Supernova models with slow energy pumping and galactic supernova remnants

The study of supernova (SN) models with slow energy pumping is continued. At maximum luminosity the main characteristics of a SN are shown to be independent of the initial structure of the model (Table I, Figure 1). However, they depend on the massM _e of the envelope, and on the intensity of energy pumpingL , with an increase ofM _e leading qualitatively to the same changes in the SN parameters as a decrease inL (Table I, Figures 2 and 3). A simple relationship connecting the important SN parameters is obtained (Equation (6)). From the inflection of the color indexB-V curve, the possibility of deriving the characteristic time of energy pumping with intensityL 10⁴⁴ erg s^–1 is pointed out. The comparison of the extragalactic type I SN observations with the results of calculations leads to the estimate ofM _e 0.3–0.7M.An investigation of the galactic type I SN remnants is carried out (Table III). The estimate ofM _e 0.2–0.3M is obtained for the remnants of supernovae SN 1006, SN 1572, and SN 1604. It completely fits the results for the extragalactic type I SNs. The total initial mass of SN 1604 presupernova was shown to be at least about 7M .It was established that the Crab nebula resulted from the outburst of a peculiar SN. The unique properties of such SNs, including SN 1054, are due to the low intensity of energy pumping (L 10⁴² erg s^–1). The mass of the envelope of the Crab nebula is evaluated to beM _e 0.7M . SN 1054 was shown to have m _max ^v =–4 _m ^. 0 at maximum luminosity.     

Late-time emission of the type II Supernovae powered by the radioactive decay56Ni−56Co−56Fe

A one-zone model for the late time SN II energized by the radioactive decay⁵⁶Ni–⁵⁶Co–⁵⁶Fe is presented. The model succeeds in reproducing for the late time evolution of H and [Oi] 6300 emission lines in SN1970g for the reasonable set of parameters: mass of ejecta 4M , boundary velocityv ₀=4000 km s^–1 and amount of⁵⁶NiM _Ni=0.02M . However, a one-zone model does not account for the late time continuum. In the case of SN1980k the radioactive model fits H and [Oi] 6300 emissions att250 day satisfactory but fails at very late time, e.g.,t=670 day when the predicted value of the ratioL(H)/L(6300) is two orders of magnitude smaller than the observed one. We suggest that the strong H emission in SN1980k on the 670th day is due to the interaction of the supernova envelope with the pre-SN wind. The radioactive model for the late time SN II predicts strong Mgii 2800 line and detectable Hei 10830 line in emission and absorption.     

Observations of the supernova 1985F with a new spectrograph

We present the spectrum of the supernova 1985F over the wavelength range 4600 to 10000 Å as recorded in one 200 s exposure on 16 May, 1985, when its age was estimated to bet240 days. This wideband measurement with a resolution of 20 Å was made with the new Faint Object Spectrograph on the Isaac Newton Telescope (INT) at the Observatorio del Roque de los Muchachos. Broad line features were observed for the ionsOi,Oii, andOiii, Caii, and Nai although broad H was noteably absent. This suggests type I rather than type II properties but Filippenko and Sargent (1985c) have concluded this object to be of neither type and of a new peculiar class. We have observed the Caii infra-red triplet at 8600 Å which has not been previously reported in the spectrum of SN1985F and alsoCi] at 9800 Å.     

Evidence for supernova-induced star formation in the monoceros OB2 association

The Monoceros ring, a circular optical nebulosity 3°.5 in diameter and centred at R.A.=6^h37^m, Dec.=6°30 (l ⁱⁱ =205°.5,b ⁱⁱ =0°.2) is in good structural agreement with radio observations. A neutral hydrogen shell is also accurately projected on the ring. These observations are consistent with the Monoceros ring being a supernova remnant 90–100 pc in diameter expanding at about 45 km s^–1 and having an age of the order of a million years. Bright Hii regions containing early-type stars (e.g., galactic cluster NGC 2244 in the Rosette nebula) and extremely young stars of the OB association Mon OB2 lie at the edges of the ring. The positional and temporal coincidence of the Mon OB2 association with a supernova remnant suggests that probably the star formation in this region is induced or speeded up by the passage of a supernova shock wave through the clumpy interstellar medium.     

Mesure des Raies de [Sii] dans Trois Nébuleuses planétaires de L'hémisphère Austral

Three southern planetary nebulae (NGC 2818, He 2-130, and NGC 3132) have been observed with the IDS (Image Dessector Scanner) combined with the Boller and Chivens spectrograph mounted at the Cassegrain focus of the 1.52 m telescope of the ESO in Chile. The spectrograph dispersion was 60 Å mm^–1 in the spectral range 6170–7298 Å. The slit aperture was 4×4. Spectra were obtained from an array of positions across each nebula along the E-W direction and/or N-S direction. The data reduction followed the standard IHAP routines for IDS observations. In order to derive electron density, only the [Sii] lines (6617 Å–6731 Å) are given in this paper. The results are in agreement with a shell structure for the observed nebulae.

