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Catalogue POP – Notice individuelle de publication

Abada-Simon Meil, Casares J., Evans Aaron S., Eyres S., Fender R., Garrington S. T., De Jager O. C., Kuno N., Martínez-Pais I. G., De Martino Domitilla, Matsuo H., Mouchet Martine, Pooley Guy G., Ramsay G., Salama Alberto, Schulz B.

First detections of the cataclysmic variable AE Aquarii in the near to far infrared with ISO and IRAS: Investigating the various possible thermal and non-thermal contributions

Astronomy and Astrophysics, 2005, vol. 433, pp. 1063-1077

Référence DOI : 10.1051/0004-6361:20042066
Référence ADS : 2005A&A...433.1063A

Résumé :

We have used ISO to observe the Magnetic Cataclysmic Variable AE Aquarii in the previously unexplored range from 4.8 mum up to 170 mum in the framework of a coordinated multi-wavelength campaign from the radio to optical wavelengths. We have obtained for the first time a spectrum between 4.8 and 7.3 mum with ISOCAM and ISOPHOT-P: the major contribution comes from the secondary star spectrum, with some thermal emission from the accretion stream, and possibly some additional cyclotron radiation from the post-shock accretion material close to the magnetised white dwarf. Having reprocessed ISOPHOT-C data, we confirm AE Aqr detection at 90~mum and we have re-estimated its upper limit at 170 mum. In addition, having re-processed IRAS data, we have detected AE Aqr at 60 mum and we have estimated its upper limits at 12, 25, and 100 mum. The literature shows that the time-averaged spectrum of AE Aqr increases roughly with frequency from the radio wavelengths up to &tilde; 761~ mum; our results indicate that it seems to be approximately flat between ~761 and &tilde; 90 ~mum, at the same level as the 3sigma upper limit at 170 mum; and it then decreases from &tilde; 90~ mum to &tilde; 7~ mum. Thermal emission from dust grains or from a circum-binary disc seems to be very unlikely in AE Aqr, unless such a disc has properties substantially different from those predicted recently. Since various measurements and the usual assumptions on the source size suggest a brightness temperature below 10<SUP>9</SUP> K at lambda = 80 times the binary separation) could be the source of thermal bremsstrahlung which would dominate from &tilde; 10 ~mum to the ~millimetre, with, inside, a non-thermal source of synchrotron which dominates in radio; or, more probably, an initially small infrared source composed of several distributions (possibly both thermal, and non-thermal, mildly relativistic electrons) radiates gyro-synchrotron and expands moderately: it requires to be re-energised in order to lead to the observed, larger, radio source of highly relativistic electrons (in the form of several non-thermal distributions) which produce synchrotron.

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