Barrel-like supernova remnants

The origin of cylindrically-symmetric supernova remnants is discussed. The results of numerical simulations of two most distinguished barrel-like remnants SNR 1006 and G296.5+10.0 are presented.     

On the expansion of supernova shells

We have investigated a simple model for the effects of a central pulsar on the expansion of supernova shells. Some numerical results relevant to the Crab Nebula are also reported.     

Focusing supernova gamma rays

Despite their great intrinsic interest and extensive use as tools in other areas of astronomy, fundamental questions remain as to the nature of supernovae of all types. The radioactivity produced by nuclear fusion reactions in the explosions provides several excellent diagnostics, observable through gamma-ray emission. This great potential is largely unrealized because the fluxes from events at common distances are very small. Instrument sensitivity is paramount, and gamma-ray optics offer an excellent possibility for greatly increasing collecting area, without a large increase in background rates, and reaching the required sensitivities. Here we outline some of the major open questions about supernovae and discuss how gamma-ray spectroscopy can address them, including instrument requirements for a future focusing gamma-ray telescope.Supported by NASA and CESR.     

The next galactic supernova

It is pointed out that there is a better than even chance that a galactic supernova will occur during the lifetime of the present generation of astronomers. A brief discussion is given of a number of types of observations that could be made of such a unique event. It would be particularly important to obtain speckle interferometry of the expanding supernova. High time-resolution spectroscopy and photometry should be obtained during the early phases of the outburst.     

On the supernova remnants produced by pulsars

We conclude that pulsar-driven supernova remnants (SNRs) are extremely rare objects. Indeed an analysis of the known sample of plerions suggests a very low birthrate ∼ 1 in 240 years. Long-lived and bright plerions like the Crab nebula are likely to be produced only when the pulsar has an initial period ∼ 10–20 milliseconds and a field ∼ 10¹² G. Such pulsars inside rapidly expanding shell remnants should also produce detectable plerions. The extreme rarity of SNRs with such hybrid morphology leads us to conclude that these pulsars must have been born with an initial period larger than ∼ 35–70 milliseconds. Joint Astronomy Program, Department of Physics, Indian Institute of Science, Bangalore 560012.     

The nearby supernova factory

The Nearby Supernova Factory is an international project dedicated to the study of the nearby thermonuclear (type Ia) supernovæ. Based upon the NEAT search for the target discovery and the dedicated integral field spectrograph SNIFS for the follow‐up, the goal is to study, over a continuous period of 4 years, the spectro‐photometric evolution of ∼300 SNe Ia at z < 0.08 from −15 to +50 days in the extended optical range (320–1000 nm). This will allow to probe in detail the local Hubble diagram, SNe Ia physics and the SNe‐host galaxy correlations, serving as an unprecedented nearby benchmark for the high‐z cosmological studies to come. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the spherical-axial transition in supernova remnants

A new law of motion for supernova remnant (SNR) which introduces the quantity of swept matter in the thin layer approximation is introduced. This new law of motion is tested on 10 years observations of SN 1993J. The introduction of an exponential gradient in the surrounding medium allows to model an aspherical expansion. A weakly asymmetric SNR, SN 1006, and a strongly asymmetric SNR, SN 1987A, are modeled. In the case of SN 1987A the three observed rings are simulated.     

The galactic evolution of the supernova rates

Supernova rates (hypernova, type II, type Ib/c and type Ia) in a particular galaxy depend on the metallicity (i.e. on the galaxy age), on the physics of star formation and on the binary population. In order to study the time evolution of the galactic supernova rates, we use our chemical evolutionary model that accounts in detail for the evolution of single stars and binaries. In particular, supernovae of type Ia are considered to arise from exploding white dwarfs in interacting binaries and we adopt the two most plausible physical models: the single degenerate model and the double degenerate model. Comparison between theoretical prediction and observations of supernova rates in different types of galaxies allows to put constraints on the population of intermediate mass and massive close binaries.

The temporal evolution of the absolute galactic rates of different types of supernovae (including the type Ia rate) is presented in such a way that the results can be directly implemented into a galactic chemical evolutionary model. Particularly for type Ia’s the inclusion of binary evolution leads to results considerably different from those in earlier population synthesis approaches, in which binary evolution was not included in detail.     

X-ray detection of the monoceros supernova remnant

The Monoceros nebula is seen in the optical and in radio as a 3°.5 degree diameter ring. It is believed to be an old supernova remnant. Here is reported the detection of X-rays from the Monoceros nebula, confirming its supernova remnant nature.Einstein imaging proportional counter observations of 0.2 to 5 keV X-rays were analyzed to produce a surface brightness map. Preliminary modeling of the Monoceros supernova remnant yields an age of 50 000 years. A large age is expected for such a large remnant. However, the remnant is found to still be in the adiabatic blast wave stage of evolution.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Near-infrared [Fe ii] emission from supernova remnants and the supernova rate of starburst galaxies

In an effort better to calibrate the supernova rate of starburst galaxies as determined from near-infrared [Fe  ii ] features, we report on a [Fe  ii ] λ 1.644 μm line-imaging survey of a sample of 42 optically selected supernova remnants (SNRs) in M33. A wide range of [Fe  ii ] luminosities are observed within our sample (from less than 6 to 695 L_⊙). Our data suggest that the bright [Fe  ii ] SNRs are entering the radiative phase and that the density of the local interstellar medium (ISM) largely controls the amount of [Fe  ii ] emission. We derive the following relation between the [Fe  ii ] λ 1.644 μm line luminosity of radiative SNRs and the electronic density of the post-shock gas, n _e: L _{[Fe  ii ]}     (cm⁻³). We also find a correlation in our data between L _{[Fe  ii ]} and the metallicity of the shock-heated gas, but the physical interpretation of this result remains inconclusive, as our data also show a correlation between the metallicity and n _e. The dramatically higher level of [Fe  ii ] emission from SNRs in the central regions of starburst galaxies is most likely due to their dense environments, although metallicity effects might also be important. The typical [Fe  ii ]-emitting lifetime of a SNR in the central regions of starburst galaxies is found to be of the order of 10⁴ yr. On the basis of these results, we provide a new empirical relation allowing the determination of the current supernova rate of starburst galaxies from their integrated near-infrared [Fe  ii ] luminosity.     