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Toutes les observations ont été faites à l'Observatoire européen Austral (ESO) au Chili.     

On the theory of the light curves of supernovae

An account of the theory of the light curves of supernovae is presented, based on certain assumptions concerning the passage through the stellar atmosphere of powerful shock waves. The investigation is based on numerical integration of appropriate equations of gas dynamics and radiative heat-conductivity. The calculations substantially involve the ionization and recombination of hydrogen in the envelope of a supernova. Changes are traced in the curves arising from the transition from compact stars with small radius (10R ), to stars with very extensive envelopes (10000R ). The light curves for compact stars agree well with observations of the peculiar supernovae in NGC 5457, NGC 6946 and NGC 5236. The characteristics of the light curves with the passage of shock waves through the extended atmosphere coincide within an order of magnitude with observations of the supernovae of type II and type I near their maximum brightness. A powerful heat-wave propagates before the shock-front in the extensive atmosphere which gives rise to a detached supernova envelope in the form of a thin spherical layer. We investigated the condition in an ascending wave of cooling and recombination in the supernova envelope. It is shown that part of the hydrogen may recombine to attain full transparency for radiation passing through it. The observations are compared with the results of the theory of radioactive decay of the elements. This explanation of the light curves by the passage of shock waves requires energies of 10⁵⁰ to 10⁵² ergs, which are in agreement with mechanisms of thermonuclear explosions.Translated from the Russian by E. Budding.     

Sur l'existence d'un champ magnetique dans les nebuleuses planetaires

Résumé Après avoir écrit le système d'équations de la magnétohydrodynamique régissant le transport du champ magnétique avecla matière nébulaire, nous montrons, sous des hypothèses simples, que sa résolution conduit naturellement à la présence d'un champ magnétique 10^–3–10^–4 G au sein du gaz nébulaire, le champ au voisinage de l'étoile centrale étant supposé de l'ordre de Gauss. La conditionH ²/8nkT étant vérifiée dans la nébuleuse, le champ peut alors faire appraître des structures typiquement magnétiques telles que dans NGC 650-1, NGC 7293, etc ....

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On the existence of the magnetic field in planetary nebulae

The resolution of a set of magnetohydrodynamic equations governing the ejected matter, under some simple assumptions, lead to the existence of a magnetic field about 10^–3–10^–4 G within the shell of planetary nebulae. The stellar magnetic field, at the time of ejection, is supposed equal to 1 G. The conditionH ²/8nkT is then satisfied in most of planetary nebulae showing magnetic features such as NGC 650-1, NG 7293, etc ....

     

S xi Emission Lines in Active Region Spectra Obtained with the Solar euv Rocket Telescope and Spectrograph (Serts)

Theoretical electron density sensitive emission line ratios involving a total of eleven 2s ²2p ²–2s2p ³ transitions in Sxi between 187 and 292 Å are presented. A comparison of these with solar active region observations obtained during rocket flights by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals generally good agreement between theory and experiment. However, the 186.87 Å line is masked by fairly strong Fexii emission at the same wavelength, while 239.83 Å is blended with an unknown feature, and 285.58 Å is blended with possibly Niv 285.56 Å. In addition, the 191.23 Å line appears to be more seriously blended with an Fexiii feature than previously believed. The presence of several new Sxi lines is confirmed in the SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Å, in excellent agreement with laboratory measurements. In particular, the detection of the 2s ²2p ^{2 3} P ₁ –2s2p ^{3 3} P _0,1 transitions at 242.91 Å is the first time (to our knowledge) that this feature has been identified in the solar spectrum. The potential usefulness of the Sxi line ratios as electron density diagnostics for the solar transition region and corona is briefly discussed.     

