Open AccessHot white dwarfs and the UV delay in dwarf novae
Author(s) -
Hameury JeanMarie,
Lasota JeanPierre,
Dubus Guillaume
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02239.x
Subject(s) - white dwarf , physics , black dwarf , dwarf nova , astrophysics , cataclysmic variable star , blue dwarf , astronomy , accretion (finance) , light curve , brown dwarf , effective temperature , intermediate polar , radiation , stars , optics
We calculate the effect of illumination of dwarf nova accretion discs by radiation from a hot, central, white dwarf. We show that, only for very hot white dwarfs (T eff ≈ 40 000 K), the inner region of quiescent dwarf nova discs are partially depleted so that the delay between the rise to outburst of the optical and UV fluxes would be increased as suggested recently by King. This depletion, however, must create several small outbursts between the main outbursts, contrary to observations. Lower white dwarf temperatures may cause the outbursts to be of the `inside‐out' type, thus removing the UV delay. We conclude that white dwarf irradiation of dwarf nova discs is not very efficient because, for example, the UV radiation from the hot white dwarf does not penetrate deep enough in the disc atmosphere. The total ablation of the inner disc by, e.g., evaporation (possibly related to illumination) appears to be a very promising possibility, accounting for both the extreme UV (EUV) delay and the general properties of the light curves.