1,721,354 research outputs found
On core-collapse supernovae in normal and in Seyfert galaxies
No full textThis paper estimates the relative frequency of different types of core-collapse supernovae, in terms of the ratio S between the number of Type Ib-Ic and of Type H supernovae. We estimate S independently for all normal and Seyfert galaxies whose radial velocity is less than or equal to 14 000 km s(-1), and which had at least one supernova event recorded in the Asiago catalogue from 1986 January to 2000 August. We find that the ratio S is approximate to 0.23 +/- 0.05 in normal galaxies. This value is consistent with constant star formation rate and with a Salpeter initial mass function and an average binary rate approximate to50 per cent. On the contrary, Seyfert galaxies exceed the ratio S in normal galaxies by a factor approximate to4 at a confidence level; greater than or similar to20sigma. A caveat is that the numbers for Seyferts are still small (six of Type lb-Ic and six of Type H supernovae discovered as yet). Assumed to be real, this excess of Type We supernovae may indicate a burst of low-age star formation (tau less than or similar to 20 Myr), a high incidence of binary systems in the inner regions (r less than or similar to 0.4R(25)) of Seyfert galaxies, or a top-loaded mass function
Kanytella. Cristianizzazione e riuso dello spazio urbano in una città paleobizantina della Cilicia
No full textAwake tracheostomy in a patient with acute upper airway obstruction: an emergency application of an elective percutaneous procedure.
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Fifty-two Novae discovered in M31 from 1970 to 1986
No full textThe nova survey of M31, carried out at the Asiago Astrophysical Observatory since 1954, has led to the discovery of 52 other novae on plates taken from 1971 to 1986 with the 1.22 and 1.82 m telescopes, in addition to the 90 novae previously found. Positions, magnitudes, and identification charts of the 52 novae are reported. Light curves have been obtained for 18 of them. They show the same variety of shapes as in previous research
Applicazione di un modello di fugacità allo studio dei flussi di diossine e furani nella laguna veneta
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