Theoretical X-ray power spectra of intermediate polars

A “giant” outburst of A 0535+262, a transient X-ray binary pulsar, was observed in 1994 February and March with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory. During the outburst power spectra of the hard X-ray flux contained a QPO-like component with a FWHM of approximately 50% of its center frequency. Over the course of the outburst the center frequency rose smoothly from 35 mHz to 70 mHz and then fell to below 40 mHz. We compare this QPO frequency with the neutron star spin-up rate, and discuss the observed correlation in terms of the beat frequency and Keplerian frequency QPO models in conjunction with the Ghosh-Lamb accretion torque model.

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A minimal timescale for the continuum in 4U 1608-52 and Aql X-1

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slab004 ◽

2021 ◽

Vol 502 (1) ◽

pp. L72-L78

Author(s):

K Mohamed ◽

E Sonbas ◽

K S Dhuga ◽

E Göğüş ◽

A Tuncer ◽

...

Keyword(s):

Black Hole ◽

Neutron Star ◽

Power Spectra ◽

Light Curves ◽

State Transitions ◽

Strong Positive Correlation ◽

Present Evidence ◽

X Ray ◽

X Ray Binaries ◽

The Continuum

ABSTRACT Similar to black hole X-ray binary transients, hysteresis-like state transitions are also seen in some neutron-star X-ray binaries. Using a method based on wavelets and light curves constructed from archival Rossi X-ray Timing Explorer observations, we extract a minimal timescale over the complete range of transitions for 4U 1608-52 during the 2002 and 2007 outbursts and the 1999 and 2000 outbursts for Aql X-1. We present evidence for a strong positive correlation between this minimal timescale and a similar timescale extracted from the corresponding power spectra of these sources.

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Hard X-ray view on intermediate polars in theGaiaera

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty2952 ◽

2018 ◽

Vol 482 (3) ◽

pp. 3622-3635 ◽

Cited By ~ 16

Author(s):

Valery F Suleimanov ◽

Victor Doroshenko ◽

Klaus Werner

Keyword(s):

X Ray ◽

Intermediate Polars

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Detection of distinct power spectra in soft and hard X-ray bands in the hard state of GRS 1915+105★

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stu646 ◽

2014 ◽

Vol 441 (2) ◽

pp. 1177-1185 ◽

Cited By ~ 5

Author(s):

H. Stiele ◽

W. Yu

Keyword(s):

Power Spectra ◽

X Ray ◽

Hard State

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The Intermediate Polars

International Astronomical Union Colloquium ◽

10.1017/s0252921100090291 ◽

1983 ◽

Vol 72 ◽

pp. 155-172

Author(s):

Brian Warner

Keyword(s):

Magnetic Fields ◽

White Dwarf ◽

Variable Star ◽

Theoretical Models ◽

Cataclysmic Variable ◽

General Role ◽

X Ray ◽

Low Mass ◽

Intermediate Polars ◽

X Ray Binaries

Until 1976, cataclysmic variable star research proceeded with few requirements for the inclusion of magnetic fields in theoretical models. Although models for low-mass X-ray binaries stressed the importance of magnetic fields (Lamb et at. 1973) and there was an increasing number of known magnetic single white dwarfs (Angel 1977), and a magnetised white dwarf had been one of the models proposed to explain the rapid oscillations in DQ Her (Herbst et al. 1974, Katz 1975), there was no anticipation of the more general role that magnetic fields now seem destined to play. The two major reviews of the time (Robinson 1976, Warner 1976) scarcely considered the presence of magnetic fields.

