Probing the outer edge of an accretion disk: a Her X-1 turn-on observed with<i>RXTE</i>

Kuster, M.; Wilms, J.; Staubert, R.; Heindl, W. A.; Rothschild, R. E.; Шакура, Н. И.; Постнов, К. А.

doi:10.1051/0004-6361:20042355

Cited by 33 publications

(39 citation statements)

References 34 publications

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“…This fits very well within that picture (Schandl & Meyer 1994). This model is also discussed in detail by Kuster et al (2005), who investigated the turn-on of the main-on and find similar columns, although a little bit earlier in the 35 day phase than observation I. We found that the energy of the CRSF does not depend on the 35 day phase, neither in the phase-averaged spectrum nor on the pulse peak data.…”

Section: Day Phase Dependencesupporting

confidence: 89%

“…The interpulse peak around φ = 0.8 is very weak at this 35 day phase. This is a well known behavior in Her X-1, see, e.g., Scott et al (2000), and has been extensively studied in the literature (see, e.g., Deeter et al 1998;Kuster et al 2005). These energy-resolved pulse profiles are the basis for the phase-resolved spectroscopy described in Section 5.…”

Section: Light Curves and Timingmentioning

confidence: 92%

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The Smooth Cyclotron Line in Her X-1 as Seen With Nuclear Spectroscopic Telescope Array

Fürst

Grefenstette

Staubert

et al. 2013

ApJ

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Her X-1, one of the brightest and best studied X-ray binaries, shows a cyclotron resonant scattering feature (CRSF) near 37 keV. This makes it an ideal target for detailed study with the Nuclear Spectroscopic Telescope Array (NuSTAR ), taking advantage of its excellent hard X-ray spectral resolution. We observed Her X-1 three times, coordinated with Suzaku, during one of the high flux intervals of its 35 d super-orbital period. This paper focuses on the shape and evolution of the hard X-ray spectrum. The broad-band spectra can be fitted with a powerlaw with a high-energy cutoff, an iron line, and a CRSF. We find that the CRSF has a very smooth and symmetric shape, in all observations and at all pulse-phases. We compare the residuals of a line with a Gaussian optical depth profile to a Lorentzian optical depth profile and find no significant differences, strongly constraining the very smooth shape of the line. Even though the line energy changes dramatically with pulse phase, we find that its smooth shape does not. Additionally, our data show that the continuum is only changing marginally between the three observations. These changes can be explained with varying amounts of Thomson scattering in the hot corona of the accretion disk. The average, luminosity-corrected CRSF energy is lower than in past observations and follows a secular decline. The excellent data quality of NuSTAR provides the best constraint on the CRSF energy to date.

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Section: Day Phase Dependencesupporting

confidence: 89%

Section: Light Curves and Timingmentioning

confidence: 92%

The Smooth Cyclotron Line in Her X-1 as Seen With Nuclear Spectroscopic Telescope Array

Fürst

Grefenstette

Staubert

et al. 2013

ApJ

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“…the detection of pulsations. A search for pulsations in the range between 1 s and 10 ks was negative, while shorter period pulsations are probably not detectable due to the smearing of pulsations by Compton scattering (Kuster et al 2005). Turning to the emission lines, we note that our fit requires a slight overabundance of iron with respect to the ISM values of Wilms et al (2000), as one would expect for an evolved star.…”

Section: Discussionmentioning

confidence: 73%

Suzakuobservation of IGR J16318-4848

Barragán

Wilms

Pottschmidt

et al. 2009

A&A

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We report on the first Suzaku observation of IGR J16318−4848, the most extreme example of a new group of highly absorbed X-ray binaries that have recently been discovered by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The Suzaku observation was carried out between 2006 August 14 and 17, with a net exposure time of 97 ks. The average X-ray spectrum of the source can be well described (χ 2 red = 0.99) with a continuum model typical for neutron stars i.e., a strongly absorbed power law continuum with a photon index of 0.676(42) and an exponential cutoff at 20.5(6) keV. The absorbing column is N H = 1.95(3) × 10 24 cm −2 . Consistent with earlier work, strong fluorescent emission lines of Fe Kα, Fe Kβ, and Ni Kα are observed. Despite the large N H , no Compton shoulder is seen in the lines, arguing for a non-spherical and inhomogeneous absorber. Seen at an average 5-60 keV absorbed flux of 3.4×10 −10 erg cm −2 s −1 , the source exhibits significant variability on timescales of hours.

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“…The emission measures determined in classical ADC sources such as 4U 1822À37 (Cottam et al 2001), EXO 0748À676 (JimenezGarate et al 2003), 2S 0921À63 (Kallman et al 2003), and Her X-1 (Jimenez-Garate et al 2005) are greater than the ADC model can produce based on the observed luminosity. In the case of Her X-1 it has been suggested that the energy range is indeed much dominated by absorption (Kuster et al 2005;L. Ji et al 2008, in preparation) and the luminosity in its low state may be higher than observed.…”

Section: à3mentioning

confidence: 95%

The Variable Warm Absorber in Circinus X‐1

Schulz

Kallman

Brandt

2008

ApJ

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We observed Circinus X-1 twice during a newly reached low-flux phase near zero orbital phase using the HighEnergy Transmission Grating Spectrometer (HETGS) onboard Chandra. In both observations the source did not show the P Cygni lines we observed during the high-flux phases of the source in 2000 and 2001. During the prezero phase the source did not exhibit significant variability but did exhibit an emission-line spectrum rich in H-and He-like lines from high-Z elements such as Si, S, Ar, and Ca. The light curve in the postdip observation showed quiescent and flaring episodes. Only in these flaring episodes was the source luminosity significantly higher than observed during the prezero phase. We analyzed all high-resolution X-ray spectra by fitting photoionization and absorption models from the most recent version of the XSTAR code. The prezero-phase spectrum could be fully modeled with a very hot photoionized plasma with an ionization parameter of log ¼ 3:0, down from log ¼ 4:0 in the high-flux state. The ionization balances we measure from the spectra during the postzero-phase episodes are significantly different. Both episodes feature absorbers with variable high columns, ionization parameters, and luminosity. While cold absorption remains at levels quite similar to that observed in previous years, the new observations show unprecedented levels of variable warm absorption. The line emissivities also indicate that the observed low source luminosity is inconsistent with a static hot accretion disk corona (ADC), an effect that seems common to other near-edge-on ADC sources as well. We conclude that unless there exists some means of coronal heating other than X-rays, the true source luminosity is likely much higher, and we observe obscuration in analogy to the extragalactic Seyfert 2 sources. We discuss possible consequences and relate cold, lukewarm, warm, and hot absorbers to dynamic accretion scenarios.

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Probing the outer edge of an accretion disk: a Her X-1 turn-on observed withRXTE

Cited by 33 publications

References 34 publications

The Smooth Cyclotron Line in Her X-1 as Seen With Nuclear Spectroscopic Telescope Array

The Smooth Cyclotron Line in Her X-1 as Seen With Nuclear Spectroscopic Telescope Array

Suzakuobservation of IGR J16318-4848

The Variable Warm Absorber in Circinus X‐1

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