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1.
Photographic image-tube spectra (150 Å mm–1, 4500 Å-7000 Å) of the type I supernova (1974g) in the Sc galaxy NGC 4414 obtained at phases+ 14 days and + 40 days past maximum light have been reduced to absolute flux. The positions of various spectral features and the overall appearance of the spectra of SN 1974g closely match previously observed type I SN spectra at similar phases. An electronographic isophotal map of NGC 4414 is presented, and an accurate position of SN 1974g given. A distance to NGC 4414 of 15 Mpc was determined from the recessional velocities and the diameters of Hii regions; while the absolute magnitude at maximum light of SN 1974g was found to beM B(max)=–19.0. Estimates of the radius of the expanding photosphere of SN 1974g, cetermined by two independent methods, giveR1015 cm in the early post-maximum phases. The time of outburst,t=–25 days, has been estimated for SN 1974g. By assuming the broad emission feature observed at 6480 Å to be H, very rough estimates of the electron density and the mass of ionized hydrogen in the expanding supernova envelope are given. The total (observed) luminous energy of SN 1974g was 1051 erg.  相似文献   

2.
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.  相似文献   

3.
The galactic distribution of pulsars and shell remnants of supernovae (SN) as investigated on the basis of newly-estimated parameters. Special attention was paid to taking into account all possible selection effects and an attempt was made to reveal a statistically-pure ensemble of objects. On the basis of this ensemble we studied the radial andz-distribution of pulsars and supernova remnants (SNR).It is shown that the radial distribution of both objects is considered to have an annular structure with the maximum surface density at a distance of 4.5–5.3 kpc (if the distance of the Sun from the galactic centre is assumed to be equal to 8.5 kpc). The scle-height of the progenitors of SNRs is not more than 110 pc and only 15% of the SNRs, whose progenitors may also be massive runaway stars, are situated at 300 pc. The mean application of the pulsars is not more than 300 pc which agrees with the hypothesis about the genetic connection with type-II SN outbursts at the kinematic aget k5×106 yr and thez-component of spatial velocity beingV z=120 km s–1.The possible precursors of type-I SNRs by the shape of their radial distribution in late spirals and the various model calculations given in the literature, are also discussed.  相似文献   

4.
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.  相似文献   

5.
In the starburst-warmers scenario, we have used a supernova (SN) explosion model to construct theoretical light curves for active galactic nuclei (AGN). The ionizing flux, in this model, should show variability according to the SN rate in the galaxy.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.  相似文献   

6.
General models for the secular behavior of the radio and X-ray emission from supernova remnants are examined and compared with the observations. Hot plasma and synchrotron models for the X-ray emission are considered. Among other things, it is concluded that (1) the total kinetic energy released in most supernova outbursts is probably less than about 1051 ergs; (2) continuous injection probably occurs for at least 10 yr in every case and about 1000 yr in most supernova remnants, in which case the supernova remnants 3C392, W28, Pup A and IC443 should produce 1–10 keV X-ray fluxes 10–10 ergs/cm2 sec; and (3) the X-ray sources in the Crab Nebula, Cas A and Tycho can be explained in terms of a model wherein continuous injection occurs for 300 yr for the Crab Nebula, much less than 250 yr for Cas A and much longer than 400 yr for Tycho. Finally, it is shown that if Tycho and Cas A contain an X-ray star such as NP0532, it is quite possible that the X-ray emission from those sources is predominantly due to the X-ray star.Supported by the Air Force Office of Scientific Research under Contract No. F44620-67-C-0065.  相似文献   

7.
It is shown that a universal steady X-ray background with the energy flux 10–7 erg cm–2 s–1 sr–1 can arise as a superposition of radiation from pulsars (neutron stars) in various galaxies when it is taken into account that supernova outburst occurs in a galaxy at the rate of 10–2/year.  相似文献   

