A model atmosphere investigation of the effects of irradiation on the secondary star in a dwarf nova

Brett, J. M.; Smith, Robert C.

doi:10.1093/mnras/264.3.641

Cited by 35 publications

(38 citation statements)

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“…An interesting effect that was already observed by Brett & Smith (1993) in irradiated models (10 000 K blackbody primary) is that the optical depth at a given geometrical depth increases with increasing irradiative flux, i.e., the radiation makes the surface layers more opaque. We see a similar effect for primary temperatures up to roughly 85 000 K, at even higher temperatures the opposite occurs and the surface layers of the secondary start to become less opaque again, because some species become fully ionised.…”

Section: The Secondarymentioning

confidence: 70%

Structure and spectra of irradiated secondaries in close binaries

Wawrzyn¹,

Barman²,

Günther

et al. 2009

A&A

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Context. The standard stellar model atmosphere ignores the influence of external radiation. This assumption, while sufficient for most stars, fails for many short-period binaries. Aims. In setting up combined model atmospheres for close binaries, we want to constrain the parameters of both components, especially in the case of a hot primary component strongly influencing its cool secondary companion. This situation can be found after common envelope evolution (CEE). The status of both components today allows one to retrace the CEE itself. Methods. We used our stellar atmosphere code PHOENIX, which includes the effect of irradiation in its radiation transport equation, to investigate the close binary star UU Sge. We combined our calculated spectra of both components, weighted by their visible size, and adjusted the input parameters until reasonable agreement with observations is reached. Results. We derive a range of 80 000−85 000 K for the effective temperature of the primary (T eff, p ) and give a rough estimate for the primary's abundances, particularly the nitrogen enrichment. The heated day-side of the secondary has an apparent "effective" or equilibrium temperature of 24 000−26 000 K, nearly independent of its intrinsic luminosity. It shows an enhancement in nitrogen and carbon. Conclusions. The evolution of the primary and secondary stars were strongly influenced by the other's presence. Radiation from the primary on the secondary's day-side is still an important factor in understanding the secondary's atmospheric structure.

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Section: The Secondarymentioning

confidence: 70%

Structure and spectra of irradiated secondaries in close binaries

Wawrzyn¹,

Barman²,

Günther

et al. 2009

A&A

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“…Modeling the UV-emitting spots in polars requires us to consider incoming radiation fluxes that exceed the flux emerging from the unheated atmosphere of the white dwarf by factors up to ∼200 in the high state. Irradiated stellar atmospheres have been studied by several authors for a variety of conditions which differ, however, from those considered here (e.g., London et al 1981;van Teeseling et al 1994;Brett & Smith 1993;Barman et al 2004). In this paper, we present a pilot study of the structure and the angle-dependent spectra of white dwarfs irradiated by an intense source of infrared to ultraviolet radiation.…”

Section: Introductionmentioning

confidence: 91%

Irradiated atmospheres of accreting magnetic white dwarfs with an application to the polar AM Herculis

König

Beuermann

Gänsicke³

2006

A&A

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We present a pilot study of atmospheres of accreting magnetic white dwarfs irradiated by intense fluxes at ultraviolet to infrared wavelengths. The model uses a standard LTE stellar atmosphere code which is expanded by introducing an angle-dependent external radiation source. The present results are obtained for an external source with the spectral shape of a 10 000 K blackbody and a freely adjustable spectral flux. The model provides an explanation for the observed largely filled-up Lyman lines in the prototype polar AM Herculis during its high states. It also confirms the hypotheses (i) that irradiation by cyclotron radiation and other radiation sources is the principle cause for the large heated polar caps surrounding the accretion spots on white dwarfs in polars and (ii) that much of the reprocessed light appears in the far ultraviolet and not in the soft X-ray regime as suggested in the original simple theories. We also briefly discuss the role played by hard X-rays in heating the polar cap.

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“…It is well established that the temperature of the outer layers of the companion can be upset by external heating (e.g. Brett & Smith 1993), which removes the vertical temperature gradient of the heated star and quench the absorption lines within the irradiated regions. In order to compute our curves we have considered the limit case in which absorption lines are totally quenched (i.e.…”

Section: The Optical Light Curve Of the Companionmentioning

confidence: 99%

A search for evidence of irradiation in Centaurus X-4 during quiescence

D’Avanzo

Muñoz-Darias

Casares

et al. 2006

A&A

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Aims. We present a study of the neutron star X-Ray Transient Cen X-4. Our aim is to look for any evidence of irradiation of the companion with a detailed analysis of its radial velocity curve, relative contribution of the donor star and Doppler tomography of the main emission lines. Methods. To improve our study all our data are compared with a set of simulations that consider different physical parameters of the system, like the disc aperture angle and the mass ratio. Results. We conclude that neither the radial velocity curve nor the orbital variation of the relative donor's contribution to the total flux are affected by irradiation. On the other hand, we do see emission from the donor star at Hα and HeI λ5876 which we tentatively attribute to irradiation effects. In particular, the Hα emission from the companion is clearly asymmetric and we suggest is produced by irradiation from the hot-spot. Finally, from the velocity of the HeI λ5876 spot we constrain the disc opening angle to α = 7• −14• .

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A model atmosphere investigation of the effects of irradiation on the secondary star in a dwarf nova

Cited by 35 publications

References 0 publications

Structure and spectra of irradiated secondaries in close binaries

Structure and spectra of irradiated secondaries in close binaries

Irradiated atmospheres of accreting magnetic white dwarfs with an application to the polar AM Herculis

A search for evidence of irradiation in Centaurus X-4 during quiescence

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