An Apparent Hard X-Ray Decline of CH Cygni

Mukai, K.; Ishida, M.; Kilbourne, Caroline A.; Mori, Hajime; Terada, Y.; Chan, Kai-Wing; Soong, Yang

doi:10.1093/pasj/59.sp1.s177

Cited by 29 publications

(36 citation statements)

References 21 publications

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“…Variability with timescales of minutes to hours is typically observed in symbiotics where X-rays originate in the accretion flow (e.g., SS73 17; Eze et al 2010, or CH Cyg;Mukai et al 2007). However, because the X-ray count rate from V1329 Cyg leads to large error bars, we cannot definitively exclude flickering.…”

Section: Discussionmentioning

confidence: 99%

“…All objects with jets, detected in other wavelengths when observed in X-rays, show soft components with k T < 2 keV (additionally to sometimes present super-soft emission): R Aqr (Kellogg et al 2001, CH Cyg ( (Sokoloski et al 2006). The three objects CH Cyg, R Aqr, and MWC 560 also emit hard components (Mukai et al 2007;Nichols et al 2007;Stute & Sahai 2009). Z And showed hard emission in one of the three observations only (Sokoloski et al 2006).…”

Section: Introductionmentioning

confidence: 96%

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DETECTION OF X-RAYS FROM THE SYMBIOTIC STAR V1329 Cyg

Stute¹,

Luna²,

Sokoloski³

2011

ApJ

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We report the detection of X-ray emission from the symbiotic star V1329 Cyg with XMM-Newton. The spectrum from the EPIC pn, MOS1, and MOS2 instruments consists of a two-temperature plasma with k T 1 = 0.11 +0.02 −0.02 keV and k T 2 = 0.93 +0.12 −0.14 keV. Unlike the vast majority of symbiotic stars detected in X-rays, the soft component of the spectrum seems to be absorbed only by interstellar material. The shock velocities corresponding to the observed temperatures are about 300 km s −1 and about 900 km s −1 . We did not find either periodic or aperiodic X-ray variability, with upper limits on the amplitudes of such variations being 46% and 16% (rms), respectively. We also did not find any ultraviolet variability with an rms amplitude of more than approximately 1%. The derived velocities and the unabsorbed nature of the soft component of the X-ray spectrum suggest that some portion of the high energy emission could originate in shocks within a jet and beyond the symbiotic nebula. The lower velocity is consistent with the expansion velocity of the extended structure present in Hubble Space Telescope observations. The higher velocity could be associated with an internal shock at the base of the jet or with shocks in the accretion region.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

DETECTION OF X-RAYS FROM THE SYMBIOTIC STAR V1329 Cyg

Stute¹,

Luna²,

Sokoloski³

2011

ApJ

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“…Such hard X-ray emission has so far been detected from four symbiotics thought to harbor WDs: RT Cru (Chernyakova et al 2005;Bird et al 2007), T CrB (Tueller et al 2005b;G. J. M. Luna et al 2008, in preparation), CH Cyg (Mukai et al 2007), and CD À57 3057 (Masetti et al 2006;Bird et al 2007). Although the origin of this hard X-ray emission is not known, there are some underlying similarities between these hard X-rayYemitting symbiotics.…”

Section: Introductionmentioning

confidence: 99%

The Nature of the Hard X‐Ray–Emitting Symbiotic Star RT Cru

Luna

Sokoloski

2007

ApJ

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We describe Chandra High Energy Transmission Grating Spectrometer observations of RT Cru, the first of a new subclass of symbiotic stars that appear to contain white dwarfs ( WDs) capable of producing hard X-ray emission out to greater than 50 keV. The production of such hard X-ray emission from the objects in this subclass (which also includes CD À57 3057, T CrB, and CH Cyg) challenges our understanding of accreting WDs. We find that the 0.3Y8.0 keV X-ray spectrum of RT Cru emanates from an isobaric cooling flow, as in the optically thin accretion disk boundary layers of some dwarf novae. The parameters of the spectral fit confirm that the compact accretor is a WD, and they are consistent with the WD being massive. We detect rapid, stochastic variability from the X-ray emission below 4 keV. The combination of flickering variability and a cooling flow spectrum indicates that RT Cru is likely powered by accretion through a disk. Whereas the cataclysmic variable stars with the hardest X-ray emission are typically magnetic accretors with X-ray flux modulated at the WD spin period, we find that the X-ray emission from RT Cru is not pulsed. RT Cru therefore shows no evidence for magnetically channeled accretion, consistent with our interpretation that the Chandra spectrum arises from an accretion disk boundary layer.

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“…This scenario changed dramatically with the discovery of very hard X-ray emission (E > 50 keV) from the symbiotic star RT Cru with INTEGRAL (Chernyakova et al 2005) and Swift (Tueller et al 2005) in 2005. Since then, three more systems were observed to have X-ray emission with energies higher than ≈10 keV (T CrB, V648 Car, CH Cyg; Smith et al 2008;Kennea et al 2009;Mukai et al 2007). The observed spectra are all compatible with highly absorbed (n H ≈ 10 22−23 cm −2 ) optically thin thermal emission with plasma temperatures corresponding to kT ≈ 5−50 keV.…”

Section: Introductionmentioning

confidence: 99%

Symbiotic stars in X-rays

Luna

Sokoloski

Mukai

et al. 2013

A&A

119

175

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Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of nine white dwarf symbiotics that were not previously known to be X-ray sources and one that had previously been detected as a supersoft X-ray source. The nine new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. The Swift/XRT telescope detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component that we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component that probably originates in a region where low-velocity shocks produce X-ray emission, i.e., a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the α/β/γ classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new δ classification for sources with hard X-ray emission from the innermost accretion region. Because we have identified the elusive accretion component in the emission from a sample of symbiotic stars, our results have implications for the understanding of wind-fed mass transfer in wide binaries, and the accretion rate in one class of candidate progenitors of type Ia supernovae.

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An Apparent Hard X-Ray Decline of CH Cygni

Cited by 29 publications

References 21 publications

DETECTION OF X-RAYS FROM THE SYMBIOTIC STAR V1329 Cyg

DETECTION OF X-RAYS FROM THE SYMBIOTIC STAR V1329 Cyg

The Nature of the Hard X‐Ray–Emitting Symbiotic Star RT Cru

Symbiotic stars in X-rays

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