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X-Ray and Optical Observations of a New X-Ray Soft Intermediate Polar: RX J0512.2–3241

International Astronomical Union Colloquium ◽

10.1017/s0252921100043438 ◽

1997 ◽

Vol 163 ◽

pp. 689-689

Author(s):

V. Burwitz ◽

K. Reinsch ◽

K. Beuermann ◽

H.-C. Thomas

Keyword(s):

Optical Observations ◽

Galactic Latitude ◽

Ccd Photometry ◽

X Ray ◽

Probable Spin ◽

Sky Survey ◽

Intermediate Polars ◽

Orbital Periods ◽

Low Magnetic Field

The V~17.6 mag optical counterpart of the bright, soft, high-galactic latitude X-ray source RX J0512.2–3241 detected during the ROSAT All-Sky Survey, has been identified as a new, asynchronously rotating, magnetic cataclysmic variable (intermediate polar). The X-ray spectrum of RXJ0512–32 is similar to that of polars, it shows a soft component with no intrinsic absorption and a blackbody temperature kTbb~38 eV. From our optical follow-up B and V CCD photometry (cf. Fig. 1) we derive most probable spin and orbital periods of (863.5 ± 0.7) s and (3.45 ± 0.03) h respectively. A lower limit for the distance to the system is d > 740 pc. From this evidence we suggest that RXJ0512-32 is a further member of the ROSAT discovered class of soft X-ray intermediate polars (for details see Burwitz et al., 1996, A&A 310, L25). This still small class of systems (see Haberl and Motch 1995, A&A 297, L37) has X-ray characteristics similar to those of low magnetic field polars and may be their long sought evolutionary progenitors.

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A Fuse Survey of Disk-Accreting Cataclysmic Variables

International Astronomical Union Colloquium ◽

10.1017/s0252921100152960 ◽

2004 ◽

Vol 194 ◽

pp. 251-251

Author(s):

C. S. Froning ◽

K. S. Long ◽

P. Szkody ◽

B. T. Gänsicke

Keyword(s):

Cataclysmic Variables ◽

Dwarf Novae ◽

X Ray ◽

Intermediate Polars ◽

Far Ultraviolet ◽

X Ray Binaries ◽

Initial Results

We present initial results of a survey of the FUV spectra of disk-accreting cataclysmic variables obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE).FUSE covers the 905 - 1188 Å range at spectral resolutions ≃0.1 Å. To date, FUSE has observed more than 65 cataclysmic variables (CVs). Publicly-available data include observations of 11 dwarf novae (DN), 15 non-magnetic novalikes (NLs), 7 intermediate polars and DQ Her stars, at least 15 polars, and 4 super-soft X-ray binaries.

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Accretion Disc Formation in Intermediate Polars

International Astronomical Union Colloquium ◽

10.1017/s0252921100038501 ◽

1996 ◽

Vol 158 ◽

pp. 161-164

Author(s):

G. A. Wynn ◽

A. R. King

Keyword(s):

Magnetic Field ◽

Accretion Disc ◽

Local Magnetic Field ◽

Magnetic Systems ◽

X Ray ◽

Accretion Flow ◽

Intermediate Polars ◽

X Ray Binaries ◽

The Magnetic Field ◽

Disc Formation

The large-scale accretion flow in the intermediate polars (IPs) is still a matter of vigorous debate. It is known that the magnetic field of the white dwarf (WD) controls the accretion flow close to the surface, channeling the plasma onto the polecaps and giving rise to X-ray emission modulated at the WD spin period (Pspin). After their discovery it was assumed that IPs were the WD analogues of the pulsing X-ray binaries, where a magnetic neutron star accretes from a disrupted accretion disc. However, a number of authors have pointed out that the criteria for disc formation in IPs are less certain than those for the X-ray binaries.The simplest possible criterion for disc formation in a binary is that the accretion flow should be able to orbit freely about the primary star (see Frank, King & Raine 1991 for a review). In non-magnetic systems this is merely the condition that the minimum approach distance of the free stream (Rmin) should exceed the radius of the primary. The situation in magnetic systems is more complex, as the magnetic field of the primary presents an obstacle to the infalling accretion stream. In many treatments of IPs it is assumed that the plasma stream is able to orbit freely about the WD until the ram pressure of the stream is of the same order as the magnetic pressureρv2~B2/8π, whereρis the stream density,vthe stream velocity andBthe local magnetic field strength. This condition fixes the magnetospheric radius,Rmag, inside which the magnetic field is assumed to thread the stream material and direct the accretion flow along the fieldlines.

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