. SN II-L are recognizably distinct from typical SN II-P and must undergo a significantly different evolution. Despite indications that SN II-L have small envelopes that may be helium enriched, they are also distinct from events like SN 1993J that must have yet again a different evolution. The SN II-L that share a common luminosity seem to have ejected a small nickel mass and hence may come from stars with O-Ne-Mg cores. The amount of nickel ejected by the exceptionally bright events, SN 1980K and SN 1979C, remains controversial. SN Ib require the complete loss of the H envelope, either to a binary companion or to a wind. The few identified have relatively large ejecta masses. It is not clear what evolutionary processes distinguish SN Ib’s evolving in binary systems from hybrid events that retain some H in the envelope. SN Ic events are both H and He deficient. Binary models.that can account for transfer of an extended helium envelope from low mass helium cores, ∼ 2 to 4 M⊙, imply C-O core masses that are roughly consistent with that deduced from the ejecta mass plus a neutron star, ∼ 2 to 3 M⊙. It is possible that the hybrid events are the result of Roche lobe overflow and that the “pure” events, SN Ib or SN Ic, result from common envelope evolution.

We present radio observations of the Type Ic (helium-poor Type Ib) supernova SN 1990B in NGC 4568 made with the Very Large Array at 20, 6, 3.6, and 2 cm from 1990 February through 1990 October. We find that its radio properties are quite similar to those of the two previously known Type Ib radio supernovae, SN 1983N and SN 1984L, and clearly distinguishable from the radio emission from Type II radio supernovae such as SN 1979C and SN 1986J. Nevertheless, there appear to be smaller, albeit significant, differences in the radio emission and physical properties of Type Ic from Type Ib radio supernovae

The radio emission from supernovae provides a direct probe of a supernova’s circumstellar environment, which presumably was established by mass-loss episodes in the late stages of the progenitor’s presupernova evolution. The observed synchrotron emission is generated by the SN shock interacting with the relatively high-density circumstellar medium which has been fully ionized and heated by the initial UV/X-ray flash. The study of radio supernovae therefore provides many clues to and constraints on stellar evolution. We will present the recent results on several cases, including SN 1980K, whose recent abrupt decline provides us with a stringent constraint on the progenitor’s initial mass; SN 1993J, for which the profile of the wind matter supports the picture of the progenitor’s evolution in an interacting binary system; and SN 1979C, where a clear change in presupernova mass-loss rate occurred about 104 years before explosion. Other examples, such as SNe 19941 and 1996cb, will also be discussed.

Massive stars are the workhorse of the Universe. While accounting for a minute fraction of baryonic mass, their influence on the cosmos is profound. Their lives and deaths lead to nucleosynthesis of all elements heavier than helium, including those essential to life. They produce some of the most energetic eruptions and explosions, core-collapse (CC) supernovae (SNe) at the end of their life. These explosions are common, about once per century per galaxy, and are one of the primary drivers of the gas dynamics of their host galaxies. Despite their importance, many facets of the massive stars' evolution and their eventual death in CCSNe are still uncertain. In this thesis, I use a variety of observations in the infrared (IR) part of the electromagnetic spectrum to probe aspects of these stellar explosions elusive to visible light. IR observations of SNe remain sparse compared to the optical, even for the most nearby events. I present the first systematic study of CCSNe light curves from the Spitzer Space Telescope showing trends in IR properties of CCSNe and identifying outliers that exhibit signs of interactions between the SN shock and the circumstellar medium (CSM) ejected from the star. I also present in-depth explorations of nearby SN 2017eaw, a typical and common hydrogen-rich explosion; and SN 2014C, a hydrogen-poor explosion whose shock wave crashes into the CSM containing material lost from the star. IR observations provide insights into the chemical evolution and circumstellar environment in these SNe. In the second part of this thesis, I present the development and commissioning of a near-IR spectropolarimeter WIRC+Pol at Palomar Observatory. WIRC+Pol utilizes a novel, highly efficient polarization grating as its polarimetric beam splitter and spectral disperser. The resulting high sensitivity allows WIRC+Pol to observe sources as faint as J = 14.5 to 0.1% polarimetric accuracy in 2 hours. I also present the first scientific results from the instrument: the spectropolarimetric measurements of four nearby SNe, which are the first such observations in the IR. We detected polarization from SN 2018hna, which allowed us to constrain that its explosion geometry looks similar to the very well-studied SN 1987A observed from a different angle, suggesting the same underlying geometry.

There is observational evidence at a number of wavelengths for the interaction of the supernovae SN 1979c and SN 1980k with a circumstellar medium created by presupernova mass loss. Distance independent quantities can be used to develop a model for the interaction region. When these results are combined with a distance dependent quantity, the distance to the supernova is determined. The most useful distance dependent quantities are the radio angular diameter (from VLBI observations) and the X-ray flux. This method for distance determination is applied to the supernova SN 1979c.

The observational characteristics of the bright supernova 1979c discovered in the weak-barred spiral galaxy M100 are discussed. The UBV light and color curves of SN 1979c were derived from coordinated visual, photographic and photoelectric photometry carried out from April 15 to August 4, 1979 and supplementary prediscovery observations and IUE data. Values of 0.12 + or - 0.03 and 0.08 are estimated for the interstellar reddening in M100 in B-V and U-B, respectively, while values of 0.06 + or - 0.02 and 0.04 are adopted for the corresponding reddenings in the Galaxy. Total color excesses in B-V and U-B of 0.18 + or - 0.04 and 0.12 + or - 0.03, respectively, are thus obtained, corresponding to total extinctions in B of 0.75 and v of 0.55 magnitudes. A distance modulus of M100 of 30.30 + or - 0.15 is derived, which leads to a corrected absolute B magnitude for SN 1979c of -19.45, making it the brightest type II supernova on record.

view Abstract Citations (20) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS VLBI Observations of SN 1986J: Deviations from Spherical Symmetry in Its Radio Brightness Distribution Bartel, Norbert ; Rupen, Michael R. ; Shapiro, Irwin I. Abstract The 1987.4 radio brightness distribution at 5 GHz of the unusual supernova SN 1986J can be described by an elliptical Gaussian model with a half-width at half-maximum of the major axis of 0.80 +/- 0.12 mas and a ratio between the minor axis and the major axis of 0.62 +/- 0.12. This result could be due to an anisotropic flow pattern of the expanding gas and/or to peculiar variations of the brightness across the emission region. We discuss the implications of these possibilities for the understanding of the explosion process, the density distribution of the ambient medium, and the brightness distribution of a possible pulsar nebula. Publication: The Astrophysical Journal Pub Date: February 1989 DOI: 10.1086/185384 Bibcode: 1989ApJ...337L..85B Keywords: Brightness Distribution; Radio Spectra; Supernovae; Very Long Base Interferometry; Anisotropy; Astronomical Models; Radio Sources (Astronomy); Stellar Envelopes; Astronomy; INTERFEROMETRY; RADIO SOURCES: GENERAL; STARS: SUPERNOVAE full text sources ADS | data products NED (4) SIMBAD (3)