Photometric observations of the supernova 2009nr

We present the results of our UBVRI CCD photometry for the second brightest supernova of 2009, SN 2009nr, discovered during a sky survey with the telescopes of the MASTER robotic network. Its light and color curves and bolometric light curves have been constructed. The light-curve parameters and the maximum luminosity have been determined. SN 2009nr is shown to be similar in light-curve shape and maximum luminosity to SN 1991T, which is the prototype of the class of supernovae Ia with an enhanced luminosity. SN 2009nr exploded far from the center of the spiral galaxy UGC 8255 and most likely belongs to its old halo population. We hypothesize that this explosion is a consequence of the merger of white dwarfs.     

On the initial energy of supernova remnants

An examination of the histogram of the supernova remnants radii allows one to deduce: (1) some support for the existence of a fairly dense galactic halo at least up to a few kpc from the galactic plane; (2) a first approximation for the initial energy distribution. Although the precise shape is still in doubt and various possibilities exist, one can conclude that the supernova rate should be no less than 1/150 SN yr^–1, and no more than 1/70 SN yr^–1; the average initial energy should be larger than 1.4×10⁴⁹ erg.     

Five supernova survey galaxies in the southern hemisphere. I. Optical and near-infrared database

The determination of the supernova (SN) rate is based not only on the number of detected events, but also on the properties of the parent galaxy population. This is the first paper of a series aimed at obtaining new, refined, SN rates from a set of five SN surveys, by making use of a joint analysis of near-infrared (NIR) data. We describe the properties of the 3838 galaxies that were monitored for SNe events, including newly determined morphologies and their DENIS, and POSS-II/UKST I, 2MASS and DENIS J and K_s and 2MASS H magnitudes. We have compared 2MASS, DENIS and POSS-II/UKST IJK magnitudes in order to find possible systematic photometric shifts in the measurements. The DENIS and POSS-II/UKST I band magnitudes show large discrepancies (mean absolute difference of 0.4 mag.), mostly due to different spectral responses of the two instruments, with an important contribution (0.33 mag rms) from the large uncertainties in the photometric calibration of the POSS-II and UKST photographic plates. In the other wavebands, the limiting near infrared magnitude, morphology, and inclination of the galaxies are the most influential factors which affect the determination of photometry of the galaxies. Nevertheless, no significant systematic differences have been found between any pair of NIR magnitude measurements, except for a few percent of galaxies showing large discrepancies. This allows us to combine DENIS and 2MASS data for the J and K_s filters. Published in Astrofizika, Vol. 52, No. 1, pp. 47–62 (Februay 2009).     

On the evolution of the cosmic supernova rates

The Galactic radio-emitting X-ray binary Cygnus X-3 is known to be a source of large-scale radio jets associated with periods of intense radio flaring. These jets have been found to have an expansion velocity of ∼0.3 c and are believed (on kinematic grounds) to lie close to the plane of the sky. We present new observations of Cygnus X-3 using the VLBA at 15 GHz. These observations, which included the detection of two small flares, show an additional kind of behaviour with apparent superluminal expansion along both major and minor axes. Evidence for superluminal activity has been found in a number of X-ray binary systems such as GRS 1915+105 and GRO J1655−40 with their superluminal radio jets. Apparently similar morphologies of the Galactic and extragalactic jet sources have led to the X-ray binaries being described as 'micro-quasars'. The superluminal expansion seen in our results appears to be different in nature from these other two sources, and a number of mechanisms are presented and discussed.     

Synchrotron X-ray emission from supernova remnants. Exponential cut-off in the electron spectrum

We present a model which describes the evolution of the energy spectrum of relativistic electrons in supernova remnants, with radiation losses of electrons taken into account. The model can be used to calculate the synchrotron X-ray emission from supernova remnants in the uniform interstellar medium and in the uniform interstellar magnetic field. The importance of various factors in the variations of spatial distributions of nonthermal electrons and their synchrotron emissive capacity is demonstrated. We analyze the errors which arise in the magnetic field strength when it is estimated with the use of the models which ignore the detailed pattern of the evolution of the magnetic field and the electron spectrum behind the shock front in the remnant. The evolution of synchrotron emission spectrum and the ratio between the synchrotron radio and X-ray fluxes from supernova remnants are calculated.     

Scalability of supernova remnant simulations

The simulation or solution of the supernova remnant evolution may be scaled from one interstellar environment to another. We systematically examine this scalability, the use of which is so far still very limited in astrophysical literature. We show how the scalability is affected by various constraints imposed by physical processes and initial conditions, and demonstrate the use of the scaling as a powerful tool to explore the interdependence among relevant parameters, based on a minimum set of simulations. In particular, we devise a scaling scheme that can be used to adaptively generate numerous seed remnants and plant them into 3D hydrodynamic simulations of the supernova-dominated interstellar medium.