Supernova SN 1961v: An explosion of a very massive star

An investigation of the outburst of the unique supernova SN 1961v in the galaxy NGC 1058 is carried out. An analysis of hydrodynamic models of supernova outbursts and a comparison with a considerable body of observational data on SN 1961v clearly show that the SN 1961v phenomenon is an explosion of a very massive star (VMS) of a mass of 2000M and a radius of about 100R which results in expelling the envelope with a kinetic energy of 1.8×10⁵² erg. The light curve of SN 1961v (Figures 1, 7a, and 7b) furnishes direct evidence for the heterogeneity of the presupernova interior. The chemical composition profile produced during the evolution of the VMS and in the final explosion must have a number of the essential features (Figure 11). In particular, hydrogen has to be underabundant relative to the solar content and distributed in a specific manner throughout the star. At the late stages from February, 1963 to February, 1967, the light curve of SN 1961v (Figure 1) may be accounted for by the interaction of the expelled envelope with the stellar wind of the presupernova. The latest observations of SN 1961v in 1968 and 1970 are virtually those of a giantHii region created by the VMS before the explosion. Two astrophysical phenomena-the peculiar outburst of SN 1961v and the most luminous object R136a in the Large Magellacnic Cloud (LMC) which reveals a striking similarity with the presupernova-are evidence for the existence of VMSs. The evolution of VMSs similar to the object R136a may be terminated by explosions like the outburst of SN 1961v. Such explosions give rise to the formation of energetic supernova remnants whose examples may be the Cygnus superbubble and the supergiant shells in the LMC. A comparison of the internal structure of the presupernova with the available evolutionary calculations allows one to conclude that the influence of mass loss on the evolution of VMSs is negligible.     

The solar continuum from 900 to 130 000 Å and the photospheric temperature model

In order to obtain a better agreement between observed and computed values of the solar intensity, an improved temperature distribution is deduced for the range 0.02<0< 10. The intensity observations here considered refer to the wavelength region between 1980 and 129 500, and the center-limb variations generally go down to cos = 0.1. The improved model, given in Figure 4 and Table II, differs rather little from the Utrecht 1964 model, used here as a reference.It appears necessary to introduce an empirical correction function to be applied to the continuous absorption coefficient. This function was derived for the spectral region between 2000 and 130000 Å; it is shown in Figure 5.Furthermore, an extension of the model (1.10^–7<0< 2.10^–2) is deduced (see Table III and Figure 8), which reasonably well represents the observations of the ultraviolet solar flux ( 900–1700 Å).     

Smoke rings around supernova 1987a

Detailed observations of the [Oiii]5007 Å emission from the elliptical rings around SN 1987A suggest a model wherein the two faint, outer rings are due to emission from two circular toroids moving outwards (at 25 km s^–1) along a bipolar cone centred on the site of the supernova. The brighter, central ring is expanding radially outward at 8.3 km s^–1. The rings must have been created 2-3 × 10⁴ years before the supernova explosion and are thought to be a consequence of the interaction of stellar winds emanating from the progenitor system during the final stages of its evolution to a supernova.     

Circumstellar line of Cai λ6572 in Zeta Aurigae and 31 Cygni

In the 1974 eclipse of Zeta Aurigae the satellite line of the Cai intercombination line at 6572 Å appeared in all the phases observed, i.e., near the mid-eclipse and egress, although its equivalent width, 100–200 mÅ, and velocity deviation, –20 im s^–1, from the principal line were considerably less than those for the satellite line found just after the fourth contact of the 1971–72 eclipse. 31 Cygni also showed a similar satellite line to Zeta Aurigae's in the 1974 eclipse, not only in the 1972 eclipse but also outside the eclipse. These satellite lines should be due to the circumstellar gas expanding from the binary systems.     

Iron whiskers in supernova SN 1987A

The far-infrared flux measurements for supernova SN 1987A are modelled in terms of length distributions of iron whiskers. The excess emission detected at 1.3µm can be explained on the basis of such a model.     

The ionization mechanism in low level emission galaxy nuclei: Shocks

We analyze the emission component of galaxy nuclei at very low intensity levels (W(H)2Å). This emission level is considerably lower than that of classical LINERS like NGC 1052. We have access to weaker emission lines by averaging spectra with similar line ratios for H [NII], and [SII]. From the resulting spectrum for very low level emission nuclei, the [SII] 6717, 6731/[SIII] 9069, 9532 line ratio criterion (Diazet al., 1985a) unambiguously shows that shock-wave heating is the mechanism responsible for the ionization in such objects.     

Ultra-violet nightglow spectrum from 1900 Å to 3400 Å

Two spectra of the ultra-violet nightglow from 1900 Å to 3400 Å have been recorded by a fast wide-field spectrograph during balloon flights from Aire sur Adour, France on 15 September, 1969 and on 5 October, 1970. These two spectra are composed of theOi line at 2972 Å, of the molecular oxygen Herzberg band systemA ³ _u ⁺ X ³ _g ^– and of a molecular band system that seems to belong to the NO SystemX ² C ² X ⁺, situated at 1991 ű4 Å, 2060 ű4 Å and 2136 ű4 Å. Around 2540 Å, there is absorption by ozone at the altitudes at which the spectra were recorded (35 km and 40 km). We present our calculated value of ozone absorption at 35 km, and the zenith-horizon variation of the nightglow emission.     