8.
Cosmic soft X-rays in the energy range between 0.14 and 7 keV were observed with thin polypropylene window proportional counters on board a sounding rocket. The field of view crossed the galactic plane in the Cygnus-Cassiopeia region at a large angle and reached the galactic latitudes of –55° and +30°. Referring also to the result with Be window counters, we obtained the energy spectrum of Cyg XR-2, the flux from the Cas A region and the distribution of the intensity of diffuse X-rays over the scanned region. The turn-over of the Cyg XR-2 spectrum at about 1 keV indicates that the distance of the Cyg XR-2 source lies between 600 and 800 pc, if the turn-over is due entirely to interstellar absorption. The flux from the Cas A region is obtained as 0.23±0.05 photons cm–2 sec–1 in the energy range between 1.1 and 4.1 keV. The intensity of diffuse soft X-rays depends on the galactic latitude more weakly than expected from the interstellar absorption of extragalactic X-rays and shows asymmetry with respect to the galactic equator, thus suggesting a contribution of galactic X-rays. The spectrum of extragalactic X-rays is approximately represented by a power lawE –1.8.  相似文献   

9.
The Monoceros ring, a circular optical nebulosity 3°.5 in diameter and centred at R.A.=6h37m, 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.  相似文献   

10.
Cosmic-ray propagation in the vicinity of 1 kpc from the Sun is considered. The data on the 1012–1015 eV particle anisotropy, on 1012 eV electron spectrum, and on temporal cosmic-ray variations are analyzed. The diffusion coefficientD(1012–1013 eV)=1029–1030 cm2s–1 inferred from the analysis coincides with its standard value in the large-halo model withh=15 kpc. The total power of cosmic-ray generation, about 3×1049 erg per SN in the proton component and about 1048 erg per SN in the electron component, typical of the galactic diffusion model is in agreement with the obtained parameters of local sources.  相似文献   

11.
The isotropic cumulative burst rate of 7030 –6000 +10000 yr–1 at a fluence ofS=8.47×10–9 erg–1 cm–2 determined by Beurleet al. from their observation of two gamma-ray bursts is shown to be statistically improbable. The difficulty arises from their assumption that the power law cumulative distribution function index equals one. Their observations are rediscussed and an upper limit ofN(>8.47×10–9 erg cm–2)<5400 yr–1 is proposed.  相似文献   

12.
A two-dimensional hydrodynamic code has been developed for numerical studies of stellar collisions. The motivation for the study has been the suggestion by Colgate that collisions among stars in a dense galactic core can lead to growth of stellar masses by coalescence and thus to an enhanced rate of supernova activity. The specific results reported here refer to head-on collisions between identical polytropes of index 3 having solar mass and radius. If the polytropes were initially at rest at infinity, then about five percent of the combined mass is lost by ejection following collision. The volatilized mass fraction rises to about 18% for an initial relative collision velocity of 1000 km s–1 at infinite separation, and to about 60% for the 2000 km s–1 case. Since the initial kinetic and gravitational energies balance for a relative velocity of 1512 km s–1 at infinity, it may be seen that net coalescence persists to velocities somewhat in excess of this figure. Mass ejection takes place in two ways simultaneously: (1) by a rapid sideward expulsion of fluid in a massive lateral sheet normal to the collision axis, and (2) as a result of two recoil shocks which lead momentum flows backwards along this axis. The lateral effect has similarities to the expansion of gas into a vacuum; that is, shocks are not involved. However, the ejection of material from the rear colliding hemisphere due to the recoil shocks predominates at low collision velocities. As the velocity increases, both effects strengthen, but the lateral expulsion intensifies more rapidly than the recoil shocks.  相似文献   

13.
The galactic nebula S206 contains a half shell of high excitation nebulosity which is centred on the associated exciting star. The suggestion has been made that this structure is caused by the interaction of stellar mass loss from the star with nebular gas. A steady state model of such an interaction is investigated quantitatively. The required mass loss rate from the star is about 10–7 M yr–1 which is compatible with the observationally derived mass-loss rates from early-type stars.  相似文献   

14.
We present the spectrum of the supernova SN1987L in NGC 2336 over the wavelength range 4000–9700 Å as recorded in one 500 s exposure on 20–21 October, 1987. This spectrum was taken using the new Faint Object Spectrograph on the 4.2 m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos.We conclude that SN1987L was a type Ia supernova, and approximately 100 days post maximum at the time of the observation.  相似文献   

