11,553 research outputs found
No surviving evolved companions to the progenitor of supernova SN 1006
Type Ia supernovae are thought to occur as a white dwarf made of carbon and
oxygen accretes sufficient mass to trigger a thermonuclear explosion. The
accretion could occur slowly from an unevolved (main-sequence) or evolved
(subgiant or giant) star, that being dubbed the single-degenerate
channel, or rapidly as it breaks up a smaller orbiting white dwarf (the double-
degenerate channel). Obviously, a companion will survive the explosion
only in the single-degenerate channel. Both channels might contribute to
the production of type Ia supernovae but their relative proportions
still remain a fundamental puzzle in astronomy. Previous searches for remnant
companions have revealed one possible case for SN 1572, though that has
been criticized. More recently, observations have restricted surviving
companions to be small, main-sequence stars, ruling out giant
companions, though still allowing the single-degenerate channel. Here we report
the result of a search for surviving companions to the progenitor of SN
1006. None of the stars within 4' of the apparent site of the explosion
is associated with the supernova remnant, so we can firmly exclude all giant
and subgiant companions to the progenitor. Combined with the previous results,
less than 20 per cent of type Iae occur through the single degenerate channel.Comment: Published as a letter in Nature (2012 September 27
Model-independent bounds probing on the electromagnetic dipole moments of the -lepton at the CLIC
We establish model independent bounds on the anomalous magnetic and electric
dipole moments of the tau-lepton using the two-photon processes and . We use of data
collected with the future linear collider such as the CLIC at
and we consider systematic
uncertainties of . Precise bounds at
C. L. on the anomalous dipole moments to the tau-lepton and
are set from our study. Our results show that the processes under consideration
are a very good prospect for probing the dipole moments of the tau-lepton at
the future linear collider at the mode.Comment: 38 pages, 26 figure
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