Extreme Ultraviolet Emission Lines of ca xv in Solar and Laboratory Spectra

New R-matrix calculations of electron impact excitation rates in Caxv are used to derive theoretical electron density diagnostic emission line intensity ratios involving 2s ²2p ²–2s2p ³ transitions, specifically R ₁=I(208.70 Å)/I(200.98 Å), R ₂=I(181.91 Å)/I(200.98 Å), and R ₃=I(215.38 Å)/I(200.98 Å), for a range of electron temperatures (T _e=10^6.4–10^6.8 K) and densities (N _e=10⁹–10¹³ cm^–3) appropriate to solar coronal plasmas. Electron densities deduced from the observed values of R ₁, R ₂, and R ₃ for several solar flares, measured from spectra obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab, are found to be consistent. In addition, the derived electron densities are in excellent agreement with those determined from line ratios in Caxvi, which is formed at a similar electron temperature to Caxv. These results provide some experimental verification for the accuracy of the line ratio calculations, and hence the atomic data on which they are based. A set of eight theoretical Caxv line ratios involving 2s ²2p ²–2s2p ³ transitions in the wavelength range 140–216 Å are also found to be in good agreement with those measured from spectra of the TEXT tokamak plasma, for which the electron temperature and density have been independently determined. This provides additional support for the accuracy of the theoretical line ratios and atomic data.     

Correlations between statistical population indices and spectral characteristics of carbon stars

The coefficients of correlation between spectroscopic data published by Yamashita (1967) and others for carbon stars and the statistical population indices calculated for these stars at the Toru Observatory are calculated (Table II). The intensity estimates of Cai 4227 Å, Nai D lines, the C¹³/C¹² ratio, then=n(Li/Ca) index, as well as CN and probably C₂ bands are higher in population I carbon stars. The CH(G) band and probably hydrogen (H, H, H) lines as well as Baii 4554 and 4934 Å lines are stronger in population II carbon stars. The photoelectric colour indices, corrected for interstellar reddening do not show significant population effects. They can be used as spectral type equivalents. For a population criterion the CH/CN intensity ratio is proposed.     

Some peculiarities of four host galaxies,containing Seyfert nuclei

Star-like objects are found in Seyfert galaxies Markarian 290, Markarian 298, NGC 1275, and NGC 7469, being connected with the structure peculiarities of the galaxies. The absolute magnitudes of these objects are –16 ^m M–19 ^m . It has been supposed that these star formations must stimulate the instability in the disk of the galaxy followed by the matter fall toward the centre of the galaxy. The gas inflow toward the centre will allow the recent star formations and Seyfert nuclei generation.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

The Sub-Pc Scale Accretion Disk of Ngc 4258

Water megamasers have been found to trace parsec/sub-parsec, circumnuclear accretion disks in several AGN (e.g., Circinus, NGC 1068 & NGC 4258). High-spatial (0.5 mas) and velocity resolution (0.2 km s^–1) VLBA imaging of the disks reveals thin, warped pannekoeken (pancake)-style structures as opposed to thick tori in the inner regions of the central engines (40 000 R_sch). In this contribution, I will describe some current investigations into the dynamical and physical attributes of the water maser disk in NGC 4258, as revealed by VLBA, VLA and Effelsberg monitoring over 8 years.     

High-dispersion spectroscopy of the symbiotic star AX Per: A binary model with rapid mass accretion

Results of high-dispersion spectroscopy (10 Å mm^–1) of the symbiotic star AX Per carried out in the years from 1979 to 1987 are reported. The emission line [FeVII] 6086 consists of a narrow and a broad component; the radial velocity of the narrow one varies according to the photometric period 681.6 days. This variation (K=30.6±1.5 km s^–1) seems to be due to the orbital motion of the hot star. The radial velocity of absorption lines varies with an inverse phase dependence and a much smaller amplitude (K=5.6±2 km s^–1), which may reflect the orbital motion of the red giant. The variation of the radial velocity of the emission lines of FeII, ect. (K=6.7±1.5 km s^–1) might be due to the rotation of the red giant. The profile of H emission line suddenly changed around the phase of the photometric minimum, which could be explained as a result of an eclipse of the emitting region by the red giant. On the other hand, some problems remain open in the behaviour of the radial velocities of H and HeI 5876.The observed results support a binary model of AX Per consisting of a rather massive (3M ) M-type giant and a Main-Sequence star (0.6M ). AX Per seems to be in an early stage of the Case C mass transfer, and the estimated very high mass accretion rate (10^–4 M yr^–1) is consistent with the theoretical models. The narrow component of the emission line of [FeVII] 6086 might be emitted in radiatively driven polar jets on the hot star of which luminosity is close to the Eddington limit.A new identification as ZrII at 6106.47 Å is proposed for the emission line at 6106 Å.