On the nature of the X-ray source in GK Persei

Vrielmann, Sonja; Ness, J. U.; Schmitt, J. H. M. M.

doi:10.1051/0004-6361:20053017

Cited by 26 publications

(48 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Changes in the structure of the boundary layer from optically thin in quiescence to optically thick in outburst can explain a decrease in the 2-18.5 keV intensity below its quiescent value in the non-magnetic SU UMa (Collins & Wheatley 2010). Nevertheless, the spin modulation of the WD, repeatedly detected in the X-ray band in outbursts of GK Per (e.g., Watson et al 1985;Hellier et al 2004;Vrielmann et al 2005;Evans et al 2009), shows that accretion still proceeded onto the polar caps on the WD. The situation of the brightest optical outburst of this series, No.…”

Section: Discussionmentioning

confidence: 97%

See 1 more Smart Citation

The intermediate polar GK Persei: An unstable relation of the X-ray and the optical intensities in a series of outbursts

Šimon

2015

A&A

View full text Add to dashboard Cite

Context. GK Per is an intermediate polar that has been displaying dwarf nova outbursts since the middle of the twentieth century. Aims. I analyzed a series of such outbursts in the optical and X-ray bands. I pay attention to the relation of intensities of the optical and X-ray emissions, and its reproducibility in a series of these consecutive outbursts.Methods. This analysis uses the data from the BAT/Swift, ASM/RXTE, AAVSO, and AFOEV databases. It investigates the relation of the time evolution of the profiles of outbursts in the individual bands (hard X-ray, medium/hard X-ray, and optical).Results. This analysis shows that the X-ray intensity steeply rises only in the start of the optical outburst and steeply declines only when the optical outburst comes to its end. However, the 1.5-50 keV band intensity saturates and balances on a plateau during the outburst. (The longer the outburst, the longer its plateau.) The peak X-ray intensities of this series display a significantly narrower range than the optical ones (a factor of about two versus a factor of about eight). This implies a discrepancy between the mass flow through the disk and the production of the X-ray emission via bremsstrahlung at the polar caps of the white dwarf. This discrepancy is the largest in the time of the peak optical intensity when the whole disk (or at least its inner part) is in the hot state and the flow of matter through the disk is the greatest. This study shows that a series of outbursts constitutes more general properties of this discrepancy. I argue that the saturation of the X-ray luminosity in outburst cannot be caused by a dominant increase in X-ray absorption. In the interpretation, large structural changes of the accreting regions at the magnetic poles of the white dwarf occur during the outburst. A buried shock proposed by some authors for polars is also promising for explaining the X-ray light curves of outbursts of GK Per.

show abstract

Section: Discussionmentioning

confidence: 97%

“…In GK Per, the flares with E < 1 keV, which were ascribed to the thermalized emission on the WD surface, were caused by the impacts of the blobs (Vrielmann et al 2005). This speaks in favor of creating such a depression.…”

Section: Discussionmentioning

confidence: 99%

The intermediate polar GK Persei: An unstable relation of the X-ray and the optical intensities in a series of outbursts

Šimon

2015

A&A

View full text Add to dashboard Cite

show abstract

“…GK Per is a bright hard X-ray source during the outbursts and it was observed by many X-ray observatories including EXOSAT (Watson et al 1985;Norton et al 1988), Ginga (Ishida et al 1992), ASCA (Ezuka & Ishida 1999), RXTE (Hellier et al 2004;Suleimanov et al 2005), XMM-Newton (Vrielmann et al 2005;Evans & Hellier 2007), Chandra (Mauche 2004), INTEGRAL (Barlow et al 2006;Landi et al 2009), and Swift/BAT (Brunschweiger et al 2009). Some of these observations were also used to estimate the WD mass.…”

Section: Gk Permentioning

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

“…GK per. A recent analysis of XMM–Newton data of GK Per has revealed the presence of spectral complexity in the soft energy band, which has been resolved in a multitude of emission lines thanks to the high‐resolution spectroscopy performed with the Reflection Grating Spectrograph (RGS; Vrielmann & Ness 2005). Furthermore, the image of the source taken with the Advanced CCD Imaging Spectrometer (ACIS‐S) detector on board Chandra , reported by the same authors, shows the presence of extended emission (a shell with a radius of ∼50 arcsec) around the source, which disappears above ∼1.5 keV.…”

Section: Notes On a Few Individual Sourcesmentioning

confidence: 99%

INTEGRAL/IBIS andSwift/XRT observations of hard cataclysmic variables

Landi

Bassani

Dean³

et al. 2009

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The analysis of the third INTEGRAL/Imager on Board Integral Satellite (IBIS) survey has revealed several new cataclysmic variables, most of which turned out to be intermediate polars, thus confirming that these objects are strong emitters in hard X‐rays. Here, we present high‐energy spectra of all 22 cataclysmic variables detected in the third IBIS survey and provide the first average spectrum over the 20–100 keV band for this class. Our analysis indicates that the best‐fitting model is a thermal bremsstrahlung with an average temperature of 〈kT〉∼ 22 keV. Recently, 11 (10 intermediate polars and one polar) of these systems have been followed up by Swift/X‐ray telescope (XRT) (operating in the 0.3–10 keV energy band), thus allowing us to investigate their spectral behaviour over the range ∼0.3–100 keV. Thanks to this wide energy coverage, it was possible for these sources to simultaneously measure the soft and hard components and estimate their temperatures. The soft emission, thought to originate in the irradiated poles of the white dwarf atmosphere, is well described by a blackbody model with temperatures in the range ∼60–120 eV. The hard emission, which is supposed to be originated from optically thin plasma in the post‐shock region above the magnetic poles, is indeed well modelled with a bremsstrahlung model with temperatures in the range ∼16–35 keV, similar to the values obtained from the INTEGRAL data alone. In several cases, we also find the presence of a complex absorber: one totally [with NH∼ (0.4– 28) × 1021 cm−2] and one partially [with NH∼ (0.7–9) × 1023 cm−2] covering the source. Only in four cases (V709 Cas, GK Per, IGR J06253+7334 and IGR J17303−0601), we find evidence for the presence of an iron line at 6.4 keV. We discuss our findings in the light of the systems parameters and cataclysmic variables/intermediate polars modelling scenario.

show abstract

On the nature of the X-ray source in GK Persei

Cited by 26 publications

References 37 publications

The intermediate polar GK Persei: An unstable relation of the X-ray and the optical intensities in a series of outbursts

The intermediate polar GK Persei: An unstable relation of the X-ray and the optical intensities in a series of outbursts

GK Persei and EX Hydrae: Intermediate polars with small magnetospheres

INTEGRAL/IBIS andSwift/XRT observations of hard cataclysmic variables

Contact Info

Product

Resources

About