The Accretion Geometry of Intermediate Polars：（中间高偏振星的吸积的几何）.pdfVIP

The accretion geometry of intermediate p olars Co el Hellier Dept of Physics Keele University Keele Stas ST BG UK Abstract Intermediate p olars range from systems which accrete en tirely via discs eg EX Hya through systems which combine disc and discoverow accretion eg F O Aqr to discless accretors eg RX The accretion curtain mo del provides a go o d description of the optical spinpulses while in the Xray regime o ccultation combines with absorption to create complex pulseproles Intro duction The class of intermediate p olars or DQ Her stars has b een extensively reviewed by Patterson I can therefore concentrate this review on the geometry of the accretion ow b etween the companion star and the white dwarf fo cusing on the well studied systems which have given the most secure results The accretion stream The assumption that IPs p ossess an accretion disc which is magnetically dis rupted only in its inner regions was questioned by Hameury King Lasota who suggested that the eld can prevent any disc from forming Thus it is worthwhile reviewing the evidence that we see discs in the known systems The strongest evidence for discs comes from high inclination systems where the eclipse provides a spatial prob e of the accretion ow It has long b een known that EX Hya eclipses but more recently I have prop osed that three other systems FO Aqr TV Col and BG CMi are highly inclined and show partial eclipses of the accretion ow although not of the white dwarf itself Hellier et al a b The evidence is twofold First all three show optical continuum dips consistent with a shallow partial eclipse Fig Secondly optical sp ec troscopy shows Swaves which are similar to those seen in nonm