X-ray emissions from two-temperature accretion flows within a dipole magnetic funnel

Saxton, C. J.; Wu, Kinwah; Canalle, João Batista Garcia; Cropper, Mark; Ramsay, Gavin

doi:10.1111/j.1365-2966.2007.11958.x

Cited by 27 publications

(32 citation statements)

References 61 publications

(104 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A theory of the post-shock regions (PSR) on WDs was first considered by Aizu (1973) and further developed in several works where the WD gravity, influence of cyclotron cooling, dipole geometry of the magnetic field, and difference between the temperatures of the electron-ion plasma components were taken into account (Fabian et al 1976;Wu et al 1994;Cropper et al 1999;Canalle et al 2005;Saxton et al 2007; Hayashi & Ishida 2014a). Some of these models were used to estimate the WD masses in several intermediate polars and polars (Cropper et al 1998(Cropper et al , 1999Ramsay 2000;Revnivtsev et al 2004b;Suleimanov et al 2005;Falanga et al 2005;Brunschweiger et al 2009;Yuasa et al 2010;Hayashi & Ishida 2014b).…”

Section: Introductionmentioning

confidence: 99%

GK Persei and EX Hydrae: Intermediate polars with small magnetospheres

Suleimanov

Doroshenko

Ducci

et al. 2016

A&A

View full text Add to dashboard Cite

Observed hard X-ray spectra of intermediate polars are determined mainly by the accretion flow velocity at the white dwarf surface, which is normally close to the free-fall velocity. This allows us to estimate the white dwarf masses as the white dwarf mass-radius relation M − R and the expected free-fall velocities at the surface are well known. This method is widely used. However, derived white dwarf masses M can be systematically underestimated because the accretion flow is stopped at, and re-accelerates from, the magnetospheric boundary R m and, therefore, its velocity at the surface is lower than free fall. To avoid this problem, we computed a two-parameter set of model hard X-ray spectra, which allows us to constrain a degenerate M − R m dependence. Previous works showed that power spectra of accreting X-ray pulsars and intermediate polars exhibit breaks at frequencies corresponding to Keplerian frequencies at the magnetospheric boundary. Therefore, the break frequency ν b in an intermediate polar power spectrum gives another relation in the M − R m plane. The intersection of the two dependences allows us, therefore, to determine the white dwarf mass and magnetospheric radius simultaneously. To verify the method, we analysed the archival Suzaku observation of EX Hya, obtaining M/M = 0.73 ± 0.06 and R m /R = 2.6 ± 0.4, which is consistent with the values determined by other authors. Subsequently, we applied the same method to a recent NuSTAR observation of another intermediate polar GK Per performed during an outburst and found M/M = 0.86 ± 0.02 and R m /R = 2.8 ± 0.2. The long duration observations of GK Per in quiescence performed by Swift/BAT and INTEGRAL observatories indicate increase of magnetosphere radius R m at lower accretion rates.

show abstract

Section: Introductionmentioning

confidence: 99%

GK Persei and EX Hydrae: Intermediate polars with small magnetospheres

Suleimanov

Doroshenko

Ducci

et al. 2016

A&A

View full text Add to dashboard Cite

show abstract

“…The most recent investigations by Canalle et al (2005) and Saxton et al (2005Saxton et al ( , 2007 have studied the role of the two-temperature plasma and considered the dipole magnetic funneling (not the standard plane-parallel approximation).…”

Section: Introductionmentioning

confidence: 99%

Influence of Compton scattering on the broad-band X-ray spectra of intermediate polars

Suleimanov

Poutanen

Falanga

et al. 2008

A&A

View full text Add to dashboard Cite

Context. The majority of cataclysmic variables observed in the hard X-ray energy band are intermediate polars where the magnetic field is strong enough to channel the accreting matter to the magnetic poles of the white dwarf. A shock above the stellar surface heats the gas to fairly high temperatures (10-100 keV). The post-shock region cools mostly via optically thin bremsstrahlung. Aims. We investigate the influence of Compton scattering on the structure and the emergent spectrum of the post-shock region. We also study the effect it has on the mass of the white dwarfs obtained from fitting the observed X-ray spectrum of intermediate polars.Methods. We construct the model of the post-shock region taking Compton scattering into account. The radiation transfer equation is solved in the plane-parallel approximation. The feedback of Compton scattering on the structure of the post-shock region is also accounted for. A set of the post-shock region model spectra for various white dwarf masses is calculated. Results. We find that Compton scattering does not change the emergent spectra significantly for low accretion rates or low white dwarf masses. However, it becomes important at high accretion rates and high white dwarf masses. The time-averaged, broad-band X-ray spectrum of intermediate polar V709 Cas obtained by the RXTE and INTEGRAL observatories is fitted using the set of computed spectral models. We obtained the white dwarf mass of 0.91 ± 0.02 M and 0.88 ± 0.02 M using models with Compton scattering taken into account and without it, respectively.

show abstract

“…In this theoretical work we are interested in the scalability of two-temperature astrophysical radiating fluids. This type of flows is encountered in accretion environments such as the accreting column in magnetic cataclysmic variables (Imamura et al 1996) when the white dwarf has a high-mass and a high-magnetic field (Saxton et al 2007). The similarity of this radiating regime has not yet been the subject of a detailed study.…”

mentioning

confidence: 98%