A BeppoSAX observation of Her X-1 during the first main-on after an anomalous low-state: Evidence for rapid spin-down

Oosterbroek, T.; Parmar, A. N.; Orlandini, M.; Segreto, A.; Santangelo, A.; Sordo, S. Del

doi:10.1051/0004-6361:20010820

Cited by 22 publications

(49 citation statements)

References 21 publications

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“…The best-fit value corresponds to a radius of ∼250 km for the blackbody, similar to the values found by Endo et al (2000). This feature is consistently seen in all soft X-ray observations at similar temperatures, kT ≈ 130 eV; see, e.g., Ji et al (2009) and Oosterbroek et al (2001). In the FDcut model, the blackbody temperature kT was not constrained by the fit, so we fixed it to 140 eV, the average value given by the two other models.…”

Section: Soft Componentssupporting

confidence: 84%

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: Soft Componentssupporting

confidence: 84%

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 arrow in the figure indicates the epoch of present observations. It is clearly seen from the figure that present data correspond to the main-on due to a delayed onset of the source as noted by Oosterbroek et al (2001). It is also seen from the figure that in the post-anomalous state, the second main-on represents the normal behaviour during which the source intensity remained high for about 10 days, while the first main-on was of much shorter duration.…”

Section: Resultssupporting

confidence: 75%

“…(Parmar et al 1999;Levine & Corbet 1999;Coburn et al 2000). Using BeppoSAX observations during the first main-on after the anomalous low state, Oosterbroek et al (2001) have reported the evidence that the rapid spin down of the source continued during the entire ALS period and the source pulse period changed to the value observed in 1984/5. The measured pulse period of 1237.7697 corresponds to aṖ P ∼ 3 × 10 −6 yr −1 .…”

Section: Introductionmentioning

confidence: 99%

Hard X-ray behaviour of Her X-1 during second main-on after the anomalous low state

Manchanda

2003

A&A

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Abstract. The binary X-ray pulsar Her X-1 shows a variety of time variations both in luminosity and its pulse features. For the first time an about 600 days long anomalous low state was seen in the light curve of ASM on board RXTE during the period MJD 51200-51800. We observed the source in the 20-200 keV energy band during its second main-on in the post anomalous state on November 21, 2000. The source was found to be extremely bright at high energies and a total of 26 000 photons from the source were detected during the 35 min snapshot observation. The cyclotron absorption line at ∼34 keV and its second harmonics were clearly detected in the data. We present the spectral details and discuss its implication in terms of the geometrical properties of the source.

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“…Second, the hard-soft phase shift appears to vary more rapidly for SMC X-1 (a change of Ӎ90Њ between and 0.42) than for f Ӎ 0.16 SO Her X-1 (Ӎ20Њ between and 0.17; Zane et al 2004). f Ӎ 0.03 SO Third, it is not completely clear even in Her X-1 that the phase variation is caused by the 35 day disk precession; soon after the observations of Zane et al (2004), the source entered an anomalous low state, an event that may be caused by changes in the inner disk structure (Boyd & Still 2004;Oosterbroek et al 2001). Such changes could alter the shape of the inner reprocessing region, and thus the soft profiles, in a way that is not directly related to the superorbital period.…”

Section: Timing Analysismentioning

confidence: 99%

Phase Variation in the Pulse Profile of SMC X-1

Neilsen

Hickox

Vrtilek

2004

ApJ

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We present the results of the timing and spectral analysis of X-ray high-state observations of the high-mass X-ray pulsar SMC X-1 with Chandra, XMM-Newton, and ROSAT, taken between 1991 and2001. The source has ergs s Ϫ1 , and the spectra can be modeled as a power law plus blackbody withand a reprocessed emission radius cm, assuming a distance of 60 kpc to the source. Energy-8 0.18 R ∼ 2 # 10 BB resolved pulse profiles show several distinct forms, more than half of which include a second pulse in the soft profile, previously documented only in hard energies. We also detect significant variation in the phase shift between hard and soft pulses, as has recently been reported in Her X-1. We suggest an explanation for the observed characteristics of the soft pulses in terms of precession of the accretion disk.

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A BeppoSAX observation of Her X-1 during the first main-on after an anomalous low-state: Evidence for rapid spin-down

Cited by 22 publications

References 21 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

Hard X-ray behaviour of Her X-1 during second main-on after the anomalous low state

Phase Variation in the Pulse Profile of SMC X-1

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