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    Swift detection of the super-swift switch-on of the super-soft phase in nova V745 Sco (2014) (2015)
    Oxford University Press
    Details
    Publication Date: 2015-10-19
    Description: V745 Sco is a recurrent nova, with the most recent eruption occurring in February 2014. V745 Sco was first observed by Swift a mere 3.7 h after the announcement of the optical discovery, with the super-soft X-ray emission being detected around 4 d later and lasting for only ~2 d, making it both the fastest follow-up of a nova by Swift and the earliest switch-on of super-soft emission yet detected. Such an early switch-on time suggests a combination of a very high velocity outflow and low ejected mass and, together with the high effective temperature reached by the super-soft emission, a high mass white dwarf (〉1.3 M ). The X-ray spectral evolution was followed from an early epoch where shocked emission was evident, through the entirety of the super-soft phase, showing evolving column density, emission lines, absorption edges, and thermal continuum temperature. UV grism data were also obtained throughout the super-soft interval, with the spectra showing mainly emission lines from lower ionization transitions and the Balmer continuum in emission. V745 Sco is compared with both V2491 Cyg (another nova with a very short super-soft phase) and M31N 2008-12a (the most rapidly recurring nova yet discovered). The longer recurrence time compared to M31N 2008-12a could be due to a lower mass accretion rate, although inclination of the system may also play a part. Nova V745 Sco (2014) revealed the fastest evolving super-soft source phase yet discovered, providing a detailed and informative data set for study.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Quotients, automorphisms and differential operators (2014)
    Oxford University Press
    Details
    Publication Date: 2014-02-08
    Description: Let V be a G -module, where G is a complex reductive group. Let Z colone V//G denote the categorical quotient and let : V -〉 Z be the morphism dual to the inclusion O( V ) G O( V ). Let : Z -〉 Z be an algebraic automorphism. Then one can ask whether there is an algebraic map : V -〉 V which lifts , that is, (( v ))= ( ( v )) for all v V . In Kuttler ( Transform. Groups 16 (2011) 1115–1135), the case is treated where V = r g is a multiple of the adjoint representation of G . It is shown that, for r sufficiently large (often r ≥2 will do), any has a lift. We consider the case of general representations (satisfying some mild assumptions). It turns out that it is natural to consider holomorphic lifting of holomorphic automorphisms of Z , and we show that if a holomorphic and its inverse lift holomorphically, then has a lift which is an automorphism such that ( gv )= ( g )( v ), v V , g G , where is an automorphism of G . We reduce the lifting problem to the group of automorphisms of Z which preserve the natural grading of O( Z ) ~= O( V ) G . Lifting does not always hold, but we show that it always does for representations of tori in which case algebraic automorphisms lift to algebraic automorphisms. We extend Kuttler's methods to show lifting in the case where V contains a copy of g.
    Print ISSN: 0024-6107
    Electronic ISSN: 1469-7750
    Topics: Mathematics
    Published by Oxford University Press
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