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Doppler tomography of Algols
Author(s) -
Richards M. T.
Publication year - 2004
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200310206
Subject(s) - physics , astrophysics , accretion (finance) , doppler effect , astronomy , accretion disc , spectral line , photosphere , annulus (botany) , starspot , low mass , stars , botany , biology
The technique of Doppler tomography has been influential in the study of mass transfer in Algol‐type interacting binaries. The Algols contain a hot blue dwarf star with a magnetically‐active late‐type companion. In the close Algols, the gas stream flows directly into the photosphere of the blue mass‐gaining star because it does not have enough room to avoid impact with that star. Doppler tomograms of the Algols have been produced from over 2500 time‐resolved spectra at wavelengths corresponding to H α , H β , He I (6678 Å), Si II (6371 Å) and Si IV (1394 ° A). These tomograms display images of accretion structures that include a gas stream, accretion annulus, accretion disk, stream‐star impact region, and occasionally a source of chromospheric emission associated with the cool, mass‐losing companion. Some Algol systems alternate between streamlike and disk‐like states, and provide direct evidence of active mass transfer within the Algols. This work produced the very first images of the gas stream for the entire class of interacting binaries, and demonstrated that the Algols are far more active than formerly believed, with variability on time scales of weeks to months. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)