15.
The expression for the cutoff momentum of CR, accelerated by the supernova blast wave is derived. Geometrical factors (finite increase with time shock size, slowing shock speed and CR adiabatic effect in the downstream region) are shown to determine the value of the cutoff momentum. These factors are stronger than the time restriction and have a significant dynamical effect: the supernova blast wave cannot be completely smoothed by the CR backreaction even at very high Mach numbers. The shock transition always includes a pure gas subshock which strongly influences CR acceleration and shock evolution. It is shown that maximum particle energy achievable during CR acceleration by supernova shock can be as large as max ≈ Z × 1015 eV, if the diffusion coefficient is as small as the Bohm limit. Due to nonlinear effect and adiabatic heating in the downstream region in the free expansion phase the actual value of max is an order of magnitude higher than that from previous estimates based on the plane-wave consideration and is high enough to consider CR diffusive acceleration in SNRs as a main source of galactic CR at least up to the knee energy 3 × 1015 eV.  相似文献   

16.
We present a detailed study of the bremsstrahlung gamma-ray emissivity of the galactic disk. We show that there are large uncertainties in the production spectrum of photons in the medium energy range (10–100 MeV) due to our lack of knowledge of the interstellar electron spectrum below a few hundred MeV. In fact, gamma-ray observations can be of great help in determining this spectrum. At present, the spectral shape of the local gamma-ray emissivity above 30 MeV is available, thanks to the SAS-II and the COS-B satellites. Comparing it to our calculations, we determine the local interstellar electron flux in the 50–500 MeV range; the corresponding integrated gamma-ray emissivity above 100 MeV is equal to 2.4×10–25 photons s–1 (H-atom)–1, 60% higher than previously accepted values.  相似文献   

17.
An analysis of fifteen-year photoelectric observations of DI Herculis shows that the upper estimate for the relativistic part of apsidal motion in this binary system is almost three times lower than the theoretical value. The total observed angular velocity of apsidal rotation is 0 . ° 0124 yr–1. The relativistic part is less than 0 . ° 008 yr–1 instead of 0 . ° 023 yr–1 required by the theory.  相似文献   

18.
Reconstruction of Mediterranean sea level fields for the period 1945–2000   总被引：1，自引：1，他引：0  
The distribution of sea level in the Mediterranean Sea is recovered for the period 1945–2000 by using a reduced space optimal interpolation analysis. The method involves estimating empirical orthogonal functions from satellite altimeter data spanning the period 1993–2005 that are then combined with tide gauge data to recover sea level fields over the period 1945–2000. The reconstruction technique is discussed and its robustness is checked through different tests. For the altimetric period (1993–2000) the prediction skill is quantified over the whole domain by comparing the reconstructed fields with satellite altimeter observations. For past times the skill can only be tested locally, by validating the reconstruction against independent tide gauge records. The reconstructed distribution of sea level trends for the period 1945–2000 shows a positive peak in the Ionian Sea (up to 1.5 mm yr− 1) and a negative peak of − 0.5 mm yr− 1 in a small area to the south-east of Crete. Positive trends are found nearly everywhere, being larger in the western Mediterranean (between 0.5 and 1 mm yr− 1) than in the eastern Mediterranean (between 0 and 0.5 mm yr− 1). The estimated rate of mean sea level rise for the period 1945–2000 is 0.7 ± 0.2 mm yr− 1, i.e. about a half of the rate estimated for global mean sea level. These overall results do not appear to be very sensitive to the distribution of tide gauges. The poorest results are obtained in open-sea regions with intense mesoscale variability not correlated with any tide gauge station, such as the Algerian Basin.  相似文献   

19.
On December 15, 1978, an omnidirectional gamma-ray detector for the energy range 0.3 to 10 MeV was flown from São José dos Campos, Brazil at a latitude of about -23°. Around noon time, when the Sun was in the field of view of the detector, various solar flares of importance SN and SF occurred. The 2.2 MeV line flux was monitored during this time. A statistically significant line flux of (1.55 ± 0.50) × 10–2 photons cm–2 s–1 and (9.97 ± 4.85) × 10–3 photons cm–2 s–1 was observed within a few minutes of t maxima of the two long-duration SN flares respectively, whereas during SF flares only upper limits were obtained.  相似文献   

20.
Mean-sea-level data from coastal tide gauges in the north Indian Ocean were used to show that low-frequency variability is consistent among the stations in the basin. Statistically significant trends obtained from records longer than 40 years yielded sea-level-rise estimates between 1.06–1.75 mm yr− 1, with a regional average of 1.29 mm yr− 1, when corrected for global isostatic adjustment (GIA) using model data. These estimates are consistent with the 1–2 mm yr− 1 global sea-level-rise estimates reported by the Intergovernmental Panel on Climate Change.  相似文献   

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