A search for OB stars in supernova remnants

A massive binary, in which the primary becomes a supernova, should leave a luminous secondary near the centre of its remnant. Contrary to expectation no statistically significant excess of OB stars is, however, found near the centres of optically visible galactic supernova remnants.     

Pulsar activity and the morphology of supernova remnants

We use the recently introduced concept of a ‘window’ of magnetic field strengths in which pulsars can be active to explain the variation in morphology of supernova remnants. The striking difference between shell-type and filled-type remnants is attributed to differences in he magnetic field strengths of the neutron stars left by the respective Supernovae. Field strengths of a value permitting pulsar activity result in particle production and Crab-like centrally concentrated remnants. Other field values lead to strong magnetic dipole radiation and consequent shell formation (e.g. Cas A). Several apparent inconsistencies concerning pulsar-supernova associations appear to find a logical explanation on the basis of this hypothesis.     

Parameters of the classical type-IIP supernova SN 1999em

Based on observations of SN 1999em, we determined the physical parameters of this supernova using hydrodynamic calculations including nonequilibrium radiative transfer. Taking the distance to SN 1999em estimated by the expanding photosphere method (EPM) to be D = 7.5 Mpc, we found the parameters of the presupernova: radius R = 450R_⊙, mass M = 15M_⊙, and explosion energy E = 7 × 10⁵⁰ erg. For the distance D = 12 Mpc determined from Cepheids, R, M, and E must be increased to the following values: R = 1000R_⊙, M = 18M_⊙, and E = 10⁵¹ erg. We show that one cannot restrict oneself to using the simple analytical formulas relating the supernova and presupernova parameters to obtain reliable parameters for type-IIP presupernovae.     

Revised equipartition and minimum energy formula for magnetic field strength estimates from radio synchrotron observations

The commonly used classical equipartition or minimum‐energy estimate of total magnetic fields strengths from radio synchrotron intensities is of limited practical use because it is based on the hardly known ratio K of the total energies of cosmic ray protons and electrons and also has inherent problems. We present a revised formula, using the number density ratio K for which we give estimates. For particle acceleration in strong shocks K is about 40 and increases with decreasing shock strength. Our revised estimate for the field strength gives larger values than the classical estimate for flat radio spectra with spectral indices of about 0.5–0.6, but smaller values for steep spectra and total fields stronger than about 10 µG. In very young supernova remnants, for example, the classical estimate may be too large by up to 10×. On the other hand, if energy losses of cosmic ray electrons are important, K increases with particle energy and the equipartition field may be underestimated significantly. Our revised larger equipartition estimates in galaxy clusters and radio lobes are consistent with independent estimates from Faraday rotation measures, while estimates from the ratio between radio synchrotron and X‐ray inverse Compton intensities generally give much weaker fields. This may be explained e.g. by a concentration of the field in filaments. Our revised field strengths may also lead to major revisions of electron lifetimes in jets and radio lobes estimated from the synchrotron break frequency in the radio spectrum. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new look at the position of the 1604 Supernova (V843 Ophiuchi)

The position of the supernova of 1604 (V843 Oph) is re‐assessed, with relevant discussion pertaining to the present‐day remnant, 3C 358. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

山东灵山岛晚中生代滑塌沉积层的发现及区域构造意义初探

灵山岛位于青岛胶南市东南黄海近岸海域中,为中国北方第一高岛,构造上属于苏鲁造山带,但岛上很多重要的地质现象尚未在地质文献中披露过.本文作者对灵山岛进行了初步地质考察,在被看做早白垩世莱阳期的地层中发现远源浊积岩及其内部大量的滑塌沉积层,孢粉鉴定初步结果显示该地层的时代很可能为侏罗纪.滑塌构造以同沉积滑塌褶皱为主,而在滑...     

High spatial resolution spectroscopy of G292.0+1.8 with Chandra

We present high spatial resolution X-ray spectroscopy of supernova remnant G292.0+1.8 made with Chandra observations.The X-ray emitting region of this remnant was divided into 25×25 pixels with a scale of 20 " ×20" each.Spectra of328 pixels were created and fitted with an absorbed one component non-equilibrium ionization model.With the spectral analysis results,we obtained maps of absorbing column density,temperature,ionization age and abundances for O,Ne,Mg,Si,S and Fe.The abundances of O,Ne and Mg show tight correlations between each other in the range of about two orders of magnitude,suggesting that they are all from explosive C/Ne burning.Meanwhile,the abundances of Si and S are also well correlated,indicating that they are the ashes of explosive O-burning or incomplete Si-burning.The Fe emission lines are not prominent in the whole remnant,and their abundance is significantly reduced,indicating that the reverse shock may not have propagated to the Fe-rich ejecta.Based on relative abundances of O,Ne,Mg,Si and Fe to Si,we suggest a progenitor mass of 25- 30 M_⊙ for this remnant.     

X-ray spectro-imagery of supernova remnants

Supernovae and their remnants play an essential role in the Interstellar Medium as one of the main sources of mechanical energy and heavy element production and as cosmic-ray accelerators. X-ray spectro-imagery is a key approach to look at these issues, as the collision of high velocity ejecta with the ambient medium generates high temperatures of the order of ten million degrees. I present recent results from the XMM-Newton and Chandra X-ray satellites on the elemental composition of young supernova remnants, on the spatial distribution of these synthesized elements and on the constraints obtained on the efficiency of particle acceleration at the shocks. This revised version was published online in September 2006 with corrections to the Cover Date.     

A search for young Galactic supernova remnants

A sample of eight small-diameter radio sources has been selected from the Molonglo Galactic Plane Survey (MGPS) as candidates for young Galactic supernova remnants. The sources have been identified in the IRAS and Midcourse Space Experiment infrared data bases and imaged in the H107α radio recombination line (RRL) using the Australia Telescope Compact Array (ATCA). Seven of the sources display high ratios of infrared-to-radio-continuum flux density and/or detectable RRLs and are almost certainly H ii regions. One source (G282.8−1.2) is identified as a possible new young Galactic supernova remnant, based on its relatively weak infrared emission, steep radio spectrum, and possible X-ray emission. The adopted method for distinguishing thermal and non-thermal Galactic radio sources seems promising and could be fruitfully applied to more than 100 small-diameter sources listed in the MGPS.